Fatigue and Fracture Analysis of Tacho-Way Drum Assembly using Finite Element Analysis

IJSRD - International Journal for Scientific Research & Development| Vol. 4, Issue 05, 2016 | ISSN (online): 2321-0613

Fatigue and Fracture Analysis of Tacho-Way Drum Assembly using Finite Element Analysis Sangamesh Metri1 Raviprakash M2 1 PG student 2Assistant Professor 1,2 Department of Mechanical Engineering 1,2 The Oxford College of Engineering Bommanahalli, Bengaluru Abstract— Structural design is very important for functionality and safety of the modules. Due to rotation and torsional loads, the components are subjected to changing stress amplitudes by which fatigue is the main mode of failure compared to the normal structural loads. In the present a drum conveyor system using tacho way guide ways is failure under the given loads. So aim is to find the possible cause of failure. The location of failure is near the bearing.

For mounting of the bracket, the shaft has been cut with a small groove which is required for mounting of the bracket.

So analysis needs to be done to find the effect fatigue and fracture effects on the configuration. So fatigue calculations are carried out based on Ansys, which shows nearing fatigue stress with minimum factor of safety in the problem. Further cracks are created to find the fatigue fracture life of the component. The result shows increased alternating stress with crack propagation showing that any possible crack will cause the failure of the drum shaft system.

Key words: Tacho Way Drum Shaft, Static and Dynamic Analysis, Fatigue Failure, Finite Element Analysis

Conveyor pulley reliability is an integral part of conveyor availability since pulley maintains belt tensions essential for load support and belt movement. Overall conveyor reliability can be consider as the product of individual components reliability, such as structure, belt load support components.

B. Classification of Conveyors Based on the nature of working, the conveyors are classified to  Aluminum Frame Conveyors  Belt Conveyors  Cleated Belt conveyors  Plastic Chain conveyors  Stainless steel Frame conveyors  Magnetic belt conveyors  Vacuum belt conveyors  Z-Frame conveyors

I. INTRODUCTION A. Conveyors Conveyor pulley is widely used in the area of material handling equipment field. Pulley is heart of the bulk mining material handling. The main components of conveyor pulley are shaft, drum or shell, end disk or diaphragm plates, locking elements, end disk, lagging and bearing assemblies.

Fig. 1: Roller type conveyor

Fig. 3: Z Frame Conveyor C. Regions of Failure of a Shaft The shaft may fail due to  Faulty design conditions  No lubrication  Improper drilling of grooves  Sharp corners  Fatigue  Fracture  Corrosion  Wear  Cracking. etc II. MATERIAL PROPERTIES

Fig. 2: Components of Rollers

Properties

Structural Steel

Material of the shaft

Mild steel

Young’s Modulus

190 Gpa

Poison’s ratio 0.303 328.6Mpa Yield Stress Density 78E-6Kg/m3 Table1: Material Properties

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Fatigue and Fracture Analysis of Tacho-Way Drum Assembly using Finite Element Analysis (IJSRD/Vol. 4/Issue 05/2016/310)

III. GEOMETRICAL MODEL OF THE PROBLEM

Fig. 4: Geometrical model of the drum along with the shaft system The figure 4 shows built geometry using Ansys. The preprocessor is used built the key points and lines for structural mesh. Different properties are attributed to give thickness and diameter of the members. Ansys beam element is the best option for analysis of this problem which suitable for linear to nonlinear problems with any given shape.

Fig. 6: Deflection due to self-weight

A. Assumptions     

The material is assumed to isotropic and homogeneous Analysis is done with in the elastic limit The element is based on simple beam theory.

All approximations of finite element method are applied to the analysis Pipe16 element suitable for linear conditions is used.

Fig. 5: One dimensional representation of the problem Beam elements are used to be the hollow region of the drum shaft. The members are linked through coupling equations for load transfer. Full structure is line modeled and meshed with suitable properties. Since one dimensional modeling is suitable for the current problem analysis is done through beam188 element.

IV. NUMERICAL ANALYSIS AND RESULTS Analysis has been carried out in different stages. The main objective is to find the reason for failure. So different analysis is carried out to find the actual cause of failure. The following cases of analysis are carried out. .  Self-weight analysis  With external lateral and torsional load  Fatigue analysis for the problem.

Fig. 7: Stress due to self-weight The fig. 7 indicates maximum stress of 3.09Mpa for the given self-weight conditions. This stress is low compared to the allowable stress of the problem and so the structure will not fail by self-weight.

Fig. 8: Stress concentration region The figure 8 shows maximum stress region due to self-weight. This is happening at the groove area due to stress concentration and lesser moment of inertia. The red color shows area of stress concentration.

B. Case 2: With External Lateral and Torsional Load

A. Case 1: Self Weight Analysis The fig. 6 shows deflection in the problem. Maximum deflection is 0.007758mm as shown in red color region.

The deflection is minimum at the support regions.

Fig. 9: Deformation plot with external load

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Fatigue and Fracture Analysis of Tacho-Way Drum Assembly using Finite Element Analysis (IJSRD/Vol. 4/Issue 05/2016/310)

The figure 9 shows deformation in the structure equal to 0.085974mm at the center region of the problem. This can be attributed to simply supported condition of the problem.

The red color indicates region of more deformation.

Fig. 13: Vonmises Stress with 10% crack (Maximum stress: 190.26Mpa)

Fig. 10: Stress concentration region in the problem The figure 10 shows The maximum stress is taking place near the groove region again due to lesser moment of inertia of the structure. The red color indicates higher stress concentration area. The extent of stress is 31.75Mpa which is smaller than the allowable stress of the material.

Fig. 11: Maximum Stress location (Maximum Stress: 149 Mpa

Fig. 14: Vonmises Stres with15%crack (Maximum stress: 242.68Mpa) The figure shows 12 and 13 increased proportion of stress compared to the 5 and 10% crack. This can be attributed reduction in the moment of inertia. Moment inertia mainly depends on cube of diameter (d0.4/d). In the same way the stress will increase. Once the crack reach to the center of the geometry the structure will fail which should be not permitted.

D. Developed Fatigue Stress

C. Case 3: Fatique Analysis The figure 11 shows development of von mises stress equal to 169.766 Mpa with the 5 % crack initiation. The stress increase can be attributed to reduced resistance for the loads due to crack at the groove region.

Table 2: Fatigue Stress with Crack Propagation V. CONCLUSIONS

Fig. 12: Results with 5 % crack

Static, fatigue and fracture of analysis of drum shaft is carried out for structural safety and to find the reason of failure. The complete summary is as follows.  Self-weight analysis results shows safety of the structure as the stresses and deformations are well within the range.  Further analysis with external loads shows stress increase up to 32Mpa under external loading (lateral and torsional). Even this stress value is less than the allowable stress. So components will not fail by this.

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Fatigue and Fracture Analysis of Tacho-Way Drum Assembly using Finite Element Analysis (IJSRD/Vol. 4/Issue 05/2016/310)

 

Further analysis with rotational loads shows maximum stress of 149Mpa in the problem. This stress is near to the critical or allowable stress of the problem. This indicates lesser factor of safety in the problem.

Fatigue estimation is carried out based on alternating stress generation in the problem. The alternating stress is slightly less than the allowable limit of 62Mpa Stresses are captured for von mises for 5, 10 and 15% cracks. The results are represented in the table.

REFERENCES

[1] Deepan Marudachalam M.G, K.Kanthave, R.Krishnaraj “Optimization of shaft design under fatigue loading using Goodman method” IJSER VOL 2, August-2011.

[2] Devendra Kumar, R.K. Mandloi “ Analysis & Prospects of Modification in Belt Conveyors - A International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 1, January -February 2013, pp.581-587 [3] Tapan R Patel, Mr.Ronak R Patel, Prof. Shashank P Joshi. “Conveyor Pulley Failure Analysis” 2014 IJEDR Volume 2, Issue 1 | ISSN: 2321-9939.

[4] D. K. Padhal, D. B. Meshram “ Analysis and Failure Improvement of Shaft of Gear Motor in CRM Shop” International Journal Of Engineering And Science Vol.3, Issue 4 (July 2013), PP 17-24 [5] Amol B Rindhe and S R Wagh “failure analysis and evaluation of a composite material automotive driveshaft by using fem—A REVIEW”, IJMERR, Vol. 3, No. 2, April 2014.

[6] Sumit P. Raut, Laukik P. Raut, “Failure Analysis and Redesign of Shaft of Overhead Cran” in Journal of Engineering Research and Applications, ISSN: 22489622, Vol. 4, Issue 6 (Version 3), pp.130-135, June 2014.

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