Stability and Relaxation of Welding Residual Stresses
Stability and Relaxation of Welding Residual Stresses
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焊接残余应力的稳定和松弛
DOI：
10.4028/www.scientific.net/msf.681.55
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
K. Dilger
中科院分区：
文献类型：
--
作者：
M. Farajian;T. Nitschke–Pagel;K. Dilger
研究了小型钢对接焊试件在静态和循环载荷作用下的残余应力松弛。实验在屈服强度在300和1200 MPa之间的不同类型的钢上进行。应用X射线和中子衍射技术对残余应力进行了分析。初始残余应力的最大值是在焊缝中心线处测得的，并且不像通常假设的那样与材料的屈服强度一样高。从疲劳的角度来看，焊趾处的内应力是重要的。据观察，只有一小部分的最大残余应力容纳在焊缝中心线，可在焊趾。在静态拉伸和压缩载荷下，随着载荷水平的增加，残余应力场不断松弛。在压缩条件下，由于应首先克服拉伸残余应力，因此松弛开始延迟。在循环荷载下，一旦第一次松弛发生，进一步的循环松弛要么不显著，要么根据荷载条件适度地继续。在高循环疲劳中，残余应力在2x106次循环之前是稳定的。然而，在低周疲劳中，残余应力的变化持续到失效。这种变化部分与裂纹的萌生和扩展有关。以局部屈服强度作为材料塑性变形抗力的von Misses失效准则能够描述低周疲劳中表面焊接残余应力的松弛。
Residual stress relaxation of butt-welded small scale steel specimens under static and cyclic mechanical loading was investigated. The experiments were carried out on different types of steel with yield strengths between 300 and 1200MPa. The x-ray and neutron diffraction techniques were applied for the residual stresses analysis. The maximum values of initial residual stresses were measured at the weld bead centerline and were not as frequently assumed as high as the yield strength of the material. From fatigue point of view the internal stresses at the weld toe are of importance. It was observed that only a fraction of maximum residual stress accommodated in the weld bead centerline, is available at the weld toe. Under static tensile and compressive loading by increasing the load level the residual stress field relaxes continuously. The relaxation sets in with delay under compression since the tensile residual stresses should be first overcome. Under cyclic loading, once the first relaxation takes place further cyclic relaxation is either not considerable or continues moderately depending on loading conditions. In high cycle fatigue the residual stresses are stable until 2x106 cycles. In low cycle fatigue however the variation of the residual stresses continues until failure. This variation is partly related to crack initiation and propagation. The von Misses failure criterion with the local yield strength as material resistance against plastic deformation was able to describe the relaxation of surface welding residual stresses in low cycle fatigue.