共查询到19条相似文献,搜索用时 171 毫秒
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《机械工程学报》2018,(18)
轮轨摩擦因数的变化影响列车运行时的轮轨黏着特性,轮轨间的最大静摩擦因数可以界定轮轨接触区的黏着状态,轮轨黏着对于机车实现牵引制动具有重要意义。针对水、油、砂等"第三介质"对轮轨最大静摩擦因数的影响,搭建轮轨接触试验台进行轮轨接触试验与轮轨摩擦接触试验。对试验结果对比分析表明轮轨接触试验的轮轨接触斑与有限元仿真的接触斑形状及面积相同。与干燥清洁状态下的轮轨最大静摩擦因数相比,当轮轨间单独存在水或油介质时会降低该系数值,且单独存在油介质时该系数值最小;当轮轨间同时存在水、砂介质时,该系数值增大;当油、砂同时存在时,最大静摩擦因数略大于油介质工况,但依旧小于干燥工况下的系数值。撒砂可以增加轮轨最大静摩擦因数,河砂具有更好的增黏效果但会对轮轨表面造成更严重擦伤,建议使用石英砂作为轮轨增黏介质。 相似文献
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不同真空度气体对粗糙表面接触摩擦的影响 总被引:1,自引:0,他引:1
在大气压作用下,通过对不同真空度下接触物体表面摩擦力的测量,研究气体对粗糙接触物体表面摩擦的影响,该实验采用的摩擦副材料是铝合金/有机玻璃、45钢/有机玻璃。实验结果显示:随着真空度的增大,2种摩擦副的摩擦力近似呈现线性变化,静摩擦因数则先减小而后趋于稳定,再有回增的趋势;45钢/有机玻璃摩擦副静摩擦因数取得最小值所对应的真空度比铝合金/有机玻璃摩擦副的更大。通过分析得出静摩擦因数变化的原因:随着真空度的增大,摩擦副接触间隙间的气体密度减小,当固体刚开始运动时,产生摩擦的气体分子与固体表面的分子减少;随着真空度的增大,正压力增大,材料的变形程度增大。 相似文献
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齿轮、轴承、凸轮等重载接触副的性能受表面粗糙度的显著影响。高负载情况下的摩擦因数与润滑接触面粗糙度的各向异性相关。测量的表面粗糙度可以分解为一系列具有不同波长、幅值的正弦表面粗糙度,因此,考虑各向异性正弦表面粗糙度,构建粗糙表面点接触瞬态弹性流体动力润滑(TEHL)模型,提出基于多重网格算法的粗网格构造新方法,提高粗糙表面润滑问题求解的稳健性。研究表面粗糙度各向异性对高负载情况下摩擦因数的影响规律。结果表明,粗糙度的各向异性影响接触面压力、油膜厚度分布、粗糙度形变量,从而影响摩擦因数。提出一个组合函数来量化粗糙度各向异性对摩擦因数的影响,表明全膜润滑到混合润滑的过渡不仅与载荷、速度等工况参数相关,还与粗糙度各向异性相关。 相似文献
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针对材料表面高载荷条件的要求,提出了测量摩擦因数的方法,并进行了相应测试装置的设计,该测试装置由正向加载装置、侧向加载装置和数据处理装置3部分组成。可以用来测量高载荷条件下材料表面的静摩擦因数和滑动摩擦因数,同时得到整个滑动过程中摩擦因数变化情况。利用该装置对某国防减摩涂层进行了测试,结果表明在高载荷条件下该涂层对碳钢表面具有较好的减摩效果。 相似文献
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为研究表面粗糙度对轴向液压柱塞泵马达配流副润滑特性的影响,引入Weierstrass-Mandelbort分形函数,对不同幅值的表面粗糙度的表面形貌进行二维和三维模拟,建立考虑表面粗糙度的流固热耦合下的配流副油膜润滑模型,采用中差分形式的有限差分法和松弛迭代法对其进行数值求解,并分析油膜厚度、油膜压力、油膜承载力、摩擦因数等性能参数随着表面粗糙度幅值变化的规律。通过盘-盘形式的配流盘-缸体摩擦磨损试验,得到不同幅值的表面粗糙度下配流副摩擦因数,对所建立的数学模型进行验证。数值计算结果表明,表面粗糙度幅值的增大会引起油膜承载力增大,但也会引起最大油膜压力和摩擦因数的增大,导致摩擦性能下降。摩擦磨损试验发现,表面粗糙度增大,配流盘表面摩擦磨损情况加剧,配流副润滑性能和耐磨性能整体降低。因此在配流盘表面加工处理中,应适当降低其表面粗糙度。 相似文献
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Modeling the effect of skewness and kurtosis on the static friction coefficient of rough surfaces 总被引:4,自引:0,他引:4
Engineering surfaces possess roughnesses that exhibit asymmetrical height distributions. However, the Gaussian distribution is most often used to characterize the topography of surfaces, and is also used in models to predict contact and friction parameters. In this paper, the effects of kurtosis and skewness on different levels of surface roughness are investigated independently. This is accomplished by adopting the Pearson system of frequency curves and used in conjunction with a static friction model for rough surfaces to calculate the friction force and friction coefficient. This study is the first attempt to independently model the effect of kurtosis and skewness on the static friction and friction coefficient. It is predicted that surfaces with high kurtosis and positive skewness exhibit lower static friction coefficient compared to the Gaussian case. More importantly, it is predicted that, for high kurtosis values, the static friction coefficient decreases with decreasing external force rather than increasing as seen with increasing skewness. This is a very promising result for applications involving smooth lightly loaded contacts such as magnetic storage devices and microelectromechanical systems. The practical significance of the present model is specifically demonstrated on static friction predictions in magnetic storage head–disk interfaces. Such predictions can be used to determine the optimal characteristics of such devices prior to fabrication to achieve lower friction in terms of surface roughness, mechanical properties, apparent contact area, and operational environment. 相似文献
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Decreasing track width and tape thickness to increase the volumetric recording density of helical scan-tape-drive systems, which is suitable for higher volumetric recording density, will result in the failure of tracking. The displacement of tape forwarding position, which causes failure of tracking, is caused by static friction coefficient between a tape and a roller guide. It was found that surface roughness and materials of roller guides are very important to reduce static friction coefficient. 相似文献
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《Tribology - Materials, Surfaces & Interfaces》2013,7(1):43-47
AbstractThe static friction characteristic was investigated in the case of litchi picker’s clamp heads made of PVC plastic, silicone and rubber, carved with textures of circular, sawtooth, plain and grid, when in contact with litchi stalks. An experimental device was developed and used to measure the static coefficient of friction between a flat surface and cylinder. Clamp heads made of rubber were found to have the biggest static coefficient of friction, and clamp heads made of PVC plastic were found to have the smallest static coefficient of friction. Clamp heads carved with circular texture were found to have the biggest static coefficient of friction, and clamp heads carved with grid texture were found to have the smallest static coefficient of friction. And for specimens of different sizes, the bigger the diameter, the bigger the static coefficient of friction. Results suggest that the best clamp heads for a litchi picker are made of rubber, carved with circular texture, and a bigger clamping force is required to pick smaller stalks. 相似文献
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Detailed knowledge about static friction materials is required for the accurate calculation of the braking torque needed to hold a load at rest. This is particularly important for brakes in cranes, elevators, hoists and mining winding machines, which must meet specifications such as the definite value of the static safe braking factor. The study of static friction is also a useful supplement to the dynamic testing of brake friction materials. In such a study, precise control of the temperature on the surfaces is possible, as well as surface roughness, and existence of the third-body can be accurately identified. It is an important fact that the coefficient of static friction, μs, is not an invariant, and it cannot be adequately represented in many engineering applications as a single number. The study of static friction dependence upon factors such as stationary contact time, rate of tangential loading, and surface temperature, contributes to a better understanding of friction phenomena. In this paper, a test apparatus is presented, and a series of experiments is described. The experiments reveal the static friction characteristics of some brake friction materials. 相似文献
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基于切削力的PVD涂层刀具性能研究 总被引:1,自引:0,他引:1
本文在干式切削条件下,选用钴基硬质合金无涂层数控刀具和钴基硬质合金基体TiAlSiN与TiAlN/Ta涂层数控刀具,分别切削淬火态45钢(52HRC);车削时,采用SW-1车刀空间受力分析仪测量刀具在车削状态下的三向力;结合对被加工件的表面粗糙度测定,探讨TiAlSiN、TiAlN/Ta涂层刀具在相同条件下的三向力、摩擦力和摩擦系数与无涂层钴基硬质合金刀具的差异。结果表明,在车削高硬度材料时,涂层及其成分对车刀三向力和摩擦系数均有较大影响,TiAlN体系中加入稀土元素Ta形成的TiAlN/Ta多层涂层刀具的三向力、摩擦系数明显小于TiAlSiN涂层刀具,而且被加工件的表面粗糙度更小。 相似文献
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皮肤-纺织品的摩擦特性试验研究 总被引:1,自引:0,他引:1
为了定量研究纺织品与人体皮肤之间的摩擦特性,采用微观摩擦试验机对4种织物与20位男女手臂前臂皮肤之间的摩擦因数进行测试。结果表明:皮肤-织物的平均摩擦因数在0.30~0.50之间,其中男性皮肤-织物的平均摩擦因数在0.30~0.36之间,女性皮肤-织物的平均摩擦因数在0.40~0.50之间。织物表面特征,如表面形状、纹理特点、组织结构、平整度、致密度和弹性等,以及纤维本身的表面特征,是织物表面摩擦特性存在差异的根本原因。4种织物的平均摩擦因数由高到低分别为全毛绒面呢、羊皮、真丝绸和本色平纹棉布,其中丝绸和平纹棉布的平均摩擦因数比较接近;在与不同纺织品摩擦时,女性皮肤-织物的平均摩擦因数普遍比男性高。 相似文献
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Measurements were carried out for static and kinetic friction coefficients for steel as a function of the normal pressure for two surface roughness conditions of the matrix: ground and sand blasted. The samples were interstitial free steels, the tests were done at room temperature, in quasi-static and dry contact conditions. Very high pressures were applied in the range of 230–1100 MPa in order to simulate the conditions of testing in severe plastic deformation processes of metals. A new device was designed for this purpose. The results showed a decrease of the friction coefficients with the applied normal stress with stronger dependence for sand blasted surfaces. 相似文献
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Gang SHEN Jufan ZHANG David CULLITON Ruslan MELENTIEV Fengzhou FANG 《Frontiers of Mechanical Engineering》2022,17(2):26
The tribological performance of artificial joints is regarded as the main factor of the lifespan of implanted prostheses. The relationship between surface roughness and coefficient of friction (COF) under dry and lubricated conditions is studied. Results show that under dry test, friction coefficient is not reduced all the time with a decrease in surface roughness. On the contrary, a threshold of roughness value is observed, and frictional force increases again below this value. This critical value lies between 40 and 100 nm in Sa (roughness). This phenomenon is due to the transfer of friction mechanisms from abrasion to adhesion. Under wet test, COF always decreases with reduction in surface roughness. This result is mainly attributed to the existence of a thin layer of lubricant film that prevents the intimate contact of two articulating surfaces, thus greatly alleviating adhesion friction. Furthermore, surface texturing technology is successful in improving the corresponding tribological performance by decreasing friction force and mitigating surface deterioration. The even-distribution mode of texturing patterns is most suitable for artificial joints. By obtaining the optimal surface roughness and applying texturing technology, the tribological performance of polymer-based bioimplants can be greatly enhanced. 相似文献