多层焊焊接应力分布对管子局部热处理应力释放准则的影响

Effect of Residual Stress Distribution in Multi-Pass Welding on Stress Relief Criterion in Local Post Weld Heat Treatment of Pipe

采用有限元方法构造了轴对称模型下多层焊应力分布 ,用粘弹塑性有限元方法对管子多层焊后不同局部热外理条件下应力分量的分布情况进行了研究 .结果表明 ,管子内、外侧残余应力和加热宽度表现出不同的规律 :管子外侧的残余应力随加热宽度的增加缓慢下降 ;管子内侧的残余应力在较小的加热宽度下可以得到有效消除 .残余应力与加热宽度关系表现为两种类型 :一种是理想衰减型 ;另一种为局部最小型 .多层焊形式下的残余应力与加热宽度的关系表现为后一种型式 .加热宽度 2 B=5 Rt较为合理 .过大的加热宽度对局部热处理应力释放的作用不大 .最后 ,进行了管子的多层焊和局部热处理试验 ,并采用 X-射线法对局部热处理后的应力进行了测量 .

The stress distribution in multi pass welding was generated by FEM with an axisymmetric model.The distribution of stress components under different local post weld heat treatment(PWHT) conditions,with different types of multi pass welding,was studied using visco elastic plastic FEM.The results show that the welding residual stress on the outer surface and on the inner surface behave quite differently with heated band width.The residual stress on the outer surface decreases slowly with the increase of the heated band width.On the contrary,the residual stress on the inner surface can be removed effectively with relatively small heated band width.The relation between the residual stress and heated band width can be divided into two types:monotonical type and local minimum type.The relation between the residual stress and heated band width in multi pass welding behaves in the latter type.The heated band width of 5 Rt is reasonable.Excessive wide heated band width appears ineffective to further reduce the residual stress.Finally,the stress after local PWHT was measured by X ray method.