A Comprehensive Approach for Estimation of Automotive Component Life due to Thermal Effects 2018-37-0019
Due to stringent environmental requirements, the vehicle under-hood and underbody temperatures have been steadily increasing. The increased temperatures affect components life and therefore, more thermal protection measures may be necessary. In this paper, we present an algorithm for estimation of automotive component life due to thermal effects through the vehicle life. Traditional approaches consider only the maximum temperature that a component will experience during severe driving maneuvers. However, that approach does not consider the time duration or frequency of exposure to temperature. We have envisioned a more realistic and science based approach to estimate component life based on vehicle duty cycles, component temperature profile, frequency and characteristics of material thermal degradation. In the proposed algorithm, a transient thermal analysis model provides the exhaust gas and exhaust surface temperatures for all exhaust system segments, and for any driving scenario. The input boundary conditions for exhaust gas temperature are obtained by interpolation of engine dynamometer test data. Computational Fluid Dynamics (CFD) tools provide air velocities for specific vehicle speeds. The heat transfer coefficients around exhaust surface and around components that are of interest to the development engineer are evaluated based on the provided air velocities. Three-dimensional conduction models predict transient component temperatures based on material thermal properties such as density, specific heat and thermal conductivity. The transient analysis approach also considers the effect of emissivities, altitude and component rotation. After a component temperature profile is generated for a specific set of tests, thermal degradation models are applied to predict the useful component life. Thus, the estimation of component life is based on component temperature, time duration at each temperature range, and frequency of exposure and material thermal degradation behavior. This approach provides a more realistic and efficient method for evaluation of thermal effects on component life. It has proved to be very effective for evaluation of thermal protection requirements at early stages of vehicle development.