Experimental Study on Large Creepage Adhesion of Wheel/Rail Braking at 400 km · h-1 (Ⅳ)——Extremely Low Adhesion Characteristics and Adhesion Coefficient under Various Media Conditions
1.Railway Science and Technology Research & Development Center, China Academy of Railway Sciences Corporation Limited, Beijing 100081, China
2.Wheel-Rail System Laboratory, National Engineering Research Center of System Technology for High-Speed Railway and Urban Rail Transit, Beijing 100081, China
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文章历史+
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Published
2024-02-18
2025-01-01
Issue Date
2026-07-13
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摘要
针对时速400 km高速列车轮轨在多种介质条件下的制动大蠕滑极低黏着特性及黏着系数,通过高速轮轨关系试验台,模拟不同速度下轮轨间分别采用喷水、防冻液、普通润滑油15W-40及齿轮箱润滑油75W-90等介质的工况,研究轮轨间多种介质对制动大蠕滑极低黏着特性和黏着系数的影响,并探讨水介质条件下轮轨接触表面粗糙度和齿轮箱润滑油条件下超大蠕滑率对黏着系数的作用。结果表明:水介质条件下轮轨接触表面粗糙度是影响黏着系数的关键因素之一,极低粗糙度水平下速度超过100 km · h-1后便进入极低黏着状态;轮轨间不同介质条件下,黏着系数随速度的提高呈现不同的下降趋势,其中齿轮箱润滑油75W-90和防冻液在高速下更易导致极低黏着系数的出现;特别是在齿轮箱润滑油75W-90条件下黏着力系数在黏着饱和点之后随纵向蠕滑率的增加呈现持续下降趋势,即使纵向蠕滑率增加到90%也未观察到黏着力系数再次上升的现象,标志着对这类齿轮箱润滑油仅利用防滑控制技术提高黏着利用的可能性极低。
Abstract
This study conducts an in-depth experimental investigation into the braking creepage with extremely low adhesion characteristics and the adhesion coefficient of the wheel-rail system for high-speed trains traveling at 400 km · h-1 under various media conditions. Utilizing a high-speed wheel-rail relationship test rig, the study simulates conditions where water, antifreeze, conventional lubricating oil 15W-40, and gearbox oil 75W-90 are sprayed between the wheel and rail at different speeds. The impact of these media on the braking creepage, particularly under extremely low adhesion characteristics and the adhesion coefficient, was analyzed, along with the effects of surface roughness in water media and ultra-high creep rates under gearbox lubricating oil conditions on the adhesion coefficient. The results indicate that the surface roughness of the wheel-rail contact in water media serves as a critical factor influencing the adhesion coefficient. With a very low surface roughness level, speeds exceeding 100 km/h lead to an extremely low adhesion state. Under varying media conditions, the adhesion coefficient displays different decreasing trends with increasing speed, notably where gearbox lubricating oil (75W-90) and antifreeze are more likely to cause extremely low adhesion coefficients at high speeds. In particular, under gearbox lubricating oil (75W-90) conditions, the adhesion force coefficient consistently decreases beyond the adhesion saturation point with increasing longitudinal creepage, with no observed resurgence even when the creepage was increased to 90%, indicating that solely relying on anti-skid control technologies to enhance adhesion utilization in such lubricating oils is highly unlikely.
(1)300 km · h-1制动速度下,当纵向蠕滑率增至0.24%时,黏着力系数达到加载过程的极大值A点,此时黏着力系数约为0.011;随着纵向蠕滑率的进一步增加,黏着力系数反而开始下降,在纵向蠕滑率为2%~6%的区间内降至约0.001;当纵向蠕滑率超过6%后,随纵向蠕滑率的增加黏着力系数开始增大,在纵向蠕滑率为8%~9%的变化区间内快速增大。纵向蠕滑率的卸载过程中,随纵向蠕滑率的减小黏着力系数持续增大,纵向蠕滑率降至8%时增大至0.059,达到卸载过程中的最大值C点,即“卸载峰”。
(2)350和400 km · h-1制动速度下,黏着特性曲线与300 km · h-1速度时的在形态上具有相似性。然而,在黏着试验过程中,随着速度的提升,A点的黏着力系数略有下降。在纵向蠕滑率超过8%的区间内,这2个速度条件下的黏着力系数均出现再次快速增大的现象。此外,在纵向蠕滑率的卸载过程中,不同速度条件下均观察到了“卸载峰”的出现。
2.2 防冻液条件
300,350和400 km · h-1制动速度下轮轨间喷防冻液得到的极低黏着特性曲线如图3所示。从图3可以看出:300 km · h-1速度下,黏着力系数随纵向蠕滑率的增加快速增大,在纵向蠕滑率达到1%时增大趋势变得平缓,此时达到A点,其黏着力系数约为0.006;随后,黏着力系数随纵向蠕滑率的进一步增加而持续增大,在纵向蠕滑率为7%时达到卸载过程中的最大值0.050;对于350 km · h-1速度下的黏着特性曲线,其形态与300 km · h-1速度时的具有相似性,表明在这2个速度下,黏着力系数随蠕滑率的变化趋势具有一致性;400 km · h-1速度下,纵向蠕滑率增至13%时黏着力系数出现了第2个显著的峰值,此时黏着力系数达到0.050。纵向蠕滑率卸载过程中,在纵向蠕滑率降至6%时黏着力系数达到卸载峰,此时黏着力系数为0.105,表明在大蠕滑状态下黏着力系数出现了更为复杂的变化规律。
2.3 普通润滑油条件
300,350和400 km · h-1制动速度下轮轨间喷普通润滑油得到的极低黏着特性曲线如图4所示。从图4可以看出:300 km · h-1速度下,黏着力系数在开始阶段随纵向蠕滑率的增加快速增大,在纵向蠕滑率为0.9%时达到黏着饱和点(A点),此时黏着力系数约为0.030;在过饱和点之后,随着纵向蠕滑率的进一步增加,黏着力系数呈现持续下降的趋势,且未出现再次增大的现象;350和400 km · h-1速度下的黏着特性曲线形态与300 km · h-1时的具有相似性,表明在这3个速度下黏着力系数随纵向蠕滑率的变化规律具有一致性,只是随着速度的提高,黏着力系数的最大值有轻微的下降。
2.4 齿轮箱润滑油条件
轮轨间喷巴斯夫75W-90齿轮润滑油,300,350和400 km · h-1这3个不同制动速度时的极低黏着特性曲线如图5所示。从图5可以看出:300 km · h-1速度时,黏着力系数在纵向蠕滑率为0.5%时达到黏着饱和点(A点),仅为0.006;在该饱和点之后,随着纵向蠕滑率的增加,黏着力系数呈现持续下降的趋势,且未观察到黏着力系数再次增大的现象;350和400 km · h-1速度条件下的黏着特性曲线形态与300 km · h-1时的具有相似性,表明在这3个速度条件下黏着力系数随纵向蠕滑率的变化规律具有一致性,只是随着速度的提升黏着力系数的最大值略有下降;特别是在纵向蠕滑率超过10%之后,黏着力系数降至约0.001,几乎失去了黏着力,表明在高速条件下轮轨间齿轮箱润滑油的存在显著降低了轮轨黏着性能。
(1)轮轨间喷水条件下,随着速度的增加,黏着系数呈现出不同的变化趋势。具体来说,在速度从50 km · h-1增加到100 km · h-1的过程中,黏着系数经历了1个快速下降阶段,从0.075降至0.025,此时已经进入到了极低黏着状态;在速度从100 km · h-1继续增加至400 km · h-1的过程中,黏着系数的下降速度变得较为缓慢,最终降至0.007 5,整个速度区间内的黏着系数均处于极低黏着状态。拟合水介质条件下黏着系数与速度之间的关系表达式为
式中:为黏着系数;为速度,km · h-1。
(2)轮轨间喷防冻液条件下,在运行的前150 km里程内黏着系数随运行里程的增加下降较为显著,从50 km · h-1速度时的0.020降至150 km · h-1速度时的0.005;随后,在运行150 km之后,黏着系数的变化趋于平稳,维持在0.005附近。根据试验结果拟合防冻液条件下黏着系数与速度的关系表达式为
(3)轮轨间喷普通润滑油条件下,黏着系数随速度的提高呈现线性缓慢下降的趋势,从50 km · h-1速度时的0.035降至400 km · h-1速度时的0.025。根据试验结果拟合普通润滑油条件下黏着系数与速度的关系表达式为
(4)轮轨间喷齿轮箱润滑油条件下,黏着系数比喷普通润滑油时低约0.020,从50 km · h-1速度时的0.015降至400 km · h-1速度时的0.003。根据试验拟合齿轮箱润滑油条件下黏着系数与速度的关系表达式为
50 km · h-1制动速度条件下,喷不同介质时黏着系数从高到低的排序依次为:喷水时为0.075,喷普通润滑油时为0.035,喷防冻液时为0.022,喷齿轮箱润滑油为0.015;这表明在较低制动速度下,水作为第三介质时黏着系数最高,而齿轮箱润滑油的黏着系数最低。随着速度增至100~300 km · h-1范围内,黏着系数从高到低的排序变化为:喷普通润滑油、喷水、喷齿轮箱润滑油、喷防冻液,表明轮轨间喷普通润滑油较难出现极低黏着问题,而喷防冻液和齿轮箱润滑油则更易出现极低黏着问题。这一结果揭示了制动速度对不同介质下黏着系数影响的差异性。
从图7可以看出:水介质条件下,在不同车轮粗糙度水平下,随着速度的增加,黏着系数均呈现下降趋势,但不同粗糙度水平下进入极低黏着状态的速度阈值存在差异;具体来说,当车轮接触表面处于极低粗糙度水平下,速度超过100 km · h-1后黏着系数降至0.030以下,进入极低黏着系数状态;处于低粗糙度水平下,速度超过250 km · h-1后黏着系数才会降至0.030以下;而在中粗糙度水平下,速度超过370 km · h-1后黏着系数才达到极低黏着系数的标准。
进一步分析50 km · h-1制动速度时轮轨间喷齿轮箱润滑油条件下,纵向蠕滑率从20%增加至90%时的轮轨黏着特性。通过高速轮轨关系试验台获得的黏着特性曲线结果如图8所示。从图8可以看出:在黏着饱和点之后黏着力系数随纵向蠕滑率增加而呈现出持续缓慢下降的趋势,在从20%增加至90%蠕滑率变化范围内,并未观察到黏着力系数再次上升的现象。这一黏着特性的发现表明,在轮轨间存在齿轮箱润滑油的条件下,即便是增加纵向蠕滑率也难以实现黏着力系数的提升。这表明在此类润滑条件下,利用传统的防滑控制策略增强轮轨间的黏着利用几乎是不可能的。它提示我们,在设计高速列车的防滑控制系统时,需要考虑轮轨间可能存在的润滑介质对黏着特性的影响。
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