Etude et modélisation de la propagation des fissures sous chargement thermique cyclique.

Abstract

The purpose of this thesis is to present a study of the cyclic thermal behavior of crack propagation by taking the automobile brake disc as an example of a study for the prediction of their fatigue behavior. The numerical calculation strategy is based on the Ansys .15 calculation code. The latter, which is based on the finite element method and which has frictional contact management algorithms, is used to simulate in the application of braking the behavior of the mechanism despite its complexity. At first, a purely thermal study is presented whose purpose is to calculate the initial heat flux entering the disc, then the mechanical study allowed us to calculate the hydraulic pressure, then a modeling of the loading and boundary conditions applied to the disk and the pads. A numerical approach was also performed based on the finite element method. A cyclic thermal study on the one hand, and a cyclical hermomechanical study on the other hand, were first put in place, allowing us to better understand the influence of the thermal flow and the hydraulic pressure on the propagation in width and depth of the elliptical fissure quite comparable to that linear. Finally, a three-dimensional approach, with a crack remaining elliptical during propagation, resulted in a prediction of fatigue strength.