Thermomechanical fatigue life prediction of metallic materials by a gradient‐enhanced viscoplastic damage approach

Abstract

Fatigue failure plays an important role in engineering applications, especially when structural components experience significant cyclic thermal loading and complex force loading simultaneously. During the last decades, several post-processing techniques have been developed based on empirical investigations of experimental evidence to predict the fatigue life of materials. The work at hand postulates a conventional continuum damage theory for thermomechanical fatigue failure modeling. In particular, an implicit gradient-enhanced approach is employed to address the ill-posedness of the partial differential equation system when the damage onsets. An internal fatigue variable is phenomenologically defined based on the accumulation of viscoplasticity. In the sequel, a regularized fatigue variable is obtained to further yield the damage softening function, which straightforwardly applies to the stress, material tangent, and viscoplastic dissipation. A multi-field problem, consisting of the strain field, the temperature, and the non-local variable, is taken into consideration, leading to a fully coupled system. This numerical methodology is consistently derived and implemented into the context of the finite element method. Several representative and demonstrative examples are performed, which yield good numerical stability and agreement with experimental data. Conclusive findings and further perspectives close this article.

Modelado del estrés termo-mecánico en películas finas de La(Fe,Co,Si)13 depositadas en estructuras porosas

“…Ambos tipos de fractura son, comúnmente, observados en materiales semi-o frágiles, tales como rocas, cerámicas, granitos, mármol y cemento, donde estos materiales exhiben deformaciones inelásticas dependientes del tiempo [18] [19]. Debido a esta analogía, el comportamiento mecánico de La(Fe,Co,Si)13 se puede modelar como un material con propiedades visco-plásticas acopladas con el daño inducido por las grietas [20] [21]. Para este fin, se acoplan los módulos de "Viscoplasticidad" y "Daño", parte de la física de "Mecánica de Sólidos" disponible en el software COMSOL Multiphysics.…”

Concrete failure based on a localizing gradient‐enhanced damage formulation coupled with plasticity

“…Before the eventual material failure takes place, many engineering materials firstly show plastic hardening behavior to a certain extent. Apart from the isotropic hardening that describes the isotropic expansion of the initial yield surface, kinematic hardening often serves to model the Bauschinger's effect in metallic materials when undergoing cyclic loading, see for example [7]. Plastic softening manages to describe the softening behavior governed by the shrinkage of the yield surface with or without considering initial hardening behavior, see for example [8,9].…”