The objective of this paper was to present the fatigue approach in the context of automotive industry. This analysis is realised within a probabilistic method known as the Stress Strength Interference Analysts. The major difficulty is the definition of the service loading which demands long and costly statistical analysis of car usage and owner behaviour. From this analysis, and using the equivalent fatigue approach, simple loading specifications are derived allowing fatigue computations during the early stages of the project. The determination of the components fatigue strength distribution is easier but its accuracy depends strongly on the number of components tested. In practice, it is often difficult to test many components (cost at prototype stage, lengthy testing). Therefore data bases are built to appreciate the relative scatter parameters typical of each fabrication process. This allows the statistical evaluation of the risk to be improved while reducing the number of tests. The major advantage of the Stress-Strength method is that it points out the truly significant parameters and assumptions. The robustness of the approach depends more on the quality of the statistical information about stress and strength distributions than on the choice of specific fatigue model. In this context, question such as 'Miner or not Miner?' or 'Gerber or Goodmann?' are not relevant. The main message is that components which will resist high cycle fatigue cannot suffer cyclic plasticity at the macroscopic scale. In all cases, relevant to the automotive industry, the material will rapidly tend to an elastic state, due to elastic shakedown of the structure. It is important to point out that mechanical structures usually have complex geometries and that they operate under complex loading. Therefore the description of the behaviour of the structure must be as precise as possible and should provide the stress and strain elements necessary for the subsequent fatigue analysis. This fatigue analysis must be appropriate and take into account the structural behaviour and specificities (multiaxiality of the stress fields, complex geometries) and must be computerized with a fatigue routine linked to a finite element code. For that purpose it is not necessarily useful to describe in detail the damage mechanisms of the material which are anyway very complex. The relative simplicity of the application of the methods proposed here and the limited number of necessary material data allows their use in design offices by engineers and designers who are not fatigue experts.


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    Titel :

    Structural durability in automotive design


    Beteiligte:
    Thomas, J.J. (Autor:in) / Nguyen-Tajan, T.M.L. (Autor:in) / Burry, P. (Autor:in)


    Erscheinungsdatum :

    2005


    Format / Umfang :

    15 Seiten, 9 Bilder, 10 Quellen



    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Print


    Sprache :

    Englisch






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