弯管异常起皱的成因分析

指出由于制管过程操作不当，致使管坯局部产生了异常的压应力和压应变，形成“反光带”，并在“反光带”处出现弯管异常起皱。根据“反光带”厚度和硬度的微小变化形态，运用应力-应变理论揭示出在“反光带”处弯管异常起皱的成因，即:当积聚在“反光带”内的残余压应力和残余压应变与弯曲时内侧圆弧处产生的压应力及塑性压缩变形相互叠加后，导致弯曲圆弧内侧管壁上承受的压应力和压应变超过管壁自身变形抗力及壁厚增厚所能承载的塑性变形量时，管壁被压溃，进而失稳起皱。

Analysis on Reasons Caused by Bend Abnormal Wrinkle

In this article, it pointed out abnormal pressure stress and compressive strain occur in part tube blank caused due to misoperation during bend manufacturing course, which came into reflective band, and bend abnormal wrinkle appear in reflective band. According to the thickness of reflective band and tiny changing shape of hardness, the reason caused by abnormal wrinkle in reflective band was revealed by stress-strain theory. When the residual stress gathered in reflective band, the residual compressive strain, the pressure stress generated in inside arc and plasticity compressive deformation superimposed to cause the pressure stress and compressive strain exceeding deformation resistance of pipe wall and plastic deformation, the pipe wall will be squashed, and then become unstability and wrinkle.