激光冲击对小孔疲劳寿命的影响_毕业设计论文.doc

安徽工业大学 毕业设计论文 激光冲击对小孔疲劳寿命的影响 Effect of laser shock processing on fatigue life of fastener hole 学院 机械工程学院 专业 机械设计制造及其自动化 摘 要 激光冲击改性与延寿技术是利用方向.能量高度集中的激光束作为工具，对材料进行表面改性或延寿。该技术将现代物理学.化学.计算机.材料科学.先进制造技术等多方面的成果和知识进行综合运用，对构件的选择.设计.制造有重大影响。 铝合金小孔是构件上典型的应力集中结构细节，在交变载荷作用下极易产生疲劳裂纹，造成疲劳断裂。故本文采用激光冲击强化技术，通过对比分析，采用强化效果更好的先激光冲击后开孔的工艺方法。通过实验与数值模拟分析研究了不同激光冲击下小孔区域的残余应力场及其疲劳性能，并对疲劳断口进行了相应分析。 研究过程为：首先以abaqus软件为平台，制定了小孔强化数值模拟总体思路，通过对激光冲击工艺参数进行理论分析，提出激光冲击参数的优化区域，以功率密度，脉冲宽度，光斑直径，冲击次数为研究对象，系统分析在其单独改变时对残余应力场的影响。 然后通过对疲劳断口的观察，来分析材料抗疲劳性能的强弱。最后通过仿真分析式样开孔前后残余应力场和冲击前后的疲劳性能得出光斑搭接处理对疲劳寿命的影响。 关键词：激光冲击处理，疲劳寿命，数值模拟，残余应力场，疲劳断口，铝合金小孔 ABSTRACT Laser shock modification and life-extending technology is the use of the laser beam highly concentrated in the direction and energy as a tool for surface modification or extension of the material. The technology make the comprehensive use of modern physics. Chemistry. Computer. Materials science.advanced manufacturing technology and other aspects of Results or knowledge.and it has a significant impact on component selection.design manufacturing. Aluminum alloy holes are the typical locations of stress concentration which easily generate fatigue cracks under cyclic loading and yield fatigue rupture.so this text use the laser shock peening technology.through the comparative analysis.the better process of LSP before hole-drilling was adopted to study the residual stress field of fastener holes at different parameters and its fatigue property by the methods of experiments and simulations,and fatigue fracture were analyzed. The research process is as following:based on the FEM code ABAQUS,the general idea of Numerical simulation to strengthen holes was set.by the LSP parameters was analyzed,and then presented the optimizing region of LSP parameters.Then,selected the power density,pulse width,spot diameter and shot numbers as the research object,without considering the interaction between the shock parameters,the effect of l