Kontinuumsmechanische Modellierung von Stahlblechklebverbindungen für die FE-Crashanalyse

The non-associated plasticity model, based on the first and second invariant of the stress tensor, describes reasonably well the mechanical behaviour of crashoptimized high-strength adhesives in the automotive industry. This pressure sensitive model can be used only with three-dimensional solid elements which are not suitable for the discretisation of thin adhesive layers in bonded components for the simulation of a complete vehicle body in crash scenarios. In order to reduce the computing time, the thin polymeric adhesive layer is approximated with interface elements. Different proposals will be discussed in order to relate the strain tensor of the 3D-continuum to the displacement jump vector of the interface element and its stress vector to the three-dimensional stress tensor by means of an adequate model idealization. Hence, a multi yield surface function model can be advantageously expressed in terms of the components of the stress vector on the interface and be extended to material softening including damage and rate dependence. The material parameters are identified by means of the simulation of the experimental setup for a bluntly glued double steel tube sample with the adhesive BETAMATE 1496. A final comparison of the simulated results with the experimental data points out the validity of the introduced model. The combined shear and tension tests on a special bounded structure, denoted as the KS2-test, and the experiments, performed at the DCB specimen, reflect the peeling and shearing process of adhesively bonded steel sheets in a vehicle body. The crash performance of the constitutive model is finally tested at an adhesively bonded joint in the form of a T-intersection. Despite the simplicity of the constitutive model for the interface element, the complex material behaviour of the joint failure is well reproduced.

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