Holistischer Ansatz zur Versagensmodellierung von Schweiß- punkten in der Crashsimulation

A sufficient modelling of spot weld behaviour in full car crash simulations is a fundamental item due to the fact that local joint fracture can make a significant contribution to the overall crash performance. The accurate reproduction of local joint properties leads typically to highly-detailed discretisations which violate the time step restrictions in full vehicle crash models and are therefore not appropriate. For this reason only representative spot weld models can be used. The existing substitute models need comprehensive experimental testing to define each joint under relevant crash loading conditions. Consequentially, a parameterisation of all combinations in a vehicle is highly cost-intensive. The present paper introduces a new approach to provide the basis for an efficient parameterisation of substitute spot weld models. This is accomplished by using a detailed simulation model with separate damage criteria for the different weld zones in order to predict the spot weld behaviour numerically. Fracture in the weld (shear fracture) is captured by a Cohesive Zone Model, in contrast to the base material and the heat affected zone where the Gurson model with a specific set of parameters is deployed to indicate plug fracture. The necessary model parameters are identified via an inverse method. In a following verification phase a precise prediction of spot weld behaviour for similar and dissimilar joints could be demonstrated. Consequently, the experimental effort to characterise substitute spot weld models for full car crash simulations can be reduced.

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