Development of thermo conductive analysis simulation in order to aid laser welding of dissimilar metals

本研究选择钢和铝合金作为异种金属的组合。开发了边界元分析程序。通过分析得到激光焊接条件，假设界面处发生固/液相反应。在边界元分析预测的条件下，对钢与铝合金的接头进行了焊接。在接头界面处形成了Fe和Al之间的金属间相。接头的强度由这种金属间相控制，因为这种相具有较差的力学性能。即使在界面处存在脆性反应层，增大结合面积也可能是提高接头破坏载荷的一种途径。边界元分析表明，改变接头形状和/或在焊接区使用触点垫可以控制界面温度分布，增加结合面积。采用边界元法对焊接工况进行了预测。通过界面处的拉伸试验和截面观察，可以看出接头和粘结区破坏载荷的增加。基于上述界面状态假设的边界元模拟也预测了键合面积的大小。总之，本研究开发了异种金属激光焊接的计算机辅助方法，并证明了其可行性。

Steel and aluminum alloy were chosen as a combination of dissimilar metals in this study. Boundary element analysis program was developed. Laser welding condition was obtained by the analysis, assuming of solid state / liquid state reaction at the interface. A joint between steel and aluminum alloy was welded under the condition predicted by BEM analysis. Intermetallic phase between Fe and Al was formed at the interface of the joint. Strength of the joint was controlled by this intermetallic phase, because this phase has poor mechanical properties. Even if brittle reaction layer exists at the interface, increase of bonded area could be a way to improve failure load of the joint. According to BEM analysis, change of shape of joint part and/or applying contact pad at welding zone can control temperature distribution at the interface and increase bonded area. In this case also, the welding condition was predicted by BEM analysis. Increase of failure load of joint and bonded area was recognized by tensile test and cross-sectional observation at the interface. The BEM simulation with assumption of interface state as mentioned above also predicted the size of bonded area. In conclusion, the computer aiding method for dissimilar metals laser welding was developed and its availability was shown in this study.