The Research On Ball Bearing Life Prediction Based On CSALT Scheme Improvement And Optimization

Bearing life is greatly affected by material, processing technology and working condition, so it has a strong randomness. At present people predict the bearing life and reliability mainly through simulating actual working condition of the life test in engineering practice. However, test cycle of the conventional bearing life test is too long and the cost is not in control. Therefore the theory of accelerated life test developed. Ultimate goal of studying the theory is to reduce the test cost and better to predict the life of the product at the same time. In this paper, the traditional CSALT of ball bearing is improved and optimized based on the deep groove ball bearing as the research object from three parties: acceleration load limit estimation method, test truncation, sample distribution. Test void rate, test time, failure information and life prediction results of ball bearing CSALT is explored through some methods,such as Hertz contact theory analysis, finite element analysis, programming, simulation and practical,etc. The purpose is to ensure test success rate, reduce the test time cost and better predict the bearing life. Methods and conclusions are as follows:(1) The advantages and disadvantages of estimating the maximum contact stress respectively by Hertz contact theory and finite element analysis method is analyzed. The inverse process of Hertz contact theory estimating the maximum contact stress is used to deduces theoretical formula for calculating acceleration load limit. The theoretical formula for calculating acceleration load limit is revised according to the results of finite element analysis. Conclusions are as follows: The theoretical formula for calculating acceleration load limit cannot guarantee test bearing failure mechanism is not changed and the estimated results inaccurate. The revised formula for calculating the acceleration load limit can guarantee test bearing failure mechanism is not changed and more in line with the CSALT design basic premise.(2) A hybrid improved truncation is put forward for the shortcomings of ball bearing CSALT conventional truncation(fixed time, fixed failure number). The simulation empirical value is got through the total CSALT of bearing instances and the best linear unbiased estimation method. The influence of v value in the hybrid improved truncation on test void rate, average number of test invalid, life prediction results and test time are analyzed through using the monte carlo method, the maximum likelihood estimation method and MATLAB software programming. The determination method of hybrid improved truncation threshold is given. Then the influences of hybrid improved truncation and traditional truncation on life prediction results and test time are comparative analysis respectively through using programming and the results of actual test results. Conclusions are as follows: Aiming at the deep groove ball bearings that are produced in the common mode of smelting and processing level in our country, test void ratio and average number of test invalid is too large, and repeat test cost is larger in the case of v?1.1. Test void ratio and average number of test invalid is low in the case of v=1.2~1.9, and with the increase of v, gradual variance, characteristics of bearing life, shape parameter is fluctuating; test time increasing damping. Test void ratio and average number of test invalid is the lowest in the case of v ? 2.0, but gradual variance, characteristics of bearing life, shape parameter and test time have reached a fixed value. Hybrid improved truncation overcomes the disadvantages of traditional timing truncated that prediction accuracy is poorer and the disadvantages of traditional destiny truncation that test time cost is not under control. Prediction accuracy is still good, when the test time is in the constraint.(3) A set of perfect programmed optimization design scheme is formulated with using the monte carlo method, maximum likelihood estimation method, hybrid improved truncation and the minimum asymptotic variance as the optimization criterion for simulation optimization design problem of ball bearing CSALT sample distribution under interval stress level. The influence of sample distribution on the results of life prediction is analyzed with using MATLAB software to program simulation. Conclusions are as follows: Sample distribution simulation optimization design scheme that is formulated in this paper is correct and feasible, and the optimal sample distribution scheme is not the traditional interval sample distribution scheme. Sample distribution optimization is beneficial to improve prediction accuracy before undergoing ball bearing CSALT.Finally, a set of perfect ball bearing CSALT and consistency analysis is given based on the above improvement and optimization, and is applied to an example verification.