Analysis of welding on angular distortion and residual stresses in AZ31B magnesium alloy

• Main Authors: Ching-Ying Shih, 石晶瑩
• Other Authors: Ching-Min Cheng
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/68528102758594042629

碩士 === 國立臺灣師範大學 === 工業教育學系 === 95 === This study was to investigate the fundamental characteristics of the temperature and stress fields in bead-on-plat during welding process. The thermo-elastic-plastic theory and the thermo-mechanical coupled elements were employed in this analytical model with temperature dependent material properties. A two-dimensional model using ANSYS finite element method was designed to estimate the magnitude and distribution of the temperatures, thermal stresses, and residual stresses in weldment. The theoretical considerations can be divided into the thermal and mechanical model. AZ31B magnesium alloy were used as test specimens, which were welded with an GTAW. The thermal cycle temperature while welding with the thermocouple record, and cool to the room temperature, quantity examines its angular distortion amount. The analytical results were compared with the experimental data containing temperatures and angular distortion. Because of the heat source is concentrated locally, the temperature fields adjacent to the heat source are rather steep. The transient thermal stresses are in compressive state since the expansions of these regions are restrained by surrounding cold metal that is at lower temperatures. As the heat source had passed by, the fusion zones have been cooled and hence have a tendency of contraction. A great tensile residual stress was produced in solidified welds, and then rapidly decreased to zero over a distance several times the welded zone. In a situation that restrained conditions are different, the residual stress of non-restrained condition is small than the restrained one. In a situation that weld the speed differently, the speed of the residual stress of welding quickly is small than the slow one. There is a fairly good agreement between theoretical analysis and experimental results using the finite element method.