Multi-factor Coupled Lubrication of Micro-textured Spool Valve Pairs in Launch Vehicle Servo Mechanisms

doi:10.3901/JME.260011

Abstract

Abstract: In launch vehicle servo mechanisms, the spool valve serves as a fluid control unit, whose frictional lubrication characteristics at the moving interface significantly affect transmission performance and ultimately impact the vehicle's flight control accuracy. A micro-texturing-based lubrication solution is proposed to address the lubrication and wear issues of spool valve pairs. Diamond-shaped micro-textures with a depth of approximately 10 μm and surface roughness Ra of 1.66-2.33 μm were fabricated on cylindrical valve cores using femtosecond laser processing. Tribological experiments and parameter optimization were conducted. Results showed that under test conditions of T=40 ℃, F=40 N, and U=0.5 m/s, the diamond-shaped texture with parameter combinations of diagonal ratio k=3 and diagonal-to-spacing ratio x=2 exhibited the lowest friction coefficient (f=0.09965). This represents a 39.61% reduction compared to the average friction coefficient (f=0.165 02) of non-textured surfaces under identical test parameters. Experimental results further revealed that increasing velocity significantly reduces the friction coefficient. The k=3 textured surface demonstrated optimal lubrication stability across a wide speed range. Excessive or insufficient loads led to incomplete or ruptured oil films, compromising surface load-bearing capacity. Furthermore, response surface methodology (Box-Behnken design) was employed to elucidate the coupling effects of load F, diagonal ratio k, and diagonal-to-spacing ratio x. The optimized parameter combination (F=40.76 N, k=3.07, x=2.03) achieved a predicted friction reduction rate of 39.84% compared to non-textured surfaces, showing good agreement with experimental results. Post-test wear characterization revealed that the surface textures effectively prolong service life of the spool valve pair by maintaining lubricant reservoirs, trapping generated wear particles, and generating beneficial hydrodynamic lubrication - collectively reducing abrasive wear progression.

Key words: spool pair, micro-texture, drag reduction rate, response surface methodology

CLC Number:

TH117

HUANG Yuping, LIU Ao, CUI Peijuan, HOU Zhanlin, GUO Chunhai, ZHANG Wenwu. Multi-factor Coupled Lubrication of Micro-textured Spool Valve Pairs in Launch Vehicle Servo Mechanisms[J]. Journal of Mechanical Engineering, 2026, 62(1): 171-181.

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