注塑制品的翘曲变形分析

主要讨论模具结构设计及塑化、脱模等阶段引起塑件翘曲变形的机理和相关因素.     

球铁曲轴强韧化复合处理的研究

将整体加热至奥氏体化后的柴油机１９５型曲轴进行轴颈处局部喷冷处理，可以使试验曲轴的极限弯和这到２．９４－１０＾３Ｎｍ以上。装机试验３０００ｈ后轴颈处磨损量为０．０２５￣０．０３０ｍｍ，与软氮化处理曲轴的起始耐磨性能相近。从表到里轴颈径向组织分布为孪晶马氏体→下贝氏体→上贝氏体及粒状贝氏体与心部的珠光体。在过渡区没有明显的组织突变，且下贝氏体区组织极为精细。在轴颈表面存在－２４６ＭＰａ的残余压应力，     

ZMl Mg合金的表面滚压强化SCIEI

研究了表面滚压对ＺＭ１Ｍｇ合金疲劳强度和疲劳缺口敏感度的影响。结果表明，滚压可使其光滑疲劳极限提高５７％，缺口疲劳极限提高２００％，大大降低疲劳缺口敏感度，使ｑ出现负值。ｈｃｐ的ＺＭ１Ｍｇ合金滚压时以滑移和孪生方式变形和形变强化，引入高的残余压应力，有利于提高缺口疲劳极限和降低疲劳缺口敏感度。     

超声冲击对焊接结构残余应力的影响

以Q345钢结构箱型柱为对象，研究了超声冲击工艺对焊接残余应力的影响。对电渣焊和埋弧焊两种焊缝进行了超声冲击试验，其中埋弧焊焊缝采用了全覆盖冲击和焊趾冲击两种冲击工艺。残余应力测量表明，采用冲击工艺，可以在焊缝表面一定深度(小于3mm)下产生压应力，最高测得-134MPa；焊趾冲击不但使焊趾表面产生压应力，也降低了焊缝的残余应力。对非熔透埋弧焊和熔透埋弧焊焊缝的测量结果显示，在盲孔法测量的深度范围内，超声冲击可降低焊缝最大主应力约34％～55％。     

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。     

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.     

Creep-induced local lattice parameter changes in a monocrystalline nickel-base superalloy

The γ-γ lattice mismatch of specimens of the monocrystalline nickel-base superalloy SRR 99 has been measured by a high-resolution X-ray diffraction technique for the undeformed state and after high-tem-perature creep deformation. During creep deformation beyond the minimum creep rate (total strain =0.5%), the lattice mismatches, measured in and perpendicular to the [001] stress axis, respectively, un-dergo changes in opposite directions. This reflects the buildup of a complex deformation-induced triaxial state of internal stress in the phases y and γ. The overall resolved shear stresses that act in γ and y due to the combined action of the external and internal stresses are estimated, and the conditions under which cutting of the γ phase by dislocations should occur are discussed.     

掺杂石墨/Cu钎焊接头残余应力的分布特征及中间层的作用

利用有限元方法,模拟分析了掺杂石墨/Cu钎焊接头残余应力的分布特征。分析结果表明,对接头有害的较大残余应力分布在石墨棱角距离焊缝约0.8mm处的狭小区域;降低连接温度、减少连接时间及增加钎焊压力均有利于减小接头残余应力,优化接头的界面应力状态;中间层的加入在一定程度上缓和了接头的残余应力。从缓和效果来看,Cu比Mo作中间层好,而Cu/Mo复合中间层的缓和效果最好,是较理想的中间层材料。     

浸渗工艺对SiC/Al复合材料残余气孔率的影响

采用无压浸渗法制备了SiC/Al复合材料,从浸渗动力学和工艺方法的角度探讨了浸渗保温时间和降温方式对复合材料的残余气孔率的影响。结果表明:随着保温时间的适当延长,能有效地降低复合材料的残余气孔率;连续降温优于分段降温,有利于降低SiC/Al复合材料的残余气孔率。     

钢轨内残余应力的产生及其危害

从钢轨的生产工艺和使用情况人手，分析了钢轨内部残余应力的产生原因、分布状态。结果表明：钢轨在生产和使用过程中均可以产生残余应力；钢轨内部存在大且不合理的残余应力(轨头、轨底拉应力，轨腰压应力)，将会影响钢轨的使用和落锤性能，严重时会造成线路钢轨的突发性断裂或落锤试验不合格。