Fatigue design and reliability in the automotive industry

Abstract Fatigue assessment of automotive components is performed at PSA using a statistical approach to predict reliability. Calculations provide a lot of information but experimental work is always necessary to determine this reliability. Results exploitation is carried out using the “Stress-Strength interference analysis” method (SSIA). The “Stresses” represent the distribution of the car owners severity, the “Strength” represents the distribution of the fatigue strength of all the components. If the determination of the Strength is easy (fatigue tests results), the application of the “Stress-Strength” Method also requires the knowledge of the owners severity. This information is accessible as statistical distribution through owner enquiries on car usage. On the one hand a “car usage” enquiry allows conditions in which cars are driven (loading, route) to be known. On the other hand an “owner behaviour” enquiry allows the determination for a given use of the distribution of the owners' severity. The fatigue assessment of an engine subframe is used to illustrate the approach.