热冲击下含缺陷超高压管的弹塑性有限元分析

Elastic-Plastic Finite Element Analysis of an Ultra-High Pressure Tube with Defects under Thermal Shock

含有轴向裂纹的内压管,在热冲击作用下产生的热应力会使应力场发生变化,塑性极限内压也将发生变化.对热冲击下的外壁含有缺陷的超高压聚乙烯反应管的瞬态温度场和应力场进行有限元模拟.利用扩展有限元法,得到裂纹扩展过程中裂纹尖端的应力场云图.将单独内压作用时得到的塑性破坏压力值与PCORRC(Problem Context Opinion Reason Refutation Conclusion)准则的预测值进行一致性对比,验证有限元模型和采用的损伤失效准则的有效性.在热-力耦合场中,通过对裂纹前沿各位置的单元的瞬态应力以及反应管极限内压的分析,显示出瞬态温度效应对结构的承载力影响较大.热冲击下管子内壁的自增强作用使得具有外裂纹的反应管更容易产生塑性破坏.

Internal-pressure tube with axial crack under thermal shock would generate thermal stresses,which caused the change of the stress field,as well as the change of the plastic extreme internal pressure.The transient temperature and stress fields in an ultrahigh-pressure polythene reactive tube with defects on the outer wall under thermal shock are simulated by the finite element method.Using the extended finite element method,the contour diagram of stress field near the crack tip during the crack propagation process is obtained.The plastic failure pressure obtained only under the internal pressure is compared with that predicted from the PCORRC criterion,to verify the effectiveness of the finite element model and the adopted damage failure criteria.In the thermal-mechanical coupling field,the transient stress of the elements at the crack front and the ultimate pressure of the reaction tube are analyzed.It shows that the transient temperature has a significant impact on the load-bearing capacity of the structure.Moreover,the self-strengthening effect of the inner wall of the tube under the thermal shock makes the reaction tube with external cracks more prone to plastic failure.