边界约束对中厚板焊接残余应力的影响

基于已有试验数据及有限元模型计算结果,对约束、自由边界下中厚板焊接残余应力进行了数值模拟,通过改变热、力学边界,得到了焊前预热、焊后热处理,力学约束程度、约束距离改变对不同外边界焊接残余应力的影响。结果表明：预热将显著降低热影响区残余应力,约束条件下母板残余应力的降低与预热温度成正相关,自由边界残余应力基本不受预热影响；焊后热处理使得高温非线性区(焊缝及热影响区)纵、横向残余应力降低,约束条件下横向应力在整个母板表面改变明显,而自由状态下纵向应力仅在板边缘发生波动；约束增强仅增大应力值,不改变应力分布趋势；板端约束对残余应力的影响存在单向性,横向约束的改变对纵向残余应力的影响可以忽略；约束大小保持不变,约束距焊缝的远近程度的改变对近缝区残余应力的影响较小,有限元计算在保证一定精度的前提下可以适当的减小建模尺寸以提高求解速率。

The Influence of Boundary Constraint on Residual Stress of Plate Welding

Based on the existing experimental data and the calculation results of finite element model, the residual stress of plate welding under the constraint and free boundary was simulated numerically.The results show that the residual stress in the heat-affected zone is significantly reduced by preheating, the reduction of the residual stress in the mother plate under the constraint condition is positively correlated with the preheating temperature, and the residual stress in the free boundary is basically not affected by preheating.Post-weld heat treatment reduces the longitudinal and transverse residual stress in the high temperature nonlinear zone (weld seam and heat affected zone). Under the constraint condition, the transverse stress changes significantly on the surface of the whole motherboard, while the longitudinal stress only fluctuates at the edge of the board in the free state.The constraint enhancement only increases the stress value, but does not change the stress distribution trend.The influence of plate end constraint on residual stress is unidirectional, and the influence of transverse constraint on longitudinal residual stress can be ignored.The size of the constraint remains the same, and the change of the distance from the constraint to the weld has little influence on the residual stress in the near-seam area. The finite element calculation can reduce the modeling size appropriately to improve the solution rate under the premise of ensuring a certain accuracy.