JNDE by ram jnde

Volume 9 issue 2 September 2010

from the Chief Editor

This issue of the Journal of Nondestructive Testing and Evaluation has four contributed articles. The first article is a review on the current status of research and development in India authored by a leading expert from the Department of Science and Technology. This brings to light the new centers of excellence that have been developed in this decade in India and also eludes to new indigenous products and solutions development. An industrial article discusses the use of the time of flight diffraction (TOFD) ultrasonic method for the detection and more importantly sizing of the cracks in special steels. The TOFD methods have now become the norm for flaw sizing in many industries and this article demonstrates its use for the NDE of reheat cracks. The importance of flaw detection in rails cannot be over emphasized. India boasts of one of the largest networks of rails and the increasing loads and frequency of trains (both passenger and cargo) has posed increasing challenges to the Indian railways. The speed of inspection of these rails become a critical bottleneck and the technical paper from BAM in Germany describes an effort to inspect rails at 60 kmph using ultrasonic testing. Another research article on pipeline inspection using a combination of guided waves and phased array ultrasonic technologies has also been included. Both advanced ultrasonic methods are now accepted in the industries for their inherent ability to detect and characterize certain defects at rapid speeds. The combination of both these methods into a single technique for the advancement of pipe inspection can provide a new approach in NDE that may be applicable to many other industrial applications. There is a recent increase in the interests from various industries to advertise in this journal. A new section CLASSIFIEDS has been included here for the first time. It is also proposed to include new sections in the forthcoming issues including one for NEW PRODUCTS, TECHNOLOGY HORIZONS, and BACK TO BASICS.

Dr. Krishnan Balasubramaniam Professor Centre for Non Destructive Evaluation IITMadras, Chennai balas@iitm.ac.in

vol 9 issue 2 september 2010

I S N T - National Governing Council Chapter - Chairman & Secretary President Shri K. Thambithurai President-Elect Shri P. Kalyanasundaram Vice-Presidents Shri V. Pari Swapan Chakraborty Shri D.J.Varde Hon.General Secretary Shri R.J.Pardikar Hon. Treasurer Shri T.V.K.Kidao Hon. Joint Secretaries Shri Rajul R. Parikh Dr. V.R.Ravindran Hon. Co-Treasurer Shri S.V.Swamy Immediate Past President Shri Dilip P. Takbhate Past President Shri S.I.Sanklecha Members Shri Anil V. Jain Shri Dara E. Rupa Shri D.K.Gautam Shri Diwakar D. Joshi Dr. Krishnan Balasubramaniam Shri Mandar A. Vinze Shri B.B.Mate Shri G.V.Prabhugaunkar Shri B.K.Pangare Shri M.V.Rajamani Shri P.V. Sai Suryanarayana Shri Samir K. Choksi Shri B.K.Shah Shri S.V.Subba Rao Shri Sudipta Dasgupta Shri N.V.Wagle Shri R.K.Singh Shri A.K.Singh (Kota) Shri S. Subramanian Shri C. Awasthi Brig. P. Ganesham Shri Prabhat Kumar Shri V. Sathyan Shri P. Mohan Shri R. Sampath Ex-officio Members Managing Editor, JNDT&E Shri V. Pari Chairman, NCB & Secretary, QUNEST Dr. Baldev Raj Controller of Examination, NCB Dr. B. Venkatraman President, QUNEST Prof. Arcot Ramachandran All Chapter Chairmen/Secretaries Permanent Invitees Shri V.A.Chandramouli Prof. S. Rajagopal Shri G. Ramachandran & All Past Presidents of ISNT

Ahmedabad

Kota

Shri D.S. Kushwah, Chairman, NDT Services, 1st Floor, Motilal Estate, Bhairavnath Road, Maninagar, Ahmedabad 380 028. dskushwah@icenet.net Shri Rajeev Vaghmare, Hon. Secretary C/o Modsonic Instruments Mfg. Co. Pvt. Ltd. Plot No.33, Phase-III, GIDC Industrial Estate Naroda, Ahmedabad-382 330 modsonic@modsonic.com

Shri R.C. Sharma, Associate Director (QA), Rawatbhata 323 307 rlsharma@npcilraps.com Shri S.V.Lele, Hon. Secretary, T/IV – 5/F, Anu Kiran Colony, PO Bhabha Nagar, Rawatbhata 323 307. svlele@npcilraps.com

Bangalore

Shri N.V. Wagle, Chairman, A-601, CASCADE-3, Kulupwadi, Borivali East, Mumbai 400 066. offc@isnt.org Shri Samir K. Choksi, Hon. Secretary, Director, Choksi Brothers Pvt. Ltd., 4 & 5, Western India House, Sir P.M.Road, Fort, Mumbai 400 001. Choksiindia@yahoo.co.in

Dr. M.T. Shyamsunder, Chairman, NDE Modelling & Imaging Lab., Cassini Building, GE Global Research, John F. Welch Technology Center EPIP Phase 2, Whitefield Road, Bangalore-560066. Mt.shyamsunder@ge.com Nagpur Shri S. Kalyana Sundaram, Hon. Secretary Shri K.R.V.S.Mehar, Chairman Scientist, STDivision,National Aerospace Laboratories, Manager – SGS India Pvt. Ltd. B a n g a l o r e - 5 6 0 0 1 7 . i s n t b l r @ g m a i l . c o m 218 Bajaj Nagar, Nagpur-440 010 kuchimanchi.mehar@sgs.com Dr. D.R.Peshwe, Hon. Secretary, Chennai Professor, Dept. of Metall. & Materials Engineering, Shri M.V. Rajamani, Chairman Visveswaraya National Institute of Technology, Electro Magfield Controls & Services Nagpur 440 011. drpeshwe@vnitnagpur.ac.in D-22, Industrial Estate, Ambattur Ind.Estate, Chennai – 600 058 emcs@vsnl.net Shri R. Balakrishnan, Hon. Secretary, th No.13, 4 Cross Street, Indira Nagar, Adyar, Chennai 600 020. rbalkrishin@yahoo.co.in

Delhi Shri Ashok Kumar Singhi, Chairman, MD, IRC Engg Services India Pvt. Ltd., 612, Chiranjiv Tower, 43, Nehru Place New Delhi- 110 019 irc_engg@hotmail.com Shri Dinesh Gupta, Hon.Secretary, Director, Satyakiran Engineers Pvt.Ltd., BU 3 SFS Pitampura, New Delhi 110 034. satyakiran@vsnl.com

Hyderabad Shri R.N.Jayaraj, Chairman, Chief Executive, Nuclear Fuel Complex, Hyderabad 500 062. Jayaraj1950@gmail.com Shri T.B.Harikishan Rao, Hon.Secretary, Deputy General Manager (QA/QC) Mishra Dhatu Nigam Limited (Midhani), PO Kanchanbagh, Hyderabad 500 058. hkrao_tapse@yahoo.co.in

Jamshedpur Mr J. C. Pandey, Chairman, Researcher, R&D, TATA Steel, P. O. Burmamines, Jamshedpur - 831 007 jcpandey@tatasteel.com Mr. M K Verma, Hon. Secretary, Manager, SNTI, TATA Steel N-Road, Bistupur, Jamshedpur - 831 001 mk.verma@tatasteel.com

Kalpakkam Shri YC Manjunatha, Chairman Director ESG, IGCAR, Kalpakkam – 603 102 ycm@igcar.gov.in Shri BK Nashine, Hon.Secretary Head, ED &SS, C&IDD, FRTG IGCAR, Kalpakkam – 603 102 bknash@igcar.gov.in

Kochi Shri John Minu Mathew, Chairman, General Manager (Technical), Bharat Petroleum Corporation Ltd. (Kochi Refinery), PO Ambalamugal 682 302. Kochi johnminumathew@bharatpetroleum.in Shri K.D.Damien Gracious, Hon. Secretary, CM (Advisory Services), Bharat Petroleum Corporation Ltd. (Kochi Refinery), PO Ambalamugal-682 302. Kochi damiengraciousk@bharatpetroleum.in

Kolkata Shri Swapan Chakraborty, Chairman Perfect Metal Testing & Inspection Agency, 46, Incinerator Road, Dum Dum Cantonment, Kolkata 700 028. permeta@hotmail.com Shri Dipankar Gautam, Hon. Secretary, 4D, Eddis Place, Kolkata-700 019. eib1956@gmail.com

vol 9 issue 2 September 2010

Mumbai

Pune Shri PV Dhole, Chairman NDT House, 45 Dr Ambedkar Road, Sangam Bridge, Pune- 411 001 info@technofour.com Shri VB Kavishwar, Hon Secretary, NDT House, 45 Dr Ambedkar Road, Sangam Bridge, Pune- 411 001 eddysonic@gmail.com

Sriharikota Shri K. Venkata Rao, Chairman, General Manager, SPP, SDSC, SHAR Centre, Sriharikota 524124. kvrao@shar.gov.in Shri B. Munirathinam, Hon. Secretary, Engineer – SF, NDT/SPP, Satish Dhawan Space Centre, Sriharikota-524 124. bmuni@shar.gov.in

Tarapur Shri D.K.Sisodia, Chairman, CS, R&D, TMS, NPCIL 3 & 4, Tarapur 401 502. dksisodia@npcil.co.in Shri D. Mukherjee, Hon.Secretary, Superintendent, QC & NDE, AFFF, BARC, Tarapur-401 502. sorwadip@yahoo.co.in

Tiruchirapalli Shri V Thyagarajan, Chairman General Manager (WRI & Labs) BHEL Tiruchirapalli 620014 isnt_try@sancharnet.in Shri A.K.Janardhanan, Hon. Secretary, C/o NDTL Building 1, H.P.B.P., BHEL, Tiruchirapalli 620 014. akjn@bheltry.co.in

Vadodara Shri P M Shah, Chairman, Head-(QA) Nuclear Power Corporation Ltd. NBCC Plaza,Opp. Utkarsh petrol pump, Kareli Baug, Vadodara-390018. npcil.bar@gmail.com M S Hemal Mehta, Hon.Secretary, NBCC Plaza, Opp. Utkarsh petrol pump, Kareli Baug, Vadodara-390018. pmetco@gmail.com

Thiruvananthapuram Dr. V.R. Ravindran, Chairman Division Head, Rocket Propellant Plant, VSSC, ISRO, Thiruvananthapuram - 695 022 drvrravi@yahoo.co.in Shri. Imtiaz Ali Khan Hon.Secretary, Engineer, Rocket propellant Plant, VSSC, Thiruvananthapuram 695 013 imtiaz_ali@vssc.gov.in

Visakhapatnam Shri Om Prakash, Chairman, MD, Bharat Heavy Plate & Vessels Ltd. Visakhapatnam 530 012. Shri Appa Rao, Hon. Secretary, DGM (Quality), BHPV Ltd., Visakhapatnam 530 012

Journal of Non-Destructive Testing & Evaluation

Volume 9

issue 2

Contents

Chief Editor Prof. Krishnan Balasubramaniam e-mail: balas@iitm.ac.in

Co-Editor Dr. BPC Rao bpcrao@igcar.gov.in Managing Editor Sri V Pari e-mail: scaanray@vsnl.com

Topical Editors Dr D K Bhattacharya, Electromagnetic Methods

Dr T Jayakumar,

7 14 21

Radiation Methods

Review Paper: NDT- The World Scenario; A Science and Technology Perspective High Sensitivity TOFD UT to Reveal Reheat Cracks in CrMo-V Steel Weld S.P. Ghiya, Dr. D.V. Bhatt, Dr. R.V. Rao and P. Raghavendra

High speed Non-destructive rail testing with advanced Ultrasound and Eddy-current testing techniques

Thomas HECKEL, Hans-Martin THOMAS, Marc KREUTZBRUCK and Sven RĂ&#x153;HE

Sri P Kalyanasundaram, Sri K Viswanathan,

Chapter News

Milind Kulkarni

Ultrasonic & Acoustic Emission Methods Advanced NDE Methods

September 2010

Ultrasonic Guided Wave Phased Array Inspection of Pipelines S. Palit Sagar, Jia Jerry Hua and Joseph L Rose

Editorial Board Dr N N Kishore, Sri Ramesh B Parikh, Dr M V M S Rao, Dr J Lahri, Dr K R Y Simha, Sri K Sreenivasa Rao, Sri S Vaidyanathan, Dr K Rajagopal, Sri G Ramachandran, Sri B Ram Prakash

Advisory Panel Prof P Rama Rao, Dr Baldev Raj, Dr K N Raju, Sri K Balaramamoorthy, Sri V R Deenadayalu, Prof S Ramaseshan, Sri A Sreenivasulu, Lt Gen Dr V J Sundaram, Prof N Venkatraman

Objectives

ASNT NDT Level III Refresher Courses by ISNT Chennai Chapter log on to www.isntchennaichapter.org

The Journal of Non-Destructive Testing & Evaluation is published quarterly by the Indian Society for Non-Destructive Testing for promoting NDT Science and Technology. The objective of the Journal is to provide a forum for dissemination of knowledge in NDE and related fields. Papers will be accepted on the basis of their contribution to the growth of NDE Science and Technology.

The Journal is for private circulation to members only. All rights reserved throughout the world. Reproduction in any manner is prohibited. Views expressed in the Journal are those of the authors' alone.

Published by RJ Pardikar, General Secretary on behalf of Indian Society for Non Destructive Testing (ISNT) Modules 60 & 61, Readymade Garment Complex, Guindy, Chennai 600032 Phone: (044) 2250 0412 Email: isntheadoffice@gmail.com

more details on page 5

NDE 2010 December 9-11, 2010 @ Science City Convention Centre, Kolkata

www.nde2010.com

and

Printed at VRK Printing House 3, Potters Street, Saidapet, Chennai 600 015 vrkonline@gmail.com Ph: 09381004771

About the cover page: The cover page shows the MICRO-THERMOGRAM of a human hair taken at a resolution of 6 microns(um) using a special microscopic lens. This image reveals the hollow center portion of the hair which measures about 20 microns. COURTESY: Center for Nondestructive Evaluation at IIT Madras.

vol 9 issue 2 september 2010

Scaanray Metallurgical Services

Transatlantic Systems

(An ISO 9001-2000 Certified Company)

NDE Service Provider

Support for NDT Services NDT Equipments, Chemicals and Accessories

Process and Power Industry, Engineering and Fabrication Industries, Concrete Structures, Nuclear Industries, Stress Relieving

Call DN Shankar, Manager 14, Kanniah Street, Anna Colony, Saligramam, Chennai 600093 Phone 044-26250651 Email: scaanray@vsnl.com

Call M. Nakkeeran, Chief Operations, Lab: C-12, Industrial Estate, Mogappair (West), Chennai 600037 Phone 044-2625 0651 Email: scaanray@vsnl.com ; www.scaanray.com

Electro-Magfield Controls & Services & LG Inspection Services

Betz Engineering & Technology Zone An ISO 9001 : 2008 Company

We manafucture : Magnetic Crack Detectors, Demagnetizers, Magnetic Particles & Accessories, Dye Penetrant Systems etc Super Stockist & Distributors: M/s Spectonics Corporation, USA for their complete NDT range of productrs, Black Lights, Intensity Meters, etc.

49, Vellalar Street, near Mount Rail Station, Chennai 600088 Mobile 98401 75179, Phone 044 65364123 Email: betzzone@vsnl.net / rg_ganesan@yahoo.com

International Training Division Plot 165, SIDCO Industrial Estate, (Kattur) Thirumullaivoil, Vellanur Village, Ambattur Taluk Chennai 600062 Phone 044-6515 4664 Email: emcs@vsnl.net

21, Dharakeswari Nagar, Tambaram to Velachery Main Road, Sembakkam, Chennai 600073 www.betzinternational.com / www.welding-certification.com

Madras Metallurgical Services (P) Ltd

KIDAO Laboratories

Metallurgists & Engineers

Metallography Strength of Materials Non Destructive Testing Foundry Lab

NABL Accredited Laboratory carrying out Ultrasonic test, MPL and DP tests, Coating Thickness and Roughness test. We also do Chemical and Mechnical tests

Serving Industries & Educational Institutes for the past 35 years

A-3, Mogappair Indl. Area (East) JJ Nagar, Chennai 600037 Phone 044-26564255, 26563370 Email: kidaolab@giasmd01.vsnl.net.in; kidaolabs@vsnl.net www.kidaolabs.com

24, Lalithapuram street, Royapettah, Chennai 600014 Ph: 044-28133093 / 28133903 Email: mmspl@vsnl.com

Dhvani R&D Solutions Pvt. Ltd

OP TECH

01J, First Floor, IITM Research Park, Kanagam Road, Taramani, Chennai 600113 India Phone : +91 44 6646 9880

ASNT Level III Intensive Taining Educational CDs PT, UT, RT, MT, ET, Basic Metallurgy and Mechanical Testing Call 93828 12624 Land 044 - 2446 1159

B Ram Prakash A 114, Deccan Enclave, 72, T M Maistry Street, Thiruvanmiyur, Chennai 600 041

NDT Training & Level III Services in all the following ten NDT Methods

Shri. K. Ravindran, Level III RT, VT, MT, PT, NR, LT, UT, ET, IR, AE

vol 9 issue 2 September 2010

• • • •

Inspection Solutions Software Products Training Services & Consultancy

E-mail: info@dhvani-research.com

CUPS, TAPS, CRISP, TASS SIMUT, SIMDR Guided Waves, PAUT, TOFD Advanced NDE, Signal Processing C-scans, On-line Monitoring www.dhvani-research.com

No.2, 2nd Floor, Govindappa Naicker Complex, Janaki Nagar, Arcot Road, Valasaravakkam, Chennai-600 087 Tamil Nadu, India Phone : 044-2486 8785, 2486 4481 E-mail: sisins@gmail.com and sisins@hotmail.com Website: www.sisndt.com

ISNT - National Certification Board (NCB) Announcement ASNT NDT Level III Examination 1, 2 & 3 November 2010. Chennai

The Indian Society for Non - Destructive Testing (ISNT), the National Sponsoring Organization of the American Society for Non – Destructive Testing (ASNT) is pleased to announce that the Second ASNT NDT Level III Examination of 2010 (by the ASNT) in various methods is scheduled to be held at Chennai, S. India on 01st, 2nd & 03rd of November 2010. The examinations will be conducted under the auspices of the American Society for Nondestructive Testing, USA. NDT Level III certification by ASNT (which is given only by examination) will help NDT personnel and the organizations that employ them, in promoting global acceptance of their Products and Services. The importance and the necessity for Indian Industry to compete in the International arena need not be over-emphasized. In order to assist the intending aspirants in preparing for the November 2010 ASNT NDT Level III examinations, Refresher Courses in various methods will be conducted

under the arrangement of ISNT – Chennai Chapter; beginning Oct 2010 . The details of the fee structure applicable for the Examination and Refresher Courses are given below. All correspondences on the subject and request for application forms may please be addressed to: Dr. B. Venkatraman ASNT Level III Examination Coordinator, NCB – ISNT, Modules 60 & 61, Readymade Garment Complex, SIDCO Industrial Estate, Guindy, Chennai 600 032, S. India Ph: 91 44 22500412, 91 44 42038175 E Mail: ncbisnt@gmail.com ; isntheadoffice@gmail.com Alternate E Mail: isntho@dataone.in Applications for the Examinations duly completed in all respects along with requisite supporting documents and applicable fees (ASNT & ISNT) shall be sent to the Examination Coordinator mentioned above.

ASNT NDT Level III Refresher Courses by ISNT Chennai Chapter ISNT-Chennai chapter will be organizing refresher courses for assisting the candidates in preparing for the ASNT NDT Level III Examinations to be held in Chennai. The details along with fees for the courses are as given below: Table II Method Course Eddy Current** Visual Testing** Basic Liquid Penetrant Magnetic Particle Ultrasonic Basic Radiography

Course Duration

Dates

Fees for the Courses in INR

Director

4 Days 3 Days 4 Days 3 Days 3 Days 4 Days 4 Days 4 Days

1-4 Oct 2010 2-4 Oct 2010 5-8 Oct 2010 9-11 Oct 2010 12-14 Oct 2010 18-21 Oct 2010 22-25 Oct 2010 26-29 Oct 2010

6400 4800 6400 4800 4800 6400 6400 6400

Dr. O. Prabhakar Mr. R. Ramakrishnan Mr. K. Ravindran Mr. G. Jothinathan Mr. R. Ramakrishnan Dr. O. Prabhakar Mr. K. Ravindran Mr. R. Subburathinam

Basic course will be conducted in two different dates. The Candidates can choose to their convinence. Venue : ISNT Chennai Chapter – Laser Hall & Conference Hall Modules 59, Readymade Garment Complex, SIDCO Industrial Estate, Guindy, Chennai 600 032, S. India Ph: 91 44 6538 6075, 2250 0412, 4203 8175 vol 9 issue 2 september 2010

6 ** These courses will be conducted and scheduled on the basis of responses received. Those who intend to attend the courses on Visual Testing and Eddy Current Testing should intimate their intention sufficiently in advance to facilitate scheduling the courses. They may also inform the details of other courses they wish to attend. The courses for these two methods will be conducted depending on the response received latest by 15 Sept. 2010. Refresher courses will be conducted by faculties who are experts in the respective NDT Methods and Techniques with focus on ASNT NDT Level III syllabus. The course fee includes study material, lunch and tea. Candidates will have to make their own arrangement for boarding, lodging and other expenses during their stay at Chennai, both for the examination and the courses. Course material will be given to the participants on the first day of the course. If it is needed earlier, it can be sent to the participants, at their specific request to the examination coordinator, by courier service, at their cost. Once the candidates have received the course material, on no account the course fee will be refunded.

The course syllabus will be as per ASNT SNT-TC-1A 2006 requirement. The candidates can opt for one or more of the above courses as desired by them. The course fee should be sent by a crossed demand draft drawn in favor of “NCBISNT” payable at Chennai and sent to the Coordinator at the address given in first page. For Further details visit our ISNT website www.isnt.org.in ISNT Chennai Chapter website www.isntchennaichapter.org or call 044 65386075 Examination Venue will be updated soon in our website www.isnt.org.in Programme Director Dr. Krishnan Balasubramaniam Professor of Mechanical Engineering, Head, Centre for Non–Destructive Evaluation, Department of Mechanical Engineering Indian Institute of Technology Madras Chennai – 600036. Tele: 91 44 2257 4662 E-Mail: balas@iitm.ac.in

log on to www.isnt.org.in

vol 9 issue 2 September 2010

CHAPTER NEWS Chennai Chapter

Welding Inspector examination at ITT, Mahim on 18th April 2010, RT Level – I at PUNE, on 24th July, 2010; PT Level – II at Tarapur, on 24th July, 2010 EC meeting was held on 7th April, 2010, 25th June 2010 and 11th August 2010

Course & Exams: MT & PT Level-II course was conducted from 21- 30 May 2010. No. of participants were 14. In-House Training on MT Level-I held on 9th, 16th and 23rd May 2010 at M/s. M.M.Forging Limited, Chennai. No. of participants 13. UT Level-II (ISNT) course was conducted from 0518.July 2010. No. of participants were 18. RT Level-II (ASNT) course was conducted from 30 July to 08 August.2010. No. of participants were 17. ISNT DAY was celebrated on 21.04.2010 at Hotel Radha Regent, Chennai. 190 Members with their spouse and children had attended the meeting. AGM was celebrated on 17th July 2010 at ISNT, Conference Hall, Chennai. 70 Members attended the meeting. EC Meeting held on 30th May 2010, 11th July 2010 and 4th August 2010.

Vadodara

Hyderabad

Sriharikota

Technical Talk “Acoustic Emission Technology and Applications” on 21st May 2010 by Dr. MVMS Rao, Emeritus Scientist, NGRI, Hyderabad. RT Level II (ISNT) from 28 June to 10 July 2010 Candidates: 19. Courses & Exams: UT Level I & II (ISNT) from 17-28 May 2010 Candidates: 19 each . NDT awareness course for management trainees of MIDHANI from 7-9 June 2010. Executive committee meetings held on 04 April 2010. Website launch on 21 May 2010 by Shri K. Balaramamurthy, Ex.CE of NFC. 9 Life Members enlisted ; 7 annual members enlisted.

Invited lecture in April 2010 on the topic “Role of NDE in manufacturing of Nuclear Fuels”-by A.V.RamanaRao, GM, QA, NFC, Hyderabad

Mumbai ASNT Level – III Refresher courses i.e. PT, MT, RT, UT and BASIC in Mumbai from 1st to 22nd April 2010 at Hotel Jewel of Chebur.

One day joint Seminar with Guj. safety council and Petrolium & Explosive Safety organization(PESO) “NDT Technique in pressure vessels” on 18 March, 2010

Trichy Invited Lecture by Shri.S.C.Sood, from CIT,UK on “Computed Radiography”, on 25th June 2010.Courses conducted: 1) Radiographers Certification Course (RT-I) in association with BARC from 19th April 10- to 07th May 10. 2) Level-II Package Program for PSG Students : From 01st - 26th May 10 3) Level-II program on Surface NDT (LPI/MPI) :From 10st20th August 10 EC meeting was conducted on 25th May 2010

Tiruvananthapuram 1) M.R.Kurup memorial lecture by by Shri B Velayudham, DD, PCM, VSSC 2) Technical Talk by Shri R J Pardikar, BHEL, Trichy On 7th August 2010 Family Get together and Entertainment program on 7th August 2010

Pune -Technical talk by Mr. B.K. Shah on 05 June 2010 -ISNT course at Ammunition Factory, Khadki, -2 day course for Students at Bharati Vidyapeeth on13th & 14th August 2010 -Two Executive Meetings -Deputed Mr. V.B. Kavishwar to ISNT Bangalore for Level III exam -Membership increase from 97 members to 326 members as on date vol 9 issue 2 september 2010

National NDT Awards No.

Award Name

Sponsored by

ISNT - EEC National NDT Award (R&D)

M/s. Electronic & Engineering Co., Mumbai

ISNT - Modsonic National NDT Award (Industry)

M/s. Modsonic Instruments Mfg. Co. (P) Ltd., Ahmedabad

ISNT - Sievert National NDT Award (NDT Systems)

M/s. Sievert India Pvt. Ltd., Navi Mumbai

ISNT - IXAR Best Paper Award in JNDE (R & D)

M/s. Industrial X-Ray & Allied Radiographers Mumbai

ISNT - Eastwest Best Paper Award in JNDE (Industry)

M/s. Eastwest Engineering & Electronics Co., Mumbai

ISNT - Pulsecho Best Chapter Award for the Best Chapter of ISNT

M/s. Pulsecho Systems (Bombay) Pvt. Ltd. Mumbai

ISNT - Ferroflux National NDT Award

M/s. Ferroflux Products Pune

(International recognition)

ISNT - TECHNOFOUR National NDT Award for Young NDT Scientist / Engineer

ISNT - Lifetime Achievement Award

M/s. Technofour Pune

Note-1: The above National awards by ISNT are as a part of its efforts to recognise and motivate excellence in NDT professional enterpreneurs. Nomination form for the above awards can be obtained from ISNT head office at Chennai, or from the chapters. The filled application are to be sent to Chairman, Awards Committee, Indian Society for Non-destructive Testing, Module No. 60 & 61, Readymade Garment Complex, SIDCO Ind. Estate, Guindy, Chennai-600 032. Telefax : 044-2250 0412 Email: isntheadoffice@gmail.com

Advt. tariff & Journal subscription - India & SAARC countries Classified advt (Business card) BackCover (Multi Colour) Inside Cover - Front (Multi colour) Gate fold - Front (Multi colour) Inside Cover - Back (Multi Colour) Gate fold - Back (Multi colour) Inner Pages Full (Multi Colour) Inner Pages Full (Black & White) Inner Pages Half (Black & White) Panel Display (6 cm X 4 cm) Journal subscription rates

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Managing Editor Journal of Non Destructive Testing & Evaluation Modules 60 & 61, Readymade Garment Complex, Guindy, Chennai 600032 Phone: (044) 2250 0412

vol 9 issue 2 September 2010

National Seminar on Non-Destructive Evaluation December 9-11, 2010

Theme: NDE for Energy and Environment

Science City Convention Center, Kolkata

An invitation to all the NDT professionals Topics to be covered Present status and future directions in the conventional NDE techniques and practices NDE as a Quality assurance tool- choice of materials, fabrication, erection and operation of plants and life assessment and extension of components and plants beyond their design lives. NDE in the infrastructural assets such as railways, buildings, roads, bridges highways, power transmission etc. NDE in Energy efficiency measures influencing design and process alterations, and in building establishments Advanced NDT (such as digital & computed tomography, phased array ultrasonics, TOFD, nonlinear ultrasonics etc) Signal analysis and processing (conventional techniques, pattern recognition, fuzzy logic, neural network analysis etc) NDE in medical field (imaging & diagnosis) Sensors for monitoring of processes and environment NDE for materials characterization (Microstructure, physical & mechanical properties, residual stress etc) Concepts of NDE in nano-science & Technology NDE codes and standards NDE training & certification

For Paper Submission Dr. D.K. Bhattacharya Chairman, Technical Committee (E-mail: paper.nde2010@gmail.com)

log on to www.nde2010.com

Pre-Seminar Events: a) Tutorial on Radiographic and Thermographic imaging (Key person: Dr. B. Venkatraman, Head, Quality Assurance Division, Indira Gandhi Centre for Atomic Research, Kalpakkam. E-mail: bvenkat@igcar.gov.in) b) Tutorial on Signal analysis, simulation and modeling (Key person: Dr. B.P.C. Rao, Indira Gandhi Centre for Atomic Research, Kalpakkam E-mail: bpcrao@igcar.gov.in c) Workshop on Structural integrity assessment by advanced NDE (Key Person: Dr. (Mrs) Sarmistha Palit Sagar, National Metallurgical Laboratory, Jamshedpur. E-mail: sarmi@nmlindia.org

EXHIBITION: (specially arranged a/c stalls) Tariffs: Rs. 50,000/- per stall + service tax + VAT, USD1550 for foreign companies Contact : ndekolkata2010@gmail.com Souvenir Tariffs: Full page colour: Rs. 15,000/=; Full page B/W: Rs. 10,000/= Contact : ndekolkata2010@gmail.com General Enquiry

Shri Swapan Chakraborty Chairman, Organising Committee ISNT Kolkata Chapter, 4D, Ekdalia Place, Kolkata 700019 ndekolkata2010@gmail.com

ISNT NonMembers Members Seminar 3500/ Tutorial/Workshop 5000/ Combo 7000/

4000/ 5500/ 8000/

Foreign Delegates with Delegate accompanying Spouse $300 Rs5000/$450 $300 NA $450 $550

Student ISNT Member 1500/ 2000/ 3000/

Student NonMember 2000/ 2500/ 4000/

vol 9 issue 2 september 2010

vol 9 issue 2 September 2010

EPOCH 600

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vol 9 issue 2 september 2010

vol 9 issue 2 September 2010

vol 9 issue 2 september 2010

Review Paper

NDT- The World Scenario; A Science and Technology Perspective Milind Kulkarni SERC Division, Department of Science and Technology, Technology Bhavan, New Mehrauli Road, New Delhi - 110 016 Email: milind@nic.in

The use of manual non-destructive evaluation techniques is very common in day-to-day life. The examples are numerous ranging from shaking of the coconut to find its condition before buying, lightly tapping a watermelon to judge its ripeness, striking bangles or a glass item against solid to find whether it has crack/ fault or not and so on. The central theme in all these tests is “testing of a product without harming its life cycle or without impairing their future use”. The material under testing does not undergo any change in its size, shape, physical & chemical properties and its usefulness. While many of the NDT techniques used have applications in medical diagnostics field, the term is generally applied to non-medical investigations of material integrity. Medical NDT is now treated as a separate subject from industrial NDT and hence most physicians do not use the term non-destructive.

Over the decades, all these methods have and are being continuously improved upon to cater to the changing requirements. The industrial revolution saw some of the early techniques being used for NDE, but the real thrust to their usage was provided after the World War II, when there were strategic failures attributed to material faults.

American Society of Nondestruction Testing (ASNT) defines NDT as “NDT is the development and application of technical methods to examine materials or components in ways that do not impair future usefulness and serviceability in order to detect, locate, measure and evaluate discontinuities, defects and other imperfections; assess integrity, properties and composition; and measure geometrical characteristics.”

The emergence of new & sophisticated techniques combined with the rapid improvement in technology resulted in an improved capability for fault detection. The early 1970’s saw turmoil in the industrial sector since rejection of products/ components was alarmingly high. The emergence of Fracture Mechanics as a discipline was a boon to the industry since it gave laws to predict the fault behaviour on individual loading as well as cyclic loading or fatigue. The concept of “safe life” design shifted to “fail safe or damage tolerant” design. This resulted in acceptance of components/ products with known defects as long as it was established that the defects would not cause failures and hence not critical.

HISTORICAL EVOLUTION OF NDT METHODOLOGIES The art and science of Non-destructive Testing (NDT) are very old. Probably one of the most famous and wellknown examples is that of Archimedes and Hiero’s Crown. Archimedes used his now famous displacement principle to determine if the silversmiths had defrauded the king by drowning the crown in water and comparing the water displacement. The first usage of some of the now prevalent NDT techniques can be traced back to 19th Century. 1850 – Liquid Penetrants 1860 – Leak Testing 1879 – Eddy Current Testing 1895 – Radiography

The initial primary purpose of usage of NDE techniques, therefore, was detection of defects in product material. As a tool for certifying “safe life” design of a product, its usage was intended to detect defects so as to remove the component/ product from service. In response to this need, increasingly sophisticated techniques using ultrasonics, eddy currents, dye Penetrants, etc., that were based on reading and analyzing the energy patterns, emerged.

This change posed a new challenge to the NDT researchers. The challenge was to develop techniques to obtain quantitative information about the fault size. This quantitative information would then serve as input to facilitate carrying out fracture mechanics based predictions of remaining life of a product/ component. Like in many other scientific and technological areas the defence and nuclear power establishments were the first to show concerns for developing and adopting these techniques. The leading NDT Centres in the world like the Centre for Nondestructive Evaluation at Iowa State University, the Fraunhofer Institute for Nondestructive Testing in Saarbrucken, Germany; the Nondestructive Testing Centre in Harwell, England; can all trace their roots to such initiatives.

1930 – Ultrasonics

NDT – THE PROCESS 1948 – Holography 1950 – Acoustic Emission Journal of Non destructive Testing & Evaluation

A variety of NDT techniques have been developed to characterize and detect all possible defects. These Vol. 9, Issue 2 September 2010

Review Paper

techniques are based on physical principles like wave concepts; ultrasonics; x-rays; optics etc. This implies that the material to be inspected is subjected to some form of external energy source and analyzing the detected response signals through comparison with benchmarks. The essential parts of any NDT test are:

Thermal and infrared Bonding, composition, emissivity, heat contours, plating thickness, porosity, reflectivity, stress, thermal conductivity, thickness, voids Chemical and analytical Alloy identification, composition, cracks, elemental analysis and distribution, grain size, inclusions, macrostructure, porosity, segregation, surface anomalies

Application of a testing or inspection medium Modification of the testing or inspection medium by the defects or due to variation in the structure or properties of the material Detection of this change by suitable detector Conversion of this change into a suitable detector Interpretation of the information thus obtained

Auxiliary Categories & Objectives Image generation Dimensional variations, dynamic performance, anomaly characterization and definition, anomaly distribution, anomaly propagation, magnetic field configurations Signal image analysisData selection, processing and display, anomaly mapping, correlation and identification, image enhancement, separation of multiple variables, signature analysis

For example let’s take the case of X-ray film radiography. The whole process has the following parts:

X-rays are testing or inspection medium Any defects in the material being subjected to x-ray will modify the radiation intensity on the opposite side Certain Silver-Bromide emulsions are sensitive to xrays and can be used as detector The emulsions can record the intensity variations which can be stored as a permanent record Interpretation to explain variations in densities of the radiographs

(Source: American Society of Nondestructive Testing (ASNT))

The commonly used NDT methods are: z Visual Inspection

Used extensively to evaluate the condition or the quality of a weld or component.

It is easily carried out, inexpensive and usually doesn’t require special equipment.

It requires good vision, good lighting and the knowledge of what to look for. Visual inspection can be enhanced by various methods ranging from low power magnifying glasses through to boroscopes.

NDT Techniques

As informed earlier, the NDT techniques are based on physical methods and there may be one or more techniques attributed to each method. The normally accepted classification of NDT methods and the objectives of the methods are tabulated below:

z Liquid Penetration Inspection

Used to reveal surface breaking flaws by bleed-out of a coloured or fluorescent dye from the flaw.

Technique is based on the ability of a liquid to be drawn into a “clean” surface-breaking flaw by capillary action. After a period of time called the “dwell”, excess surface penetrant is removed and a developer applied. This acts as a “blotter”. It draws the penetrant from the flaw to reveal its presence. Coloured (contrast) penetrants require good white light while fluorescent penetrants need to be used in darkened conditions with an ultraviolet “black light”.

Basic Categories & Objectives Mechanical and optical Colour, cracks, dimensions, film thickness, gauging, reflectivity, strain distribution and magnitude, surface finish, surface flaws, through-cracks Penetrating radiation Cracks, density and chemistry variations, elemental distribution, foreign objects, inclusions, micro porosity, misalignment, missing parts, segregation, service degradation, shrinkage, thickness, voids Electromagnetic and electronic Alloy content, anisotropy, cavities, cold work, local strain, hardness, composition, contamination, corrosion, cracks, crack depth, crystal structure, electrical and thermal conductivities, flakes, heat treatment, hot tears, inclusions, ion concentrations, laps, lattice strain, layer thickness, moisture content, polarization, seams, segregation, shrinkage, state of cure, tensile strength, thickness, disbonds Sonic and ultrasonic Crack initiation and propagation, cracks, voids, damping factor, degree of cure, degree of impregnation, degree of sintering, delaminations, density, dimensions, elastic moduli, grain size, inclusions, mechanical degradation, misalignment, porosity, radiation degradation, structure of composites, surface stress, tensile, shear and compressive strength, disbonds, wear

Vol. 9, Issue 2 September 2010

z Acoustic Emission

Involves listening to the sounds emissions made by a material, structure or machine in use or under load and drawing conclusions about it’s “state of health”

The technique involves attaching one or more ultrasonic microphones to the object and analyzing the sounds using computer-based instruments. The noises may arise from friction (including bearing wear), crack growth, turbulence (including leakage) and material changes such as corrosion.

Has advantage of monitoring a whole structure from a few locations with possibility of continuous monitoring even for microscopic changes with multiple sensors and alarms. Journal of Non destructive Testing & Evaluation

Review Paper

Applications include testing pipelines and storage tanks (above and below the ground), fiberglass structures, rotating machinery, weld monitoring and biological and chemical changes.

z Magnetic Particle Inspection

Used to find surface and near surface flaws in ferromagnetic materials such as steel and iron. But its effectiveness quickly diminishes depending on the flaw depth and type.

The technique uses the principle that magnetic lines of force {flux) will be distorted by the presence of a flaw in a manner that will reveal it’s presence. The flaw is located from the “flux leakage”, following the application of fine iron particles, to the area under examination.

The iron particles can be applied dry or wet; suspended in a liquid, coloured or fluorescent. Surface irregularities and scratches can give misleading indications. Therefore it is necessary to ensure careful preparation of the surface before magnetic particle testing is undertaken.

z Eddy Current Inspection

It is an electromagnetic technique and can only be used on conductive materials. Used for crack detection, rapid sorting of small components for either flaws, size variations, or material variation. Commonly used in the aerospace, automotive, marine and manufacturing industries.

Eddy currents are induced when an energized coil is brought near to the surface of a metal component. These currents set-up magnetic field that tend to oppose the original magnetic field. The impedance of coil in close proximity to the specimen is affected by the presence of the induced eddy currents in the specimen.

When the eddy currents in the specimen are distorted by the presence of the flaws or material variations, the impedance in the coil is altered. This change is measured and displayed in a manner that indicates the type of flaw or material condition.

z Ultrasonic Inspection

Uses sound waves of short wavelength and high frequency to detect flaws or measure material thickness. Used on aircraft, the power stations generating plant, or welds in pressure vessels at an oil refinery or paper mill.

Usually pulsed beams of high frequency ultrasound are used via a hand-held transducer that is placed on the specimen. Any reflection of sound from that pulse is shown on a screen which gives the amplitude of the pulse and the time taken to return to the transducer. Defects anywhere through the specimen thickness reflect the sound, back to the transducer. Flaw size, distance and reflectivity can be interpreted.

Journal of Non destructive Testing & Evaluation

Because of it’s complexity considerable technician training and skill is required.

z Radiography

Uses X-rays, produced by high voltage x-ray machines, and gamma rays, produced from radioactive isotopes such as Iridium 192. The rays are placed close to the material being inspected, passing through them and then captured on film. This film is then processed and the image is obtained between black and white.

The choice of radiation to be used depends on the thickness of the material to be tested.

They have the advantage of portability, which makes them ideal for use in construction site working.

INTERNATIONAL SCENARIO These tools which were once more prevalent in the strategic sectors have attracted attention of the industries in private sector due to the enormous potential it has in saving losses – directly as well as indirectly. In the recent past, the tools have been used widely for Residual Life Assessment of various infrastructure assets such as Bridges (steel & cement structure), Rails and other steel products, Forgings, Concreted Highways, Airfields & Runways, Civil Structures, Aircraft parts, critical spares and many more. USA

The importance of the usage of these techniques is evident from the fact that the US Defense has a Defense Working Group on Non-Destructive Testing with the basic objective of providing an annual forum for engineers, scientists, technologists and managers from all departments of defense activities that are responsible for development or application of NDT methods or techniques in research, engineering, maintenance and quality assurance. In addition the National Science Foundation has set up a collaborative program aimed at enhancing NDT education and improving articulation between Community College Technician programs and University Degree programs. This is through a consortium of these Colleges and Centre for NDE (CNDE) at Iowa State University. The CNDE also has Iowa Demonstration Laboratory for NDE applications (IDL) which serves as a resource to small & medium sized engineering firms with limited resources. The focus is on capacity building and technology transfer. The NSFIndustry/ University Cooperative Research Program (IUCRC) is jointly sponsored by industry, NSF and Iowa State University. Founded in 1985 with 14 industry partners, the program now has 20 industry partners. The research is directed towards areas of industrial interest without diluting the academic requirements for the students degree program. Its emphasis is in the use of NDE for aviation, transportation, energy and manufacturing. The CNDE has also tied up with General Electric, Pratt & Whitney and Honeywell to form an Engine Titanium Vol. 9, Issue 2 September 2010

Review Paper

Consortium (ETC) to develop reliable, cost-effective methods for inspection of engine materials, components & hardware. The Centre for Aviation Systems Reliability (CASR) was established in 1990 with the support from the Federal Aviation Administration (FAA) to provide quantitative techniques, prototypes for assuring airworthiness and reliability of aviation systems. It also acts as a training centre for the FAA and manufacturers of aviation specific NDE equipment. Based on the expertise developed at CASR, recently in 1997, the Iowa State University along with other Universities formed the Airworthiness Assurance Centre of Excellence (AACE) with FAA support. Today the three Centres at Iowa State University are the focal point for inspection of aircraft and propulsion systems. The NASA – Advanced NDE for Future Aerospace Systems supports the future needs of NASA in 2 areas namely Foundations for Intelligent Sensing Materials for Ageless Aerospace Vehicles with long term goals and Application of unique CNDE capabilities to more Immediate NASA and Mission Assurance Problems with short term goals. The use of NDT techniques for Infrastructure Asset Management has been a recent phenomenon. The use of advanced NDE techniques replaced the Visual Inspection methodology for Bridge Inspection and to support this the Federal Highway Administration (FHWA) in 1996 initiated an NDE Validation Centre (NDEVC), which is the only Centre in the world dedicated to NDE technologies for Highway Inspection. In 1997 the Federal Highway Administration (FHWA) through the National Bridge Inspection Program (NBIP) concluded that 31% of the 583000 bridges on the Highways are either structurally deficient or functionally obsolete. The Centre was finally made functional in October, 1998 at the NDEVC lab at the Turner-Fairbank Highway Research Centre. The Centre now has 2 test bridges in Virginia and Pennsylvania for full-scale testing of NDE technologies under actual field conditions. The Department of Defense (DoD) has also instituted NDE related Small Business Innovative Research Awards (SBIR). These awards are in the form of projects with 3 distinct phases of Feasibility Testing (Proof of Concept) followed by Prototype Development and testing culminating in its Commercialization as the final phase. The topics of projects listed on the website are from1994 onwards and cover a variety of requirements. In addition to the above major programs there are research Centres in leading Universities that are undertaking projects in this area like the Jet Propulsion Lab at Caltech or the Mechanical Engineering Department at University of Texas. Germany

Germany, as a leading industrialized nation, has maintained a strong position in the area of NDT by providing lead in Vol. 9, Issue 2 September 2010

NDT instrument development. The steel industry, the automobile manufacturers, the Machines Manufacturing industry, the German Railways; Civil Infrastructure Management groups are the leading users of this technology in Germany. The plastic industry has been the latest user for testing blow moulds, pipes, films and as recent as 1996, the techniques have also been used for on-line flaw detection of gas plastic pipes. The Fraunhofer-Institute for Nondestructive Testing (IZFP) was founded in 1972 and is located in Saarbrücken, with a branch office in Dresden that was established in 1992. The IZFP, Saarbrucken, Germany is a leading Institute for research in the area of NDT. The Institute has close linkages with the Universität of the Saarland where the subject “Nondestructive Materials Testing” is a part of the methodological education of students studying material sciences. Research at IZFP focuses on studying the physical principles of NDT and material characterization and is oriented towards using these principles in control and monitoring of production processes either off-line or online. The Institute is also involved in using the prototypes in industrial applications to validate its usefulness in quality assurance and/or proof of technical safety. The expertise at the Institute, therefore, encompasses the physical fundamentals, sensor technology, test instrument design and manufacturing, processing technologies, techniques for data evaluation and documentation, and, in addition, the qualification and validation of new inspection and testing procedures including maintenance, personnel training, and inspection and testing services. The Institute has state-ofart facilities in almost every methodology of NDE and uses modern technologies like microelectronics, IT & Communication etc. quite extensively. Being an Institute of repute, a multitude of joint ventures provide a network of international cooperation to penetrate international markets and facilitates their industry partners. The Government through public funding funds the fundamental or basic research, while applied research and development and market implementation and commissioning are facilitated and guided by the industry. In addition, basic funding facilitates scientific processing of fundamental and strategic subjects, the development of job opportunities, and the organization of the necessary proximity to industry. Europe

Apart from IZFP in Germany, the British Institute of NDT in London is another institute of repute in the European countries. The Institute is almost 40 years old and has been pioneer in development of NDT technology in the Great Britain (GB). It is currently also providing support to the Secretariat of the European Federation for NDT (EFNDT) which was founded in May, 1998 with 27 national level NDT societies as its member. The countries include Austria, Belgium, Bulgaria, Belarus, Croatia, Czech Journal of Non destructive Testing & Evaluation

18 Republic, Denmark, Finland, France, Germany, Great Britain, Greece, Hungary, Ireland, Italy, Netherlands, Norway, Poland, Romania, Spain, Sweden, Switzerland, Ukraine, Russia, Slovenia, Slovakia and Yugoslavia. NDT societies from other countries like Brazil, India, Israel and Japan have also been made associated members. Incidentally, the Indian Society for NDT (ISNT) is an associated member of this federation. China

In China, the major use of NDT is for the safety of their railways infrastructure. The NDT Centre for China Railroad is established in Metal and Chemistry Research Institute under the China Academy of Railway Science. The Centre has three decades of research efforts behind it and is the leading Centre for research, technology development and training in China. More than 12000 persons are engaged specifically in NDT related activities for the rail system in China and about 8000 are engaged in the task of rail flaw detection with the manual detectors supported by techniques developed at this Centre. The Centre also trains 2000 technicians in this task on annually. The Centre has been also active in International collaborations and is one of the founding members of the World Federation of NDE. The other major research Centre is the Institute of Acoustics at the Nanjing University. The Institute, formally established as early as 1978, is engaged in research activities in areas that include Nonlinear Acoustics, interaction between sound and materials, Acoustic Signal Processing and PhotoAcoustic Sciences. The Institute has exchange visits in the field of NDE with Universities in US and Korea. In addition to the above Centres there are NDT Centre aimed at developing NDT techniques for specific usage. These include NDT Centre at the China Aerospace Corporation – Beijing; Centre at the China Academy of Launch Vehicle Technology – Beijing; Shantou Institute of Ultrasonic Instruments – Guangdong; Nuclear NDT Centre – Shanghai; and Centre for Quality Inspection & Testing of Hydro Steel Structure under Ministry of Water Resources. Russia

The Centre for Computer Non-destructive Evaluation (CCNDE) founded in 1992 and located in the Department of Electrical Engineering & Introscopy at the Moscow Power Engineering Institute is the leading R&D Centre in this area. Its main focus is on development of computer technologies and interfaces that could support innovative approaches for effective application of NDE techniques in defense establishments and industries. The Centre apart from its involvement in academics for teaching NDT, also provides opportunities for basic and applied research. While basic research focuses on developing techniques or identifying parameters that could be subjected to NDE, the applied component is specifically for areas such as Aircraft components; Welding parameters; Thermal & other Journal of Non destructive Testing & Evaluation

Review Paper

power generation infrastructure; Pipeline inspection etc. The EO Paton Electric Welding Institute and the National Technical University of Ukraine are major Centres dealing with teaching, research and development in the area of NDE in Ukraine. The Paton Electric Welding Institute is a powerful inter-industry complex comprising of research institute, technological design office, pilot plants, training & certification centre etc. The Department of NDT at the National Technical University of Ukraine was established in 1980 for preparation of trained NDT specialists for the industrial requirements. The establishment of the Ukrainian Society for NDT & Technical Diagnostics (USNDT&TD) in October, 1990 gave a further push to the efforts in this area. It provided a platform for the experts to disseminate their research finding. The Society is now a member of the European Committee on NDT and hosts the National Certification Committee of Ukraine that provides certification to NDT trained personnel keeping with the International standards. Korea

The Safety & Structural Integrity Research Centre (SAFE) was established in June, 1997 at the Sung Kyun Kwan University, Korea as an Engineering Research Centre by the Korean Science & Engineering Foundation (KOSEF). The research activities at this Centre aims at development of advanced NDE technologies for safety diagnosis systems for infrastructural facilities and also to establish test beds for demonstration. It has strong two-way linkages with the Korean industries in infrastructure namely Korean Electric Power Research Institute; Korea Institute for Nuclear Safety; Samsung Advanced Institute of Technology; Korea Inspection & Engineering Co. etc. in the form of sponsorship for projects. More than 30 companies and institutes in Korea support the Centre in the form of a consortium. Other Countries

Brazil, Japan, Canada and Argentina are also engaged in research and development of NDT techniques and leading Institutes in these countries are members of the World Federation of NDT or other Federations of NDT societies.

INDIAN SCENARIO In India too there has been sustained efforts by the scientists and technologists working in this area resulting in development of indigenous capability at par with the global expertise. India’s commitment to quality is depicted in its rich tradition, particularly evident in the metallic statues and pillars. NDE has been playing key roles in the strategic sectors in India too such as Atomic Energy, space, defence and power infrastructure, which have been denied access to international technology. The expertise has now broadened its horizon and today there is greater awareness among the Indian industries about NDE and its role in the total quality regime. A large number of NDE Vol. 9, Issue 2 September 2010

Review Paper

techniques have been developed by labs and industries like BARC, IGCAR, DRDO, VSSC, NML, BHEL, IOC, NTPC, HAL, NAL etc. which are working in strategic and core sectors for their in-house requirements. Academic Institutions like Indian Institute of Science (IISc), Indian Institute of Technology (IIT) â&#x20AC;&#x201C; Chennai & Mumbai, Regional Engineering College - Tiruchirapalli have played a complementary role in nurturing excellence in this area apart from ensuring continuous human resources development. Fortunately, this is an area where the country has developed expertise which is recognized at global level. Leading NDE research centre in India at the Indira Gandhi Centre for Atomic Research, Kalpakkam and Indian Institute of Technology â&#x20AC;&#x201C; Chennai have been the founder members of the World Federation of NDE (1998), along with leading NDE Centres from countries like United States, China, Russia, Korea, Ukraine, Brazil, Belarus, Argentina and South Africa. In addition, they have active research and exchange visits with other Centres that include Institute for Nondestructive Testing, IzfP, Saarbrucken, Germany; GEC Alsthom; and The British Institute of Non-destructive Testing, UK. The high level of specialization, the sophisticated expertise required, limited opportunities in the public and private domain and lack of quality consciousness among the Indian manufacturers had discouraged entrepreneurs or big players into this area. However, in spite of lack of opportunities few technopreneurs have ventured into this area and survived. Electronic & Engineering Co. (I) Pvt. Ltd., Mumbai, Modsonic Instruments, Ahmedabad, Technofour, Pune, and Dhvani Research and Development Solutions, Chennai, are few such successful ventures, which have also undertaken R&D activities in Ultrasonic Testing & Eddy Current Testing techniques. The professionals in NDE also have a forum namely the Indian Society for Non-Destructive Testing (ISNT), and S&T professional body constituted in 1972. The ISNT has since matured and today has 20 chapters across the country with 4500 members. It conducts an Annual Technical Seminar to disseminate the research activities amongst its members. The Indian participation and expertise at the Global level has not only been lauded but rewarded by accepting the Indian invitation to host the 14th World Congress on NDT way back in December, 1996. The event was successfully organized at New Delhi during 813 December, 1996 with 1500 delegates and about 100 manufacturers exhibiting their products. The ISNT through its National Certification Board (NCB) is also training and certifying the manpower in accordance with the ASNT norms. Recognizing the importance of NDE, particularly for Residual Life assessment Studies for Infrastructure Assets like bridges, highways, civil structures, power plants etc. the Department of Science & Technology (DST) has evolved and supported setting up of a NDE based National Vol. 9, Issue 2 September 2010

Facility for Infrastructure Asset Management (NF-IAM) at National Metallurgical Laboratory (NML), Jamshedpur {a laboratory under the Council of Scientific & Industrial Research (CSIR)} with a networked Centre at Indian Institute of Technology, Chennai. The project was initiated in April, 2003 at a total cost of Rs 10 crs with NML/ CSIR and DST sharing the funding. In the first phase, the Centre uses the existing knowledge to carryout studies on the Railway Bridges in coordination with the Research, Development and Standardization Organization (RDSO) of the Indian Railways. It has also tied up with the Structural Engineering Research Centre (SERC) - Chennai for developing and standardizing techniques for structural integrity testing of concrete structures. The Centre will also act as a consultancy and testing facility for the Indian industries as well as for NDE based Defense requirements in Air Force, Navy and Army.

RECENT TECHNOLOGICAL TRENDS AND ITS POSSIBLE IMPACT ON NDE With the increasing competition leading to more thrust on quality of product and services, the researchers in this area have provided techniques to be implemented for NDE and NDT during the various stages of production itself. This has facilitated in further costs savings and has now gained its recognition as decision facilitating tool. In addition some of the technological changes of the recent years and also of the past have had its impact on the field of NDE. NDE is now a matured field and efforts over the last 2 decades have been towards accurate characterization of defects/ flaws so as to predict the life of any product/ component or any large infrastructural asset. Moreover, as an interdisciplinary field NDE benefited from capabilities that were developed in many other areas of Science & Technology. The globalization of the regional boundaries and post WTO affect on the growing recognition of the value of standards on product quality, personnel certification, Corporate Quality and so on, paved way for development of lowcost on-line quality control techniques. In addition, infrastructure related accidents have attracted attention of the policy makers in using NDT techniques for Residual Life Assessment Studies of the aging high investment products like aircrafts; boilers; critical parts of machines; or heavy infrastructure like roads, highways, airways, bridges, structures, power plants, etc. While the introduction of methods like Liquid Penetrants or Magnetic Particles marked transition to sophistication in NDE, the use of microprocessor-based computers improved the data acquisition and display capabilities to record and display information about discontinuities or faults. The wave based tools like Eddy Current and Radiography paved way to sound wave based imaging tools like Acoustic Emission, Magnetic Resonance Imaging (MRI) and Shearography. In the absence of analytical tools, the analysis was based on the experience of the Journal of Non destructive Testing & Evaluation

20 personnel handling the tools. Further developments in modeling of the faults/ discontinuity using mathematical and simulation techniques are resulting in less reliance on human interpretation. The rapid advances in Computers and Communications; electronics; materials sciences and analytical modeling made major impact on many of the NDE technologies. The upsurge of Internet as a communication tool has made it a channel for sharing information and thus paved ways for creating depositories of information to share. The Internet also acted as catalysts to bring together experts who developed tools for simulating the faults. Latest simulation software can perform ray tracing of waves in 3-D and these days CAD software are being built to introduce faults and simulate its impact on the life of product/ material. Progress in microelectronics has led to miniaturization of NDE hardware that has led to production of portable and subsequently pocket size instruments for testing material on-site. Data Acquisition Cards that can be plugged on to a laptop computer were available few years back. In the nanotechnology era, the miniaturization will be at its peak and it is expected to change the size of the NDT tools. Combined with the advent of wireless communications one can only think of a fiction like application of NDT. Few years back one of the automobile tire companies had installed sensors in the tires of heavy vehicles that would keep a track of their pressure and condition but now one can think of small compressor being activated through a sensor that picks up signals to fill air if required. Or think of a small sensor that can be attached to a robot to perform NDE on the aircraft wings and send the data to an expert system located across the world with the aircraft manufacturer for monitoring the life of the aircraft. The NDT techniques also have its application in the security and safety concerns of today. The electro-magnetic techniques have found its application in detection of antipersonnel mines or unexploded ordnances. This has led to development of hand-held devices to detect such mines particularly from the border areas. An advanced application of this principle combined with the imaging technology could find application for development of attachments with scanning power that could be mounted on a platform for detecting mined area and could be of use by the paramilitary forces in the North East sector or even by the Police forces in areas infected by local insurgents. It could also be used at the airports for screening of packages and goods and for non-contact screening of passengers and visitors. The recent media reports and interviews with the Air Force officials have pointed towards engineering failures of aircrafts (engines and/or parts) being the cause for almost 30% of the total accidents in the aircrafts of the Indian Air Force. The Indian Railways, which is also under media Journal of Non destructive Testing & Evaluation

Review Paper

attention for accidents, have no scientific studies to assess the engineering health of the century old railway bridges (> 100 in numbers) or the discontinuity in railway lines due to neglect or sabotage. Both these sectors are immediate customers of NDT and its applications. In addition, over the past 2-3 years, the development of road (highways and flyovers) has been accorded top priority by the planners in India. The work on some sectors of the golden corridor is complete and toll highways have started functioning in the country in the recent past. In addition, there are overhead bridges that are almost 20 years old in the metros. Some of these assets have been candidates of official apathy towards their maintenance. The use of NDT technologies would definitely provide scientific means of assessing the health of these civil infrastructural assets of our country and facilitate in designing strategies for their maintenance. The private industry players like the TISCO, Larsen & Toubro, SAIL, BHEL, HAL, Petroleum Companies, Construction Companies, EIL, MECON, Alfa Laval, etc. which are involved in implementing turnkey projects for process plants or supply of heavy equipments should also be involved in development of applications based on NDT techniques.

CONCLUSION NDT is an area in which the countryâ&#x20AC;&#x2122;s scientific and technical expertise is at par with the world expertise and the peers have duly accepted this. Secondly, the recent orientation of the Indian industry towards quality consciousness has created opportunities for the NDT expertise to come out of the confinement of strategic areas and develop applications for the use by the Industry. The initiation of a National Facility for NDT based Infrastructure Asset Management at Jamshedpur is a step that needs to be encouraged both by the researchers and the users. The need is also to come up with standards for residual life assessment studies of the assets like bridges, civil structures etc. on an urgent basis. The training of skilled manpower to match the requirement of railways and other users is task that has to be planned in parallel. In addition, the subject being inter-disciplinary, attracting researchers from the disciplines of physics, materials science, metallurgy, information technology & communications, mechanical engineering, electrical engineering, civil engineering, applied mechanics, computer & mathematical modeling etc. to work in this arena as a team will be a challenge to our research and academic institutions. It would require some special planning efforts on their part to devise novel courses along with attractive fellowships so as to attract the talent. The need would then be to set up a network of Centres/ facilities that would provide the required laboratory support for them to show their creative skill. The applications of NDT principles are playing a leading role in the strategic areas of security but it still has the potential for further exploitation, for which initiatives have to be taken in the form of a dialogue between the security agencies and NDT experts. Vol. 9, Issue 2 September 2010

Technical Paper

High Sensitivity TOFD UT to Reveal Reheat Cracks in Cr-Mo-V Steel Weld S.P. Ghiya1, Dr. D.V. Bhatt2, Dr. R.V. Rao3 and P. Raghavendra4 1

QC & NDE, Larsen & Toubro Limited, Hazira, India Mechanical Engineering Department, SVNIT, Surat. 3 Mechanical Engineering Department, SVNIT, Surat 4 Larsen & Toubro Limited, Hazira, India Email: spg@hzw.ltindia.com; sandipghiya@hotmail.com; dvb@med.svnit.ac.in; rvr@med.svnit.ac.in; rpe@hzw.ltindia.com 2

ABSTRACT It is important to assess re-heat cracks found within weld while using Submerged Arc Welding (SAW) process in Cr-Mo-V low alloy steel materials for safe functioning of the heavy wall reactors. Since the indications are very minor in size and transverse in orientation when compared to that of centre line of the weld, the Code stipulated NDT methods such as Pulse-echo Ultrasonic testing (UT) may fail to reveal the same at the sensitivity levels prescribed. Also in order to eliminate the human skill related limitations due to fatigue, Computarised Ultrasonic methods such as Time Of Flight Diffraction (TOFD ) method was chosen to compliment the conventional pulse-echo A scan UT. TOFD is sensitive to detect all minute indications and A scan UT is utilized to distinguish and characterize re-heat cracks and other indications, if any. This paper describes the Mockup block creation, procedure development, validation and implementation on the welds of the project.

INTRODUCTION

REACTOR STEEL: Conventional Cr-Mo and Vanadium MODIFIED CR-MO:

Primarily three modified alloys have certain vanadium addition to enhance tensile strength at elevated temperature and creep rupture strength and to improve resistance to in-service degradation phenomena, such as temper embrittlement, high temperature hydrogen attack (HTHA) and hydrogen embrittlement. [2]

2.25Cr-1Mo-0.25V,

3Cr-1Mo-0.25V-Ti-B &

3Cr-1Mo-0.25-Nb-Ca

Design properties of the conventional Cr-Mo steel and vanadium modified Cr-Mo steels are summarized and properties of the modified steels at higher temperature are presented in Table 1. Increased mechanical properties allow for higher design stresses, leading to a decreased wall thickness and reduced weight of reactors.

Table 1 : Comparison of reactor steel conventional Cr - Mo and V modified Cr – Mo [2] Steel grade

Conventional 2.25Cr-1Mo

2.25Cr-1Mo -0.25V

Conventional 3Cr -1Mo

3Cr-1Mo -0.25V-Ti-B

3Cr-1Mo -0.25V-Nb-Ca

Max. Allowed temp. ASME VIII-2

482ºC

454ºC

454Cº

454ºC

Max. Allowed temp. API 941

454ºC

510ºC

Min. Tensile strength

517 MPa

586 MPa

517 MPa

586 MPa

Min. Yield strength

310 MPa

414 MPa

310 MPa

414 MPa

Design stress intensity value ASME VIII-2

at 454ºC 150 MPa at 482ºC 117MPa

at 454ºC 169 MPa at 482ºC 163 MPa

at 454ºC 131 MPa …

at 454ºC 164 MPa …

Wall thickness [1]

at 454ºC 338 mm at 482ºC 442 mm

at 454ºC 298 mm at 482ºC 310mm

at 454ºC 392 mm …

at 454ºC 307 mm …

454ºCdesign: reactor weight

1038 metric tons

916 metric tons

1203 metric tons

944 metric tons

482ºC design : reactor weight typical

1359 metric tons

953 metric tons

Vol. 9, Issue 2 September 2010

Journal of Non destructive Testing & Evaluation

22 Of late, it was noticed that certain advanced steel materials produce re-heat cracks within weld produced by Submerged Arc Welding (SAW) process after stress relieving or post weld heat treatment (PWHT) process. These cracks are within the weld, very fine and transverse in nature. Prevailing codes and standards ( such as ASME Sec.V) have limitations to detect these re-heat cracks due to their Sensitivity levels prescribed. Recent advanced steel (2.25Cr-1Mo-0.25V) materials have improved properties like high tensile property at elevated temperature, toughness at 54J at -29ยบC, increased hydrogen attack resistance, and enhanced creep resistance property, lower susceptibility to hydrogen disbonding. These properties help while designing critical reactors working at high temperature under corrosive environment. Cracks in intermediate stress relieved weld of heat resistant materials remains great practical concern in the Power generation, Refinery and Petrochemical industry. Hence it is important that the same are revelaed or detected at right time during fabrication and removed. The process of detection involves the selection of NDT method, identifying the most suitable scan direction of the same depending on the orientation of the indications of interest, design and development of a mock-up simulating the same, fingerprinting the mock up for refence, validation of the scan plans based on trials on the mockup and comparison of results with that of finger printing.

Technical Paper

Fig. 1 : Location of reheat crack in reactor

Fig. 2 : Intergranular morphology of reheat cracks in weld

2. RE-HEAT CRACKING Reheat cracking is kind of intergranular cracking in the heat affected zone (HAZ) or weld metal occurs during the stress relief heat treatment or during service at high temperature. This phenomenon happens largely with alloy steel with Cr- Mo-V alloy. An explanation, widely accepted, to re-heat cracking is significant reduction in grain boundary ductility during stress relief cycle or service due to either segregation of trace impurities or precipitation of carbides. The reduction in ductility, perhaps, to an extent that it is insufficient to accommodate the plastic deformation associated with stress relaxation. Stress relief crack may occur either on HAZ or within weld metal which will be detected either visually or by performing additional NDE testing like magnetic particle testing or ultrasonic testing methods. VISUAL APPEARANCE:

As shown in Fig. 1, re-heat cracking is found primarily in the coarse grained regions of the heat affected zone, beneath the weld, or cladding, and in the coarse grained regions with in the weld metal. The cracks can often be seen visually, usually associated with areas of stress concentration such as weld toe. A macro-crack will appear as crack, often with branching, following the coarse grain region. Cracking is intergranular Journal of Non destructive Testing & Evaluation

along prior austenite grain boundaries as shown in Fig. 2. Macro cracks in the weld metal can be oriented either longitudinal or transverse direction of welding. Crack in the HAZ is always parallel to the direction of welding. Stress relief cracking, sometimes called re-heat cracking, refers to the formation of intergranular cracks in the coarse grained regions of the heat affected zone (HAZ) or occasionally the weld metal, of a welded assembly when it is reheated to relieve residual stresses or when it is put in service at an elevated temperature. [5] Generation of stress relief cracking

Cr- Mo-V material is highly susceptible to crack in the weld metal especially after stress relieving process. The principal cause is that when heat treating susceptible steels, the grain interior becomes strengthened by carbide precipitation, forcing the relaxation of residual stresses by creep deformation at the grain boundaries. The presence of impurities which segregate to grain boundaries and promote temper embrittlement, e.g. antimony, arsenic, tin, sulphur and phosphorous will increase the susceptibility to re-heat cracking. At lower temperature during stress relief heat treatment, interstitial elements carbon and nitrogen can produce strain aging embrittlement. At higher temperature, thermally induced embrittlement such as secondary hardening and temper embrittlement, besides strain induced embrittlement Vol. 9, Issue 2 September 2010

Technical Paper

Fig. 4 : TOFD Set up with probes (Source: API 934-A Addendum A)

Fig. 3 : Principle of TOFD method (Source: TOFD of Welds by Mr.John Pitcher)

or creep embrittlement can occur. These processes are enhanced by segregation of interstitial and substitutional impurity elements and by iron and alloy element carbide transformation. [6] Vanadium carbide reduces the stress relaxation and in turn developing crack on grain boundaries. Vanadium and chromium percentage play vital role forming carbides. Increasing chromium content increases the share of chromium carbides and decreases the share of vanadium carbides. Carbides re-precipitation intragranularly during stress reliving and strengthen the grain matrix. This results

in difference in strength between grain boundaries and the grain interiors. Due to weaker grain boundaries, cracking occurs intergranularly. Since Cr-Mo-V alloy steel contain reasonable amount of carbide forming elements like Cr, Mo and V. It is considered that all three materials may be susceptible to reheat cracking. [7] Characteristics of Reheat cracks:

The reheat cracking which recently caused the major problems at multiple (but not all) rector fabrication shops can be characterized as follows: ยง

Sub surface in SAW weld deposit,

ยง

Transverse and perpendicular or at a slight angle to surface,

ยง

May have slight branching,

Fig. 5 : High sensitivity TOFD calibration block (Source: API 934-A Addendum A) Vol. 9, Issue 2 September 2010

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Occurring in circumferential, longitudinal, head meridian and nozzle welds,

to evaluate the pattern/images of the diffracted waves while performing TOFD UT.

Typically very small crack size (most are 4-10 mm in length and 2-5 mm in height),

Often many cracks in an affected weld (can be hundreds of cracks),

Occurring at various depths and various locations across the width of the weld,

Often occurring as clusters with many parallel cracks lined up in the same plane (Fig.5),

Only developing after first heat treatment step at >620ºC such as intermediate stress relief (ISR), reheating for rerolling, or post weld heat treatment (PWHT), and

TOFD is a flaw sizing and locating method based on the arrival time of flaw tip diffracted waves and the position of ultrasonic transducers. The relatively high accuracy, combined with cheaper and more portable hardware, has resulted in TOFD’s adoption within a wide range of industrial sectors, including offshore, petrochemical, and power generation. The major limitation of TOFD, which hinders its wider and further application, is that it is invalid when the section under detection is thin or the flaw top tip is located in a blind area [8]

Not occurring after welding or dehydrogenation heat treatment (DHT)

3. OBJECTIVE AND PLAN The objective was to establish appropriate technique through advanced NDE methods to identify and locate reheat cracking by simulating similar cracks on a mock up piece. To achieve the same following steps were taken. 1) Development of validation block, made of same CrMo-V steel materials 2) Procurement of required equipment and accessories 3) Procedure development and validation 4) Establishment of procedure 5) Training to the NDE personnel 6) Qualification. 7) Application on the equipment/welded joint in production

4. TOFD PRINCIPLE AND SET UP Ultrasonic method has got various techniques under its umbrella such as A scan UT; B & C scan UT, TOFD (Time Of Flight Diffraction) UT, PA (Phased Array) UT. None of the above methods are complete in all aspects as they have got inherent merits and demerits in techniques. In order to overcome their limitations, two techniques coupled with two different methods are proposed i.e. TOFD UT methods and A scan UT. TOFD UT technique was developed at Harwell laboratory in late 1977 yet industrial use of the same started few years back. TOFD UT technique is based on diffraction principle of ultrasound in the material. When ultrasound strikes on the defects like crack, tips of the crack vibrates and each point of the defect generates new elementary spherical waves i.e. diffracted waves. These waves are very low energy signals which are travelling in all directions and independent of incidence wave angle. (Refer Fig.3). There is software designed to filter all other sound waves restricting to only low energy diffracted waves, enabling Journal of Non destructive Testing & Evaluation

To understand basic TOFD setup, (refer Fig.4) shown below. Two probes (i.e. transmitter/ receiver which generate ultrasound into the test material by piezoelectric principle) are placed symmetrically to the weld centre line. Transmitting probe transmits ultrasonic wave and tip diffracted waves are received by the special receiver. Time travelled by the upper and lower tips is calculated and accurate defect height sizing can be done. Further the analog signals are converted into digital images like B scan-cross sectional view. (Refer Fig.4). To establish high sensitivity TOFD method and to validate the efficiency of the method, a test block, as recommended by API 934, developed with very fine flaws with known dimensions (0.4mm x 4mm x 4mm) induced artificially into the test block at various depths. (Refer Fig.5) In this case, block material was used for the test block as of the equipment material enabling to evaluate flaws much accurately. This process involves wire cutting to create artificial flaws with in base material of test block. Cutting is done at various depths as per the sketch shown and subsequently these locations are welded leaving flaws within the block. Each step involves critical operation of fit up, controlled welding keeping in view the critical defects. It requires high skills to produce such artificial defects. Finger print of the block was ensured certifying the dimensions of the defects for validation of block. Close monitoring of fabrication helped to produce the right flaws.

STEPS FOLLOWED

Sample preparation and TOFD parameter optimization

Detail procedure was developed including scan plan for TOFD (Refer Fig.4) in order to detect these small cracks by using various probes with different crystal diameter and frequencies at various locations to ensure best detection of these small cracks and ensuring coverage of total weld volume in block. Since TOFD technique does not characterize the flaws detected, “A” scan UT was used to characterize the defect (slag, porosity, inclusions, crack etc….) to distinguish re-heat cracking and other indications. For the trail, 300mm thick Cr-Mo-V block was procured from reputed mill from European market with indications Vol. 9, Issue 2 September 2010

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of dimentions 4mm X 4mmX 0.4mm induced at various depths as shown in Fig.5. Fingerprinting of the manufactured block was a challenge which is very essential for validation of test results. This block was manufactured under observation of experienced engineers of our team ensuring the specification requirements and imported.

Fig. 8 : 70Deg-100PCS-5Mhz-6Dia (Top Zone) (Software: TOFD aids, Veritec Sonomatic,UK)

Above sketch describes the top zone covering weld using 70 deg probes with 5 MHz & 6 mm dia. Many experiments performed before arriving right combination of probe, frequency, db level, orientation, scanning. Fig. 6 : 45Deg-480PCS-2Mhz-12Dia (Bottom Zone) (Software: TOFD aids, Veritec Sonomatic,UK)

The above sketch describes the volume covered by ultra sound while incidence using 45 deg Probe Centre Spacing (PCS), 2Mhtz frequency probes with 6.0mm in diameter. Various probes, size, diameter, frequencies, scanning of probe, scanning speed are tried.

Advanced software enables to create sharp/good image of the flaws covering entire volume using right probes. Very important part is to decide the right PCS and selection of the probes of appropriate angle and frequency depending upon the geometry, material composition and thickness of weld. The parameters optimized are used on the welds of the project by TOFD to detect reheat cracking, if any. The weld indications revealed by TOFD need to be characterized as based on images of TOFD the same is not feasible. Hence, the need of conventional pulse-echo A scan UT

Fig. 7 : 60Deg-150PCS-2Mhz-6Dia (Middle Zone) (Software: TOFD aids, Veritec Sonomatic,UK)

Above sketch describes the mid zone covering weld using 60 deg probe with 2 MHz & 6 mm dia. Many experiments performed before arriving right combination of probe, frequency, db level, orientation and scanning. Vol. 9, Issue 2 September 2010

Fig. 9 : One of the TOFD Images with flaws (Software: TOFD aids, Veritec Sonomatic,UK) Journal of Non destructive Testing & Evaluation

Technical Paper

locally and specifically performed at the locations where TOFD revealed indications. The same was carried out at higher sensitivity using high frequency probes from atleast two directions 90 deg. apart. The same is useful for distinguishing indications that are planar where the gain difference shall be more than 9dB. For those indications scrutinized as above where the dB difference is found to be less than 9dB, they are characterized as volumetric. In some cases where the indication characterization became ambiguous by above two methods, we have done more scans of TOFD from various directions with focus to the area of interest or /and by performing radiography with X rays ( LINAC) for sensitivity better than 1%.

6. MERITS OF TOFD TECHNIQUE z

By achieving Sensitivity more than Code requirements, we could win the confidence of Customer.

Data for each joint were captured in the form of digital images which can be stored for ever. Also for comparison of data during before and after heat treatment which could give us information about any discontinuities induced due to process in between the above two operations.

Faster and reliable inspection is achieved as TOFD is having higher Probability of Detection (POD) compared to other NDE methods. All Cr-Mo-V weld material NDE examination is being replaced with TOFD from RT.

7. CONCLUSION z

TOFD has proven to be a great tool for sizing in addition to detection of flaws.

The scan direction of TOFD probes with respect to weld centre line matters to reveal the indications anticipated with relevant dimensions.

TOFD is relatively unaffected by the size, shape, location or position of flaws.

For the characterization of weld defects “A” scan UT is more appropriate.

Irrespective of defect orientation and size, TOFD is sensitive enough to catch defect.

Journal of Non destructive Testing & Evaluation

Innovative ideas like high sensitivity transverse scanning which was beyond code requirement helped to achieve goal and satisfaction in the field of advanced NDE. Overall it is proved that TOFD has high probability of detection (POD) compared to RT. Small flaws of 4mm*4mm*0.4mm is almost not possible to get through normal RT and UT.

REFERENCES 1. API-934 A & B: Material and Fabrications of 2.25Cr-1Mo, 2.25Cr-1Mo-0.25V, 3Cr-1Mo, and 3Cr-1Mo-0.25V steel heavy wall pressure vessels for High-Temperature, High-pressure Hydrogen Service (2009) 2. Joanna Hucinska, Advanced vanadium modified steels for high pressure hydrogen reactors. Advanced in Material Science, Vol. 4, No. 2 (4), December 2003 3. J.C. Lippold, Hangian Zhang, Shu Shi., Reheat cracking and elevated temperature embrittlement of austenitic alloys-Literature Review. Summary Report, February 2004 4. S.A. Bashukulvir Singh and K.M. Chowdary, Evaluation of creep properties and fracture behavior of 1Cr-1Mo- ¼ V cast steel welded with 2 ¼ Cr-1Mo electrodes., Indian Welding Journal April, 1986 5. C.J. Mc.Mahon, Jr. R.J.Dobbs and D.H.Gentner, Stress relief Cracking In Mn Mo Ni and Mn Mo Ni Cr pressure vessel steels Materials Science and Engineering, Vol. 37, 1979 6. A. Dhooge , A.Vinckier , Reheat Cracking –A Review of Recent Studies., Int J. Pres. Ves & Piping, Vol. 27, 1987 7. Koreaki TAMAKI, Jippei SUZUKI and Min-Long Li,. Influence of Vanadium Carbide on Reheat Cracking of Cr-Mo steels – Study of Reheat Cracking of Cr-Mo Steels., Transaction of Japan Welding Society, Vol. 24 No.2. October 1993. 8. Tianlu Chen, Peiwen Que, Oi Zhang, and Qingkun Liu Ultrasonic Nondestructive Testing Accurate Sizing and Locating Technique Based on Time-Of-Flight-Diffraction Method, Russian Journal of Nondestructive Testing, Vol. 41 No. 9, 2005 9. American Petroleum Institute, API-941 Steels for Hydrogen Service at Elevated Temperatures and Pressures in Petroleum Refineries (2004) 10. The TOFD software of Veritech Sonomatic Micro plus: TOFD AIDS

Vol. 9, Issue 2 September 2010

Technical Paper

High speed Non-destructive rail testing with advanced Ultrasound and Eddy-current testing techniques Thomas HECKEL1, Hans-Martin THOMAS1, Marc KREUTZBRUCK1 and Sven RÜHE2 1

BAM VIII.4, Federal Institute for Materials Research and –testing, Unter den Eichen 87, 12200 Berlin, Germany. 2 PLR Prüftechnik Linke & Rühe, Altenhäuser Straße 6, 39126 Magdeburg, Germany. E-mail: thomas.heckel@bam.de, hans-martin.thomas@bam.de, marc.kreutzbruck@bam.de; ruehe@plr-magdeburg.de

ABSTRACT Today the rails face increased exposure to heavy loads, higher speeds and a very dense overall traffic. A continued development of testing methods for the rail inspection trains became necessary to match the modern needs for a fast detection and detailed classification of defects. To guarantee the safe operation of rail traffic non-destructive inspection techniques with combined ultrasound and eddy current testing methods are used to detect damages on rails. One of the main actual challenges of automated rail testing is the high inspection speed which is very close to the physical limits. To overcome these limits digital signal processing algorithms have to be used which maintain resolution and detection quality independent of operation speed. This paper presents a recently developed state of the art rail inspection system which uses advanced ultrasonic and eddy current testing techniques. Testing results are shown in a newly developed so called Glassy-Rail-Diagram which is capable to present data with a fixed resolution independent of inspection speed. Keywords: Non-destructive testing (NDT), rail inspection, ultrasound, eddy current, signal processing

INTRODUCTION

To guarantee the safe operation of rail traffic nondestructive inspection techniques are used to detect damages on rails. Nowadays rails are exposed to a constant increasing very dense overall traffic with heavy loads and high speed trains. Damages on rails increasingly originate from the surface as a result of rolling contact fatigue (RCF). Such damages became exceptionally dangerous for the operation of rail traffic. During the last years a continued development of testing methods for the rail inspection trains was carried out. This includes for example the use of additional ultrasonic probes for the detection of SQUATs and the application of eddy current methods for the detection of damages caused by rolling contact fatigue. By combination of the ultrasonic inspection results with these from the simultaneously performed eddy current inspection synergetic effects arise. These can be excellently used to overcome problematic defect classification based on the results of only one testing method. The large amount of incoming measurement data poses a challenge for the evaluation and the reviewing of the collected data. To keep this evaluation of data simple to the operator automated classification algorithms have to be developed and adapted. Testing results are shown in a newly developed high resolution Glassy-Rail-Diagram, which allows a very fast evaluation of data and sizing of defects. The detected findings are registered and fixed in position by GPS markers. The system presented in this paper was implemented into the rail inspection train SPZ1 by PLR, Magdeburg, Germany, Vol. 9, Issue 2 September 2010

in 2008. Meanwhile the train is operated by Deutsche Bahn AG.

2. SYSTEM SETUP 2.1 Sensor Frontend

For the rail testing we use ten ultrasonic probes and four eddy current probes per rail. The probe configuration is displayed in Fig. 1. There are two 2 MHz 70° angle beam probes, two 4 MHz 70° angle beam probes and one 4 MHz 0° normal probe used for the rail head, two 2 MHz 55° and two 2 MHz 35° angle beam probes used for the rail web and rail foot as well. One 4 MHz 0° normal probe is also used for the coupling check. The ultrasonic angle beam probes are operated in pulse-echo mode except the 4 MHz 0° normal probe used for the rail head which works in transmitter-receiver mode. All probes are GE type in standard housing with fix mounted wiring. Four HC-10 type eddy current sensors are situated in the region where rolling contact occurs. They are aligned according to the shape of the rail head. The sensors access a surface range of approximately 25 mm in the gauge corner of the rail. The probes are mounted on five custom designed probe holders optimized for the individual probe arrangement. There have been four main challenges for the performance optimization of the probe holders during development: design of a robust and tough holding system with quick probe change option, enhance the probe life, keep the overall system length as short as possible and minimize the couplant consumption for ultrasonic inspection. Journal of Non destructive Testing & Evaluation

Technical Paper

Fig. 1 : Probe arrangement for rail inspection

For ultrasonic inspection four slide-type holders strengthened with carbide shoes are used which house two or three ultrasonic probes. Each probe is fixed in position by springs with calibrated tension. The probes are adjusted with a special calibration device to a gap of 0.2 mm between the rail head and the probe shoe to keep abrasion minimal and coupling optimal. The holders are equipped with direction dependent and speed controlled couplant supply. For each probe a small water reservoir and a bleeder is provided. For easy access when charging the holders with probes they feature a lockable tilting mechanism. The four eddy current sensors are positioned over each rail with a trolley-type holder. The four probes are mounted on a modular mechanism, which permits individual positioning on the measurement tracks. The sensors are mounted on a guidance device carried by a measuring trolley. With a special calibration device the sensors are fixed at a distance of 1 mm from the surface of a new profile UIC 60 rail. For worn rails the distance of the sensors can be varied according to the surface. The resulting change of sensor sensitivity can be compensated by the software by the analysis of the measuring data in a range of -1 mm to +2 mm. Journal of Non destructive Testing & Evaluation

2.2 System Hardware

Due to the high inspection speed the large amount of incoming measurement data poses the main challenges for the evaluation and the reviewing of the collected data. Additionally all data have to be processed in real time for online monitoring. Therefore a powerful signal processing system is necessary. In this system all measurement data are delivered digital via network connection. The synchronisation of all devices is controlled by more than 80 hardware signals. The overall system consists of four modular multichannel ultrasound devices, two multichannel eddy current devices, eight dualcore personal computers for real time signal processing and system control, two 32 channel real time controllers, one GPS positioning system and two FPGA based custom designed signal processing hardware boards. The measurement system rack is displayed in Fig. 2. For ultrasound data acquisition the recently developed modular inspection system MODUS03 is applied. For each rail two MODUS03 equipped with five high resolution ultrasound boards each connect the ten probes. 14-Bit AScan data, four fixed hardware gates and four interactive controlled gates are recorded continuously for each channel Vol. 9, Issue 2 September 2010

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Fig. 3 : Number of successful detections as function of detection speed

measurements. The detectability of defects decreases with the increase of speed. This is shown in Fig. 3, depicting the number of detections of typical rail defects as a function of train speed with the ultrasound device running at a repetition rate of 5 kHz. These investigations were carried out at BAM for each probe on seven specimen with more than 80 reference flaws. To overcome these limits caused by the repetition rate it is necessary to use digital signal processing algorithms which maintain resolution and detection quality independent of operation speed. Therefore real time algorithms and the Glassy-Rail-Diagram have been developed and tested at BAM. The maximum testing speed is at least limited by the surface quality of the rail. On the other hand it seems to be no good idea to operate inspection trains up to more than 90 km/h due to reduced mechanical wear span of probe holders and probe maintenance costs. Fig. 2 : Rail inspection hardware system

at a repetition frequency of 4650 Hz independent of operation speed. Measurement data are merged with the GPS information, time stamps, kilometre markers and additional event markers in real time. For eddy current data acquisition two 4 channel PL300 series eddy current measuring devices are applied. The lateral resolution for eddy current data is 1 mm independent of operation speed. Measurement data are also merged with GPS information, time stamps, kilometre markers and additional event markers in real time. 2.3 Ultrasound at high speed

Speeds of more than 60 km/h are very close to the physical limits for ultrasonic testing methods. The maximum pulse repetition rate is limited by the sound velocity in the rail. This mainly affects the lateral resolution of ultrasonic Vol. 9, Issue 2 September 2010

3. THE GLASSY-RAIL-DIAGRAM To keep evaluation of data simple to the operator a user friedly interface with a well-arranged visualisation is necessary. Therefore the Glassy-Rail-Diagramm was developed at BAM. Like conventional B-Scans the GlassyRail-Diagramm gives a side view from the rail. It contains the position of probe, angle of probe and sound path corrected overlayed scan data of all ultrasonic probes channels. The pixelsize of 3 mm by 3 mm determins the diagrams resolution. The colour represents the highest achieved amplitude in the pixel. An example is shown in Fig. 4. All data processing is done in real time. Scan length can reach up to 300 km per day. For fast access to the recorded data the scan is seperated in sections of 1000 m. For normal operation a viewing range of 1000 m gives a good overview of the collected data shown in Figure 5a. A viewing range of 10 m shown in Figure 5b is normally used for inspection by the operator. Here we Journal of Non destructive Testing & Evaluation

Fig. 4 : Online construction of the Glassy-Rail-Diagram

Technical Paper

Fig. 6 : Sizing of indications

drilling is shown in Fig. 7. On the left the colour code for the probes is displayed. Figure 7 shows the user interface for the operator. The main screen contains the two diagrams for the left and the right rail. The right side of the screen presents for each rail the rail height and the amplitude of the couplant control indication. The cursor position is shown in two different ways: First as a relative value in millimetres of scan path and second as an absolute position in GPS format.

Fig. 5 : (a to c) Ultrasonic Data Display

can see some drill holes in a rail from a switch. Figure 5c shows a subsection of 64 by 64 pixels which is the standard viewing range for analyse mode. Because of the fixed reconstructed data grid sizing of indications and measuring distances becomes very easy. Measurements in length, height, width and depth can be carried out with an overall accuracy of at least 3 mm. An example is shown in Fig. 6. The backwall echo from the rail foot can be used as an excellent consecutive coupling control. The information which probes soundfield has hit the pixel respectively the reflector is recorded additional and seperately. Therefore the hardware and interactive software gate functions are used. These data give detailed information about the position, orientation and the reflectivity of a flaw. For example if the indication is more laminar respectively a crack type reflector or volumetric respectively a drilling type reflector. For a combined display of both the amplitude and the gate information the amplitude is converted from colour to grey-scale and the gates for each probe are displayed in a different colour. An example with an indication from a Journal of Non destructive Testing & Evaluation

In the upper right corner positioning measurements and markers are displayed. The middle of the screen shows a navigation bar, which allows scrolling the scan from beginning to end in different steps. The upper middle displays information about scan data, train speed and marker height at the actual cursor position. In the upper left corner information about the track and testing cycle is provided. When eddy current data are available for a certain scan these data will be shown as coloured bars in the upper area of each rail diagram.

DATA PROCESSING

4.1 Online sensitivity control

The system can be calibrated by the use of a test block. When testing the rail the overall sensitivity of the testing system depends on the quality of the rails surface quality. To compare the measured indications with these from the test block drill holes and welds can be used. An online software detection for drill holes and thermite welds is provided in the measurment software that allows the operator to present live pictures from these types of indications while measuring. With these pictures the performance of each sensor can be monitored. This information and the use of real time controller boards allows the operator online optimization of testing parameters during measurment. The parameter changes made by the Vol. 9, Issue 2 September 2010

Technical Paper

Fig. 7 : User Interface Glassy-Rail-Diagram

Fig. 8 : Analysis Flow Chart Vol. 9, Issue 2 September 2010

Journal of Non destructive Testing & Evaluation

32 operator are recorded. The offsets from the actual parameter set to these from the calibration are known for all measured positions. 4.2 Automated data analysis

When testing the rails with ultrasound and eddy current up to 250 Mbyte of data will be collected for one kilometre. For the operator it is not suitable to view these data by hand. To support evaluation of data by the operator automated classification algorithms have been developed and adapted which allow preselection of data displayed. The implemented data post processing uses algorithms based on neuronal networks and fuzzy logic. Optimizing these algorithms is an currently ongoing interactive and time consuming process based on expert knowledge. The implemented algorithms mainly focus on the suppression of indication caused by acoustic and electric noise as well as the identification of non-generic indication patterns and indication patterns caused by drill holes and welds. Rail type can be evaluated by measuring rail height. The offline data processing starts automatically when a section of 1000 m is finished. Each of the recorded clusters with a size of 64 by 64 pixels gives a feature list which is analyzed by a neuronal network. Recognized patterns are weighted with fuzzy logic to extract and mark the results. Unascertainable indications are marked also. The analysis flow chart is depicted in Figure 8. The data processing results in a classified indication list with position markers. The markers are read into the evaluation software indicating an icon underneath the Glassy-Rail-Diagram (see Figure 7). When viewing the data the operator can jump from marker to marker by display mode selection.

Technical Paper

of the rail up to very high inspection speeds above 80 km/ h. The testing results are shown in a unique Glassy-RailDiagram which allows the presentation of measured data with a fixed resolution independent of inspection speed. All data are digitally processed in real time. The system uses GPS information and time-stamps for positioning. Additional Kilometre points can be set so that a full set of results per unit distance is provided and used to locate the affected sections of rail. The status of probes, measurement devices and scan parameters are logged and indicated continuously as well as the direction and speed of train movement. Online Monitoring using the Glassy-Rail-Diagram allows real time sensitivity control. Automated data analysis tools based on trained neuronal networks and fuzzy logic give support to the operater when evaluating measured data with the Glassy-Rail-Diagram. Due to the large amount of different rail types and profiles, the adaptation and optimization of algorithms is still in progress. Additional data analysis for advanced combined eddy current and ultrasonic methods for the detection of damages have to be applied as soon as new information from the track is available. Therefore special selected track sections have to be evaluated in detail.

REFERENCES 1. H.-M. Thomas, T. Heckel and G. Hanspach; ´Advantage of a Combined Ultrasonic and Eddy Current Examination for Railway Inspection Trains´, Insight 49/6, pp. 341-344, 2007 2. T. Heckel, R. Armbruster, H. Hintze and S. Rühe, ´Neue Prüftechnik für den Schienenprüfzug, Erfahrungen, Fehlerbilder, Auswertung´, DGZfP Jahrestagung Münster, 2009

5. CONCLUSION

3. R. Pohl, R. Krull, R. Meierhofer and S. Rühe, ´Wirbelstromprüfung im Schienenschleifzug´; DACHJahrestagung Salzburg, 2004

A state of the art ultrasound and eddy current inspection system was implemented into the SPZ1 inspection train of Deutsche Bahn AG and brought into service. It uses ten ultrasonic probes and four eddy current sensors on each rail to be tested.

4. R. Krull, M. Thomas, R. Pohl and S. Rühe, ´Eddy-current Detection of Head Checks on the Gauge Corners of Rails; Recent Results´, Conference on Railway Engineering, London, 2003

A lot of detailed solutions have been developed and challenges have been overcome to allow a precise testing

Journal of Non destructive Testing & Evaluation

5. R. Krull, H. Hintze, M. Thomas and T. Heckel, ´Nondestructive testing of Rails today and in the Future´, ZEVrail Glasers Annalen 127, pp. 286-296, 2003

Vol. 9, Issue 2 September 2010

Technical Paper

Ultrasonic Guided Wave Phased Array Inspection of Pipelines S. Palit Sagara, Jia Jerry Hua and Joseph L Roseb Scientist EII, Materials Science & Technology Division, National Metallurgical Laboratory, Jamshedpur 831007, India b Paul Morrow Professor, Department of Engineering Science & Mechanics, The Pennsylvania State University, PA 16802,USA a

ABSTRACT Piping systems are often inspected ultrasonically to ensure safety. This can be accomplished by a series of point to point tests from the outside surface of the pipe. If coating covers the pipe, as is often the case, access to the outside surface requires removal of the coating to perform the test, and then re-installation when testing is complete. Removal and reinstallation of coating is not only time consuming but in most cases it is prohibitively expensive too. Ultrasonic guided waves provide an attractive alternative solution to the basic bulk wave ultrasonic test. Using Guided Waves, a probe can be applied to the pipe at a single location and several meters of the pipe can be inspected. The coating is only removed where the probe is applied. This paper describes the visco-elastic properties of two different coating materials: Bitumen tape and wax tape is considered, an FEM simulation of the propagation of axisymmetric guided waves through bare and coated pipes having different coating thicknesses. The ABAQUS FEM code is used and validation of FEM simulation results through experiments in bare and coated pipes using guided wave inspection system is reported.

INTRODUCTION

The oil, gas, chemical and petro-chemical industries operate hundreds of kilometres of pipelines for transporting chemicals, oil, water, and other necessities. Testing of these large structures using conventional bulk ultrasonic wave techniques is slow because the test region is limited to the area immediately surrounding the transducer. Therefore, scanning is required if the entire structure is to be tested. Moreover, a high proportion of industrial pipelines are insulated using visco-elastic coatings, so that even external corrosion cannot readily be detected without the removal of the coating, which in most cases is prohibitively expensive. Ultrasonic guided waves provide an attractive alternative solution to this problem [1-7]. â&#x20AC;&#x153;Guided Wavesâ&#x20AC;? are ultrasonic waves guided by the geometry of the object in which they propagate. Due to decreased attenuation loss, these waves transmit along the whole circumferential section of the pipe while propagating in the axial direction. These waves travel across the straight stretches of pipe to several meters from a single point using a pulse-echo transducer bracelet wrapped around a pipe [6]. Current long-range guided wave techniques for pipeline inspection include axisymmetric and nonaxisymmetric waves with partial loading and phased array focusing [5, 6]. It has been shown by Li and Rose [5] that among these two techniques, the focusing technique can increase energy impingement, locate defects, and greatly enhance the inspection sensitivity and propagation distance of guided waves, thus consequently reducing inspection costs. Viscoelastic coatings, such as bitumen and wax tapes, are commonly used for protection against corrosion in the pipeline industry. The presence of viscoelastic coating results in changes of guided wave propagation characteristics. Because of a variation of coating materials and the complexity of the wave mechanics in a viscoelastic coated multilayered structure, many Vol. 9, Issue 2 September 2010

aspects and questions on guided wave inspection in coated pipes are still untouched and remain quite challenging. In this work, a three-dimensional finite element method is studied for modeling guided waves in a bare pipe and also for Bitumen (BT) and Wax tape (WT) coated pipes. Viscoelastic properties of the BT and WT materials were studied and the experiments were performed on 4inch bare and BT and WT coated steel pipes using 8 channel axysymmetric torsional guided waves to validate the FEM results for practical applications.

2. SELECTION OF APPROPRIATE GUIDED WAVE MODE Guided waves in the axial direction of a hollow cylinder include longitudinal and torsional waves with both axisymmetric and nonaxisymmetric modes. Typical dispersion curves in a bare pipe are plotted in Fig. 1, showing various wave modes in a pipe.

Fig. 1 : Phase velocity dispersion curves of axysymmetric and flexural modes in 10-in. schedule 40 steel pipes [5] Journal of Non destructive Testing & Evaluation

Technical Paper

Table 1: Elastic Properties of coating materials cL (mm/ms)

cS (mm/ms)

αL( ω)/ω (1/mm)

aS( ω)/ω (1/mm)

Density kg/m3

Youngs Modulus (GPa)

Poissons’s Ratio

2.27

0.77

.047

.47

1200

2.04

0.43

2.04

0.781

.021

.21

1000

1.725

0.41

Material

Hence a key element of the inspection system is the selection and exploitation of a single mode. Indeed, even with a single mode, great care is needed for the correct identification of the reflections from defects and from normal pipe features such as welds. Therefore, although troublesome to achieve, it is essential to design the transducers and the signal to excite only the chosen mode. The mode that was chosen for excitation in the inspection system is the axially symmetric L(0,2) mode for longitudinal waves and the T(0,1) mode for torsional waves at about 40 kHz. This mode is very attractive for testing for several reasons: it is practically non-dispersive over a wide bandwidth around this frequency that is to say its velocity does not vary significantly with frequency, so that the signal shape and amplitude are retained as it travels.

3. ELASTIC AND VISCO-ELASTIC PROPERTIES EVALUATION OF BITUMEN AND WAX TAPE Ultrasonic longitudinal (cL) and shear (cS) velocities of BT and WT materials were determined by a bulk ultrasonic wave measuring technique. The Young’s modulus and the Poisson’s ratio of the coated material were determined from the measured cL and cS and are furnished in Table 1. The measured bulk wave velocities c(ω) and attenuation constants α(w) can be used to calculate the complex frequency dependent wave velocity c*(ω) using the equation(1) [8]: c*(ω) = 1/((1/c(ω)-iαL(ω)/ω)

The real part of eqns (2), (3) and (4) are related to the stiffness of the viscoelastic material, while the complex part is associated with the energy dissipation of the material. Table 2 lists the viscoelastic properties of BT and WT.

FEM SIMULATION

4.1 Wave propagation models in bare and coated pipes

The explicit direct integration method works the best for wave propagation problems due to its lower computational cost [3]. In this work, a FE package ABAQUS/Explicit was used for the modeling of guided wave propagation and focusing in pipes. A sample problem is discussed. The pipe model length is 3.2 m and the pipe wall thickness is 9 mm. The excitation frequency can be realized by using a windowed sinusoidal signal as the time-dependent amplitude of the pressure, also called a loading function. The first step in selective excitation is to use a narrow band signal to have good signal strength and to avoid dispersion over long propagation distances. However, too many cycles may result in a long time span. Usually 5–15 cycles are used. In this work a 40 kHz tone burst of 7 cycles in a Hanning window is used. A typical time record for a 7 cycle hanning windowed signal is shown in Fig. 2.

(1)

In a similar manner, the complex shear modulus G*, the complex Young’s modulus E* and the complex bulk modulus K* can be calculated using equations (2), (3) and (4): G*(ω)=cs*2r

(2)

E*(ω)=[(3-4(cS*/cL*)2)/(1-(cS*/cL*)2]G*

(3)

K*(ω)= r[ cL*(ω)]2-4/3[ cS*(ω)]2r

(4)

r is the density of the material.

Fig. 2 : 40 kHz 7 cycles hanning windowed tone burst signal

Table 2 : Estimated complex viscoelastic material properties of the coating materials c S*(mm/ms)

G*(Pa)

E*(Pa)

K*(ω)

2.177+0.225i

0.7514+0.311i

5.61e8+5.60e8i

1.67e9+1.56e9i

4.876e9+4.28e8i

1.996+0.084i

0.7504+0.1213i

5.48e8+1.82e8i

1.56e9+4.92e8i

3.247e9+0.92e8i

Coating

c L *(mm/ms)

BT WT

Journal of Non destructive Testing & Evaluation

Vol. 9, Issue 2 September 2010

Technical Paper

4.1.1 FE modeling of bare and BT and WT coated pipe with torsional guided waves

A 40 kHz Hanning windowed 7 cycles tone burst signal was applied in the circumferential direction at one end of the test pipe and the signal was received at the other end of the pipe as depicted in Fig. 3.

Fig. 6 : Photographs of tested bare and BT and WT coated pipes

Fig. 3 : Simulated coated pipe with axial load applied at one end

Result shows that the wave attenuation increases with coating thickness and the attenuation is higher in WT coated pipe compared to the BT coated pipe. A contracted view of Von-Mises stress wave propagation through simulated 3mm WT coated 3.2m long steel pipe is presented in Fig. 5 to show the stress leakage from the pipe into the coating.

Fig. 4 : Variation of wave attenuation with coating thickness for BT and WT coated steel pipes

Fig. 5 : Contracted view of the pipe showing energy leakage from the pipe wall into the wax coating

From the received signals, wave attenuation was determined for bare and BT and WT coated pipes with 1mm, 2mm and 3 mm coating thicknesses and plotted in Fig. 4. Vol. 9, Issue 2 September 2010

Fig. 7 : Received signals from bare, BT and WT coated 3.2m long pipe using low frequency torsional mode guided wave Journal of Non destructive Testing & Evaluation

Technical Paper

4.1.2 Experimental validation of FEM simulation

Experiments were performed on 3.2m long, 4In. Schedule40 bare, 1.8 mm bitumen tape coated and 2.2 mm wax tape coated steel pipes using the 4 channel low frequency ultrasonic guided wave system. Figure 6 shows the photographs of the test pipes and the probe assembly of the test system. The guided wave in a torsional mode was used and the test results of bare, BT coated and WT coated pipes at a frequency of 40 kHz are shown in Fig. 7. Wave attenuation as determined from the received signals for Bare, BT and WT coated pipes were 0.1dB/m, 1.01dB/ m and 1.87dB/m respectively. Table 4 gives the comparison of the wave attenuation as determined from FEM simulation and experimental data. The experimentally determined attenuation (dB/m) values were incorporated in the graph as shown in Fig. 4. Table 3: Comparison of FEM simulation and experimental data of wave attenuations in bare and BT and WT coated pipe Material

Coating thickness (mm)

Attenuation dB/m FEM simulation

Experimental

0.25

0.1

BT Coated

1.8

0.92

1.01

WT Coated

2.2

1.71

1.87

Bare

5. CONCLUSIONS Torsional mode guided wave ultrasonic was used to inspect the 3.2m long 4inch Schedule40 steel pipe with bitumen and wax tape coating of various thicknesses. FEM

Journal of Non destructive Testing & Evaluation

simulation shows that the single probe positioned guided wave technique can inspect the long coated pipes without removal of coatings, which is otherwise not possible by point to point inspection using bulk ultrasonic measurement technique. Experimental results successfully validate the applicability of guided wave technique in long range pipe inspection with visco-elastic coatings.

ACKNOWLEDGEMENTS This work is a part of the Raman Research Fellowship of the principal author, sponsored by Council of Scientific & Industrial Research (CSIR), Govt. of India. Authors also acknowledge the help from the graduate students of Ultrasonic group, Dept. of Engg. Science & Mechanics, The Pennsylvania State University and staffs of FBS Inc., Pennsylvania for carrying out guided wave experiments.

REFERENCES 1. Joseph L Rose, Ultrasonic Waves in Solid Media, Cambridge University Press, Book 2. J. L. Rose, IEEE Ultrasonics Symposium, (1995) 761 3. Wei Luo and J. L. Rose, J. Acoust. Soc. Am. 121 (2007) 1945 4. H. Kwun, S.Y. Kim, M.S. Choi, S.M. Walker, NDT&E International 37 (2004) 663 5. J. Li and J. L. Rose, J. Acoust. Soc. Am. 109 (2001) 457 6. J. Li and J. L. Rose, IEEE Trans. Ultrason. Ferroelectr. Freq. Control, 48 (2002)761 7. M.J.S. Lowe, D.N. Alleyne, P. Cawley, Ultrasonics, 36 (1998) 147 8. Mu Jing, â&#x20AC;&#x153;Guided Wave Propagation and Focusing in Viscoelastic Multilayered Hollow Cylindersâ&#x20AC;?, Ph. D thesis, Engineering Mechanics, The Pennsylvania State University, 2008

Vol. 9, Issue 2 September 2010

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