The effects of blast cleaning (BC) and stress relief annealing (SRA) on butt joints were investigated. BC leads to a significant increase in fatigue strength due to insertion of compressive residual stresses and cold work hardening at the surface. Additional SRA leads to a decrease of fatigue strength down to the as-welded state. It is shown that the SRA not only leads to a decrease of compressive residual stresses but also to a decrease of cold work hardness at the surface. This shows that SRA is not an appropriate method to show the effect of the reduction of residual stresses in service of mechanical post weld treated weld seams since surface hardness is decreased as well. SRA of as-welded specimens did not lead to an increase in fatigue strength. It is shown that compressive residual stresses and surface hardness are stable under high tensile loads and high cycle numbers. Fatigue tests were accompanied by strain gauge measurements to identify the structural hot-spot stresses in correlation to axial and angular misalignments. A parametric FE model was used to calculate the stress concentration factors and compared to the measured stresses. Angular misalignment shows good correlation with stress increase compared to nominal stresses.

中文翻译：

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用于海上风电支护结构的 S355J2+N 结构钢制成的抛丸清理和应力消除退火对接接头的疲劳强度


研究了喷砂清理 （BC） 和应力消除退火 （SRA） 对对对接接头的影响。BC 由于在表面插入压缩残余应力和冷作硬化，导致疲劳强度显着增加。额外的 SRA 会导致疲劳强度降低到焊时状态。结果表明，SRA 不仅导致压缩残余应力的降低，而且导致表面冷作硬度的降低。这表明 SRA 不是显示机械焊后处理焊缝服务中残余应力减少效果的合适方法，因为表面硬度也会降低。焊时试样的 SRA 不会导致疲劳强度增加。结果表明，在高拉伸载荷和高循环次数下，压缩残余应力和表面硬度是稳定的。疲劳测试伴随着应变片测量，以确定与轴向和角度不对中相关的结构热点应力。参数有限元模型用于计算应力集中因子，并与测得的应力进行比较。与名义应力相比，角度错位与应力增加具有良好的相关性。