Publications and presentations

This paper presents numerical calculations of welding residual stresses and the evolution of microstructure in stud joints embedded in common structural steels S235 and S355. The study deals with a numerical transient thermal modelling of stud welding using the commercial software suite SYSWELD FE. Microstructure phase fraction of Martensite, Bainite and Ferrite-Pearlite are also calculated by trajectory tracking of the thermal profile on the CCT diagram for the weld region. Thermal loading from welding as non-moving heat source is further fed into the stress solver and welding residual stresses are computed. The computational stresses are validated by comparison with stresses of XRD experimental measurements. The aim of this paper is to specify the stress distributions regarding residual stresses from the manufacturing and welding processes as well as stress states due to operational loads, which can constitute the basis of fatigue analyses.

We present a mathematical model to describe laser beam welding based on the heat equation. Since the material coeff cients depend on the temperature, this leads to a quasi-linear parabolic partial differential equation. It is our goal to prevent solidif cation cracking. We address this problem by means of optimal control. It is the intensity prof le of the laser beam which acts as the control function. The main challenge is the formulation of a suitable objective function. In particular, high velocities of the solidif cation interface need to be properly penalized in order to deal with and avoid cracking phenomena.