大厚度焊接结构残余应力分析测试及超声冲击处理影响研究

Analysis of Residual Stress in Large-thickness Welded Structure and Effect of Ultrasonic Impact Treatment

为了解核电典型大厚度焊接结构残余应力分布特征,明确超声冲击处理对焊接残余应力的调控效果,采用XRD法、小孔法和轮廓法分析了不锈钢厚板接头在焊态及超声冲击状态下表层与内部应力的分布规律。结果表明:焊态焊缝区域上下表面的应力(距上、下表面0、2 mm)大于内部应力,横向应力从上表面到下表面为拉伸应力-压缩应力-拉伸应力典型分布形式。轮廓法可实现厚度方向上的应力分布全貌测试,沿厚度方向内部纵向应力为拉伸应力,峰值在距上表面8 mm处,幅值达到420 MPa左右。超声冲击处理对结构表层的纵向和横向焊接残余应力具有显著调控作用,表面呈现为压缩应力,焊缝区内部纵向应力则仍保持拉伸应力,内部横向应力在距表层1~3 mm处由焊态原始拉伸应力转变为压缩应力,达到焊材屈服强度的87%,而冲击区域外的焊接残余应力受影响较小。

In order to understand the residual stress distribution characteristics of typical large-thickness welded structures for nuclear power,and investigate the effect of ultrasonic impact treatment on the regulation of weld residual stress,the surface and internal stress distributions of stainless steel thick plate joints were measured by the XRD method,the hole-drilling method and the contour method,which were used to compare the difference between the weld state and the ultrasonic impact state.Results show that the stress in the top surface and bottom surface of the weld state(the region of 0 and 2 mm)is greater than the internal stress.The measured transverse stress at the weld centerline exhibits a trend of tensile stress-compressive stress-tensile stress from the top surface to bottom surface and the longitudinal stress within the thickness direction is tensile stress.The contour method can realize the overall test of the stress distribution in the thickness direction.The peak value appears at the weld centerline with an 8 mm distance below the top surface and the measured stress is about 420 MPa.Ultrasonic impact treatment has a significant regulatory effect on the surface longitudinal and transverse welding residual stress of the structure,the top surface presents as compressive stress and the internal longitudinal stress at the weld centerline is still maintained tensile stress.The internal transverse stress as the original tensile stress within the region of 1-3 mm is transformed from tensile stress,which reaches 87%of the yield strength of the weld material.However,ultrasonic impact treatment has little effect on the welding residual stress outside of the impact zone.