Weld Durability Analysis by Equilibrium-Equivalent Structural Stress Approach

Welding has been used extensively in automotive components design due to its flexibility to be applied in manufacturing, high structural strength and low cost. To improve fuel economy and reduce material cost, weight reduction by optimized structural design has been a high priority in auto industry. In the majority of heavy duty vehicle's chassis components design, the ability to predict the mechanical performance of welded joints is the key to success of structural optimization. FEA (finite element analysis) has been used in the industry to analyze welded parts. However, mesh sensitivity and material properties have been major issues due to geometry irregularity, metallurgical degradation of the base material, and inherent residual stress associated with welded joints. An approach, equilibrium-equivalent structural stress method, led by Battelle and through several joint industrial projects (JIP), has been developed. The method uses a combination of FEA, linear elastic fracture mechanics (LEFM) and the Master S-N Curve for life prediction of welded joints. In this paper, the methodology of using structural stress and Master S-N Curve is summarized. Application of this methodology in product development support is exemplified by three case studies on welded joints in spring seat, axle bracket, and drive train component.