Structural Reliability Optimization Design Of EMU Motor Hanger

With the development of high-speed rail vehicle technology,higher requirements are put forward for the structural reliability of the vehicle and its key components.As an important suspension device of EMU,the structural reliability of motor hanger has an important influence on the safe operation of the vehicle.Therefore,considering the influence of uncertain factors such as structural geometry size and material properties,it is of great significance to optimize the structural reliability design.Based on the static/dynamic analysis theory of structure and reliability optimization theory,this thesis adopts the approximate model technology and multidisciplinary optimization method to realize the structural reliability optimization design of motor hanger with the help of computer simulation,aiming at improving the comprehensive performance of motor hanger and providing guarantee for the safe operation of EMU.The main research work of this thesis is as follows:Firstly,a structural reliability analysis method based on response surface model combined with the first order second moment method is proposed.Based on the geometrical model of the motor hanger,the finite element analysis model is established after proper simplification of the structure;according to UIC615-4-2003 standard,three different abnormal load conditions were added to check the static strength.In order to save calculation resources,a response surface model of the maximum equivalent stress under the first working condition was constructed.Considering the influence of the uncertainty of structure geometry size and material properties on the static strength of the structure,the limit state equation of the static strength was established based on the stress-strength interference theory,and the static strength reliability of the motor hanger was analyzed by the first order second moment method to obtain its reliability value.Secondly,a simplified chaotic particle swarm optimization algorithm with fast convergence speed and the ability to get rid of local extremum is proposed.By removing the particle velocity term and using chaotic sequence to perturb the extreme value of the particle,the convergence speed and precision of the algorithm are improved.Aiming at the problem of insufficient reliability of structural static strength,a single objective reliability optimization mathematical model of the motor hanger was established.The simplified chaotic particle swarm optimization algorithm was used to optimize and the optimization results were verified by simulation.In order to further improve the robustness of the structure,multi-objective reliability optimization was carried out on the motor hanger,and the Pareto optimal solution set was obtained by using the multi-objective simplified chaotic particle swarm optimization algorithm,according to the design requirements,a group of optimization schemes were selected from the Pareto optimal solution set and verified by simulation.Finally,the reliability-based multidisciplinary design optimization of motor hanger is realized based on the collaborative optimization framework.In order to evaluate the vibration characteristics of motor hanger,the modal analysis and harmonic response analysis were carried out.Considering the influence of vibration frequency of traction motor on motor hanger under the maximum operating speed of EMU,the resonance threshold was introduced to obtain the resonance interval of the structure,and the vibration failure mode of the motor hanger was determined.The vibration limit state equation was established,and the vibration reliability was analyzed by Monte Carlo method and the vibration reliability was obtained.In addition,the response surface function of the first order natural frequency is fitted,and the upper limit of the resonance interval is used as the constraint to construct the functional function to obtain the vibration reliability index function.Considering the mass,static strength,vibration characteristics and reliability of the motor hanger,collaborative optimization strategy is adopted to carry out system classification,set up an optimization framework and obtain the best solution with the help of Isight platform,the accuracy and effectiveness of the optimization process were verified by simulation analysis of the optimization results.