IJSTE - International Journal of Science Technology & Engineering | Volume 2 | Issue 08 | February 2016 ISSN (online): 2349-784X
Experimental Approach for Selection of Tool Steel Using Heat Treatment Process with MTTF and MTBF Prof. Kiran S. Phad Assistant Professor Department of Mechanical Engineering Amrutvahini College of Engineering, Sangamner, Maharashtra, India
Prof. Ravindra E. Gite Assistant Professor Department of Mechanical Engineering Amrutvahini College of Engineering, Sangamner, Maharashtra, India
Prof. Amol L. Khatode Assistant Professor Department of Mechanical Engineering Samarth College of Engineering, Junnar, Maharashtra, India
Prof. Dipak S. Bajaj Associate Professor Department of Mechanical Engineering Amrutvahini College of Engineering, Sangamner, Maharashtra, India
Abstract Tools steels are generally used in forming process of operation under definite mechanical properties of the sheet metal. At the same time failure of tools steels take place because of many number causes or insufficient material selection criteria. Under this paper we have taken the five samples as punch materials i.e. EN-31, OHNS, D-2, EN-9 and D-3 to find out the different causes of punch failures. Main objective is to study the effect on the hardness of tool steel after heat treatment processes. Also MTBF and MTTF are reliability terms based on methods and procedures for lifecycle predictions for a product. These terms providing a numeric value based on a compilation of data to quantify a failure rate and the resulting time of expected performance. The numeric value can be expressed using any measure of time, but hours is the most common unit in practice. Fracture surface displays typical ductile fracture, and the outer and inner surface of the part punched off is full of little bowings around which there are many micro cracks caused by the stretch stress under biaxial strain/stress state. This survey also helps to find out the failure mode appraisal in inner lower control arm and punch with their preventive methods. Keywords: Heat treatment; Rockwell hardness; Brinell hardness; Vickers hardness; MTTF (Mean Time to Failure) and MTBF (Mean Time between Failure) ________________________________________________________________________________________________________
I. INTRODUCTION Commonly used tools which are major components of press working are punches and dies. Punch is an important part of the system which is fastened to the ram and forced into the die where work piece to be processed is supported. Die is a work holding device, designed specifically for a particular design of a product. Die is rigidly held on the base of the press. Die carries an opening which is perfectly aligned with the punch and its movement. Both die and punch work together as a unit and this is called a die set. Tool steels are broadly divided into six categories like cold work, shock resisting, hot work, high speed, water hardening, plastic mould and special-purpose tool steels. Among them, cold work tool steels are the most important category, as they are used for many types of tools, dies and other applications where high wear resistance and low cost are needed. [4] During manufacturing and forming process cracking is a major problem, also at punch nose cracks are normally seen, the paper will focus on these areas and try to find best possible solutions for failure modes in an automobile Inner lower control arm component. Process Identification: Different types of processes involved in sheet metal work, which produce burr are given in table 1.
Operations
Table – 1 Processes and their harmful effects Defect Found Effect
Action Taken
Shearing
No Defect
No Effect
Ok
Blanking
No Defect
No Effect
Ok
Drawing
Wrinkles
Quality Issue
Rework
Forming
Spring Back
Rework
Die Design
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