Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Investigation of the application of a C-ring geometry to validate the stress relief heat treatment simulation of additive manufactured austenitic stainless steel parts via displacement
    ( 2020)
    El-Sari, B.
    ;
    Biegler, M.
    ;
    Rethmeier, M.
    Directed energy deposition is a metal additive manufacturing process that builds parts by joining material in a layer-by-layer fashion on a substrate. Those parts are exposed to rapid thermo-cycles which cause steep stress gradients and the layer-upon-layer manufacturing fosters an anisotropic microstructure, therefore stress relief heat treatment is necessary. The numerical simulation can be used to find suitable parameters for the heat treatment and to reduce the necessary efforts to perform an effective stress relieving. Suitable validation experiments are necessary to verify the results of the numerical simulation. In this paper, a 3D coupled thermo-mechanical model is used to simulate the heat treatment of an additive manufactured component to investigate the application of a C-ring geometry for the distortion-based validation of the numerical simulation. Therefore, the C-ring samples were 3D scanned using a structured light 3D scanner to quantify the distortion af ter each process step.
  • Publication
    Avoidance of liquid metal embrittlement during resistance spot welding by heat input dependent hold time adaption
    ( 2020)
    Böhne, C.
    ;
    Meschut, G.
    ;
    Biegler, M.
    ;
    Rethmeier, M.
    Liquid metal embrittlement (LME) cracking can occur during resistance spot welding (RSW) in zinc-coated advanced high-strength steels (AHSS) for automotive production. In this study, a methodological variation of hold time is performed to investigate the process-related crack influence factors. A combination of numerical and experimental investigations confirms, that the extent of heat dissipation and re-heating of the sheet surface can be influenced and thus the degree of crack formation can be controlled in a targeted manner by the parameterisation of the hold time. The temperature and stress history of crack-free and crack-afflicted spot welds are analysed and a conclusion on the borders defining the LME active region is derived.