No abstract

No abstract

The fatigue design is realized at PSA within a probabilistic approach. This approach takes into account the industrial context of the design. It includes the analysis of customer distribution, the handling of the production scatter, and the definition of relevant loading specifications ad acceptance criterion for the designers. This approach avoids variable amplitude analysis by the mean of an appropriate fatigue equivalence method, and by the mean of the Dang Van criterion for the fatigue analysis of the FEM results. Extension of this work to structures undergoing damage due to vibrations is adressed.

It is well-known that rubber exhibits hysteretic mechanical behavior and has a low thermal conductivity. The main consequences are the heat generation and heat build-up phenomena which occur in a rubber component when subjected to repeated deformations. Estimating the heat build-up temperature implies the solution of a coupled thermomechanical problem. Due to the difference between the mechanical and the thermal diffusion characteristic times, a cyclic uncoupled approach is often used to solve the heat build-up problem.In the uncoupled approach, the heat sources are first determined with a mechanical analysis, and the heat equation is then solved on a fixed geometry. At finite strains, the geometry of the body varies with the deformation but the foregoing method does not account for such changes in geometry. The exact solution would require describing the body deformation while solving the thermal problem, but this does not take advantage of the difference between the characteristic times of the thermal diffusion and the mechanical behaviour, respectively, and the exact numerical resolution is therefore unnecessarily time-consuming.The purpose of the current work is to take into account kinematics in the thermal problem when using a cyclic uncoupled approach. The heat problem is written in the reference configuration. That implies that the problem is defined on a fixed domain: the initial configuration of the body. The changes in geometry in the reference heat equation are thus described by mechanical time-dependent variables. The cyclic assumption allows mean variables to be defined, for example the mean temperature. A timeintegration method and an approximation of the heat equation are developed, leading to a simplified formulation with mechanical time-independent terms. This simplified heat problem is based on the mean variables.

In the automotive industry, temporal, financial and human constraints require continuous improvements in the design process of new vehicles, by delivering relevant specifications and providing reliability and robustness in design. In order to analyze factors like behaviors of drivers and types of roads and guarantee the reliability of car components, measurements of forces from wheels are stored when the vehicle is tested on tracks and used by customers. The measurements represent the time history of multi-dimensional forces on the four wheels in the longitudinal, vertical and transversal directions. They are applied on structures (suspensions or motoring for instance) during the design life of the vehicles. The context of this paper is the fatigue analysis of multi-input loadings. The study will be focused on random and possibly correlated multi-input processes, representing multidimensional forces. The goal of this paper is to present an approach to generate simple multi-input loadings equivalent to measurements in terms of damage. The simple loadings have to be equivalent for any arbitrary structure, satisfying the reliability requirements imposed by the car manufacturer.