Camshaft timing belt reliability modelling

Abstract

This paper presents a generic approach to life prediction modelling for automotive components, which aims to establish a correlation between the degradation mechanism, the real world customer usage profile and rig life testing. The approach is illustrated with the development of a life model for the camshaft-timing belt, for which tooth shear fatigue mechanism leads to the common cause failure mode. Previous research consisting of dynamometer studies and analytical modelling have demonstrated that the fatigue life of the timing belt can be expressed as a function of tooth load or tooth deflection, and has belt operating temperature as an explanatory variable. A stochastic linear damage accumulation process was assumed in order to derive a timing-belt life model in correlation with customer usage. The model was calibrated by using results of engine dynamometer tests. The model. is useful in many ways. It provides a simple and direct way of establishing a correlation between damage accumulation in real world conditions and belt life testing under laboratory conditions. The timing-belt life model can be used either as a life prediction tool for different usage profiles, or as a risk assessment tool in establishing the service interval.