飞机结构件连接孔制造技术

孔结构是机械零件常见的细节结构，存在显著的应力集中，成为许多零件疲劳失效的裂纹起源。针对该结构开展包括直接芯棒冷挤压、开缝衬套冷挤压、激光冲击强化、喷丸强化及部分新技术研究的进展分析，从结构适应性、强化效果、尺寸保障等3个维度对比上述技术的特点，为针对性选用适宜表面强化工艺提供参考。结果表明：直接芯棒冷挤压工艺简单，其疲劳强化效果最佳，孔结构尺寸保障效果好，适用于两侧无干涉的孔结构强化；开缝衬套冷挤压强化采用C型衬套并需进行后加工以保障挤后孔径，工艺过程相对复杂，但其工艺特性适用于应力集中敏感材料制造的单侧干涉孔结构；激光冲击和喷丸强化影响层深度明显低于冷挤压强化，适用于光线可达或能够使茅枪伸入、实现弹丸反射的孔结构。

Experimental investigation and fatigue life prediction for 7475-T7351 aluminum alloy with and without shot peening-induced residual stresses

Hole structure is the most common detail structure of mechanical parts, which has become the crack origin of many fatigue-failed parts because of its significant stress concentration. As for this structure, the research progress analysis on direct mandrel cold expansion, split sleeve cold expansion, laser shock peening, shot peening and some innovative techniques was carried out, and the characteristics of the above techniques were compared from three dimensions, including structural adaptability, strengthening effect and size assurance, providing a reference for selecting appropriate surface strengthening processes. The results show that the process of direct mandrel cold expansion is simple, with the best fatigue-strengthening effect reported and the good effect of hole structure size assurance, and it is applicable to the hole structure without interference on both sides. The split sleeve cold expansion adopts C-type sleeve and requires post-processing to ensure the hole diameter after expansion. This process is relatively complex, but it is suitable for the hole structure with unilateral interference made of stress-concentration-sensitive materials due to its special process characteristics. The influenced layer depth of laser shock peening and shot peening is obviously lower than that of cold expansion, indicating that they are applicable to the hole structure which light can reach or the gun can reach to achieve shot reflection.