曲轴激光喷丸强化试验研究

采用实验的方法,研究了激光冲击强化对175A型柴油机曲轴疲劳寿命的影响,取得了激光冲击强化试验条件下曲轴过渡圆角处残余应力场的数据。并将激光冲击强化工艺效果和曲轴滚压强化效果做了对比性分析,结果表明：虽然激光冲击强化效果不如曲轴滚压强化,但考虑到激光工艺参数精确可控、加工质量好、成本低以及可避免滚压强化所造成的表面疲劳、撕痕等,激光冲击强化工艺可望代替滚压强化成为新型的曲轴强化手段。通过此类激光冲击强化强化实验可优化激光冲击的相关参数,使曲轴过渡圆角产生有利的残余应力场。     

表面强化件的疲劳强度分析及金属的内部疲劳极限

本文通过对喷丸，渗氮及碳氮共渗试样疲劳行为的研究，提出了金属内部疲劳极限的概念，指出内部疲劳极限约为表面疲劳极限（一般意义上的疲劳极限）的１．３５倍，并利用这个概念分析了表面强化件的疲劳强度。     

弹簧表层优化喷丸残余应力场的工程计算方法

以往多是依靠疲劳试验或经验来选择弹簧的喷丸强化工艺参数，这种传统作法不仅人力和物力耗费大，而且所确定的工艺参数也不一定具有最佳的强化效果。依据作者提出的并已获得试验验证的“内部疲劳极限理论”，提出一种通过工程计算获得达到预先规定疲劳强度应具备的“优化残余应力场”。这样便有可能把喷丸强化工艺技术在制造业中的应用由以往单纯依靠试验和经验而步入到以工程计算为基础与少量典型试验相结合的更科学的途径。     

高能喷丸过程中的物质转移现象

采用高能喷丸技术在铝合金表面制备出纳米晶结构层，利用金相显微镜（OM），扫描电子显微镜（SEM／EDS），透射电子显微镜（TEM）及X射线衍射仪（XRD）等设备对高能喷丸铝合金表面层的显微结构及成分进行分析。结果表明：在高能喷丸表面纳米化过程中，弹丸中的Fe，cr原子在强制机械力的作用下转移进入铝合金表面，在材料表层约30μm的深度范围内形成分布不均匀的合金化层。这可能是纳米晶体中大量界面的形成使合金元素原子能够快速扩散和偏聚的结果。     

Evaluation of Surface Residual Stresses in Friction Stir Welds Due to Laser and Shot Peening

The effects of laser, and shot peening on the residual stresses in friction stir welds (FSW) has been investigated. The surface residual stresses were measured at five different locations across the weld in order to produce an adequate residual stress profile. The residual stresses before and after sectioning the coupon from the welded plate were also measured, and the effect of coupon size on the residual stress relaxation was determined and characterized. Measurements indicate that residual stresses were not uniform along the welded plate, and large variation in stress magnitude could be exhibited at various locations along the FSW plate. Sectioning resulted in significant residual stress relaxation in the longitudinal direction attributed to the large change in dimensions in this direction. Overall, laser and shot peening resulted in a significant reduction in tensile residual stresses at the surface of the specimens.     

表面完整性对马氏体不锈钢疲劳性能的影响

研究了马氏体不锈钢表面喷丸强化后表面粗糙度，表面形貌，表面残余应力和表面层残余压应力场等表面完整性的变化及其对疲劳性能的影响，结果表明：马氏体不锈钢对表面粗糙度比较敏感，经喷丸强化后产生的残余压应力有利于提高疲劳寿命，且采用低喷丸强度时对疲劳性能更加有利。     

钛合金表面高能喷丸纳米化后的组织与性能

通过光镜、扫描电镜、硬度仪和透射电镜对TC4钛合金表面高能喷丸纳米化后的金相组织、晶粒尺寸、显微硬度进行测试分析。结果表明,处理后材料表面平均晶粒尺寸达到了纳米量级;在横截面上沿深度方向的晶粒细化程度逐渐减小;随距被处理表面距离增加,硬度增加程度越来越小;随处理时间延长,表面硬度有增加的趋势。并对其纳米化机理进行了讨论。     

Surface nanocrystallization of commercial pure titanium by shot peening

The surface nanostructures of commercial pure titanium was realized by the modified shot peening equipment commonly used in industry through the special treatment process. The results show that high-energy-shot-peening(HESP) commonly used to prepare nanostructured surface layers can be achieved by the increase of pill size, pill speed, and treatment time in the commercial shot peening equipment. XRD, SEM and TEM were used to characterize the surface layer microstructure of treated specimens. The analytic results show that the main deformation mode of commercial pure Ti is twinning. At the beginning of deformation, the dislocations are formed and twins occur within or on plane, then twins in intersection plane appear, and at last the twin characteristics disappear in the surface layer after longer treatment time. The deformation layer depth increases with treatment time in a certain period when the pill size and speed are unchanged. And in the severe plastic deformation (SPD) layer in which the twins are not identified easily by using SEM, the nanocrystalline microstructures are found under TEM. The finest grain size in the surface layer is about 40 nm, and the depth of nanostructured layers is over 60 μm. The microhardness of the nanostructured surface layers is enhanced significantly after shot peening compared with that of the initial simple.     

NUMERICAL SIMULATION OF CONTROLLING IN TITANIUM ALLOY SHEETS WELDING RESIDUAL STRESS BY TRAILING PEENING

It is a promising and new technology to apply welding with trailing peening to control welding stress and distortion of titanium alloy. Numerical simulation of conventional welding and welding with trailing peening of the titanium alloy sheet is carried out, using nonlinear finite element theory and the engineering analysis software MARC. The result shows that welding with trailing peening technology reduces longitudinal residual stress in welding joint effectively, and it is more effective to reduce residual stress to peen the weld than to peen the weld toe. It is a effective result that other technolooy and method used in welding can never achieved.     

TC18超高强度钛合金喷丸残余压应力场的研究

采用X射线衍射及相应交相关定峰法，通过电解抛光逐层测定了TC18超高强度钛合金喷丸的残余压应力，并分析了残余压应力场的特征及规律，同时研究了在交变应力和温度下残余压应力的松弛，结果表明，残余压应力场中的最大值为材料的本征参数，它与喷丸强化工艺无关，这对超高强度钛合金喷丸工艺的制定和应用具有重要意义。