Friction properties of groove texture on Cr12MoV surface

To analyze the influence of surface texture on friction properties of Crl2MoV＇, ordinary grinder and spinning technology were adopted to obtain the grooved surface morphology of samples, and then the impact of spindle speed and feed in z-direction on surface morphology in the process of spinning was studied. In addition, the corresponding friction coefficient of sample was obtained through friction and wear tests. The results show that the peak clipping and the valley filling were conducted on the grinding surface, which could improve the surface roughness effectively and make the grinding trench-type wear scar more uniform. Both the area ratio of groove and groove spacing increased initially and then decreased with the increase of the spindle speed or the feed in z-direction. As a kind of micro-process, the groove could influence the friction coefficient of sample surface, whose distribution was beneficial to the reduction of friction coefficient. Compared with the surface obtained through ordinary grinding, grooved surface morphology through spinning technology was more conductive to reduce the friction coefficient, which could be reduced by 25%. When the friction coefficient of sample was reduced to the minimum, the texture of groove corresponded had an optimal area ratio and an optimal groove spacing, 37.5% and 27.5 μm, respectively.

Anisotropic tribology and electrification properties of slidingmode triboelectric nanogenerator with groove textures

Sliding-mode triboelectric nanogenerator(S-TENG)is based on the coupling of triboelectrification and electrostatic induction,converting electrical energy from sliding motion.Introducing micro-textures into the sliding surface,and adjusting the angle between the texture and sliding direction(direction angle)may achieve performance anisotropy,which provides novel ideas for optimizing the tribology and electrification performance of S-TENG.To guide the performance optimization based on the anisotropy,in this paper,groove micro-textures were fabricated on the surface of S-TENG,and anisotropic tribology and electrification performance were obtained through changing the direction angle.Based on the surface analysis and after-cleaning tests,the mechanism of the anisotropy was explained.It is shown that the anisotropy of friction coefficient can be attributed to the changes of texture edge induced resistance and groove captured wear debris,while the voltage anisotropy is due to the variations of debris accumulated on the sliding interface and the resulting charge neutralization.Among the selected 0°–90°direction angles,S-TENG at angle of 90°exhibits relatively small stable friction coefficient and high open-circuit voltage,and thus it is recommended for the performance optimization.The open-circuit voltage is not directly associated with the friction coefficient,but closely related to the wear debris accumulated on the sliding interface.This study presents a simple and convenient method to optimize the performance of S-TENG,and help understand the correlation between its tribology and electrical performance.

Numerical Analysis of the Hydrodynamic Lubrication of Micro-grooved Friction Pair

A growing interest is given to the hydrodynamic lubricated friction pair with surface textured. Because of its relatively simple processing methods and low manufacturing costs,micro-groove has become the most valuable form of surface texture,and definitely has broad application prospects in mechanical engineering. Based on numerical simulation,the present study aims to examine the effects of surface forms and cross-section types of micro-groove on the hydrodynamic lubrication performance,and to find out the optimal structural parameter for designing logical micro-grooves. Different surface form and cross-section types are designed to maximize the texture hydrodynamic effect. The average pressure of such microgrooved surface is evaluated in detail,and the variation trends with changes of the length of micro-groove,lp,or the depth,hp,are discussed. The theoretical results show that micro-grooves with rational design contribute to the improvement of hydrodynamic lubrication performance of friction pair largely. For a specific micro-grooved friction pair,the optimal surface form and crosssection type make the lubrication performance best.

深沟球轴承织构化滚道表面润滑性能的数值分析

织构化深沟球轴承摩擦副表面的接触形式、织构形态对轴承润滑性能的影响机制尚不明确。为探究微织构对深沟球轴承椭圆接触摩擦副表面弹流润滑性能的影响,基于弹流润滑理论,考虑滚道织构对于摩擦表面间油膜厚度的影响作用,建立一种适用于深沟球轴承的织构化表面接触弹流润滑分析模型。然后,采用多重网格法进行数值计算,根据结果分析不同载荷及卷吸速度下织构深度和半径对接触表面油膜压力和厚度分布的影响规律。结果表明,摩擦副表面的润滑性能随着载荷的增大而变差,随着卷吸速度的增大而变好;织构化表面的流体动压效应则随着织构深度的增加而逐渐增大,随着织构半径的增大而逐渐减小,当典型深沟球轴承的滚道织构深度在1.5~2.7μm,半径在3~7μm范围时,织构化摩擦副表面的润滑性能表现最佳,证明适当的织构型式可有效改善深沟球轴承摩擦副表面的润滑性能。研究织构对深沟球轴承摩擦副表面的润滑特性规律,可以为椭圆接触类型摩擦副的织构化优化设计提供理论参考。

取向型微沟槽高速球铣加工制备方法及其减摩性能研究

探究直接利用高速球铣加工工艺制备取向型表面微沟槽织构的方法,并对该类型表面微织构的减摩性能进行研究.鉴于高速球铣加工工艺走刀路径灵活可变、表面材料残留几何尺寸与分布形态具备可控性的特点,利用Matlab仿真对高速球铣加工表面形貌进行预测,通过高速球铣加工试验验证仿真结果,并基于流体动压润滑理论,结合Fluent流体仿真分析与高速环-块摩擦磨损试验,对该类型表面微织构的减摩性能进行分析.当切削参数选用径向切深明显大于每齿进给量的组合时,高速球铣加工表面残留材料能够形成明显的微沟槽形貌,且微沟槽特征的取向可由球头铣刀的走刀路径进行控制;微沟槽承载能力与其取向密切相关,随着微沟槽取向角由90°减小至20°,负压区与正压区范围呈现扩大趋势,油膜内逆流效应逐渐减弱,动压效应逐渐增强,微沟槽承载能力提高了20.64%,表面摩擦系数由0.02845降低至0.02165;然而,当取向角过小时,负压区与正压区的范围过小,不能形成有效的收敛楔,微沟槽承载能力下降,表面摩擦系数上升.通过高速球铣加工工艺能够实现取向型表面微沟槽织构的可控制备,且该类表面的减摩性能与取向角α密切相关,在本文研究范围内,取向角为20°时表现出最小的摩擦系数与最高的油膜承载力.本文研究结果可为表面织构造型方法提供一种新思路,能够为满足零件表面的减摩需求提供很好的解决方法.

齿槽表面多级微织构构筑及其润湿机理

目的使外科手术器械表面具有超疏水功能,有效防止感染,解决医疗器械的清洁问题,降低设备维护成本。方法通过电火花线切割(WEDM)复合纳秒激光烧蚀在3Cr13不锈钢表面制备了亚毫米/微米多级复合织构表面,随后在表面上制备了1H,1H,2H,2H-全氟癸基三乙氧基硅烷溶液(PFDS)自组装超疏水涂层。利用台式扫描电镜和激光共聚焦显微镜观察复合织构表面形貌特征,使用接触角测量仪对水滴与复合织构表面的接触状态进行观察,并测量水滴的接触角与滚动角。利用表界面张力仪对多级织构表面黏附力进行表征。结果微米沟槽在亚毫米齿槽斜面上均布且不同高度的沟槽形状一致,方向与齿槽平行。水滴与齿槽阵列表面为Wenzel模型接触,水滴与多级结构表面为Cassie-Baxter模型接触。齿槽阵列试样最大黏附力为164.1μN,最小黏附力为123.5μN,多级织构试样的黏附力分别为77.2、47、24.1μN。结论微米沟槽的存在改变了水滴接触状态,在亚毫米尺度上水滴与表面的接触状态由Wenzel状态转为Cassie-Baxter状态,有效改善了水滴的接触性能与滚动性能。多级织构试样齿槽顶角的减小,有效减小了固液接触面积,水滴接触角最大为163.2°。

基于NSGA-Ⅱ的微槽刀具微槽位置参数优化

在GH4169高温镍基合金的切削加工中,较大的切削力和切削温度会加剧刀具磨损,降低刀具寿命。在刀具温度场合理置入微槽织构可以有效改善刀具切削性能和延长刀具寿命。对微槽刃边距、微槽长度、微槽与主切削刃所成角度进行参数优化,基于切削力经验公式建立切削力和刀具最高切削温度关于微槽位置参数的函数,借助NSGA-Ⅱ算法建立切削力和最高切削温度的多目标优化模型,经优化得到微槽刀具微槽的最佳位置参数组合为刃边距0.11mm,微槽长度1mm,角度46.1°。与原刀具相比,优化后的微槽刀具切削力和切削温度得到有效降低,具有更好的切削性能。

闸片沟槽织构对盘式制动尖叫的影响

为研究制动闸片沟槽织构对盘式制动系统制动尖叫的影响,基于摩擦自激振动理论,建立盘式制动系统普通闸片和沟槽闸片有限元模型,采用复特征值分析法研究该盘式制动系统的摩擦自激振动特性。利用该有限元模型开展沟槽的宽度和深度的参数化分析,获得其对制动尖叫的影响规律。结果表明:制动闸片与制动盘间的摩擦自激振动是导致制动尖叫发生的主要原因,沟槽型闸片对抑制制动尖叫具有明显效果;当闸片沟槽深度在5~20 mm区间内,盘式制动系统的稳定性随沟槽深度的增大而呈现逐渐降低的趋势,表明沟槽深度越小,发生摩擦自激振动的可能性越小;在沟槽宽度5~20 mm范围内,随沟槽宽度的增大,盘式制动系统的稳定性先增大后降低,在沟槽宽度为10 mm时,系统发生制动噪声的可能达到最大。

横纵有序微纹理设计的干气密封T型槽微纹理变量分析

为探究有序微纹理设计对干气密封T型槽动压效果的影响,基于气膜润滑原理,采用有限差分法,研究了微纹理排列间距、微纹理长度、T型槽基底长宽增幅、微纹理梯度倾斜角度等有序微纹理变量对密封参数的影响,并对四种微纹理的设计变量进行了对比。结果表明,T型槽的微纹理变量与T型槽的结构参数一样能改变槽的动压效应,但不改变干气密封槽型的动力学规律;微纹理变量对干气密封T型槽开启力的影响按微纹理梯度倾斜角度>微纹理排列间距>微纹理长宽>T型槽基底长宽增幅的顺序减小;对泄漏量的影响按微纹理长宽>微纹理排列间距>T型槽基底长宽增幅>微纹理梯度倾斜角度的顺序减小。研究结果对双向旋转式端面气膜密封的优化和设计具有一定的借鉴作用。

Optimization of groove texture profile to improve hydrodynamic lubrication performance:Theory and experiments

It is well known that groove texture with a careful design can be used to enhance the load‐carrying capacity of oil film under the conditions of hydrodynamic lubrication.In this study,a general parametric model was developed,and agenetic algorithm‐sequential quadratic programming hybrid method was adopted to obtain the global‐optimum profile of the groove texture.The optimized profiles at different rotating speeds are all chevrons.The numerical analysis results verified the effect of the optimization.In addition to the numerical optimization,experiments were conducted to validate the superiority of the optimized results.The experimental results show that the optimized groove texture can efficiently reduce the coefficient of friction(COF)and the temperature rise of the specimen.In particular,the optimized groove textures can achieve stable ultra‐low COF values(COF<0.01)under certain conditions.

Influence of groove surface texture on temperature rise under dry sliding friction

Parallel groove surface textures with different area densities were fabricated on ASTM 1045 steel. Friction tests were con- ducted under dry sliding condition. Temperature rise, friction coefficient and wear of both the textured and untextured speci- mens were studied. An embedded K-type thermocouple beneath the friction surfaces was employed to measure frictional tem- perature rise. The results indicated that the temperature rise of the textured specimen was obviously reduced compared with that of the untextured specimen, although the difference between the friction coefficients was not significan.. The specimen with high texture density exhibited a small temperature rise. The difference in temperature rise between the specimens with different texture densities can be primarily attributed to differences in heat dissipation and energy allocation between the tri- bo-pairs caused by the textured structure. The energy consumed by wear and plastic deformation was small in ~：omparison with the total energy input by friction, thus, the influence of these factors on temperature rise can be considered to be~ negligible.

沟槽结构对水润滑轴承润滑特性影响机制

为了研究沟槽结构对船用水润滑轴承润滑特性的影响机制,采用有限元法,通过对简化后的椭圆形沟槽的二维模型进行流体动力学CFD分析,从迹线以及涡流等方面分析沟槽结构参数对沟槽内部流体特征的影响,得到不同状态下沟槽内部的压力轮廓,并分析沟槽结构参数对水润滑轴承摩擦因数的影响和轴承的润滑机制。结果表明:沟槽的大小影响轴承间隙内流体的流通面积,沟槽的结构特征影响沟槽内的流体黏度。研究结果可为水润滑轴承优化设计提供参考。

沟槽型织构化火箭橇滑块磨损行为的有限元模拟

火箭橇系统的服役工况条件直接导致火箭橇滑块磨损,而滑块的磨损严重威胁着火箭橇系统的可靠运行和长寿命服役安全,更是制约火箭橇系统发展和应用的主要技术瓶颈。因束缚于极端服役工况条件和高昂的试验成本,以及仅通过二维模型或只考虑局部碰撞变形的模拟仿真,尚且未能克服这一问题。根据Archard磨损理论、非线性自适应几何更新和弹塑性变形等有限元分析方法及表面织构技术,建立由0Cr18Ni9Ti不锈钢滑块和U71Mn钢轨钢滑轨组成的有限元三维磨损模型,并分别对火箭橇滑块光滑表面、沟槽型织构化表面进行磨损仿真,揭示滑块磨损过程中接触面磨损、Von-mises等效应力以及接触压力等接触特征的变化。结果表明:沟槽型织构能够显著影响滑块磨损,织构密度增加促进了接触面均匀磨损,使得应力分布均匀、梯度变化平稳,缓解了应力集中,避免了长时间的剧烈磨损;接触压力也随织构密度的增加而增加,使得接触面与目标面接触紧密、间隙更小,可有效避免磨粒或磨屑引起的三体磨损。有限元模拟表明,通过恰当表面设计获得沟槽型表面织构能够显著影响磨损,也可为实现兼具减摩抗磨性与结构可设计性于一体的火箭橇滑块提供技术参考和理论支撑。

退火温度对耐热型取向硅钢组织与磁性能的影响

采用OM和EBSD技术对两种耐热型取向硅钢的微观组织进行了检测分析,研究了不同退火温度下组织的变化规律及耐热机理。结果表明:齿状辊沟槽法是在带材表层形成小晶粒组织和“缝隙”,激光照射法是在带材表层形成“V”字型沟槽。激光照射法取向硅钢耐热温度约为850℃,齿状辊沟槽法取向硅钢耐热温度约为800℃,前者耐热性更为优异。随着退火温度的升高,两种带材的损耗逐渐升高。齿状辊沟槽法取向硅钢损耗升高主要是刻痕区与两侧的Goss晶粒取向差降低所致,而激光照射法取向硅钢损耗升高可能与沟槽附近处Goss晶粒取向的变化有关。

Investigations for vibration and friction torque behaviors of thrust ball bearing with self-driven textured guiding surface

In order to improve the starved lubrication condition of rolling bearings,three kinds of textures,namely dimple,groove texture,and gradient groove texture,were developed on the guiding surface of thrust ball bearings in this study.The results show that gradient groove texture has the one-way self-driving function of liquid droplets.The root mean square(RMS)value of vibration acceleration of gradient groove textured bearing(GGB)decreased by 49.1% and the kurtosis decreased by 24.6% compared with non-textured bearing(NB)due to the directional spreading effect of gradient groove textures on oil.The frequency domain analysis showed that the textures mainly suppressed the medium and high-frequency energy of bearing vibration,and the GGB was reduced the most with 65.3% and 48%,respectively.In addition,whether the grease is sufficiently sheared has a large impact on the oil guiding effect,and the friction torque of GGB could decrease by 10.5% compared with NB in the sufficiently sheared condition.Therefore,the gradient groove texture with oil self-driven effect on the guiding surface of rolling bearing can effectively improve the lubrication condition of the bearing and thus reduce the bearing vibration and friction torque,which has a promising application prospect.

等差分布微槽平行滑动轴承油膜承载力分析

为提升平行滑动轴承的油膜承载力,在平行滑动轴承上加工了间距为等差数列的槽织构,并建立轴承的油膜模型;基于入口吸入理论和连续性方程,对轴承的油膜承载力进行解析计算。解析解表明,在各个槽都空化的前提下,与均匀分布的槽织构相比,槽间距为等差分布的槽织构能提升油膜承载力,且油膜承载力随织构等差分布的公差的增大呈抛物线形式增大。基于Fluent多相流空化模型,计算了带有等差分布微槽轴承的油膜承载力,并结合解析计算和数值计算结果分析不同因素对油膜承载力的影响。结果表明:在满足空化条件时,解析计算与数值计算结果均显示出相同规律,验证了解析计算的正确性;与均布槽织构比较,在不同压差下,等差分布槽织构最大使油膜承载力提升了32.57%,在不同槽深时,等差分布槽织构最大使油膜承载力提升了24.43%,在不同油膜厚度下,等差分布槽织构最大使油膜承载力提升了27.51%。

高副接触下沟槽形织构对40Cr表面摩擦性能的影响

目前,面面低副接触情况下织构的减摩降磨性能已经得到广泛的研究,然而针对点面高副接触下的织构对表面摩擦学性能影响的研究仍然较少。主要利用有限元仿真技术建立点面接触下仿生沟槽织构表面流体动压润滑仿真模型,通过ANSYS的Fluent模块进行求解,获取试样表面的润滑油膜承载力与织构几何参数的变化关系。用激光在40Cr试样上加工出仿生沟槽形织构,并采用销盘摩擦副,开展点面高副接触下的织构减摩性能实验研究,综合分析织构几何参数对表面摩擦性能的影响规律。结果表明:试验与仿真具有较高的一致性,随着沟槽织构宽度W和织构深度H的增加,摩擦因数呈先减小后增加的趋势;沟槽织构对改善工件表面摩擦性能具有重要影响,微织构的存在有助于实现流体动压润滑,提高表面承载力,降低摩擦因数,从而改善工件的摩擦性能。

不同刻槽纹理的水泥混凝土路面行车噪声特性分析

为了优化路表刻槽纹理,有效降低行车过程中轮胎/路面噪声,依托实际工程,开展了车载声强测试,分析了等间距横向刻槽、不等间距横向刻槽、拉毛深度和不同刻槽纹理类型对路面噪声强度的影响。研究结果表明:应关注不同刻槽工况下噪声强度的频谱分布,需重点关注连续噪声强度达85 dB(A)以上且介于2000~4000 Hz的噪声;可适当增大刻槽间距,减小刻槽深度,将噪声能量分散到更大的频率范围内,但需确保在人耳敏感的噪声强度范围内降低噪声强度;不等间距横向刻槽和浅刻槽虽然减少了轮胎/路面的声调尖峰,但增加了2000~4000 Hz的噪声强度;拉毛工艺对轮胎/路面噪声的影响很小,相比于横向刻槽,纵向刻槽没有明显的声调尖峰,整体噪声强度较为平缓。该研究成果可为优化城市水泥混凝土路面的刻槽方案提供参考,对减少城市交通噪声具有重要意义。

纳米磁性流体与表面织构对钛合金的协同减摩作用机制

目的 提高钛合金表面的摩擦学性能。方法 采用纳秒激光器在钛合金表面构造沟槽型微织构图案,并以水基纳米磁流体和去离子水为润滑剂,利用UMT-3摩擦磨损试验机探究了织构与纳米磁流体的协同减摩作用机制。结果 分析了不同润滑条件下,沟槽型织构的分布间距对钛合金表面摩擦磨损性能的影响,在织构与纳米磁流体的协同作用下,钛合金表面的摩擦学性能得到改善,织构间距为250μm时的摩擦学性能最好,摩擦因数最大降低约51.5%,磨损率最大降低77.6%。当织构间距过小,织构化表面承载区减少,导致织构磨损较快,而织构间距过大会弱化织构效果。其次,以最优织构间距为基础,进一步探究了不同表面织构形貌和深度对钛合金表面摩擦学性能的影响。最后,研究了最优织构参数下,滑动速度和加载载荷对钛合金减摩性能的影响。结论 在润滑条件下,织构的表面形貌和深度影响钛合金表面的摩擦学性能,织构深度太浅或太深时,其流体动压效应都会减弱,从而导致摩擦因数和磨损量增大;当产生足够大的动压效应时,织构边缘的凸起结构能够对织构起到保护作用,延缓织构磨损。

45钢表面制备V形凹槽及其摩擦学特性

采用声光调Q固体Nd:YAG激光器在45钢试样表面制备了V形凹槽织构,利用UMT-2的销盘式摩擦方式考察了V形凹槽的几何参数对表面摩擦性能的影响。结果表明:45钢表面制备的V形凹槽织构,在油润滑条件下能有效减小表面的摩擦因数;特别是在载荷较低、速度较大的工况下,织构面的平均摩擦因数最大可比未织构面减小64%。在试验范围内,平均摩擦因数普遍随着V形凹槽角度的增加而减小,随着边长的增大而减小,存在最优的横向和横向槽间距使得平均摩擦因数达到最小。