PPREDICTION OF FREE BOUNDARY IN SOLIDIFICATION ANALYSIS BASED ON INTEGRAL PENALTY METHOD AND ALE CONTROL

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In order to describe the phase change in metals, particularly welding and solidification, the following investigations are carried out ; 1. Fundamental study of numerical analysis in free boundary problem, 2. Development of numerical code based on so-called "Integral Penalty Method, " and 3. Mechanical properties of phase boundary and heat affected zone in welding process in metals.1. Fundamental study of numerical analysis in free boundary problem Regarding the welding and solidification processes as the Stefan problem, the governing equations are formulated in terms of spatial description as well as material description. The Stefan condition at the free surface boundary is replaced by the integral form by use of the integral penalty method, and so this method is advantageous for real utilization in numerical analysis.2. Development of numerical code based on the integral penalty method A finite element code for predicting the Stefan problem is developed with reference to the integral … More penalty method. Numerical studies are carried out to clarify the stability condition between the penalty number, the spatial step, and the time increment. A two-phase/two-dimensional problem is also calculated to demonstrate the applicability of the proposed method.3. Mechanical properties of phase boundary and heat affected zone A one point weld processing is performed on a circular plate of SUs304 stainless steel, and the temperature history is evaluated through the process. Both the hardness and the microstructure change remarkably at the phase boundary, particularly at the heat affected zone where the temperature comes across the AC1 transformation point, and so the phase boundary can be identified from these tests. A welding process is performed for an aluminum plate, from which a small size specimen is prepared for a tension test. Microgrid indentation is used to measure the local deformation over the weld. The strain distribution is calculated from the displacement of the movement of the grids. Less