Priority Order And Sensitivity Analysis Of Failure Mode Improvement For Mechanical System

Failure Modes and Effect Analysis is a reliable analysis method that supports reverse thingking.It can distinguish kinds of potential failure modes,failuer reasons and their effects which come from the process of system.In line with the established prior grade to judge if necessary to improve by the degree of priorities,formulate improvement measures and so on.Ttradition FMEA is a method that the occurrence,severity,and detection is multiplied and Risk Priority Numberis obtained.This method thus as RPN value sorting chaos,discontinous,low precision and sensitivity of defects also restricted the FMEA advantage in the product life cycle management.In view of the above defects,this paper takes the diesel engine as the research object,aiming at the deficiency of the traditional risk priority number,combining the fuzzy theory,the Technique for Order Preference by Similarity to an Ideal Solution(TOPSIS)theory,the possibility degree theory with the quality function deployment(QFD)method to analyze and study the quality and reliability of the system.The main research contents of this paper are as follows:(1).The FMEA research method based on corss-entropy and TOPSIS theory is proposed.In order to reduce the subjective preferences of decision makers in FMEA,the influence of uncertain factors on the results,and to get the system failure mode priorities for improvementm,the interval intuitionistic fuzzy sets into the intuitionistic fuzzy sets based on qpH,conversion operator,and the comprehensive performance value is obtained by Cross-entropy.With the goal of maximizing the value of comprehensive performance and attribute weights values range as constraint conditions,the fuzzy linear programming model is established to solve the weight coefficient of each attribute.Taking the turbocharged system of diesel engine as an example,the evaluation values are converted to interval-valued intuitionistic fuzzy sets by the SQ9000 evaluation criteria.Sorting,analyzing and comparing the danger of each failure mode are performed based on the RPN value,TOPSIS and the possible degree theory.Results show that this method helps to avoid information loss in the process of analysis,improve the accuracy of the risk priority number,avoid the sorting chaos,and have been able to focus on the key failure mode.Weak links in the system were identified and improvements were proposed.(2).The FMEA sensitivity analysis is researched.The weight and evaluation value of occurrence degree,severity degree and detection degree will directly affect the sorting result.A FMEA sensitivity analysis method that an approach to obtain the stable interval based on RPN value,TOPSIS,possible degree theory is put forward to determine the priorities of parts and analyzed the stability of ranking results.Finally,the feasibility and effectiveness of the proposed method is illustrated by the P-FMEA of transmission output shaft.(3).In order to fully consider the mutual influence between each failure mode and the satisfaction degree of the customer to the product performance and economic service,the FMEA analysis method based on QFD theory is put forward.Taking the fuel system as an example,the importance of customer demand is obtained by using analytic hierarchy process,and the importance of technical characteristics is acquired by using weighted geometric average arithmetic method.The importance of technical characteristics is converted to correction coefficient to feedback the FMEA evaluation,and the relative damage degree of each failuremodel is obtained.Through integration with QFD,the defects of unable considering the customer needs and technical characteristics in FMEA are remedied,and the information and basis of each failure modes’ depioyment and evaluation is provided.