Reliability Optimization Of Turning Process Parameters Based On The Copula Theory

In the process of turning,the regenerative chatter is the most common phenomenon.It's the main cause of cutting-tool wear too.Reliability analysis is turning system damping,stiffness and uncertainty quality parameter's effective method.But in practice,these parameters are correlated,and the correlation between them have great influence on the reliability analysis results.However,in order to simplify the calculation,most of the reliability methods assume that the parameters are independent of each other,which results in great errors in the results.Therefore,in allusion to the uncertainty and correlation of the parameters in the cutting off system with finite conditions,a new method called Copula function is introduced in this paper to deal with the Turning processing reliability analysis and cutting parameters optimization research.The main work is as follows:(1)Based on the Copula function,a joint probability density function is constructed.Based on this,a new method of dealing with the reliability of related variables is proposed based on Copula Rosenblatt transform,the geometric meanings of reliability indicators and the optimization method.The Vine Copula function is introduced to establish a structural reliability analysis method,which is used for the reliability analysis of multidimensional variables.(2)Based on the turning process and the regenerative chattering mechanism,the reliability model of the chattering system is established.Firstly,the stability of the turning system is analyzed to provide a reference for selecting the cutting width in the actual turning process.The turning method is used to calculate the turning Process reliability of flutter stability,the original test data and simulated sample points were compared to determine the correctness of the calculation.(3)In view of the fact that there are too few sample data of the chattering system,and the uncertainty of sample mean caused by small sample data will greatly affect the result of AIC,we introduce the Bootstrap theory of statistics to expand the sample data,to further improve the reliability analysis of turning process.(4)By turning the flutter stability reliability system obtains the maximum objective function,considering the design variable equivalent stiffness and equivalent damping,the relationship between the equivalent mass,natural frequency and damping ratio to lathe performance constraints as constraint conditions,establish turning processing system reliability optimization model of cutting parameters,cutting parameters reliability optimization design.The optimized result is the initial value,the design variables have different degree of change,the target reliability is greatly increased.