Research On The Durability And Reliability Of Jet Pipe Servo Valve

With the rapid development of science and technology and the substantial increase manufacturing level,the complex electromechanical systems are more and more widely used in the advanced military fields of aviation,aerospace,ships and weapons.As the core of advanced military field,the complex electromechanical systems generally have features of long life,high reliability,complex structure and higher research costs.On the one hand,the system will involve multiple disciplines of mechanical,electrical,hydraulic,control and their coupling.On the other hand,its constantly abundant structure and function and complex operating conditions will cause system failure,casualties,huge economic losses.Therefore,the durability life's calculation and the reliability level's assessment of the complex electromechanical system is the major issues related to not only current national security and stability but also national life and property safety.The jet pipe servo valve is a typical high-precision complex electromechanical system,it is named for its pre-stage is a particular structure of jet pipe amplifier.Since having a good performance on sensitivity,anti-pollution and dynamic response,etc,the jet pipe servo valve has been widely used to take the place of nozzle flapper servo valve in the military fields of aviation and ships,whose durability life and reliability will directly constraint the stability and security of whole military equipment,now in engineering its durability life and reliability is ensured relying on the conducting of requested experiments before leaving the factory,but this method has drawbacks of long cycle,high cost and low accuracy.Therefore,taking the jet pipe servo valve as an example,to research a method for durability life prediction and reliability assessment of complex electromechanical system,which would be of great importance for failures'qualitative analysis,quantitative prediction and theoretical life calculation of similar products.In this paper,based on the physics of failure theory and reliability theory,the jet pipe valve durability and reliability have been researched by means of numerical simulation methods,the main research work includes:(1)Based on in-depth analysis of jet pipe servo valve's the composition structure and working principle,the mathematical models of torque motor,armature feedback component,the jet pipe amplifier and the slide valve are established respectively.Now the method of lumped parameter model mostly simplify the flow field of jet pipe amplifier to linear equation for calculating,in this paper,the formula derivation of receivers'area distribution and the analysis of jet flow field based on conservation of energy are combined to finish the model establish of jet pipe amplifier.Considering leakage and oil compression,an improved spool valve model is established.At last the entire mathematical model's derivation of jet pipe servo valve has been finished.Furthermore,the simulation model of jet pipe servo valve are established and simulated through software of MATLAB,which is the basis of failure mechanism and failure critical value's identification during durability analysis,and also provides the objective function for optimization design.(2)Integrating dual points Grey Relation Projection(GRP)theory and intuition fuzzy theory,the improved study of FMECA has been conducted.Traditional FMECA method has the shortcomings of unable to consider the weight of impact factors,to appear parallel and highly sensitive phenomenon of RPN value,not to cover fuzzy hesitate degree,the dual points GPR theory and intuition fuzzy theory is especially introduced to FMECA to propose the intuition fuzzy FMECA model based on dual points GRP.Impact factors levels are determined using intuition fuzzy numbers considering hesitation degree,the weight set of impact factors are determined using Analytic Hierarchy Process(AHP)method,relative projection(RP)matrix is calculated using dual points GPR theory,and the criticality sort of failure mode is conducted in accordance with the ascending of matrix elements RP_i.At last,this method is used to analyze and sort the criticality of jet pipe valve's failure mode,which provides the basis for weak items'selection during durability analysis and the failure components and modes'determination during reliability analysis.(3)The physics of failure's principle and common failure mechanisms of complex electromechanical system are analyzed deeply,on the base of which this paper proposed a method for the durability analysis of complex electromechanical system,and the specific content of mechanism analysis,modeling of durability analysis,simulation analysis and durability index calculation is determined.Based on the third chapter,the weak items of jet pipe servo valve are determined and are respectively analyzed:the probability theory and fuzzy theory are introduced into traditional Miner theory to get fatigue life prediction model of specimen,the model involves two parts:fatigue dispersion model and fatigue damage model,which is used to further calculate the durability fatigue life of spring tube and the feedback lever;combining the theory of Computational Fluid Dynamics(CFD)with the erosion theory,applying of reynolds averaged Navier-Stokes equations,standard k-?two equation model,discrete phase flow model and the erosion wear model of plastic material,the erosion wear is simulated and the durability life is calculated of jet pipe servo valve's nozzle receiver parts;The linear wear degree is used to quantitatively describe the adhesive wear value between spool and valve sleeve,combining the descending wear value of spool's one stroke and the maximum wear value,the durability life of spool and valve sleeve's radial is calculated,while combining the theory of CFD and erosion wear,a spool valve sleeve working edge erosion model is established and the durability life is calculated;the equivalent stress of gasket ring is calculated through software of ANSYS,and the durability life of gasket ring can be determined based on the model of fracture mechanics.Finally,the whole valve's durability analysis was carried out.(4)The reliability of jet pipe servo valve has obvious randomness and dynamic,for solving deficiencies of traditional reliability modeling method in the description of time and dynamic process,at first,a dynamic reliability analysis method for complex electromechanical system was proposed based on Generalized Stochastic Petri Net(GSPN),which treat the system reliability as center,the dynamic reliability model considering repair time was established using GSPN.Secondly,another dynamic reliability analysis method for complex electromechanical system was proposed based on the Monte Carlo method,which set maintenance cost rate as optimization objective,the dynamic reliability model was established using Monte Carlo method,in which the different maintenance effect had been taken into account.Finally,the dynamic reliability of jet pipe valve were analyzed using the two proposed methods.(5)The jet pipe amplifier is the core component of of jet pipe servovalve,its amplification efficiency depends on the value of the structure parameter,which will affect the durability life of the jet pipe amplifier.Firstly,the maximum p_f of jet pipe amplifier is determined as optimization target and the requirements of durability life is determined as restrictions.Secondly,the chaos theory and PSO algorithm are combined to form chaos particle swarm algorithm,which not only improve the optimization efficiency but also avoid prematurity,and the chaos particle swarm algorithm is set as tool to conduct the structure parameter optimization of jet pipe amplifier.Finally,the erosion wear rate and spool displacement of the optimized structure is simulated to verify its validity.