ISSN   1004-0595

CN  62-1224/O4

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温度-速度场下摩擦副界面油液热驱蠕爬与润滑特性研究

Migration-Lubrication Performance at Friction Pair Interfaces under Temperature-Velocity Fields

  • 摘要: 热驱蠕爬(也称蠕爬,Migration)是指摩擦副界面油液不受外力作用,从高温区向低温区定向铺展的行为. 在空间机构及精密仪器的滚动轴承中,润滑油蠕爬流失将导致摩擦阻力增大,进而影响机构的运行精度. 由于摩擦和磨损在机械运动中是无法避免的,同时会伴随摩擦生热,而摩擦生热会引起摩擦副表面产生温度梯度,而运动副在空间极端工况下,液体润滑剂易受表面张力的影响,极小的温度梯度就会引起润滑剂的蠕爬流失. 在现代机械工业领域,油液蠕爬流失问题常见于轴承中,工作时轴承滚道的温度较高,导致润滑剂向温度较低的滚道外围区域蠕爬流失,大大缩减了轴承寿命,导致机械设备润滑故障,降低了生产效率. 对此,本文中以GCr15和Si3N4等典型滚动轴承球与304不锈钢平面构成的点-面接触摩擦副为研究对象,探索了温度梯度和界面运动协同作用下油液热驱蠕爬行为与润滑特性,研究了水平和竖直温度梯度作用下,干摩擦、硅油润滑以及引入不同方向温度梯度后摩擦力的变化规律,分析了滚子直径、滚子材料以及温度梯度方向对摩擦润滑性能的影响. 引入了重力因素,探究了重力方向与温度梯度方向相同/相反条件下摩擦力的变化规律并观测了摩擦运动过程中接触角的变化规律. 研究结果表明:在相同的试验条件下,不同直径的球摩擦力变化规律一致;当温度梯度垂直/平行于运动方向以及竖直时,会导致往返运动过程中摩擦力变化不一致,出现“对称”与“不对称”现象;当温度梯度方向与重力方向相同时,会加速硅油的热驱蠕爬;而当温度梯度方向与重力方向相反时,会对硅油的热驱蠕爬起到一定的抑制作用,进一步分析了热驱蠕爬方向对摩擦力的影响规律和接触角的变化规律. 揭示了温度-速度场协同作用下界面热驱蠕爬与摩擦学行为差异产生的机制. 论文的研究成果有望为空间机构和精密仪器等特殊工况下的持久定区域润滑设计提供参考,有望为复杂机械设备实现小型化、高效化以及提高设备可靠性等方面提供重要支撑,对提升航空航天高端装备设计水平有一定的借鉴意义.

     

    Abstract: Thermally driven creeping (also known as creeping or migration) refers to the behavior in which lubricant spreads directionally from a high-temperature area to a low-temperature area at the friction interface without external forces. In the rolling bearings of space mechanisms and precision instruments, lubricant creeping and loss increase frictional resistance, which in turn affects the operational accuracy of the system. Friction and wear are inevitable in mechanical motion, and the heat generated by friction leads to the formation of a temperature gradient on the surface of the friction pair. In extreme operating conditions, liquid lubricants are easily affected by surface tension, and even a small temperature gradient can cause lubricant to creep and migrate. In modern mechanical industries, the problem of lubricant creeping loss is common in bearings. During operation, the high temperature of the bearing raceway causes the lubricant to creep and migrate to the lower-temperature outer regions of the raceway, significantly reducing the bearing’s lifespan, leading to lubrication failures in mechanical equipment, and lowering production efficiency. This study used point-to-surface contact friction pairs consisting of typical rolling bearing balls made of GCr15 and Si3N4 and a 304 stainless steel flat surface, exploring the thermally driven creeping behavior and lubrication characteristics of lubricants under the combined effects of temperature gradients and interface motion. The study examined the changes in friction force under horizontal and vertical temperature gradients, including dry friction, silicone oil lubrication and different temperature gradient directions. The impact of roller diameter, roller material, and temperature gradient direction on friction and lubrication performance was also analyzed. The study introduced gravity as a factor and investigated how friction force changed when the gravity direction aligned or opposed the temperature gradient direction. It also observed the variation in contact angle during friction motion. The results showed that under the same experimental conditions, the friction force variation pattern was consistent for balls of different diameters. When the temperature gradient was perpendicular or parallel to the motion direction or vertical, the friction force changed inconsistently during reciprocating motion, exhibiting “symmetric” and “asymmetric” phenomena. When the temperature gradient direction was the same as the gravity direction, it accelerated the thermally driven creeping of silicone oil. However, when the temperature gradient direction opposed the gravity direction, it inhibited the thermally driven creeping of silicone oil. Further analysis revealed the effect of the creeping direction on friction force and contact angle variation. This research uncovered the mechanisms behind the differences in interfacial thermally driven creeping and tribological behavior under the synergistic effects of temperature and velocity fields. The findings were expected to provide valuable insights for designing durable localized lubrication in special operating conditions for space mechanisms and precision instruments. Additionally, it was expected to support the miniaturization, efficiency improvement and reliability enhancement of complex mechanical equipment, offering important guidance for advancing the design standards of high-end aerospace equipment.

     

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