Multiaxial damage assessment and life estimation: Application to an automotive exhaust manifold

Some mechanical components are subjected to thermo-mechanical fatigue, which occurs when both thermal and mechanical loads vary with time. Due to the complexity of the components geometry, stresses and strains field becomes multiaxial, worsening the fatigue resistance. In this paper several damage models are applied and compared on a case study, an automotive exhaust manifold simulacrum replying the material and the geometrical features of the commercial component. A complete thermo-structural FE analysis has been run and results have been post-processed by means of a numerical code implementing several multiaxial damage models available in literature and based both on a critical plane approach (Kandil-Brown-Miller, Fatemi-Socie) and strain-based models (Von Mises, ASME Code and Sonsino-Grubisic). The model calibration has been carried out by means of literature experimental data referred to commercial exhaust manifolds of similar geometry and material.