## Reliability estimation for non linear degradation measurements: application on fatigue crack

An important issue in the validation of mechanical parts for vehicles is reliability assessment for high mileages, by means of tests. Since the tests should be as short as possible, and for parts subjected to degradation mechanism, such as wear or crack propagation, it would be appropriate using degradation measurements (such as mass loss or crack length) in order to estimate reliability. In this study, we compare some models for reliability estimation using non-linear degradation measurements and more particularly crack length. Different kind of data can be available : some measures at different times, for each part, can be available, or only a single measure (one measure for each part). We study some statistical approaches responding to· this concern : a non-linear extrapolation path model and a modeling of the degradation increase by a Wiener and Gamma process. Then we compare these models on two types of fatigue· crack length data.

Julien BAUSSARON, Mihaela BARREAU, Léo GERVILLE-REACHE, Fabrice GUERIN, Paul SCHIMMERLING