激光冲击强化是一种先进的材料表面抗疲劳制造技术，本文采用正交试验方法研究了激光冲击2050铝锂合金表面残余应力分布规律，获得了优化的激光冲击参数，并在此参数下验证了疲劳寿命增益。研究结果表明：激光冲击强化诱导的残余应力与试样的几何特性相关性较强，而激光冲击参数本身搭接率对残余应力的影响大于激光能量、大于冲击次数，最佳工艺参数为激光功率密度5.30 GW·cm^-2、搭接率50%、2次冲击。采用此参数冲击后260 MPa和200 MPa应力水平下疲劳寿命分别提高了22%和63%。

激光冲击强化(Laser Shock Processing)又称激光喷丸(Laser Peening)是一种新型表面强化技术, 是利用高功率密度(可达GW/cm2)、短脉冲(ns量级)激光辐照材料表面时, 材料表面的表面吸收层(涂覆层)吸收激光能量发生爆炸性汽化蒸发, 产生高压(GPa)等离子体, 该等离子体受到约束层的约束爆炸时产生高压冲击波, 作用于金属表面并向内部传播。在材料表层形成密集、稳定的位错结构的同时, 使材料表层产生应变硬化, 残留很大的压应力, 显著的提高材料的抗疲劳和抗应力腐蚀等性能。介绍了激光诱导等离子体的原理、激光在材料表面诱导冲击压力模型、激光冲击致材料表层纳米化、激光冲击诱导等离子体强化技术应用于钛合金和铝合金在航空工业中的应用, 并对该技术的国内外研究现状进行了阐述及展望。

利用脉宽30 ns的钕玻璃激光器对7050铝合金紧固孔进行激光冲击强化, 采用先强化材料表面, 再钻紧固孔的方式对双联疲劳试件进行强化, 并在飞机中机身随机载荷条件下进行疲劳试验。试验结果表明: 激光冲击强化后的紧固孔的疲劳寿命比未强化紧固孔的疲劳寿命提高1.5 倍, 强化后紧固孔的裂纹均起裂于次表层, 且出现多个疲劳裂纹源。疲劳增益主要得益于激光冲击强化后紧固孔周围为残余压应力分布, 强化表层的较小的冷作硬化程度, 以及超高应变速率塑性应变引起的高密度位错, 激光冲击强化技术可有效提高小尺寸紧固孔的疲劳寿命。

In order to meet high pulse laser output, the laser shock power supply based on insulated gate bipolar transistor (IGBT) inverter technology, constant current-constant voltage charger mode, high voltage pulse spark, and high pulse current discharger technology is designed. The master oscillator stage and two amplifier stages for xenon flash lamp spark and discharge circuits are designed in this power supply. The voltage of energy storage capacitors can be adjusted from 1 000 to 3 000 V. A variety of measures, such as FREE and Q-switch mode, trigger signal delay, water confining layer control, cooling water control are provided for laser shock processing technology optimization.

Laser shock processing (LSP) is an innovative surface treatment technique with high peak power, short pulse, and cold hardening for strengthening metal materials. This process induces intensive plastic deformation and deeper compressive residual stress and improves the surface performance of materials. The titanium alloy of TC4-DT is the important materials in many industry fields including aviation, which is used widely on hole and welding structure. However, the researches of surface treatment on TC4-DT welding structure using LSP technology are seldom reported by now. The performances of TC4-DT, including mircrohardness and surface profiles, are improved through the technology of LSP.

采用脉宽30 ns，能量40 J的调Q掺钕玻璃激光对TC4 钛合金钨极惰性气体(TIG)焊焊缝进行了1～3次的激光冲击强化(LSP)处理，并与未经LSP处理的焊缝的表面显微硬度、焊缝微观组织、接头的拉伸力学性能和拉伸断口的扫描电镜(SEM)照片进行比较，研究LSP处理次数对TC4 钛合金TIG焊焊缝组织性能的影响。结果表明，LSP能够使焊缝横截面靠近材料表面的区域针状α′相数量减少，热影响区靠近材料表面的区域细小等轴晶数量增加；随着LSP处理次数的增加，TC4钛合金 TIG焊接头表面的显微硬度增加；焊接接头的抗拉强度和屈服强度变化不明显，而断后延伸率出现降低趋势。

The fatigue properties of laser peened aluminum alloy 7050 specimens with fastener holes were investigated. The surface profile and residual stress induced in the shock affected zone were characterized. Then, the fatigue specimens with notch were treated by laser peening (LP), and the fatigue lifes of LP-treated specimens were measured and compared with base materials without LP. The results indicated that LP improved the fatigue lifes of all tested specimens. The average fatigue lifes of specimens treated by LP before hole-drilling were 173% longer than those of untreated samples and had better effects than those specimens treated by LP after hole-drilling.

对1Cr11Ni2W2MoV马氏体不锈钢进行了激光冲击处理(LSP)的基础性研究。激光器最大输出能量为50 J,激光功率密度3.7～7.5 GW/cm2。吸收层和约束层分别选取Al箔和均匀流水层,激光束采用倾斜入射方式,实验对单光斑试样、搭接光斑试样、疲劳试样分别进行冲击。通过表面形貌、显微硬度和残余应力等检测,验证了激光功率密度对冲击区性能的影响。三组疲劳试件进行对比表明,先冲击后打孔试件的疲劳性能最好,其表面高幅值的残余压应力层能很好地抑制疲劳裂纹的萌生和延长裂纹扩展的速率。实验证明激光冲击处理可以有效提高马氏体不锈钢的疲劳性能。