Study on Improvement of Fatigue Strength Reliability in Machine and Structure by Laser Peening Treatment

它通过赋予高功能性能来提高机器和结构的疲劳强度可靠性，有利于减轻重量、降低能源、减少材料和提高效率。在本研究中，对机械和结构材料进行了激光强化（LP）处理，目的是提高材料的疲劳强度可靠性，并明确提高材料疲劳强度可靠性的机理。采用无保护涂层的低能量YAG激光器在水中进行激光处理。汽车零件用铸造铝合金和高强度工具钢。研究得出的主要结论如下：1。在所研究的所有材料中，均证实LP处理能提高材料的疲劳强度。结果表明，LP处理的改善效果是由材料表层的压缩残余应力和应变硬化引起的。结果表明，低压处理对预裂材料的疲劳裂纹扩展具有抑制作用，其抑制作用主要是由残余压应力和裂纹尖端附近塑性变形引起的裂纹闭合效应引起的。利用同步辐射设备的微计算机断层扫描（μ CT）成像技术，成功实现了表面疲劳裂纹的无损三维可视化。

It is useful for the reducing of weight, energy, materials and the high efficiency to improve the fatigue strength reliability of machines and structures by giving high functional property. In the present research, the laser peening (LP) treatment is performed on machines and structural materials, and it is the porpose of the research to improve the fatigue strength reliability in the materials and to make clear the mechanism of the improvement The laser treatment of low energy YAG laser without protective coating is wsasused in water The materials used in the research a were austenitic stainless steels for nuclear plant structures, cast aluminum alloy for automobile parts and high strength tool steels.The main conclusions obtained in the research are as followings1. In all of the materials used in the research, it is confirmed to improve the fatigue strength by the LP treatment. And it is clear that the improvement effects were induced from compressive residual stress and the strain hardening in the surface layer of materials by the LP treatment.2. The restrained effects for fatigue crack propagation process were confirmed for the pre-cracked materials by the LP treatment And, the effects were induced from the compressive residual stress and the crack closure effect by plastic deformation near crack tip by the LP treatment.3.By the micro computed tomographic (μ CT) imaging technology with syncroton radiation equipment, surface fatigue cracks were successfully visualized non-destructively and three-dimensionally.