Research On Reliability Modeling Of Oil Contamination In Hydraulic System Of CNC Machine Tools Based On Response Surface Methodology

Numerical control machine tools,known as the "mother machine" of manufacturing industry and the cornerstone of national industrial development,have played an important role in the remarkable achievements of China’s domestic equipment manufacturing industry.However,compared with advanced foreign brands,the reliability of domestically produced NC machine tools is significantly lower,leading to negative impacts on their market share and brand reputation.The reliability of hydraulic systems has always been the main factor affecting the overall reliability of NC machine tools.Data shows that the failure of hydraulic systems is mainly concentrated in the valve components,and the majority of valve failures are caused by particle contamination in the hydraulic oil.This paper focuses on the reliability modeling research of the hydraulic system and key components of NC machine tools,aiming to address the issue of hydraulic oil contamination,and provide a basis for improving their reliability.The main research contents of this paper are as follows:(1)Research on the influence of working condition factors on hydraulic oil contamination in NC machine tools based on uniform experiments.Firstly,compared with the orthogonal experimental design method,the reliability test of the influence of working condition factors on hydraulic oil contamination is designed and conducted based on the uniform experimental method.Then,the influence trends of multi-working condition factors and single working condition factors on particle variation are obtained by pre-processing the experimental data.Finally,through uniform experimental regression analysis,the functional relationship between working condition factors and particle variation of oil contamination is constructed,revealing the influence law of working condition factors on the variation of pollutant particles.(2)Research on the influence of pollutant particle size factors on hydraulic system performance based on deep density clustering algorithm.Firstly,the pollution particle size factor is tested for hydraulic oil contamination in the hydraulic system using the relief valve in the circuit as the test detection object.The pressure difference before and after the overflow valve is taken as an indicator to indirectly characterize the wear of the valve core caused by pollutant particles.Then,through the deep density clustering algorithm,pollutant particles that affect valve wear are clustered and analyzed according to particle size factors,and random variables for reliability modeling are determined.Finally,based on the number of pollutant particles that have the main impact,the calculation formula for the weight values of random variables in different size intervals is derived.(3)Establishment of a reliability model for hydraulic oil contamination based on response surface method.Addressing the implicit limit state function between the reliability of hydraulic oil contamination and pollutant particles under actual operating conditions,the applicability of the response surface model in the research of oil contamination reliability modeling is demonstrated.The dimension reduction approximation method and weight assignment are introduced to establish a reliability model for oil contamination based on the response surface method.The reliability model is solved by introducing adaptive functional forms and dynamic iterative step size,obtaining a functional expression of the probability of hydraulic oil contamination failure.The accuracy of the model is verified through experimental examples.(4)MATLAB was selected as the software development platform to design and develop a reliability evaluation system for hydraulic oil contamination in CNC machine tools based on the response surface method.The system integrates three modules:preprocessing of reliability test data,analysis of the variation of pollutant particles due to operating conditions,and modeling of the reliability of hydraulic oil contamination based on the response surface method,to achieve convenient,fast,and accurate evaluation of the reliability of hydraulic oil contamination in the system.