Fatigue Analysis of Steel MIG Welds in Automotive Structures

MIG weld failures are commonly seen in chassis and frame structures in automobile industry. Until now, testing and CAE analysis based on local stresses in the vicinity of MIG weld were driving the design of these welds. With the advent of advanced methods and tools, it is possible to estimate fatigue life of MIG welds and support the design in the early stages of the vehicle program. Recently, fatigue damage models are developed for assessing the durability of MIG welds in aluminum auto structures. These damage models are based on advanced technologies like mesh-insensitive structural stress method, virtual node method, estimation of notch stress intensities and life predictions based on two-stage crack growth law. This paper outlines the theoretical aspects involved in deriving the master S-N curve. The applicability of steel MIG weld damage model developed based on the same structural stress approach in assessing the life of MIG welds in automotive steel structures is verified by analyzing different automotive components and correlating with test data. The results are very promising and it can be used to support the design of MIG welds in automotive steel structures.