ISSN   1004-0595

CN  62-1224/O4

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表面粗糙度改善磁流变阻尼器密封副摩擦学性能的试验研究

Experimental Study of Surface Roughness on Improving the Tribological Performance of Sealing Pairs in Magnetorheological Damper

  • 摘要: 利用自制试验装置与高速往复摩擦磨损试验机模拟磁流变阻尼器密封副非线性磨损行为,通过与参考介质甲基硅油环境下形成的摩擦系数时变曲线对比分析,揭示磁流变液工况下表面粗糙度对密封副摩擦学性能的影响. 此外,在动力学特性分析的基础上对密封副磨损表面采用扫描电镜和能谱仪进行分析,探究密封副在磁流变液工况下的磨损机制. 结果表明,密封副在2种试验介质下的摩擦系数曲线变化形成了鲜明的对比,常规液压系统推荐的表面粗糙度参考范围已不再适合作为磁流变阻尼器密封系统的设计准则. 具体地说:磁流变液环境下粗糙样本展现出较低的摩擦系数和材料磨耗,磨损机制主要以三体磨粒磨损为主;而抛光样本对应的曲线波动剧烈且磨损严重,磨损机制主要以两体磨粒磨损为主. 经数据拟合方式得到的优化样本Topt ( R_\mathrmo\mathrmp\mathrmt=3.2\text μm) 在密封磨损试验研究中展现出良好的减摩特性和抗接触疲劳特性,揭示了配副表面粗糙度与悬浮铁粉平均粒径接近时有助于改善密封磨损性能,为延长磁流变装置密封系统使用寿命提供参考依据.

     

    Abstract: During the reciprocating dynamic sealing process, hydroxy iron powders suspended in magnetorheological fluid (MRF) enter the sealing interface under the combined action of hydrodynamic pressure and shear forces, which accelerating the friction and wear between piston rod and O-ring, eventually leading to the sealing leakage. This seriously endangers the working performance and even lifespan of magnetorheological damper. A self-made test device and a high-speed reciprocating friction wear testing machine were used to simulate the wear behavior of sealing pairs in magnetorheological damper. Through comparing the time-varying curve of friction coefficient formed in the reference medium methyl silicone oil, the influence of surface roughness on the tribological performance of sealing pairs under magnetorheological fluid is revealed. It should be pointed out that methyl silicone oil was the carrier fluid for the preparation of magnetorheological fluid and did not contain any particles. The purpose of choosing methyl silicone oil as the experimental benchmark in this article was to highlight the effect of hydroxy iron powders on the wear mechanism of sealing pairs. The results showed that the friction coefficient curves of sealing pairs under two experimental media were in sharp contrast, and the surface roughness reference range recommended by conventional hydraulic system was no longer suitable for the design criterion of magnetorheological damper sealing system. Specifically, the rough sample in magnetorheological fluid exhibited lower friction coefficient and material wear, which was mainly caused by three-body abrasive wear. While the curves corresponding to polished sample fluctuated sharply and wear seriously, primarily dominated by two-body abrasive wear. Moreover, the optimized sample Topt ( \sigma _\mathrmo\mathrmp\mathrmt=3.2\text μm) obtained by the data fitting method showed excellent anti-friction characteristics and anti-contact fatigue properties. It revealed that the surface roughness of piston rod was close to average particle size in suspended iron powder, which helped to improve the sealing wear performance, and provided a reference for extending the service life of MR device sealing system. Based on the analysis of dynamic characteristics, the wear morphology of sealing pairs was observed by scanning electron microscopy (SEM) and ultra-depth-of-field microscope to explore the influence of surface roughness on the tribological performance of sealing pairs under magnetorheological fluid condition. It revealed that the instantaneous coupling between iron powders and rough texture weakened the hysterical friction generated by asperities on the O-ring surface, thereby avoiding premature sealing failure. In addition, element distribution characteristics of O-ring wear surface were analyzed by energy dispersive spectrometer (EDS). It was further proved that change of contact state (i.e. embedding and/or rolling), and movement pattern of iron powder in the seal gap caused by surface roughness were the main reasons for the difference in wear mechanism of sealing pairs.

     

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