【作者】 王伟；

【导师】 张永康；

【作者基本信息】 江苏大学 ， 机械制造及其自动化， 2008， 硕士

【摘要】 激光冲击打标是一种新型的标记技术,它将激光冲击和激光标记很好地结合起来。本文从激光打标技术的分类出发,介绍了几种不同的激光打标技术,分析了激光打标技术的基本原理,并对激光冲击打标过程进行了实验研究和数值模拟,论文研究的主要内容如下:通过改变激光脉沖能量、约束层等,以6061铝合金和AZ91镁合金为研究对象,设计了不同的激光冲击打标实验方案。对于6061铝合金材料,用水为约束层,黑色涂层为吸收层,从实验结果可以得出随着激光能量的增加,标记区域的深度和残余应力值逐渐增加,在材料发生塑性变形的同时,由于位错运动、增殖、滑移使内部的位错密度急剧增加,使材料表面的强度和硬度显著增强;对于AZ91镁合金材料,考虑到水对镁合金的腐蚀作用,选用K9玻璃为约束层,铝箔为吸收层,山于等离子的屏蔽效应,标记区域的深度并没有随着激光能量的增加而逐渐增加,由于金属表层承受冲击时发生了激烈的塑性变形,标记区域的硬度有了明显的提高。在实验研究的基础上,基于ANSYS/LS-DYNA建立了激光冲击打标的三维有限元模型,通过激光诱导的冲击波的加载,进行了打标的数值模拟。模拟结果表明,激光冲击波作用后的标记区域网格形成了与载荷直径相仿的凹坑,其残余应力均表现为压应力,随着形变量的逐渐增加,在标记中心残余压应力达到最大值;板厚方向的残余压应力随着板厚的增加而不断减小;变形量的大小与残余应力大小存在一定的对应关系。最终将实验与模拟结果进行对比,二者基本相符合。更多还原

【Abstract】 Laser shock marking is a novel technique which combines of laser shock with marking. Starting from classification of laser marking, the paper introduces several different laser markings and analyses the principal of laser markings. Experimental studies and simulation were carried out on laser shock marking. In this paper, the main contents were as following:Through the changes of laser pulse energy and the material of constrained layers, the experimental schemes of laser shock marking with 6061 Al alloy and AZ91 Mg alloy were designed. For 6061 Al alloy, using water as the constrained layer, black coating as the absorption, the results show that as the amount of the laser energy increases, depth and residual stress of marking zone increases gradually. While plastic deformation occurs, strength and hardness of the material surface increases significantly because dislocation density increases rapidly due to dislocation motion, proliferation and slip. For AZ91 Mg alloy, considering water corrosion to Mg alloy, using K9 glass as the constrained layer, aluminum foil as the absorption, the depth of marking zone does not increase with the increasing of laser pulse energy because of shielding effect of the plasma. Hardness of the material surface increases significantly because of plastic deformation on the material surface.In order to study distributing of residual stress and distortion on the basis of experiments, a FEM model of marking by laser shock waves based on ANSYS/LS-DYNA was established in this paper. By loading the shock waves induced by laser, a numerical simulation on marking had been carried out. The simulated result shows that the mesh of marking zone acted by laser shock waves forms a crater with dimension similar to the diameter of the load, and its residual stress is compressive stress. As the amount of the deformation increases gradually, the residual compressive stress in the center of marking zone reaches the maximum; the residual compressive stress along the thickness of the plate declines as the thickness increases.更多还原