Research Progress of Anti-fatigue Surface Strengthening Technology for Load-bearing Hole Structure

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.