Reliability Research Of Machining Center Turntable Based On Dynamic Fault Tree

Machining center turntable is an essential functional part of machining center.Its reliability level has a great influence on the performance of the whole machining center.The research on the reliability of the machining center is the basis of ensuring the safe operation and production of the machining center.The research has important theoretical and practical value.It has been 60 years since the appearance of the first machining center.The complexity of machining centers is becoming higher and higher,and the failure modes of the parts are also varied.The system has the relation and dynamic characteristic.The reliability analysis of a system with dynamic characteristics,traditional methods such as reliability diagram and fault tree,Markoff can not describe dynamic process for the failure to establish the accurate logical model has certain limitations.Therefore,this thesis proposes a dynamic fault tree method to analyze the reliability of the machining center.In this thesis,the dynamic fault tree of the machining center is established,and the static and dynamic subtree is obtained by the method of solving the dynamic fault tree.The static subtree is analyzed by the method of two element decision graph,and the dynamic subtree is transformed into a Markov model for qualitative and quantitative analysis.Finally,we obtain the reliability index of the dynamic fault tree by using the combined algorithm of the dynamic subtree and the static subtree.In addition,the reliability analysis and safety evaluation of the machining center is carried out based on the Markov chain.However,for complex systems,it is not convenient to use the above mentioned Markov models.Because the amount of computation is too general to produce the combinatorial explosion problem,and the use of the Markov method is conditional,it requires that the failure rate of all the bottom events of the fault tree is exponentially distributed.However,in real life,the failure rate of most parts is similar to Weibull distribution.The dynamic fault tree analysis method based on the trapezoidal formula does not limit the failure probability distribution of the bottom of the fault tree.This thesis uses this method to analyze the reliability of the machining center table,dynamic fault tree and Monte Carlo method turntable on the machining center is simulated.The results show that the Monte Carlo simulation of bottom event failure probability distribution is not restricted.Finally,the FMEA method is used to analyze the failure mode of the machining center.According to the relationship between the probability of bottom event,each between severity and detection of the three to calculate the risk priority number,and the failure mode risk priority number higher proposed solutions and preventive measures,improve the reliability and safety of the machining center of the turntable.