随焊加载冷源或位移控制载荷的无应力焊接方法

应用一维杆模型论证了随焊加载冷源或位移控制载荷实现无应力焊接的原理. 应用数值模拟探讨了其实现方式，对7种加载方案下杆件中心点应力、塑性应变等物理量的时程分布进行了数值模拟对比研究，认为任意时刻外加位移控制载荷产生的机械应变和热输入满足一定条件时焊后残余应力为零. 随焊降低残余应力的工艺在焊件局部区域产生的变形速率与该局部区域的热膨胀或收缩变形量速率大小相同时，降低残余应力的效果达到最优. 应用模型导出的原理对焊前预拉伸、焊前温差拉伸、动态温差拉伸、低应力无变形焊接(LSND)等工艺的原理和参数设置依据进行了讨论. 结果表明，使焊件内部在冷却时产生足够大的拉伸塑性应变，是降低焊接残余应力的有效途径.

Principle of stress-free welding with cold source or displacement-controled load

The principle of the stress-free welding with cold source or displacement-controled load was demonstrated by using one-dimensional rod model. The numerical simulation experiment was used to discuss the way to realize the welding method. The time history distributions of physical quantities such as stress and plastic strain at the center point of the bar under seven loading schemes were numerically simulated and compared in detail. It was considered that the welding residual stress would be zero when the mechanical strain generated by the external displacement-controled load and thermal input at any time satisfied certain conditions. The best residual stress reducing effect was obtained when the deformation rate produced by the process of reducing residual stress with welding is the same as that of thermal expansion or thermal shrinkage in the local area. Based on the principle derived from this model, the principles and parameter setting basis of process, such as pre-stretching, pre-welding thermal tensioning, dynamic thermal tensioning and low stress and non-deformation (LSND), were discussed. It is an effective way to reduce welding residual stress by generating a large enough tensile plastic strain when the weldment is cooled.