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Modelling and Simulation of the Plasma-Arc Cutting of Steel Slabs

Leadership: Dr. Arsen Narimanyan
Processor:
Project partner: IWT, Stiftung Institut für Werkstofftechnik
Stahlwerke Bremen GmbH, Stahlwerke Bremen GmbH
Time period: since 01.07.2001
Bild des Projekts Modellierung und Simulation des Plasmaschneidens von Stahlbrammen Plasma-arc cutting is one of the preferred thermal cutting processes in steel machining along with laser cutting. With this method, the cutting apart of a steel workpiece is the result of a melting or vaporisation process whereby the steel piece is smelted by the strong heating and the melt product subsequently ejected from the kerf. The heat input by the plasma beam on the surface of the material is responsible for the majority of the phenomena which occur (shrinkage of the material, material- phase transitions, mechanical deformations etc.). To obtain a quantitative description of the process it is necessary to develop a mathematical model which covers the said phenomena.
Plasmaschneider Prinzip
The modelling leads to a Stefan-Signorini problem which is described as a free boundary value problem on the time-dependent region of the solid piece of steel. The two unknowns (temperature and free boundary) in the problem can be determined as a transport equation from the equation of heat conduction with a Signorini boundary condition and the Stefan condition. The resulting, coupled system is analysed and simulated with the aid of variation inequations and level set theory.

An extension of the model also includes thermo-elastic plasticity and solid-solid phase transitions in the material close to the cut. Models and simulation programs for these effects are already being developed in the SFB 570 sub-projects, c.f. Sections "Mathematical Investigations of Processes with Distortion" and " Multiple Scale Modelling of Phase Transitions, Distortion and Distortion Potential ". This time-dependent coupled problem also leads to complex computations. Three-dimensional computations which also especially take into account the elastic-plastic effects require the computational resource of a cluster.