ISSN   1004-0595

CN  62-1224/O4

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固体摩擦调节剂成分优化与轮轨磨损行为研究

Composition Optimization of Solid Friction Modifier and the Wheel/Rail Wear Behavior

  • 摘要: 固体摩擦调节剂作为轮轨摩擦调控技术的手段之一,具有施用精准、便捷且环保的特点,可以有效地缓解轮轨磨损与滚动接触疲劳现象. 但固体摩擦调节剂存在制备成本高且施用过程中黏着系数过高、易碎裂及难以维持长时间等问题. 本研究中采用酚醛树脂(PF)作为粘结剂,二硫化钼(MoS2)、聚四氟乙烯(PTFE)和石墨(Graphite)为填料,通过冷等静压和热处理制备了固体摩擦调节剂,利用正交试验研究了PF、MoS2、PTFE和Graphite对固体摩擦调节剂黏着性能和压缩强度的影响,并通过轮轨滚动接触模拟试验研究了固体摩擦调节剂对轮轨的磨损行为的影响. 结果表明:MoS2对固体摩擦调节剂黏着系数和有效保持转数的影响最为显著,黏着系数随MoS2含量的增大而减小,有效保持转数随MoS2含量的增大而增大;PF对固体摩擦调节剂压缩强度的影响最为显著,压缩强度随PF含量的增加而减小;施加本研究中制得的固体摩擦调节剂后,在轮轨接触界面形成摩擦控制膜,使轮轨之间的摩擦转化成轮-摩擦控制膜-轨之间的摩擦,轮轨间作用力减小,进而使得黏着系数降低至合适范围内,且轮轨试样的磨损率降低;同时由于固体摩擦调节剂颗粒填充至疲劳裂纹缝隙中,从内部对裂纹起到了支撑作用,在接触应力作用下,使疲劳裂纹开口紧闭,缓解了疲劳裂纹的扩展趋势. 综合黏着系数、有效保持转数、压缩强度以及轮轨磨损损伤行为,样品1-3# (FM-A)为最优配比,此时PF、MoS2、PTFE和Graphite的质量分数分别为20.4%、24.5%、36.7%和18.4%.

     

    Abstract: At present, the domestic solid friction modifier products are not yet mature, and there is a lack of systematic optimization of the formulation and preparation process. In order to achieve the friction control ability of the solid friction modifier, thermosetting phenolic resin was used as a binder, while molybdenum disulfide, polytetrafluoroethylene, and graphite were used as fillers in this study. The orthogonal test group of the formula was designed to obtain a solid friction modifier with excellent friction control ability and stability. The preparation steps of the solid friction modifier were mixing evenly, loading raw materials, cold isostatic pressing and heat treatment. The crushing strength test of solid friction modifier was carried out on a uniaxial compression device with a loading rate of 0.02 mm/s. The wheel-rail rolling contact simulation test was used to study the wheel-rail wear rate and rolling contact fatigue damage behavior under dry conditions and under the condition of applying the preferred solid friction modifier. The wheel-rail rolling contact simulation test were carried out under dry conditions and at the room temperature, The contact stress was 900 MPa, the wheel speed was 400 r/min, the rail speed was 395 r/min, and the creep rate was 2%. Firstly, the adhesion performance of solid friction modifier was tested, the specific methods were as follows, adding solid friction modifier for 2 minutes, then removing the solid friction modifier, recording the average adhesion coefficient of wheel and rail and the effective holding speed. Next, wheel-rail wear and rolling contact fatigue tests were carried out, the wheel/rail specimens experienced 5 000 dry cycles at room temperature, and then 20 000 dry cycles and 20 000 solid friction modifier cycles were carried out respectively. The total number of cycles under drying and solid friction modifier conditions was 25 000. The results showed that MoS2 and PTFE as fillers had the most significant effect on the adhesion performance of solid friction modifiers, which could effectively improve the adhesion coefficient control ability of solid friction modifiers and effectively maintain the number of revolutions; PF as a binder had the most significant effect on the crushing strength of solid friction modifier. Based on the comprehensive adhesion performance, crushing strength and wheel-rail wear damage behavior, sample 1-3 # ( FM-A ) was the optimal ratio. At this time, the mass fractions of PF, MoS2, PTFE and Graphite were 20.4%, 24.5%, 36.7% and 18.4%, respectively. After applying the solid friction modifier, a friction control film was formed at the wheel-rail contact interface, so that the friction between the wheel-rail was transformed into the friction between the wheel-rail-friction control film, the force between the wheel-rail was reduced, and the adhesion coefficient was reduced to a suitable range, and the wear rate of the wheel-rail sample was reduced. At the same time, when the fatigue crack passed through the wheel-rail contact zone, the fatigue crack opening was closed under the action of contact stress and solid friction modifier. Under these two effects, the solid friction modifier effectively reduced the surface damage, plastic deformation and fatigue damage behavior of the wheel and rail.

     

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