Abstract

Correction method for microstructure effect on residual stress of self-reacting friction stir weld joint measured with longitudinal critically refracted wave was discussed in this study. Two longitudinal critically refracted wave transducers, the spacing between which was fixed, were used, then the acoustoelastic formula was optimized, and difference in time of flight between longitudinal critically refracted wave, which replaced propagation velocity as characteristic parameter for residual stress measurement, was determined by the cross correlation theory, at last the influence of microstructure on residual stress of self-reacting friction stir weld joint was solved. Results show that as stress increases, the deviation in difference in time of flight becomes obvious, and when stress reaches stress turning point, experimental result is not agreed with the acoustoelastic theory as stress increases further. Step length is an important factor for difference in time of flight, and one cycle is seen as optimal step length. For acoustoelastic coefficient, the value of nugget zone is biggest, and the value of (heat affected zone + thermal mechanical affected zone) is smallest, in addition, the value of advancing side is slightly bigger than that of retreating side. Finally, residual stress of self-reacting friction stir weld joint was corrected with longitudinal critically refracted wave, and the result is verified by hole-drilling.

中文翻译：

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L cr波对SR-FSW接头残余应力测量的微观结构影响的校正

摘要

研究了用纵向临界折射波测量自反应搅拌摩擦焊缝残余应力对显微组织影响的校正方法。使用两个间隔固定的纵向临界折射波换能器，然后优化声弹公式，确定纵向临界折射波之间的飞行时间差，该传播速度代替传播速度作为残余应力测量的特征参数通过互相关理论，最终解决了微观结构对搅拌摩擦自焊接接头残余应力的影响。结果表明，随着应力的增加，飞行时间差的偏差变得明显，当应力达到应力转折点时，随着应力的进一步增加，实验结果与声弹性理论不一致。步长是影响飞行时间差异的重要因素，一个周期被视为最佳步长。对于声弹性系数，熔核区的值最大，（热影响区+热机械影响区）的值最小，此外，前进侧的值略大于后退侧的值。最后，通过纵向临界折射波校正了自反应摩擦搅拌焊缝的残余应力，并通过钻孔验证了结果。熔核区的值最大，（热影响区+热机械影响区）的值最小，此外，前进侧的值略大于后退侧的值。最后，通过纵向临界折射波校正了自反应摩擦搅拌焊缝的残余应力，并通过钻孔验证了结果。熔核区的值最大，（热影响区+热机械影响区）的值最小，此外，前进侧的值略大于后退侧的值。最后，通过纵向临界折射波校正了自反应摩擦搅拌焊缝的残余应力，并通过钻孔验证了结果。