Fatigue, resulting in the failure of a vital component may have serious consequences. There are a number of different reasons for a fatigue failure such as design faults, manufacturing faults, material faults and faults in predicting the operating environment. In this paper, verification of vehicle components with respect to fatigue is discussed. The two most common methods, i.e. the safety factor approach and the load-strength method are studied. The traditional safety factor approach is based on long time experience and includes no probability theory. It has the main drawback that it cannot be updated in a rational way, since its origin often is difficult to analyse. The load-strength approach for fatigue sensitive components uses a probabilistic approach and assigns distributions to the strength and load, respectively. It is in theory a good solution, since the different influences can be distinguished form each other and measures of reliability can be obtained. However, in practise the available information is usually weak, and the involved distributions become uncertain and often objects for subjective choice. A set of problems with the methods is identified. An alternative using the advantages of the two techniques is developed. This combined approach uses a signal-to-noise ratio, which can be related to classical safety factors. It is then possible to evaluate the performance based on probability theory as well as updating in a rational way when new observations are obtained. Assumptions of the distribution tails are not necessary, but can be replaced by a rough judgement based on experience and field failure statistics. A set of measurements on steering knuckles is used to exemplify the method.
Verification of safety critical components
Verifizierung sicherheitskritischer Komponenten
2005
15 Seiten, 2 Bilder, 2 Tabellen, 8 Quellen
Aufsatz (Konferenz)
Englisch
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