微动接触中分形粗糙表面的温升分布研究

目的 研究不同分形参数下表面粗糙度对微动接触表面温升的影响。方法 通过创建Python脚本,将MATLAB中利用Weierstrass-Mandelbrot函数构造的分形表面轮廓坐标导入ABAQUS中,使用样条曲线拟合轮廓坐标,构建包含粗糙表面的二维柱面-平面接触模型,研究表面粗糙度、法向载荷、切向载荷以及材料属性对接触表面温升的影响规律。结果 微动接触状态下,温升在接触宽度方向上呈先增后减的趋势,且沿深度方向温升幅值逐渐减小。不同粗糙度的表面节点具有相似的温升分布历程,热影响区主要分布于接触区表层附近,并在此表层产生高的温度场。粗糙接触模型会出现局部温升峰值,同时剪切摩擦应力和接触压力分布具有离散性,与文献中已有结论一致。结论 接触表面温升幅值随着粗糙度的增大而增大。当表面粗糙度和法向载荷一定时,随着切向载荷幅值的增大,上试件的相对滑移距离和摩擦热产生率增加,引起温升幅值增大。考虑材料属性时,发现温升幅值大小与材料导热性密切相关,材料导热性能越好,接触表面温升幅值越小。     

表面粗糙峰坐标点云重构的金属-橡胶接触分析

目的 通过金属-橡胶微观接触面粗糙峰坐标点云重构,建立外部载荷与接触面积、微观接触状态之间的联系.方法 基于粗糙表面的自相关函数和高斯分布函数,获得金属-橡胶粗糙接触面数据点云坐标,利用ANSYS APDL方法,建立金属-橡胶接触模型,对两种表面粗糙度(分别为1.6μm和3.2μm)的4种接触情形进行有限元接触分析,确定模型的可靠性.结果 随着外部载荷的增加,经数据点云重构后的粗糙表面,其接触面积呈非线性增加.载荷较小时,外加载荷每增加0.1 MPa,接触面积增加约6％;大载荷时,外加载荷每增加0.1 MPa,接触面积增加约1.5％.接触状态中,滑移占比为12％左右,近场和粘着呈完全相反的变化趋势.结论 随着外加载荷的增加,界面的真实接触面积呈幂指关系增加.同一载荷下,真实接触面积随表面粗糙度的增加而减小;随着外加载荷的增加,界面间的接触状态由近场接触向粘着接触转变.接触面积和粘着状态是界面间磨损粒子的分布范围和大小的确定因素,对于准确描述载荷传递和随之发生的磨损过程有着重要意义.根据橡胶表面的应力分布和变形情况,解释了粘着接触状态促使橡胶一侧微凸体脱落成为磨损颗粒,证明磨粒磨损是刚柔接触界面的主要磨损形式.     

加载相位差对微动磨损影响的数值模拟研究

目的研究不同加载相位差下微动磨损量随切向载荷幅值的变化规律。方法在ABAQUS中建立柱面/平面微动磨损模型,设置不同的加载相位差,结合能量模型和UMESHMOTION子程序,进行仿真试验,对不同情况下的磨损深度进行仿真分析。结果法向载荷、位移载荷和应变载荷取定值时,0°相位差的磨损深度最小,180°相位差的磨损深度最大,90°和270°相位差的磨损深度相同,且介于二者之间;当法向载荷和位移载荷为定值时,0°相位差的磨损深度随应变载荷的增大而减小,90°相位差的磨损深度不受应变载荷幅值的影响,180°相位差的磨损深度随应变载荷的增大而增加,且接触状态由部分滑移向完全滑移逐渐过渡;当法向载荷和应变载荷一定时,随位移载荷的增加,各相位差下磨损宽度和磨损深度都呈现出增大的趋势;在部分滑移状态下,当应变载荷较大时,0°相位差的最大磨损深度发生在接触区后缘,180°相位差的最大磨损深度发生在接触区前缘,90°相位差的前、后缘磨损深度极大值接近。结论两切向载荷间加载相位差对磨损深度随切向载荷幅值变化的趋势影响明显,0°相位差的磨损深度最小,相位差对最大磨损深度的产生位置也有影响。     

表面润湿性与粗糙度对配流副摩擦特性的影响

为改善高压海水轴向柱塞泵配流副摩擦磨损性能，以SAF2507为缸体衬托板上试件，以CFR/PEEK为配流盘下试件，采用Taylor Hobson粗糙度轮廓仪测量表面粗糙度，采用HARKE SPCAX1接触角测量仪测量表面接触角，采用 OLYMPUS OLS-3100激光共聚焦显微镜观察试件在磨损前后的表面形貌，采用MMD-5A标准摩擦磨损试验机在海水润滑条件下进行摩擦磨损试验，探究配流副表面润湿性与粗糙度对摩擦特性的影响。试验结果表明：光滑表面试件下，粗糙度为0.12 μm的上试件与粗糙度为1.2 μm的下试件配对摩擦时，摩擦因数最小，进入稳定摩擦的时间最短，磨损量最小;在下试件表面为带有半球凹坑的仿生非光滑表面下，粗糙度为0.02 μm的上试件与粗糙度为0.7 μm的下试件配对摩擦时，摩擦因数最小，进入稳定摩擦的时间最短，磨损量最小;粗糙度小的试件表面损伤主要为黏着磨损，粗糙度大的试件表面损伤主要为磨粒磨损。     

TC4合金在不同表面强化状态下的微动磨损性能研究

目的 研究喷丸(SP)及表面超声滚压(USRP)强化后摩擦系数、残余应力场及塑性应变场对TC4合金微动磨损性能的影响。方法 分别对TC4合金表面进行SP及USRP强化处理,通过试验测得强化前后的表面粗糙度、残余应力以及显微硬度。基于改进的Archard磨损方程,在ABAQUS有限元软件中建立微动磨损的二维柱面/平面接触模型,借助ABAQUS中的子程序SIGINI和HARDINI分别将残余应力场、塑性应变场引入到表征微动磨损的UMESHMOTION子程序中,从而探究表面强化后摩擦系数、残余应力场以及塑性应变场对平面微动磨损性能的影响。结果 原试样经SP强化后,表面粗糙度增加,而经USRP强化后,表面粗糙度得以改善。经SP和USRP强化后,试样的显微硬度分别为原试样的1.28倍和1.23倍。TC4合金经USRP处理后,最大残余应力为–550 MPa,而SP处理后为–380 MPa。引入残余应力场后,试样的磨损深度明显减少,相比原试样,USRP、SP试样的磨损深度分别降低15%、10%。引入塑性应变场后,TC4合金的磨损深度降低了约6%。结论 相同载荷条件下,摩擦系数越大,磨损越严重。磨损轮廓会随着摩擦系数的增大而逐渐往外侧偏移,接触中心区域的磨损深度也随着摩擦系数的增大而越来越深。塑性形变行为会随着摩擦系数的增加而变得明显,且最终会使得塑性变形的区域变得越来越大。引入残余应力场和塑性应变场后,磨损量均会减小,残余应力的影响更为显著。通过微动疲劳试验发现,加入微动磨损作用后,试样寿命显著降低,USRP试样的抗磨损性能最显著。     

基于切削技术的金刚石刀具磨损特征分析

金刚石刀具的磨损情况决定其使用寿命。用金刚石PCD刀具切削6061-T6镁铝合金工件,通过不同切削速度、切削深度、振动频率、刀具后角时的切削力及切削温度变化,研究不同刀具前后角、进给量、切削转速时的工件表面粗糙度及刀具磨损面积。结果表明:金刚石刀具的切削力和切削温度随切削速度、切削深度的增加而增大,随振动频率的增加而减小;刀具后角增大,金刚石刀具的切削力呈先下降而后缓缓上升趋势,但对切削温度的影响很小。当刀具前角为10°,刀具后角为8°,切削速度为0.46?m/s,切削深度为28?μm,进给量为0.10?mm/r,切削转速为4100?r/min,振动频率为22?kHz,切削振幅为9?μm时,金刚石刀具的磨损面积最小,磨损程度最低,使用寿命最长,但工件的表面粗糙度稍高。      

微弧氧化对TC4钛合金微动磨损行为的影响

采用微弧氧化技术,在TC4钛合金表面制备高硬度氧化陶瓷层(MAO),对比研究了TC4钛合金基体与微弧氧化陶瓷层在2种不同位移幅值下的微动磨损行为。结果表明:位移幅值由80μm增大到150μm时,TC4钛合金基体微动损伤机制由粘着磨损和磨粒磨损转变为疲劳磨损和氧化磨损,而微弧氧化陶瓷层的损伤机制始终以氧化磨损为主;位移幅值为80μm时,TC4钛合金基体与微弧氧化陶瓷层磨损量均较小,而摩擦系数大且波动大;位移幅值为150μm时,两者磨损量出现不同程度的增大,而摩擦系数略有下降且趋于平稳;与TC4钛合金基体相比,微弧氧化陶瓷层的平均摩擦系数小,磨损轮廓浅,且磨损量仅为钛合金基体的70%。微弧氧化陶瓷涂层能够保护钛合金基体表面,有效改善TC4钛合金耐磨性。     

电泳沉积法制备氧化石墨烯膜的微动电接触性能

目的 研究氧化石墨烯膜在不同表面粗糙度条件下的微动电接触性能.方法 采用金属铜为基底,使用不同粒度的砂纸进行处理,制备不同表面粗糙度的试样.通过电泳沉积法在不同粗糙度的铜表面制备氧化石墨烯膜.通过微动电接触试验装置,研究氧化石墨烯膜在不同表面粗糙度条件下的微动电接触性能.采用拉曼光谱仪分析氧化石墨烯膜的沉积情况.使用白光干涉仪、扫描电镜及能谱仪对磨痕形貌、磨损体积和成分进行分析.结合摩擦因数及接触电阻,分析氧化石墨烯膜在微动磨损下的电接触性能.结果 表面粗糙度为1.51、1.27μm时,氧化石墨烯膜的D峰和G峰强度高于其他试样.在室温条件下,接触电阻最低可降至10 m?,且更加稳定.与未处理试样相比,摩擦因数减少的最大幅度为50％,从0.46减少至0.23(Ra=0.88μm);磨损体积减少的最大幅度为90％,从6.28×105μm3减少至6.40×104μm3(Ra=1.27μm).在100℃时,接触电阻基本不超过200 m?,摩擦因数增加至0.51及以上,磨损体积增加至1.45×105μm3及以上.表面粗糙度为1.51、1.27μm的试样磨损体积明显低于其他两个表面粗糙度的试样.在200℃时,接触电阻最终超过了400 m?,摩擦因数不低于0.49,磨损体积增加至4.05×105μm3及以上.结论 氧化石墨烯膜在表面粗糙度为1.51、1.27μm时的沉积效果较好.氧化石墨烯膜能显著降低接触电阻、摩擦因数和磨损体积.高温下,接触电阻和摩擦因数上升,磨损加剧.     

激光加工网状微织构对不锈钢微丝摩擦磨损性能的影响

目的 研究网状微织构对316L不锈钢微丝摩擦磨损性能的影响,为提高金属橡胶的使用寿命提供参考思路.方法 利用LQL-F20A型激光打标机在直径为0.4 mm的316L不锈钢微丝表面加工不同深度和间距的网状微织构,采用Leica-DM6A显微系统测量织构深度和宽度.用往复式小行程微动摩擦磨损试验机进行摩擦磨损试验,测量和记录不同载荷下不锈钢微丝表面摩擦因数和磨损深度.用扫描电子显微镜观察并对比分析不锈钢微丝摩擦磨损前后的表面形貌.结果相同试验条件下,网状织构化试件与无织构试件相比,摩擦因数和磨损深度分别降低了28％和72％.织构深度为25μm试件与深度为11μm试件相比,摩擦因数和磨损深度分别降低了11％和14％;不同织构间距的试件,表面摩擦因数十分接近,磨损深度相差也不大.不同载荷作用下试件表面摩擦因数变化不大,但磨损深度随载荷的增大而增大.结论 对不锈钢微丝表面进行网状织构化处理可以显著改善其摩擦磨损性能,微织构深度是影响不锈钢微丝耐磨性的重要因素,微织构间距与深度对不锈钢微丝摩擦磨损性能具有细微的协同影响,不锈钢微丝的磨损深度与外载荷呈正相关.     

SLM成形打印件振动辅助磁力研磨试验

目的 研究使用振动辅助磁力研磨去除选区激光熔化(SLM)成形打印件表面的未熔融粉末时,各加工参数对试样表面粗糙度降低率和表面形貌的影响。方法 结合波导管工件,采用SLM成形打印AlSi10Mg试样,并利用自行研制的振动辅助磁力研磨装置进行加工间隙、磁极转速、振动频率、加工时间等4个因素各5个水平的单因素试验,以表面粗糙度降低率为评价指标,探究各加工因素对试样表面粗糙度降低率和表面形貌的影响规律。结果 对于采用选区激光熔化成形的试样来说,当加工间隙从3 mm增大到7 mm时,试样的表面粗糙度降低率显著降低,最大降低率为84.7%,最小降低率为6%。当加工间隙为3 mm时,试样表面的未熔融粉末基本去除,表面较平整。当磁极转速从200 r/min增大到1 000 r/min时,表面粗糙度降低率先增大后趋于稳定,在转速为200 r/min时表面粗糙度降低率最小(24.3%)。当转速达到400 r/min甚至更高时,表面粗糙度降低率趋于稳定,表面粗糙度降低率保持在80%左右。表面粗糙度降低率随着振动频率增大的变化情况较为复杂,但是总体呈现先增大后减小的趋势,并且在振动频率为15 Hz时,表面粗糙度降低率最大(84.7%)。当加工时间从10 min增大到50 min时,表面粗糙度降低率呈现先增大后减小的变化趋势,在加工时间为40 min时,表面粗糙度降低率最大(81.7%)。结论 加工间隙、磁极转速、振动频率和加工时间对表面粗糙度降低率都有不同程度的影响,SLM成形的试样经过振动辅助磁力研磨之后,表面粗糙度显著降低,表面未熔融粉末得到有效去除。     

Fretting wear of micro-arc oxidation coating prepared on Ti6Al4V alloy

Micro-arc oxidation(MAO)coating was prepared on Ti6Al4V alloy surface and its characterizations were detected by Vickers hardness tester,profilometer,scanning electric microscope(SEM),energy dispersive X-ray spectrometer(EDX)and X-ray diffractometer(XRD).Fretting wear behaviors of the coating and its substrate were comparatively tested without lubrication under varied displacement amplitudes(D)in a range of 3-40μm,constant normal load(Fn)of 300 N and frequency of 5 Hz.The results showed that the MAO coating,presenting rough and porous surface and high hardness,mainly consisted of rutile and anatase TiO2 phases.Compared with the substrate,the MAO coating could shift the mixed fretting regime(MFR)and slip regime(SR)to a direction of smaller displacement amplitude.In the partial slip regime(PSR),lower friction coefficients and slight damage appeared due to the coordination of elastic deformation of contact zones.In the MFR,the friction coefficient of the coating was lower than that of the substrate as a result of the prevention of plastic deformation by the hard ceramic surface.With the increase of the displacement amplitude,the degradation of the MAO coating and the substrate increased extremely.The fretting wear mechanisms of the coating were abrasive wear and delamination with some material transfer of specimen.In addition,the coating presented a better property for alleviating fretting wear.     

Effect of fretting amplitude and frequency on the fretting corrosion behaviour of tin plated contacts

The fretting corrosion behaviour of tin plated copper alloy contacts at 3, 10 and 20 Hz and at two different track lengths (fretting amplitude) of ± 5 and ± 25 μm is studied. The change in contact resistance as a function of fretting cycles, surface profile of the contact zone, extent of fretting damage, extent of oxidation and elemental distribution across the contact zone were used to assess the fretting corrosion behaviour. The time to reach a threshold value of contact resistance of 0.1 Ω is found to be early for the track length of ± 5 μm compared to that of ± 25 μm, at all the three frequencies. For a given track length, this threshold value reaches early at 20 Hz. The roughness and the nature of surface profile suggest considerable amount of oxidation have occurred at the track length of ± 25 μm compared to that of ± 5 μm. The surface morphology of the fretted zone reveals severe damage of the contact zone for samples with a track length of ± 25 μm at all the three frequencies. A pictorial model is proposed to describe the evolution of change in area of the contact zone. Based on the length and width of the contact zone, the fretted area is calculated. The change is fretted area as a function fretting frequency and track length is analyzed. Delamination wear is found to be operative at both track lengths and at all three frequencies. EDX line scanning also indicates higher levels of oxidation at the track length of ± 25 μm compared to that of ± 5 μm. The variation in the atomic ratios of tin, copper and oxygen of the oxide debris present at the centre and edges of the fretted zone is plotted as an area plot as a function of experimental conditions. The debris is predominantly oxides of copper for the track length of ± 25 μm whereas they are mostly oxides of tin for the track length of ± 5 μm at all the three frequencies. The narrow and deep surface profile, lower R_a values, overlapping of the tin and copper lines in the EDX line scan and the predominance of oxides of tin support the view that the chances of accumulation of wear debris at the contact zone is very high at the track length of ± 5 μm. The study concludes that tin plated contacts could encounter an early failure even at shorter track lengths of ± 5 μm, if there is sufficient accumulation of the wear debris at the contact zone.     

Fretting corrosion characteristics of electrodeposited and hot dipped tin coating contacts

Electrodeposited (ED) tin was coated on the copper substrate for electrical contact instead of conventional hot dipped (HD) tin and subjected to fretting tests. The fretting wear behavior was investigated with various fretting cycles at ± 25 μm displacement amplitude, 0.5 N normal load, 3 Hz frequency, 45-50% relative humidity, and 25 ± 1 °C temperature. The contact resistance variation was recorded with fretting cycles. The fretting corrosion performance of ED tin enhanced with that of HD tin. The grain structure of ED tin was not removed even at 9000 fretting cycles, whereas HD tin removed at 1000 fretting cycles. The interdependence of extent of wear and oxidation on the fretted zone increases the complexity of the fretting corrosion behavior. The extent of wear and the elemental distribution at the center and edges of the fretting zone was characterized using scanning electron microscope (SEM) and energy dispersive analyzer of X-ray (EDAX). The surface profile of the fretted surface was examined using laser-scanning microscope (LSM). The fretting behavior difference between ED tin and HD tin was correlated to the grain structure as well as the absence of the abrasive debris in ED tin.     

机器人减速器传动粗糙表面接触参数研究

针对机器人减速器传动界面广泛存在的粗糙表面接触特性开展相关研究。以GW接触模型为基础,考虑粗糙峰接触过程中相互作用的影响,对它进行修正得到新的模型。采用修正模型计算粗糙表面接触载荷并推导出接触刚度,然后与原始GW接触模型的计算结果进行对比。在进一步的研究中,讨论了不同表面粗糙度与不同接触表面材料对接触载荷与接触刚度的影响。结果表明：粗糙表面接触参数不仅受粗糙峰相互作用的影响,还与粗糙度与接触表面材料有密切的联系。     

接触载荷对TC4钛合金微动磨损行为的影响

目的在不同的载荷和位移幅值下,结合微动图研究微动接触状态、滑移状态、损伤体积三者对微动摩擦磨损的影响以及不同微动接触状态和滑移状态下材料的损伤机理,为机械构件的微动磨损防护设计提供一定的理论支持。方法在相对湿度为50%、干摩擦条件下,运用SRV-V摩擦实验机,采用球/平面接触形式研究了TC4钛合金/GCr15钢球摩擦副的微动摩擦磨损行为。实验后,用原子力显微镜、纳米压痕仪、三维光学轮廓仪、场发射扫描电子显微镜及其自带的EDS,测试TC4试样的表面形貌及粗糙度、弹性模量与硬度、磨损体积与截面形貌和显微结构及磨斑、磨屑形貌成分等。结果在较低法向载荷下,完全滑移(GSR)占主导地位。磨粒磨损、粘着磨损、氧化磨损以及疲劳脱层是主要的损伤机理。另一方面,在较高法向载荷下,混合滑移(MSR)、部分滑移(PSR)占主导地位。损伤机制是由于高的应力集中,导致疲劳裂纹。此外,不同的微动运行条件下和材料损伤区域也不相同。完全滑移条件下,损伤主要集中在磨斑中心,而部分滑移条件下,损伤主要集中在磨斑边缘。结论切向摩擦力、微动振幅是影响微动磨损的重要因素。小位移幅值下,磨屑可以减缓接触面钛合金基体材料的微动磨损;而大位移幅值下,磨屑会加剧接触面基体材料的微动磨损。     

一种船用低温钢板在干态室温下的往复摩擦特性研究

目的研究新型船用低温钢板的摩擦磨损性能。方法采用UMT-2型多功能摩擦磨损实验机,测试了船用低温钢板在室温干态环境、不同载荷(10、20、30 N)、不同频率(2、5 Hz)下的往复摩擦试验行为。采用光学显微镜(OM)、扫描电子显微镜(SEM)分析了船用低温钢板的磨痕表面形貌,用光学轮廓仪分析了磨损表面轮廓,用EDS对试样磨损表面进行了成分分析。结果随着试验法向载荷从10 N增加到30 N时,船用低温钢板的摩擦系数从0.51逐渐增加到0.63,磨损率先增加后降低,再逐渐增加。在相同载荷下,摩擦系数随着往复频率的提高而降低。载荷为30 N时,往复频率为5 Hz,摩擦2 h后,磨损断面轮廓宽度和深度分别为750μm和3871 nm。接触面从磨粒磨损转向疲劳磨损,接触面出现氧化层、表面硬化层和转移层。结论载荷较低时,船用低温钢磨损主要为氧化磨损和疲劳磨损;载荷增大时,接触面磨损出现疲劳磨损。同等载荷下,摩擦系数会随着移动速度的提高有所下降,接触面在摩擦热作用下形成的金属膜有助于降低表面粗糙度,减小摩擦系数。     

基于C17200与34CrNiMo6材料的摩擦磨损特性与数值模拟研究

目的 探究干摩擦下载荷与速度对于C17200与34CrNiMo6材料摩擦学特性的影响,以探寻C17200材料作为风力机制动闸片的可行性,开展考虑表面粗糙度和接触压力分布不均因素的磨损深度的数值模拟。方法 以C17200与34CrNiMo6材料组成销–盘摩擦副,基于风力发电机的制动工况,利用试验探究其摩擦学特性与磨损机理。在ABAQUS中建立三维销–盘平面/平面磨损模型,设置不同载荷与速度,基于销–盘摩擦副理论模型与UMESHMOTION子程序,结合ALE自适应网格技术,对不同工况下的表面磨损深度进行数值计算,通过试验验证提出的理论模型的合理性。结果 在载荷为3 MPa时,随速度的增加,平均摩擦系数先减小、后增加,速度为125.664 mm/s时,平均摩擦系数取最小值0.575;在速度为62.832 mm/s时,随载荷的增大,平均摩擦系数近似线性增大。载荷为1.5MPa时,平均摩擦系数取最小值0.509。C17200与34CrNiMo6试样的磨损量随速度与载荷的增大而增大,但转速对于磨损量的影响更大。C17200与34CrNiMo6的磨损机理主要为粘着磨损和磨粒磨损。C17200材料磨损...     

Studies of tin coated brass contacts in fretting conditions under different normal loads and frequencies

The fretting corrosion behavior of tin-plated brass contacts is studied at various normal loads (0.25, 0.5, 1.0 and 1.5 N) and fretting frequencies (1, 3 and 8 Hz). The typical characteristics of the change in contact resistance with fretting cycles and time are explained. Irrespective of the frequencies under study, 1 N normal load suppressed the fretting corrosion of tin contacts by maintaining the mechanical stability and good electrical contact between the contacting members which makes less accumulation of wear debris at the fretted zone. For a given normal load, the fretting corrosion of tin-plated contacts occur much faster at higher frequencies as it provides more fresh metal for oxidation and generates more accumulation of oxide wear debris at the contact zone. The failure time, i.e. the time for contact resistance at the fretted surface to reach 0.1 Ω is delayed with increasing normal loads at the studied frequencies. For a given normal load, the failure time reaches early at 8 Hz, i.e. at higher fretting frequencies. The fretted surface is examined using laser scanning microscope, scanning electron microscope and energy dispersive X-ray analysis to assess the surface profile, extent of fretting damage, extent of oxidation and elemental distribution across the contact zone. From the surface profile data, the fretted area and the wear rate is calculated and correlated with the observed extent of oxidation and earlier failure of electrical contacts. The surface morphology and EDX analysis results of the fretted surface clearly revealed the severe fretting damage at 0.25 N and 8 Hz.