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Finite Element Analysis (FEA)-based structural simulations are typically used to assess the durability of automotive components. Many parts experience vibration in use, and resonance effects are directly linked to many structural problems. In this case, dynamics must be included in the structural analysis. Dynamic FEA can be more realistic than static analysis, but it requires knowledge of additional characteristics such as mass and damping. Damping is an important property when performing dynamic FEA, whether transient or steady state dynamics, as it governs the magnitude of the dynamic stress response and hence durability. Unfortunately the importance of damping is often overlooked; sometimes a default damping value is erroneously assumed for all modes. Errors in damping lead to errors in the stress response, which in turn lead to significant changes in the fatigue life estimates.

Understanding total fatigue life of welded joints is crucial to developing durable products. Traditional fatigue analysis methods have focused independently on either crack initiation or crack growth. Each of these methods has strengths but neither method predicts the total life of the part from fabrication to fracture. Recently the SAE Fatigue Design and Evaluation committee evaluated and validated a fatigue analysis technique that can predict the total life of the weld, from microscopic crack initiation to crack growth and finally to fracture. This paper describes a finite element-based (FE) methodology for implementing this total life fatigue analysis in a CAE environment.