The fatigue performance and microstructure of polycrystalline copper treated by one (UUV1), two (UUV2), three (UUV3) passes of unconstraint ultrasonic vibration (UUV) treatment were investigated in this paper. The surface roughness, fatigue life, microstructure, and plastic strain energy before and after UUV treatment were compared. The results revealed that the surface integrity of the sample for UUV treatment higher than that of the original sample, and the microscope observation found that the grain orientation, the dislocation density, the low angle grain boundaries, the plastic strain energy of the damaged sample restored to the original state to a great extent after UUV treatment. The fatigue crack initiation life increased by 3 times after UUV3 treatment.

中文翻译：

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无约束超声振动处理下多晶铜的损伤愈合机制

研究了经过1道(UUV1)、2道(UUV2)、3道(UUV3)无约束超声振动(UUV)处理的多晶铜的疲劳性能和显微组织。比较UUV处理前后的表面粗糙度、疲劳寿命、显微组织和塑性应变能。结果表明，经过UUV处理的样品表面完整性高于原始样品，并且显微镜观察发现，受损样品的晶粒取向、位错密度、小角度晶界、塑性应变能均恢复了经过UUV处理后很大程度上恢复到原来的状态。 UUV3处理后疲劳裂纹萌生寿命提高了3倍。