激光冲击+机械喷丸复合强化对铆接件微动疲劳性能的影响

Effect of Laser Shock Peening and Shot Peening Composite Strengthening on Fretting Fatigue Performance of Riveted Piece

研究机械喷丸、激光冲击+机械喷丸复合强化2种表面强化技术对铝合金铆接构件微动疲劳行为的影响。利用微动磨损实验机、疲劳实验机、X射线衍射仪、激光共聚焦显微镜、场发射扫描电镜等设备,测试表面强化技术对铝合金表面完整性、耐磨性、疲劳性能和微动损伤特征的影响。结果表明:机械喷丸、激光冲击+机械复合强化均可提升铆接件微动疲劳性能,机械喷丸提高12倍,复合强化提升5.4倍。表面强化处理改变疲劳裂纹源位置,原始件裂纹萌生于铆接件圆孔30°左右,喷丸强化后裂纹在圆孔接近90°位置萌生。复合强化的残余压应力层深度为1.00 mm,远大于机械喷丸的0.25 mm。总体上,复合强化效果不理想,这是由于激光冲击技术不便于在小尺寸的铆接孔实施,同时强化过程连接孔变形,影响服役性能。

The effect of shot peening as well as laser shock peening and shot peening composite strengthening on the fretting fatigue behavior of aluminum alloy riveted pieces was studied.The effect of surface strengthening technology on the surface integrity,fretting wear resistance,fatigue properties and fretting damage characteristics of aluminum alloy was studied with fretting wear test machine,fatigue test machine,X-ray diffractometer,laser confocal microscope,and field emission scanning electron microscope.The results show that shot peening as well as laser shock peening and shot peening composite strengthening can improve the fretting fatigue performance of riveted pieces,with the fretting fatigue life increasing 12 times after shot peening and 5.4 times after composite shot peening strengthening.The surface strengthening treatment changed the location of the fatigue crack source.The crack initiation location of the original riveted piece was about 30°in the round hole of the riveted piece,and changed to nearly 90°after shot peening.The depth of residual compressive stress layer of composite shot peening strengthening is 1 mm,which is much deeper than that of shot peening,0.25 mm.Overall,the strengthening effect of composite shot peening is not ideal.This is because laser shock technology is not easy to implement in the riveting holes of small size.In addition,the strengthening process induced the deformation of the connecting holes,affecting the service performance.