SUMMARYThe paper discusses the derivation and the numerical implementation of a finite strain material model for non-linear kinematic and isotropic hardening. The kinematic hardening component represents a continuum extension of the classical rheological model of Armstrong-Frederick kinematic hardening. In addition, a comparison between several numerical algorithms for the integration of the evolution equations is conducted. In particular, a new form of the exponential map that preserves the plastic volume and the symmetry of the internal variables, as well as two modifications of the backward Euler scheme are discussed. Finally, the applicability of the model for springback prediction is demonstrated by performing simulations of the draw-bending process and a comparison with experiments. The results show an excellent agreement between simulation and experiment.

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Roll bonding is a joining-by-forming process, in which two or more metals are permanently joined through pressure and plastic deformation, which causes the creation of a metallic bond. The bond formation is a complex process based on various process conditions in the joining zone, such as strain, normal pressure, temperature, strain rate, shear strain and surface condition. Since an individual variation and analysis of the influencing parameters is usually not possible during the rolling process, a specific experimental setup for the investigation of the joining mechanisms is necessary. In this paper, a testing procedure has been developed to determine the bond strength in joining-by-forming processes. The material combination chosen was AA2024/AA1050 as used in aircraft applications. AA2024 sheets are cladded with pure aluminum to improve the corrosion resistance. The performed experimental parameter study confirms the expected influencing factors and is used to determine parameters of a bonding model, which can be integrated in a finite element simulation.