Performance Degradation Mechanism And Experimental Research Of Ball Screw Pair

This project was supported by the National Science and Technology Major Project.The paper explores the performance degradation of ball screw,designs the accelerated performance degradation test,and carries out reliability analysis based on performance degradation data to achieve a reasonable prediction of the ball screw failure life,so as to guide enterprises to maintain the CNC and reduce the economic losses,with great value of engineering application.The main contents of this paper are as follows:Firstly,from the perspective of contact properties,friction and wear,the performance degradation of ball screw is studied.Two main performance characteristics that affect the actual function of ball screw-accuracy and preload are selected as the main research goals.As a theoretical basis for the accelerated performance degradation test.Secondly,aiming at the problem of the friction coefficient value in the preload calculation,the kinematics and dynamics model of the ball and raceway are established based on the structural characteristics of the ball screw.The formula for calculating the friction coefficient is deduced.The coefficient of friction was measured by the preload adjusting device and the friction torque measuring system,and the reasonable selection criterion of the friction coefficient of the ball screw was given.Furthermore,seting up the performance degradation test platform of the ball screw.Through the degeneration test of the normal stress performance of the ball screw,the failure threshold of the preload and accuracy was determined.The accelerated performance degradation test of accuracy and preload under three levels of constant stress is completed.Finally,based on the degradation data of accelerating performance,the performance degradation model of ball screw was established and the failure life of preload and accuracy of the screw under different stress conditions was calculated with reference to the failure threshold.On this basis,the reliability analysis is carried out by means of the virtual augmentation method of small sample test results and the data processing method of two-parameter Weibull distribution model.Based on the data of the average life expectancy of failure,an accelerated degradation model of the tested ball screw is established.The model can reasonably predict the accuracy and preload failure life under different accelerating stress conditions.