界面摩擦对5A02/SUS304覆层板胀形性能影响的理论及有限元分析

针对成形板与覆板之间的界面摩擦对成形过程的影响,采用理论分析和有限元方法对不同润滑条件下5A02/SUS304覆层板胀形过程进行了分析。得到了不同界面摩擦条件下胀形试件的经向拉应力和等效应力的变化规律。研究结果表明,胀形试件高度低于单层成形板极限胀形高度时,由于成形板与覆板的变形规律相似,界面摩擦对成形板的影响较小;胀形试件高度大于单层成形板极限胀形高度时,由于成形板与覆板变形规律相差较大,界面摩擦对成形板的影响较大;较大的界面摩擦系数有助于成形板经向拉应力的降低和胀形性能的提高。     

摩擦对汽车零件拼焊板成形行为影响

为了提高拼焊板成形性能,通过改变成形过程中模具与板料之间的摩擦以控制其成形特征。以极限胀形高度试验为研究对象,采用理论方法分析了摩擦系数对拼焊板成形行为影响的力学机制。结合试验和有限元法研究了摩擦系数对拼焊板极限胀形高度、焊缝移动及应变分布等的影响。结果表明:摩擦系数对拼焊板成形行为有显著影响,随着摩擦系数的增大,极限胀形高度先增大后逐渐减小,而焊缝移动量则一直减小,拼焊板主应变分布逐渐变得均匀;当摩擦系数增大到一定值时,极限应变位置突然从焊缝临近位置转变为距焊缝约30.0mm位置的薄侧母材上,拼焊板失效模式发生了变化。     

摩擦对汽车零件拼焊板成形行为影响

为了提高拼焊板成形性能,通过改变成形过程中模具与板料之间的摩擦以控制其成形特征.以极限胀形高度试验为研究对象,采用理论方法分析了摩擦系数对拼焊板成形行为影响的力学机制.结合试验和有限元法研究了摩擦系数对拼焊板极限胀形高度、焊缝移动及应变分布等的影响.结果表明:摩擦系数对拼焊板成形行为有显著影响,随着摩擦系数的增大,极限胀形高度先增大后逐渐减小,而焊缝移动量则一直减小,拼焊板主应变分布逐渐变得均匀;当摩擦系数增大到一定值时,极限应变位置突然从焊缝临近位置转变为距焊缝约30.0 mm位置的薄侧母材上,拼焊板失效模式发生了变化.     

铝合金板温成形过程拉深筋部位摩擦系数的测试

基于板料成形时法兰区周向收缩、厚向增厚的特点和温成形的环境,针对铝合金板温成形过程拉深筋部位摩擦系数的测量,研制了一套新型摩擦测试装置.探讨了压边力、成形温度、润滑状态三种工艺参数和铝合金板试样楔形角对拉深筋部位摩擦系数的影响.研究表明,成形温度和润滑剂对摩擦系数影响比压边力明显;当不采用润滑剂时,随着成形温度从室温上升到250℃,摩擦系数有明显的增加;在高温状态下,三种润滑剂的使用,都可以大大降低温成形时的摩擦系数,但这三种润滑剂之间的润滑效果差异并不明显;在不同楔形角的铝合金试样成形过程中,拉深筋部位的摩擦系数随着角度的增大而增大.     

镁合金板温成形过程模具圆角部位摩擦系数的实验研究

利用自行研制的新型摩擦测试装置,对镁合金板温成形过程模具圆角部位摩擦系数进行了测试实验.通过正交实验,研究了温度、压边力、润滑状态等三种工艺参数对模具圆角部位摩擦系数的影响,并采用统计方法对所得到的数据进行了分析,确定了影响摩擦系数的主次关系和最优工艺参数组合.研究结果表明:三种工艺参数中,温度因素的影响最为显著,压边力因素影响一般,而润滑因素影响最小;最优工艺参数组合为温度240℃、压边力3MPa和二硫化钼润滑.     

板成形中摩擦系数测定的研究进展

本文阐述了摩擦系数在板成形中的作用及板成形中摩擦系数测定的国内外的发展状况 ,采用作者设计的新型摩擦系数测定装置进行了摩擦系数测定的实验研究 ,为进一步开展摩擦系数测定及摩擦边界的研究打下了基础 ,为有限元模拟的真实性提供了重要的参考依据。     

铝合金板温成形过程中拉深筋处摩擦的测量

在温成形过程中铝合金板与模具表面的接触和摩擦行为十分复杂,不同的接触区域摩擦状况不尽相同.分析了板料成形中摩擦测量的国内外发展状况,采用自行设计的新型摩擦测量装置完成了铝合金板温成形过程中拉深筋处摩擦系数的测量.该测量装置的特点是可以模拟板料的真实变形过程,采用楔形铝合金板试件,通过楔形槽产生周向挤压,来模拟法兰区板料成形时的增厚趋势,添加了加温和温控装置来模拟温成形时的温度环境,从而获得更为准确的测量结果.     

铝合金板温成形过程摩擦在线检测系统的研究

介绍并分析了对板料成形过程摩擦问题研究的发展与现状。设计出一种用于动态测量板料成形真实过程摩擦系数的探针传感器,并在此基础上开发出铝合金板料温成形过程摩擦在线检测系统。利用该系统进行了铝镁合金板(5182)筒形件温成形过程摩擦在线检测,得到了合理的实验结果。     

润滑条件对拉延筋部位钢板表面摩擦系数的影响

借助拉延珠模拟试验机,分析了6种冲压润滑剂对5种汽车板料成形时拉延筋处摩擦系数的影响。结果表明：不同润滑剂对不同汽车板料成形时拉延筋处的摩擦系数的影响程度不同;随着润滑剂的运动粘度的增加,板料的摩擦系数相应降低;5种板材中电镀锌预磷化板的摩擦系数最低。     

基于平板滑动摩擦实验的镀锌板摩擦特性研究

利用平板滑动摩擦实验研究了模具粗糙度、正压力以及滑动速度对合金化热镀锌板表面摩擦系数的影响规律,结合摩擦学理论对摩擦系数变化的原因进行深入的分析,采用光镜观察钢板摩擦后的截面形貌,对比不同实验条件下的锌层截面失效情况,进而验证摩擦系数变化规律的正确性。结果表明,模具粗糙度在0.4μm~1.2μm范围时,摩擦系数随着模具粗糙度的增加先减小后增大,模具粗糙度约0.8μm时最佳,此时锌层发生少量粉化失效;摩擦系数随着正压力增加而减小,在较高压力范围内减小的趋势变缓,随着正压力增加,锌层粉化与剥落失效加重;摩擦系数随着滑动速度增加而减小,当滑动速度增加到一定值时,摩擦系数减小的趋势变慢并趋于稳定,随着滑动速度增加,锌层粉化与剥落失效情况转好。     

齿面微织构面积率及形状对其摩擦性能的基础研究

为研究齿面微织构面积率和形状对齿轮副摩擦学性能的影响,采用激光打标机在经热处理后的45钢试件表面加工出不同形状和面积率的织构,利用往复式摩擦磨损试验机分析织构面积率和形状对摩擦因数的影响规律,并与Fluent仿真结果进行对比。仿真结果表明：随着织构面积率的增大,摩擦因数逐渐减小,油膜承载力和油膜刚度逐渐增大,长方形织构具有更佳的减摩性能。试验结果与仿真结果基本一致,与无织构表面相比,长方形织构面积率为17%时平均摩擦因数降低了18.06%,正方形和圆形织构面积率为4.7%时,不仅没有减摩,反而将摩擦因数分别增大了4.17%和1.39%。织构化表面可提高油膜承载力和刚度,使油膜不易破裂,减小了摩擦副之间的接触,降低了摩擦因数。获得了微织构形状和面积率对齿轮副摩擦性能的影响规律,为改善齿轮系统的寿命提供试验支持。     

摩擦系数对齿圈压板精冲剪切面光亮带比的影响

在数值模拟中分别改变板料-凸模界面摩擦系数、板料-凹模界面摩擦系数和同时改变这两个界面摩擦系数,研究减小不同界面摩擦系数变化对齿圈压板精冲剪切面光亮带比的影响规律。结果表明,减小板料-凸模界面摩擦系数获得的光亮带比最大,减小板料-凹模界面摩擦系数次之,同时改变两个界面摩擦系数的情况下光亮带比最小;当板料接触界面摩擦系数较小时,改变板料-凸模界面摩擦系数可以获得最大的光亮带比;当摩擦系数较大时,同时改变板料上下表面摩擦系数可以获得最大的光亮带比。改变板料摩擦系数可以显著扩大剪切区内静水压应力分布的范围,抑制凹模刃口附近裂纹的萌生。     

Evaluation of frictional characteristic for Zinc-coated steel sheet

Draw bead simulator (DBS) tests were performed to investigate the friction behaviors of various zinc-coated steel sheets. The friction of the coated steel sheet was evaluated by the ratio of drawing force for the coated steel sheet, T_c, to that for the uncoated steel sheet, T_s. The drawing force ratio, T_c/T_s, was compared with the coefficient of friction measured from Nine’s DBS test. It is clear that the drawing force ratio can be used as a convenient parameter to evaluate the friction of a coated steel sheet compared to the coefficient of friction. Due to the simplicity of the test procedure, this evaluation method is a useful for assessing the stamping formability of the coated steel sheet with respect to the friction behavior and also to investigate the lubricity of the stamping lubricant.     

谐波光面摩擦传动三波最小传动比的研究

用弹性理论推导出了谐波光面摩擦传动三波柔轮的特征曲线方程.根据强度理论,由曲线方程建立了谐波光面摩擦传动三波最小传动比公式,由此得到谐波光面摩擦传动三波最小传动比的设计准则--柔轮半径﹑柔轮壁厚与最小传动比的关系式.分析了影响最小传动比的诸多因素.     

Friction analysis of thermally sprayed coatings finished by ball burnishing and grinding

Thermally sprayed coatings offer a promising approach as efficient method to increase the wear-resistance of sheet metal forming tools. However, the roughness of thermally sprayed surfaces is quite high. The use of these coatings for deep drawing tools results in poor sheet surface qualities and low drawing ratios. Because it is suspected that high friction is the reason for the low drawability, hard metal coatings (WC–12Co), deposited by high velocity oxygen fuel flame-spraying, were machined by grinding and ball burnishing to improve their friction behavior and the accuracy of the tool shape. The investigation was conducted by plane strip drawing tests. Strips of high strength steel were mated with these novel and effective coatings at different normal contact pressures and drawing velocities. Uncoated friction elements made of C60 steel were considered as reference during the analysis. The results revealed that coated but unmachined friction elements showed high friction values, which led to scratch marks on the sheet surface after drawing. Applying the finishing processes, the friction coefficient could be reduced significantly. Additionally, deep drawing tests were carried out to determine the drawing ratio for coated, unmachined as well as for processed, coated dies. Thermally sprayed and ball burnished as well as thermally sprayed and ground coatings are feasible for deep drawing. Due to the post treatment, the drawing ratio β = 1.8 was increased to 2.0. This is consistent to the results of the friction tests.     

Abrasion Mechanism of Stainless Steel/Carbon Fiber-Reinforced Polyether-Ether-Ketone (PEEK) Composites

A new type of composite material, stainless steel fiber and carbon fiber-reinforced polyether-ether-ketone (PEEK), was investigated to study its friction and wear properties and mechanisms. The friction materials containing 11 ingredients were hot-pressed and tested using a pad-on-disc type wear tester under unlubricated sliding friction and wear conditions at a constant sliding speed. The worn surface morphology was observed by Field-emission Scanning Electron Microscope (FE-SEM) and Atomic Force Microscope (AFM). The role of transfer film was studied using X-ray photoelectron spectroscopy (XPS) to investigate the thermal decomposition of the friction material. The fade ratio of the composites was only 4.8%, the recovery ratio 107%, and the total wear ratio was as low as 0.99 × 10⁻⁷ cm³(N m)⁻¹, showing the perfect properties of heat stability and recovery, as well as high antiwear ability of the composites. Adherence abrasion and particle abrasion take place at higher temperature. A transfer film is formed, which may improve abrasive resistant performance to get stable friction coefficient and low abrasion value for composite friction materials.     

组合柔性机械臂抑振性能研究

将柔性机械臂做成组合结构,利用接触面间的摩擦效应消耗能量以达到抑制柔性机械臂振动的目的。以直波纹板作为组合柔性机械臂的叠层,采用有限元软件ANSYS对组合柔性机械臂进行静态和动态仿真。用能量耗散率作为组合柔性机械臂迟滞性能评定指标。研究结果表明:与直板作为叠层的组合柔性机械臂相比,用波纹板作为叠层的组合机械臂可以用较少的材料获得较好的抑振性能;选择合适的预紧力和结构尺寸参数可得到最佳的抑振性能。     

表面织构润滑减摩的国内外研究现状及进展

表面织构是源自于自然界生物非光滑表面的微纳米结构,这些微观结构使得生物在进化过程中呈现出优异的自润滑和抗磨减摩性能.国内外研究也一致表明,表面织构是改善表界面摩擦学特性的一种有效手段,可使材料表面实现自润滑效果,并且能够减少摩擦磨损带来的机械设备提前失效和能源耗损.从表面织构的形态特征及其作用机制出发,对近年来表面织构在润滑减摩方面的国内外研究现状及进展进行调研分析.讨论了表面织构形状(规则织构、不规则织构等)、织构分布形式(全织构分布、部分织构分布等)、织构几何参数(深度、面积比、深径比等)、工况参数(载荷、速度等)等因素,对织构化表面润滑减摩性能的影响,同时总结了表面织构润滑减摩作用机制研究中面临的难题.提出未来应重点开展极端工况、混合润滑状态下多类型复合织构的润滑减摩作用机制,考虑动态磨损的表面粗糙度与织构协同作用润滑减摩规律和仿生微织构与涂层耦合作用下抗磨性能等方面的研究,从而进一步推动表面织构在润滑减摩领域的工程应用.     

T-shape upsetting–extruding test for evaluating friction conditions during rib–web part forming

Since the deformation features of existing friction testing methods are not as similar as those of the closed die forging process of rib–web parts, the friction conditions evaluated by these methods are not consistent with the actual situation. In this paper, a new friction testing method, the T-shape upsetting–extruding process employing a rectangular blank, is proposed for evaluating the friction conditions during rib–web part forming process. It was found that rib height and the web width are both sensitive to friction conditions. Therefore, the ratio of rib height to web width was chosen as a criterion for friction evaluation. With the utilization of a commercial FEM program, DEFORM, the effects of the geometrical parameters and testing variables on the friction sensitivity were investigated, and the friction conditions between different interfaces were analyzed. In order to verify the proposed method, friction factors of a water-based graphite lubricant measured by three different methods (the proposed one, the ring compression test and the double-cup extrusion test) at 723 K were used to simulate the isothermal deformation process of a cross-rib part. The experimental results suggest that the proposed method is more accurate than the other two methods for rib–web part forming process.     

楔形长板辊轧过程中工艺参数的模拟优化

为了获得综合性能良好的某7A04铝合金楔形长板辊轧件,结合其复杂的形状结构特点,提出采用整体辊轧成形的工艺方案。通过在轧辊上开设一定形状的孔型,用来成形出满足尺寸要求的轧件。并对所提出的工艺方案进行有限元模拟,在控制其他工艺参数不变的条件下,通过模拟不同温度、辊轧角速度、摩擦系数条件下辊轧力的大小变化情况,总结出不同工艺参数下辊轧力的变化规律。最终确定了合理的辊轧工艺参数为:温度470℃,辊轧角速度0.1 r·s~(-1),摩擦系数0.7,且工艺试验得到的辊轧件与有限元模拟得到的辊轧件形状尺寸基本一致。