| Wear caused by friction is considered as the main cause of mechanical system failure and the main source of energy loss.Tribological phenomenon of friction and wear is a design problem that almost all mechanical equipment must consider.The wear resistance of parts can be improved by selecting metal materials with good wear resistance,improving manufacturing methods,heat treatment and surface coating.However,the friction and wear problem of mechanical transmission interface is still very serious and still needs to be continuously improved.Many animals and plants in nature live in harsh friction environment,and their surface structural characteristics,mechanical properties,material properties and other factors are coupled,which makes them have innate tolerance to friction,which has important reference value for friction reduction of mechanical transmission.Inspired by this,flexible and elastic surfaces,stimulated lubrication interfaces,wear-resistant microstructures,etc.are built in the transmission interface to realize the optimization of drag reduction and wear resistance and vibration suppression of mechanical transmission parts.The variable pore size and easily adjustable porosity of metal porous materials have certain elastic mechanical properties,as well as the ability to store and control lubricating oil.Under the action of or torque in mechanical transmission,this characteristic has positive significance for improving the lubrication conditions of transmission interface and alleviating friction and wear.In this paper,the properties and potential application possibilities of porous materials in self-lubrication and wear resistance are studied.Firstly,the design method and processing technology of porous metal materials for oil control are put forward.Simplify the pore size design of porous materials with the method of capillary pore size,and combine the simulation and experimental data to determine the design values or intervals of unknown parameters,and determine the size range of equivalent micro-pore capillary to control fluid exudation under the condition of differential pressure as transmission interface material [9.08),14.68)].According to the powder stacking theory and porosity design principle,[20%,40%] is selected as the design porosity interval of metal porous materials.At the same time,based on the powder metallurgy method,a preparation method with controllable porosity and pore size is designed,which takes vacuum sintering at 850℃,-0.1MPa and 4 hours as the main process after cold forming at 8～10MPa pressure.Secondly,through the observation and analysis of the microstructure characteristics of porous materials,this paper explores whether it has the potential of optimal application of friction reduction in transmission interface.The microscopic characterization and general formation law of porous metal materials are clarified.The typical sintering bridge structure on its surface is classified and discussed,and its characteristics,causes,functions and control methods are clarified.By measuring the porosity of porous samples with design values of 27%,20% and 14%,the state of pore connectivity of the internal space bridge-pore structure which constitutes the porous structure is further illustrated.Determine the proportion and causes of closed pores,blind pores and through pores in porous materials.It provides theoretical preparation for the application of porous metal materials in the optimization of friction reduction of transmission interface,and is of great significance for the evaluation of fluid control ability and the design of bearing capacity when it is applied to the optimization of oil control and friction reduction of transmission interface.Thirdly,the contact angle test is used to evaluate the micro-control ability of porous metal materials to the fluid lubrication medium.The solid-liquid contact angles between the measured oil droplets and the samples all fall between 12.0°～29.7°and less than 90°.Therefore,the stability of wear resistance of "Oil-mixing" porous materials under friction conditions with little or no oil supplement is discussed.The macroscopic mechanical properties of oil-containing porous materials were tested by compression test,and it was found that the elastic modulus decreased with the increase of porosity（25%,28%,40%）（494.7MPa,419.2MPa,176.8MPa）.Under the action of alternating stress,the oil-containing porous materials with low elastic modulus could provide driving force for the internal circulation of fluid in pores through extrusion effect,thus realizing body surface control.Finally,combined with the friction and wear experiments and simulation results,the comprehensive performance of porous metal materials in the optimal application of oil control and wear reduction in transmission interface is evaluated.Observe the micro-friction and wear test samples,compare and analyze the friction coefficient curves,and simulate and evaluate the stress-strain state of porous materials in friction behavior.Comprehensive analysis of the effectiveness of oil-containing porous materials in the friction reduction and optimization of transmission interface."Oil-mixing" treatment reduced the load change of porous samples from 80 N to 4 N in 120 min friction test.The average friction coefficient decreased from 0.68 to 0.13;The overall wear resistance is better than that of dense samples.In order to expand the application scenario of porous materials in the optimization of oil control and wear reduction of transmission interface,ANSYS was used to simulate and evaluate the application of porous materials of oil control metals to helical gears.The results show that the stress at the maximum stress point of the porous helical gear before and after "oiling" is 2.0983 MPa and 0.68013 MPa,respectively,which are less than its compressive strength of 43.6MPa and 43.5MPa.At the same time,"Oil-mixing" treatment can effectively reduce the maximum stress value of the porous helical gear and avoid stress concentration.The oil antifriction layer with uniform and stable oil porous structure and the oil circulation lubrication system with low elastic modulus can reduce friction and meshing loss,thus realizing the improved application of oil-controlled porous materials in helical gear meshing. |
