Time-varying Reliability Optimization Design Of Drum Brake Based On Sensitivity Analysis

In the past two decades,as automobiles have entered people’s lives widely,the frequent occurrence of traffic accidents has also attracted more and more attention.As a key part of the brake system,the safety and reliability of the brake directly affect the safety of the car.In actual experiments,various structural parameters of automobile brakes show that the braking performance and reliability of automobiles are importantly related to them,so it is of great practical significance to optimize the structure of automobile drum brakes.In this paper,the reliability sensitivity analysis is added into the time-varying reliability optimization design of drum brakes,and the reliability sensitivity analysis is carried out for the random structural parameters that need to be optimized,which saves the cost and time of the optimization design.First of all,the time-varying reliability of the drum brake is taken as one of the constraints of the three elements of its optimal design,which can better solve the problems of the declining life and braking reliability of the drum brake in long-term use.The relationship among the braking reliability,braking distance and braking time of drum brake is obtained from the road test standard,and the time-varying reliability constraint condition is constructed.Secondly,by measuring the relationship between the structural parameters of the automobile drum brake and the impact on the braking performance,the optimal design variables,objective function and constraint conditions of the brake are finally determined,and the primary range of the design parameters is discussed and proposed.A new weighted coupling function with the maximum braking efficiency factor and the lowest braking temperature rise was established as the objective function of the mathematical model of time-varying reliability optimization design for drum brakes.Then,an example of the drum brake is given.The mathematical model of optimal design established above is used,and the genetic operator particle swarm optimization algorithm(PSO)program written based on MATLAB is used to optimize the solution.The optimization results show that: after optimization,the braking efficiency factor of the brake is 12.20% higher than that before optimization,and the temperature rise of the brake is13.59% lower than that before optimization.Then,according to the fourth strength theory of mechanical parts,the mathematical model among the strength,load and reliability of drum brake is established,that is,the reliability state equation of drum brake.Based on the perturbation method and the second moment of the structural parameters of the drum brake,the reliability design theory is presented,and the mean and variance sensitivity of the parameters to the reliability are calculated.The results are compared with the Monte Carlo numerical simulation results,and the reliability sensitivity analysis method is proposed.Finally,the prestressed modal analysis of the optimized drum was carried out based on ANSYS Workbench software,and the factor of the drum rotating along with the hub was introduced into the parameter design of the modal analysis.The results show that the drum brake can satisfy the natural frequency characteristics of road test under the prestressed modal analysis.