Research On Structure Durability Analysis And Optimization Design Approachs For Special Vehicle

With the development of special vehicle such as tank,self-propelled gun etc.on speeding up and lightweighting,the volume and weight of mechanical product require significant reducing,while the demand for high-reliability or long-life products is enhanced.In the development of new generation armored vehicle,the goal for speeding up and lightweighting of equipment is to be a reality,but the problem for machinery equipment with a shorter lifespan than before became acute,because redundant strength of key parts is reduced.It is a key technique to design product how to maintain or improve durability under the premise of meeting performance requirements or reducing weight and volume of product.Therefore,it is very necessary that research about structure durability analysis and optimization design technology is carried out.Combining durability analysis technology with optimization design technology and applying to product design,this durability technology will achieve balance and optimization among various quality characteristics such as performance,reliability,volume,weight,and cost and so on.The goal of existing durability analysis technology is mainly to predict economic life of product,and the difference between prediction result and actual data is large for generally considering randomness of life to be a diversity factor.Therefore,the researches of this thesis consider randomness of durability factors,and focus on reliable life prediction,reliable life sensitivity analysis,and multidisciplinary optimization with reliable life as object or constraint.This thesis provides a series of practical durability analysis and optimization technology for engineering,presents the following contributions:(1)The fatigue load spectrum processing method for structure under complicated conditions is studied,and the strain fatigue reliability analysis algorithm is improved.For machinery equipment structure such as armored vehicle with complex conditions,the fatigue load spectrum processing and spectrum method for multiple working conditions is researched.Because strain fatigue life is usually obtained by Manson-coffin formula and Neuber method,which have high nonlinear degree,it is difficult to convergence for calculating reliability degree by second order moment method.In view of the strain fatigue life analysis process,a steady strain fatigue reliability analysis algorithm is studied by using the methods of automatic step length adjustment.(2)The structure fatigue reliable life analysis method based on probability performance measure,which is a quick measure way for reliable life,is proposed by introducing performance measure approach.This method need not know the specific distribution of life.For solving reliable life,some steadier algorithms,such as conjugate gradient algorithm and improved search algorithm,are proposed by improving convergence and efficiency of performance measure approach.Moreover,the sensitivity degree for each random variable and deterministic variable can be calculated by using some intermediate variables in the optimizing process.And the improvement measure for structure can be point out by sensitivity degree result.(3)Considering the time-dependence and randomness behavior of wear process,the wear random process model is developed on the basis of wear mechanism,and a new method for predicting wear reliable life is proposed.Analyzing the essential characteristics of wear process,the flowcharts and methods for building wear random process model based on wear mechanism model are studied,and a series of method for assessing dynamic reliability degree and reliable life is proposed.(4)The durability optimization models with reliable life as object or constraint are developed,and the corresponding optimization algorithms are proposed.Considering the randomness of durability factors,the workflows and methods establishing durability based multidisciplinary co-simulation models are proposed by using CAD software,finite element analysis software,multi-body dynamics software etc.,and design of experiment method,response surface method.Combining sequential quadratic programming algorithm with reliable life prediction method,the double-loop performance measure approach and single-loop performance measure approach for durability optimization are studied with reference to structure reliability based optimization method.What's more,the hybrid-loop performance measure approach is proposed by analyzing on their advantages and disadvantages in computational efficiency and accuracy.(5)Because optimization gradient algorithm like sequence quadratic program(SQP)has shortcoming of trapping in local optimum when solving the multi-extreme value problem,the improved cuckoo search algorithm for structure durability optimization is proposed by introducing a new type of swarm intelligence algorithm.This algorithm can be used for global optimization.First of all,with the goal of intensifying convergence and increasing efficiency,the cuckoo search algorithm is improved in various ways,such as migration strategy,convergence criterion,constraint handling.Then,the improved algorithm is combined with durability based optimization method,and can be applied to complex structure durability optimization.(6)For a special vehicle,the output torque spectra of engine under complex vehicle driving cycles are drawn up to structure design and analysis.The torsion shaft in running system,piston ring in power system and gear box in drive system have been chosen as subjects,applying structure durability analysis and optimization design technology to check validity for above methods.Above all,considering randomness of factors influencing structure life and strong-nonlinearity of life model,a number of new methods are proposed to analysis reliability life and sensitivity degree for structural wear-out failure,like fatigue and wear.These methods include the following:reliable life and its sensitivity analysis method based on probabilistic performance measure,and wear reliable life analysis method based on stochastic process.The durability optimization models with reliable life as object or constraint are developed,and the corresponding local and global optimization algorithms are proposed on the basis of SQP and improved cuckoo search algorithm.All these endeavors to provide a series of structural durability design and analysis theories and methods for machinery equipment such as vehicle,weapon etc.