Stress Analysis of Butt Welded Joint using Finite Element Method (FEM)

Daso Dokibo ¹ , Mbuide Saturday B ² , Nwidebom Deesibari E ³ , Opuiyo Seseipiriala ⁴

^1,2,3,4 Lecturer, Department of Mechanical Engineering, Ken Saro-Wiwa Polytechnic, Bori, Rivers State, Nigeria.

Abstract

Mechanical steel structures , mostly fabricated by the welding process, are often subjected to cyclic stresses which affect their connections or joints. These joints are the most vulnerable points prone to structural failure when stressed. Analyzing the stresses of the welded joints is essential for determining the strength of the structures.
The objective of this study is to evaluate equivalent stresses at double vee-butt welded joints using the finite element method (FEM). ANYSYS structural 16.0 Workbench is used to simulate cyclic stresses under the influence of repeated load application at the weld. Solid works is used to model the joint.
A double vee butt welded joint of A36 structural steel material is considered in this study. It was revealed that higher tensile stresses on the weld are a major influence on the strength of the weld, especially at the toe of the weld resulting to crack initiation at that region leading to plausible failure. Simulation result shows that the weld risks shear fatigue failure at higher maximum stress of 353.63 MPa, 361.66 MPa, 381.76 MPa at loads of 17.6, 18 and 19N along the plane of the weld throat or toe since it has exceeded the yield strength limit of the material/weldment of 250MPa. A reduction in stress concentration due to lower cyclic tensile load application increases the fatigue life of the weld, as illustrated from the S-N curve.
The study demonstrates that butt welded joint are reliable in fatigue strength when stressed in a cyclic loading condition, as proven from the simulation results, yielding a simplistic software based evaluation of stresses at welded joints.

Keywords: Fatigue life, Welded joint, Weldment, Simulation, Stress concentration, Fatigue strength

References

1. Akbarnejad.S. (2012) “Investigation of static strength of butt welded joint’, Royal Institute of Technology Stockholm, Sweden.
2. AWS (2010) Structural Welding Code Steel. American Welding Society.
3. Dong, P., Lu, F., Hong, J.K. and Cao, Z. (2001) ‘Coupled thermomechanical analysis of friction stir welding process using simplified models’, Science and Technology of welding and joining, 6(5), pp. 281-287.
4. Fricke, W. (2012) Guideline for the Assessment of Weld Root Fatigue: Table of Contents. IIW Doc. XIII-2380r3-11.
5. Friedrich, N. (2020) ‘Experimental investigation on the influence of welding residual stresses on fatigue for two different weld geometries’, Fatigue & Fracture of Engineering Materials & Structures, 43(11), pp. 2715-2730.
6.  Gao, H., Zhang, X., Huang, P., Jiang, H. and Li, Z. (2022) ‘Fatigue reliability of welded joints accounting for uncertainties in weld geometry’, Advances in Mechanical Engineering, 14(5), 16878132221098892.
7. Khan, M.I. (2007) Welding science and Technology.1^st edition’. New Age Publishers.
8. Kumar, G.A. and Murali J.V. (2015) ‘Stress and strain analysis of Welded joints’, Proceedings of International Conference on Recent Trends in Mechanical Engineering, 1(2), pp. 5.
9. Radaj, D., Sonsino, C.M. and Fricke, W. (2006) Fatigue assessment of welded joints by local   approaches. 2^nd ed. New Age Publisher.
10. Sonsino, C. M. (2009) ‘A consideration of allowable equivalent stresses for fatigue design of welded joints’ according to the notch stress concept with the reference radii rref= 1.00 and 0.05 mm’, Welding in the World, 53(3), pp. 64-75.
11.  Zhang, N., Deng, C., Lin, Z., Wang, Z. and Wu, S. (2024) ‘The effect of misalignment on stress concentration and fatigue life for circumferential weld joints of pipeline’, Metals, 14(5), pp. 545.
12. Zhang, W., Dong, Z. and Liu, Z. (2017) ‘Present situation and development trend of welding robot’, 2^nd International Conference on Materials Science, Machinery and Energy Engineering (MSMEE 2017). Atlantis Press.