转速对高压扭转Cu试样的组织与性能的影响

通过高压扭转(HPT)技术在不同转速条件下实现了Cu试样的晶粒细化.利用光学显微镜(OM)、透射电镜(TEM)及显微硬度计观察并测试了组织的结构与性能,并基于有限元计算了变形诱导试样的温升,研究了转速对Cu试样的组织细化与性能的影响.结果表明:转速由1/3 r·min-1增大至1 r·min-1,经1圈扭转变形,试样温度由40.8℃升高到54.1℃,变形组织均为100～600 nm的高位错密度位错胞/亚晶组织,显微硬度由初始态的52HV0.05增大至140 HV0.05;经16圈扭转变形,试样温度由50.4℃升高到97.4℃,组织细化到200 nm.慢速扭转变形试样晶内位错密度高,微观组织处于严重变形状态;而快速扭转试样晶内衬度均匀,位错较少,微观组织经历明显的动态回复,显微硬度较慢速扭转变形试样低6%.     

滚珠丝杠扭转变形对机电综合传动刚度的影响

机电综合传动刚度影响数控机床的定位精度,正确计算此传动刚度是机床设计的前题,传统设计方法中忽略了扭转刚度的作用.应用力学方法对比分析了丝杠扭转变形与拉压变形的关系,结果表明,当丝杠的导程与直径的比值足够大时,扭转变形对传动刚度会有显著的影响.     

焊接扭转变形的试验研究

通过对扭转变形的动态观测，研究了焊接扭转变形的机理，为进一步搞清构件形式，工艺参数对焊接扭转变形的影响提供了依据。     

楔横轧轧件扭转变形影响因素的研究

应用ANSYS/LS-DYNA有限元软件,对楔横轧轴类件进行轧制过程的模拟,分析了轧件扭转变形的形成原因,总结出成形角、展宽角、断面收缩率、摩擦系数及模具脱空宽度对轧件扭转变形的影响规律,指出采用脱空模具是降低轧件扭转变形的最有效措施.本研究为合理确定楔横轧工艺参数,改善轧件的质量提供了重要的理论依据.     

扭转预变形对定向凝固DZ4合金低周疲劳寿命的影响

对定向凝固DZ4合金进行扭转预变形和热处理后的高温低周疲劳寿命与断裂行为进行测试与研究,分析不同的扭转变形程度、变形速率等对低周疲劳寿命和再结晶的影响,研究沿晶特征区的形成机制.结果表明,定向凝固DZ4合金在扭转预变形和热处理后其低周疲劳寿命急剧下降,分析发现与塑性变形区产生的再结晶组织有关.再结晶区与基体变形不协调导致在再结晶与基体界面处出现损伤和裂纹,裂纹沿再结晶晶界扩展形成沿晶特征区,使高温低周疲劳寿命下降,且疲劳寿命随着再结晶深度的增大而急剧降低.扭转预变形程度较小时,低周疲劳断口上的沿晶特征区的深度与断面沿再结晶区扩展的深度一致;扭转预变形程度较大时,沿晶特征区的深度相对较小.另外,应变速率增大,加剧了不协调变形,再结晶具有局部化倾向,且再结晶程度增加,使高温低周疲劳寿命下降更严重.     

Al—Li合金高温扭转变形行为

在Ｇｌｅｅｂｌｅ２０００热模拟机上对一种２０１９Ａｌ－Ｌｉ合金进行高温扭转试验,研究了合金扭转时的等效应力－应变关系和扭转变形组织特征,研究结果表明：合金表现出与压缩变形类似的稳态流变特征,扭转等效应力随变形温度的升高和应变速率的降低而减小;其变形过程属于受位错速率机制控制的热激活过程,等效应力、等效应变速率和温度之间基本上满足以曲正弦函数关系,扭转等效应力随变形温度的升高和应变速率的降低而减小。     

T2纯铜扭转挤压成形有限元数值分析

通过Deform-3D软件对T2纯铜扭转挤压成形过程进行数值分析。采用刚塑性有限元法,分析了不同模角下的挤压力行程曲线、坯料应变和温度场的变化,研究不同扭转速度对成形制品的应变和温度影响,并将扭转挤压与传统挤压成形效果进行对比。结果表明,模具模角变大,挤压力和挤压温度会变大,但坯料的变形增加,变形更均匀。与传统挤压成形相比,扭转挤压变形更加剧烈,随着扭转速度的增加,坯料的应变也增加。     

高压扭转变形对纯W再结晶行为的影响

在较低温度条件下完成了难熔金属烧结纯W高压扭转实验,通过改变扭转圈数,利用EBSD、XRD、DSC等多种检测与计算方法分析了高压扭转变形纯W在后续加热过程中再结晶组织及行为的变化。结果表明:高压扭转变形后,纯钨组织的形变储存能增大,激活能降低,但变形后组织的再结晶温度仍处于高值。DSC测试后,原始烧结组织发生明显的晶粒长大情况,而由高压扭转法(HPT)变形产生的细晶钨再结晶组织仍较为细小,平均晶粒尺寸为4～6μm,且随着扭转圈数增大晶粒尺寸未发生明显变化,变形组织的热稳定性较好。     

扭转矫正过程中的参数计算

钢材在使用辊式矫直机矫直轴向弯曲变形之前, 必须要将其扭转变形进行矫正。本文分析了金属扭转矫正过程中角度随扭矩的变化, 建立了扭转矫正时的力学模型, 并推导出扭转矫正的力学公式。     

Microstructures and compression properties of copper processed by high-pressure torsion

通过高压扭转对铜试样施加不同程度的变形, 研究了样品扭转面(ND面)和纵截面(TD面)上微观组织特征. 对ND面, 在较小的剪应变下, 原始晶粒形貌模糊, 晶粒内部形成等轴状的位错胞及亚晶结构; 随变形量的增大, 亚晶 间取向差及亚晶内部的位错密度增大, 最后形成亚微米尺度的等轴晶粒. 对TD面, 变形初期原始晶粒被拉长, 晶粒内 部为位错墙分割成的层状结构, 层内为拉长的位错胞; 随变形程度的增大, 拉长晶粒的宽度减小, 与剪切方向的夹 角减小, 晶内层状组织间距减小, 并逐渐演化成拉长的亚晶组织; 进一步增大变形, 晶粒拉长痕迹消失, 变形组织 与ND面相似, 为等轴状亚微米晶粒. 压缩实验表明, 经16圈扭转后, 整个试样上的压缩性能基本均匀, σ0.2达到385 MPa, 应变率敏感性指数增大至0.021.     

Monitoring Damage Evolution in a Titanium Matrix Composite Shaft Under Torsion Loading Using Acoustic Emission

The damage behaviors of a titanium matrix composite shaft under torsion loading were monitored using the acoustic emission technique. The composite shaft with SiC fibers at ± 45° orientations was prepared by the solid-state fabrication process. Both the torsional rigidity and torsional strength of the TMC shaft were improved by SiC fibers. The acoustic emission responses during the loading–unloading–reloading, under quasi-static and cyclic torsion tests were investigated. Multiple acoustic emission signals were grouped as mechanical noise, matrix deformation, interface debonding and fiber fracture using amplitude, waveform shape and frequency centroid parameters. A substantial reduction of signals generated by matrix deformation was found in the reloading test. During the quasi-static torsion test, interface debonding and progressive breaks of SiC fibers occurred. According to different acoustic emission behaviors, the failure process in the torsion fatigue test can be divided into three stages: the initial stage, the fiber fracture stage and the fast fracture stage.     

Influence of Torsion Deformation on Textures of Cold Drawing Pearlitic Steel Wires

The influence of torsion deformation on textures of cold drawing pearlitic steel wires was investigated by twisting the wires to different number of revolutions. Macro-texture(over the entire wire cross section) associated with torsion deformation was investigated by X-ray diffraction, while micro-texture(near the wire surface) was characterized by EBSD. The results show that the 110macro-texture increases at the beginning of torsion and then decreases with increasing of torsion strain, while the 110 micro-texture decreases linearly with increasing of torsion strain. The relationships between the 110 fiber texture and the microhardness of the wires are also discussed.     

摩托车启动主动齿轮的精密成形

通过合理分配变形程度、控制金属流动，设计出精密成形工艺的合理中间预制坯，并采用温锻制坯与冷挤压相结合的复合成形工艺，成功地进行了启动主动齿轮精锻件的生产。精锻件不仅表面光洁、尺寸精度高、外表面的后续加工余量小，而且冷挤压成形的锯齿状内齿无需后续加工就可以装配使用。因此，精密成形具有显著的节能、节材效果，经济效益十分显著。     

风电机组行星传动柔性齿圈变形特点分析

以风力发电机行星传动系统为研究对象,为揭示齿圈变形特点,将齿圈离散为多段刚性轮齿段,对每两轮齿段用理论长度为零的双向扭转弹簧及铰链连接。在行星架随动坐标系下,综合考虑支撑刚度、齿轮啮合时变刚度和齿圈柔性,建立了风力发电机行星传动系统刚-柔耦合动力学模型。分析各构件间的相对运动微位移及齿圈的受力情况,运用牛顿力学推出动力学方程;基于所建模型,分别讨论了不同扭簧扭转刚度、负载力矩、支撑点处径向支撑刚度和周向支撑刚度条件,得到了齿圈的变形特点。该结果可为风力发电机行星传动的设计提供参考。     

数控插齿机驱动箱系统综合变形下齿轮承载能力分析

以某企业YK51160C数控插齿机驱动箱系统为对象,建立了包含扭转、弯曲和横向耦合振动的驱动箱系统力学模型,分析了驱动箱系统综合变形引起的齿轮啮合错位对齿轮齿面载荷分布情况的影响,采用Romax软件基于ISO6336-1～3:1996标准,在考虑系统变形引起齿轮啮合错位的情况下,对驱动箱系统中的圆柱齿轮进行齿轮承载能力分析。结果表明驱动箱系统中的圆柱齿轮的强度均满足要求,为YK51160C数控插齿机驱动箱系统的进一步分析、优化提供了参考。     

Effects of continuous cast section size on torsion deformation and fatigue of induction hardened 1050 steel shafts

This study investigates the influence of continuous cast section size on the mechanical performance of induction hardened parts produced from steel bars. SAE 1050 steel from commercially produced Jumbo Blooms, Blooms, Rotary Round, and Billet were hot rolled into round bars with diameters of 37-44 mm. These bars were then normalized, machined into test specimens, the gauge sections were polished, and the specimens were case-hardened by induction hardening. Torsional monotonic and fully reversed cyclic fatigue tests were conducted to study the effect of the initial continuous cast section size on deformation and fatigue behaviors. Reduction ratios in this study ranged from a low of 20.4:1 for the Billet, up to a high of 142:1 for the Jumbo Bloom. Test results indicate that the continuous cast section size has only small effects on the torsion monotonic and cyclic deformation properties and negligible effect on the torsion fatigue performance. Small differences observed in deformation and fatigue properties between the four processes are attributed mostly to the variation in case and core hardness levels caused by small differences in chemistry, particularly carbon content. Variations in sulfur content also influence ductility and fatigue behavior. At high strains, the cracks initiated in shear as longitudinal cracks for all four materials. At low strains, the cracks initiated at the surface in tension as spiral cracks due to normal tensile stresses.     

板材多点成形设备中基本体的调平技术

介绍了板材多点成形设备基本体的结构特点，提出了加压调平法。在对基本体调平时，通过施加压力消除机械间隙及弹性变形等因素对基本体高度的影响，提高了基本体调平的精度。此外，还论述了通过控制伺服电机转矩来实现基本体调平的方法。     

球面磨床专用夹具非线性接触夹紧性能分析

运用ANSYS Workbench对球面磨床的专用夹具部件进行多工况的非线性接触分析,研究夹具各个零件之间的接触状态,分析夹具整体结构和球体的变形量、极限应力、扭转角度以及结合面之间滑移量,确定夹紧螺栓预紧力,校核夹紧机构的可靠性。此方法为球面磨床专用夹具的设计与校核提供参考。     

带滚珠丝杠齿轮自动脱螺纹机构的压铸模

铸件螺纹脱模是压铸模设计的难点之一.自动旋转脱螺纹一般采用齿轮-齿条机构或液压-齿轮机构.本压铸模则采用一种新机构--滚珠丝杠-齿轮脱螺纹机构.该机构利用压铸机推杆为螺纹型环旋转脱模提供动力,通过滚珠丝杠-齿轮机构将压铸机推杆的直线运动,转变为螺纹型环旋转运动,实现螺纹铸件自动脱模.