Increasingly rigorous legal demands for pollution control of cars can only be fulfilled if the catalytic system operates at maximum efficiency with short operation times before the light-off temperature is reached. This is achieved by new designs of the exhaust system with the catalyst being located as close as possible to the engine, and with very thin-walled exhaust manifolds. Modern exhaust systems must withstand severe cyclic mechanical and thermal loads throughout the whole life cycle. Up to now, highly loaded parts of exhaust systems are predominantly designed experimentall by means of lengthy and expensive component tests. A further shortening of development time without quality loss is possible only by an increasing application of computer simulation. A procdure is presented which supports the component development already in an early design stage and which aims at reducing the number of component tests. The numerical model is capable of handling complex thermal-mechanical loadung histories by a viscoplastic constitutive model. The local damage processes are modeled based on the growth of microcracks, including relaxation and hold-time effects. This tool is currently evaluated by BMW with respect to its predictive capabilities. Its utilization will help to speed up the development process and to further increase product quality. The cyclic-plasticity model of Jiang was implemented into the commercial finite element code ABAQUS for solid and for shell elements as a user-defined material routine (UMAT). The good agreement between the predicted and the measured lifetime in the present case is encouraging. However, the method should be qualified for different materials and thermal cycles. This method may be applied to other components the lifetime of which is limited by the growth of microcracks.


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    Titel :

    Modelling of the fatigue life of automobile exhaust components


    Weitere Titelangaben:

    Modellierung der Ermüdungslebensdauer von Auto-Abgasbauteilen


    Beteiligte:
    Schmitt, W. (Autor:in) / Mohrmann, R. (Autor:in) / Riedel, H. (Autor:in) / Dietsche, A. (Autor:in) / Fischersworring-Bunk, A. (Autor:in)


    Erscheinungsdatum :

    2002


    Format / Umfang :

    8 Seiten, 6 Bilder, 7 Quellen



    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Print


    Sprache :

    Englisch




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