This paper presents a 'global' damaged elastoplastic model which represents the overall response of the welded junction and which is identified on experimental results. The identification procedure is also presented. The validation on experiments is presented. The model has been implemented in the Radioss commercial finite element dynamic explicit crash code. In crash analysis, one usually represents thin structures by shell elements such as MITC4 elements or, more likely for explicit codes, under integrated elements like Belytschko-Tsai or QPPS assumed-strain quadrilateral elements. The weld is represented by a single beam attached to two points located anywhere within the finite elements. The welded region is a very complex zone for which the geometry is not very well-known, the actual material properties are complex and highly variable from point to point. We stall ignore these details and replace the whole 'welded zone' by a single non-linear spring which represents the 'global' behavior of the region. The non-linear response will be considered ,elastic-plastic. In order to be able to simulate the failure of the welded region a damage model is also introduced. The damage model is based on the ductile failure model: we introduce a damage variable denoted D. When damage reaches same critical value denoted Dc the material fails. This model is represented by an evolution of the Young's modulus. The model presented in this paper is rather simple to implement and seems to be efficient to represent the global behaviour of a spot welded junction. It has been identified and validated on a series of experimental results, and seems to be efficient. Nevertheless it has not been compared with experiments in true impact situations. One thinks that this type of model (which does not include any rate effects) will still be valid until the tearing of the series of weld starts, because the strain rate of the weld remains small before tearing occurs. The damage model can also been improved by taking into account the influence of the damage parameter on the yield stress and not only on the Young modulus. This should help to represent better the post-peak behaviour of the model. Finally a more general model which does not need any new test for a new plate assembly has to be developed. The proposed approach is nevertheless a significant improvement to the classical approach of modelling of welded plates in crash simulations.


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    Title :

    A "global" finite element model for the simulation of failure of spot welded assemblies during impact


    Additional title:

    Ein 'globales' Finite-Element-Modell zur Simulation des Ausfalls punktgeschweißter Verbindungen bei Stoßeinwirkung


    Contributors:
    Combescure, A. (author) / Delcroix, F. (author) / Caplain, L. (author) / Espanol, S. (author) / Langrand, B. (author)


    Publication date :

    2003


    Size :

    4 Seiten, 4 Bilder, 8 Quellen




    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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