Research On Preparation And Tribological Properties Of Bn Modified Insulating Friction Materials For Ultrasonic Motor

Ultrasonic motor is a new type of driving motor,which has the advantages of large torque,light weight and no electromagnetic interference.It is widely used in aerospace,military and other fields.As a key component of ultrasonic motor,friction material is directly related to the service life and driving performance of ultrasonic motor.The application in aerospace and other precision fields requires the friction materials of ultrasonic motor to have insulation,but most of the friction materials for ultrasonic motor are polymer composites filled with a large number of metal particles and carbon fibers.The friction materials of ultrasonic motor still have the problems of poor insulation performance,short service life and low motor performance.Therefore,it is of great significance to develop a kind of insulating friction materials for ultrasonic motors with excellent mechanical properties,tribological properties and motor performance.This paper first studies the insulation mechanism and conductive mechanism of conductive particle filled polymer.Based on percolation theory,a simulation model of conductive characteristics of conductive particle filled polymer is established,and the influence of particle size and dosage of bronze powder on the conductive characteristics of polymer composite is simulated and analyzed.The simulation results show that when the amount of bronze powder is small,the material has good insulation.With the increase of the amount of filling,the material filled with large particle size bronze powder first occurs percolation conduction.Secondly,the effects of the amount and particle size of bronze powder on the mechanical properties,tribological properties and insulation properties of polytetrafluoroethylene(PTFE)were further studied by experiments.The results show that the tribological properties of PTFE are improved better by the large particle size of bronze powder.And the better particle size and dosage of copper powder were obtained.When the amount of bronze powder is small,the insulation of the material will decline even if there is no percolation.In order to further ensure the insulation performance,h-BN was used to replace part of bronze powder.Therefore,the effect of the amount and particle size of high insulating filler hexagonal boron nitride(h-BN)on the modification of polytetrafluoroethylene was studied.The results show that the larger the particle size of hexagonal boron nitride is,the better the modification effect is.And the modification effect of h-BN replacing part of bronze powder on PTFE is studied,the better dosage ratio of bronze powder / h-BN was obtained.Finally,the better dosage ratio and particle size of bronze powder / h-BN were applied to the formulation design of friction materials for ultrasonic motor.The mechanical properties,tribological properties,insulation properties and motor properties of each formulation were compared and evaluated,the results show that the friction material with 18% bronze powder and 6% h-BN has better comprehensive properties.