有限元分析热物理参量对焊接残余应力峰值特征的影响

利用非线性有限元方法对平板TIG焊进行了数值模拟.使用随温度变化的材料热物理参量,采用双椭球热源模型,研究了热导率、比热容及密度三个热物理参量对焊接残余应力的影响.结果表明,热导率降低可使焊接残余应力升高,纵向残余应力峰值会从双峰特征过渡到单峰特征;比热容降低可使焊接残余应力峰值降低;密度增大可使焊接残余应力增加,纵向残余应力峰值的双峰效应逐渐减弱;因此,热导率、比热容和密度3个参量是导致铝合金纵向焊接残余应力峰值比屈服极限低以及焊缝附近呈现双峰分布特征的重要原因.使用切条释放法对材料参量为2024—T4的铝合金平板中纵向焊接残余应力模拟结果进行试验验证,模拟结果与试验结果吻合良好,证明了模拟结果的正确性.

Effect of thermophysical parameters on the hump feature of welding residual stress by finite element analysis

Numerical simulation of TIG welding of thin plate by thermo-elastic finite element method (FEM) was conducted. By double ellipsoid thermal source,thermophysical parameters varying with temperature were used to compare the influence of heat conductivity,specific heat capacity and density on the welding residual stress. The result shows that the drop of the heat conductivity will lead to the increment of the welding residual stress,and the longitudinal residual stress transits from the double hump to the single one; the falling of the specific heat capacity can also reduce the welding residual stress,which can greatly be affected by the difference of density between aluminum alloy and mild steel,and the double hump of the longitudinal residual stress will disappear with the density increasing. Then the three thermo-physical parameters,heat conductivity,specific heat capacity and density,make the longitudinal welding residual stress of aluminum alloy is lower than its yield limit and appears double hump effect near the weld seal. The welding longitudinal residual stress for the flat plates of 2024-T4 aluminum alloy is simulated by using cutting pieces stress relieving method. The simulation results are well accordant with the test ones,which prove the validity of the simulation results.