Numerical prediction of edge cracks during multi-pass hot-rolling of an AlMg4.5Mn alloyThursday (09.11.2017) 15:20 - 15:40 Part of:
The mechanical loading conditions at the edge of an ingot during hot-rolling differ considerably from those at the center. Massive thickness reductions lead to either convex or concave shapes of the edge, depending on the initial shape and process parameters. Additionally, adjacent to the edge, tensile stresses favour decohesion of intermetallic particles from the aluminium matrix. As a consequence, the heavily deformed edges have to be trimmed after hot rolling. Suboptimal rolling schedules may even provoke edge cracks which cannot be easily removed by trimming. In a constant effort to minimize material losses due to trimming and to evite the occurrence of edge cracks, process engineers have gained considerable experience on this issue. The industry’s need for even more precise optimizations leads to an increasing demand for reliable numerical methods.
The purpose of this contribution is to share recent results on the numerical prediction of edge deformation and edge cracks with the help of a Finite-Element model. The model has been specifically developed to investigate the deformation at the edge of an ingot and it allows the efficient simulation of industrial multi-pass hot-rolling. A user-defined material model for ductile failure has been implemented in the commercial LS-Dyna Finite-Element software. The model is based on the microscopic mechanism of nucleation, growth and coalescence of voids. The microstructure as well as the mechanical properties of an AlMg4.5Mn-alloy have been characterized experimentally and the experimental characterization has been used for model calibration. Special emphasis is put on the fracture behavior at high temperatures. The numerical predictions of edge shape and cracking agree well with results from the industrial process. The role of individual process parameters in relation to edge deformation is discussed.
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