压力容器环焊缝局部短错边装配应力数值分析

The numerical analysis for the assembly stress in the local short fault of a vessel girth joint

针对1台乙二醇不锈钢蒸发器封头与筒体之间存在的局部错边,现场采用强制组对焊接完成制造,由此产生了装配应力。经检测分析表明,此应力是诱发焊缝区域产生晶间应力腐蚀开裂失效的原因之一。运用有限元方法,通过建立3-D壳单元模型对局部错边强制组装后产生的装配应力进行模拟分析,分别对相同错边长度不同错边量、相同错边量不同错边长度等多种情况进行分类分析讨论。其分析结果表明,经过强制组装后的环焊缝在最大错边处的邻近区域存在较大装配应力且分布具有明显的局部性。错边角度越小、错边量越大,其装配后的峰值应力越高。错边角度较小时,采用3-D模型更能准确地描述应力分布。

For the appearance of the fault in local girth weld seam of a glycol evaporator, the forced assembly and then welding were carried out, the induced assembly stress was one reason of intergranular stress corrosion crack （IGSCC）. Using FEM and based on the theory of thin shell, more effective 3-D models were builtand were applied in the assembly stress analysis, varied fault magnitude for the same fault length and varied fault length for the same fault magnitude were all analyzed. The result showed that the maximum stress appeared in the maxi fault field of the girth joint after forced assembly ,the stress distribution showed apparent locality and the smaller the fault angle or the bigger the fault magnitude is the higher the peak value of the stress after assembly. For the problem of small fault angle, it is preferred in describing the assembly stress distribution to develop a 3-D analysis model.