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    Numerical simulation of high-frequency induction welding in longitudinal welded tubes
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2019) Asperheim, John Inge; Das, Prerana; Grande, Bjørnar; Hömberg, Dietmar; Petzold, Thomas
    In the present paper the high-frequency induction (HFI) welding process is studied numerically. The mathematical model comprises a harmonic vector potential formulation of the Maxwell equations and a quasi-static, convection dominated heat equation coupled through the joule heat term and nonlinear constitutive relations. Its main novelties are twofold: A new analytic approach permits to compute a spatially varying feed velocity depending on the angle of the Vee-opening and additional spring-back effects. Moreover, a numerical stabilization approach for the finite element discretization allows to consider realistic weld-line speeds and thus a fairly comprehensive three-dimensional simulation of the tube welding process.
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    A model for resistance welding including phase transitions and Joule heating
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2010) Hömberg, Dietmar; Rocca, Elisabetta
    In this paper we introduce a new model for solid-liquid phase transitions triggered by Joule heating as they arise in the case of resistance welding of metal parts. The main novelties of the paper are the coupling of the thermistor problem with a phase field model and the consideration of phase dependent physical parameters through a mixture ansatz. The PDE system resulting from our modelling approach couples a strongly nonlinear heat equation, a non-smooth equation for the the phase parameter (standing for the local proportion of one of the two phases) with quasistatic electric charge conservation law. We prove existence of weak solutions in the 3D case, while the regularity result and the uniqueness of solution is stated only in the 2D case. Indeed, uniqueness for the three dimensional system is still an open problem.