Fatigue Life Assessment of Welded Structures with the Linear Traction Stress Analysis Approach 2012-01-0524

Structural stress methods are now widely used in fatigue life assessment of welded structures and structures with stress concentrations. The structural stress concept is based on the assumption of a global stress distribution at critical locations such as weld toes or weld throats, and there are several variants of structural stress approaches available. In this paper, the linear traction stress approach, a nodal force based structural stress approach, is reviewed first. The linear traction stress approach offers a robust procedure for extracting linear traction stress components by post-processing the finite element analysis results at any given hypothetical crack location of interest. Pertinent concepts such as mesh-insensitivity, master S-N curve, fatigue crack initiation and growth mechanisms are also discussed. Then, fatigue life assessment of automotive exhaust systems is conducted and the data correlation with a recently developed equilibrium data analysis method is provided and compared. Finally, the needs for further development of more physically sound analysis approaches are indicated.