The flow behavior in a typical arc welding process is very complex and features rapid melting and solidification. In this work, the flow in the melted region was determined by the effect of surface tension, viscosity, and gravity. Two-dimensional change of the geometry of the melted region was analyzed using the MPS (moving particle semi-implicit) method to melt a small upper plate in a hole at the center of a base plate. The relation between the initial geometry of the upper plate and the surface flatness after welding was calculated. The calculation results showed that the upper plate with a triangular notch at its center minimized the surface unevenness after welding. The depth of notch and thickness of the upper plate were optimized.
In rapid thermal processing of semiconductor wafers, it is very important to keep a given temperature rising speed of the wafer during the heating process. We calculated the effect of various heating control methods on the error of the temperature rising speed of the wafer. We calculated the PID control, the control method by correcting with temperature rising speed, the control using a thermal model, the control using a prepared correlation equation, and the combined methods. We found that the combined method with a thermal model and rising speed is a good method to decrease the error of the temperature rising speed. The minimum error of the temperature rising speed at 700°C is less than 0.1°C/s during the temperature rising process of 100°C/s and the monitoring time step of 0.05 s. We calculated the effects of control-delay-time and measuring error of the monitoring temperature on the error of the temperature rising speed.
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