| Aviation self-lubricating joint bearings are very important dynamic components in aircraft control systems and power transmission paths.However,they often fail due to the wear of self-lubricating liners,which directly affect the stability and safety of aircraft operations.Therefore,it is urgent to explore the wear mechanism of the liners.The self-lubricating liners of aviation self-lubricating joint bearings often use PTFE/Kevlar braided composite materials.However,the wear mechanism of joint bearings in engineering applications and the wear characteristics of PTFE/Kevlar fabric materials are still not clearly revealed in the existing literature.Therefore,this paper selected Robinson R44 helicopter,which has the largest quantity in the world,as the research object,and carried out a detailed failure analysis on the key wear parts of the main rotor joint bearing after its service.Then,sliding wear tests of PTFE/Kevlar fabric liners were carried out by using friction and wear testing machine,and the influencing factors of the friction and wear properties and the evolution law of wear damage were explored,so as to reveal its wear characteristics,which has scientific theoretical significance and engineering application value.The sliding wear tests of PTFE/Kevlar fabrics were carried out.The influences of sliding friction type,friction load and cycle number on the wear behavior were systematically analyzed.Then,the wear morphology and damage mechanism of PTFE/Kevlar fabric liners were discussed by combining various tribological analysis and testing methods.The research results show that:(1)The failure analysis of the main rotor joint bearing found that the fiber wear and tear in the PTFE/Kevlar fabric liner are the main reasons for the failure of the joint bearing;Affected by the service load,the wear damage degree of the fabric liner at different circumferential positions is significantly different;In addition,the wear mechanism of joint bearings is fatigue wear,adhesion wear,abrasive wear and oxidation wear.(2)Under the reciprocating and rotating sliding friction conditions,the friction coefficients of the fabric liners show a trend of decreasing first and then increasing with the increase of load,but the tribological properties of the fabric liners are better under the rotating sliding conditions.When the load is 2 N(84 MPa),the tribological properties of the fabric are the best.When the load reaches 10 N(143 MPa),the wear of the fabric is serious and the tribological properties are the worst.(3)After reciprocating sliding wear,PTFE/Kevlar fabric liners wear damage part is PTFE fiber.In the early stage of reciprocating sliding wear test under small load,PTFE has good film forming ability and plays a lubrication and protection role on Kevlar fiber.With the increase of reciprocating times,PTFE wear was aggravated and accompanied by the spalling damage of the transfer film;At the initial stage of reciprocating sliding wear test under large load,PTFE fibers were directly worn off and torn;With the increase of reciprocating times,the worn fibers are continuously rolled into lamellar PTFE transfer film to accumulate and cover the wear marks,so that the wear accumulation rate decreases.(4)The reciprocating/rotating sliding wear mechanism of the fabric materials is characterized by fatigue wear and adhesive wear,accompanied by abrasive wear and oxidative wear to a certain extent.The degree of tribochemical behavior between friction interfaces is closely related to loads and cycles.(5)The laboratory sliding wear test can better simulate the wear damage mechanism of the aviation self-lubricating joint bearing gasket material,so as to provide a certain theoretical basis for the service of engineering materials and the anti-friction and wear-resistant design.. |
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