Cyclic behaviour of structures under thermomechanical loadings: Application to exhaust manifolds

A structure subjected to thermomechanical cyclic loadings may exhibit various cyclic behaviours: perfect elasticity, elastic shakedown, plastic shakedown and ratchetting. The quantitative characterization of these different asymptotic states is addressed in this paper, in the context of the Generalized Standard Materials (GSM). Criteria are established to identify them and capture the trend line of their evolution, in the context of numerical simulation. The definitions are extended to the case of temperature dependent mechanical properties. Simple strain paths are first considered to illustrate the relevancy of the proposition. Finally, as an application, the example of an exhaust manifold subjected to a classical thermomechanical fatigue test is analyzed.

► New method to characterize the asymptotic behaviour under cyclic thermomechanical loading.
► Better consideration of out of phase loadings.
► The trend line of the structure response is established.
► Estimation of the structural integrity of an exhaust manifold under cyclic loading.