Research On Improved Bi-directional Evolutionary Structural Optimization Method And Its Application In Crash Topology Optimization Of Highway Guardrail

With the continuous increase of car ownership in China,road traffic safety has become a major challenge faced by the traffic industry.The importance of highway guardrail structure as the last"safety belt" to protect drivers is self-evident.Crashworthiness guardrail structure lightweight and design has become improve guardrail use function and safety of important basis,and the structure of lightweight and crashworthiness design belongs to the contradiction and unity relations,due to the topology optimization of the crashworthiness guardrail structure belongs to the typical structure of strongly nonlinear dynamic response topology optimization problem,is one of the more complex optimization problems.Based on bi-directional evolutionary method under impact load crashworthiness structure topology optimization analysis,the numerical instability,iteration is difficult,computational efficiency is low,the two-way gradual method(0-1)unit neighborhood of the criterion and method of cellular automata thought,the combination of improved bi-directional evolutionary algorithm(in this paper,hybrid algorithm for short),and to our country representation-in structural crashworthiness guardrail structure as an example to carry out the single objective optimization,the cyclic periodic single objective optimization,multi-objective optimization of crashworthiness structure topology optimization research,The optimization results show that the proposed hybrid algorithm can well solve the impact loads crashworthiness structure topology optimization problem,and the computational efficiency,the iteration speed,the numerical stability are improved than the traditional algorithm,the conceptual model to extract the corresponding structural topology optimization,the guardrail design standards and requirements for simulation technology in our country,through the satisfaction function will be treated as single objective optimization by a weighted,carry out structural multi-objective robust optimization,in order to design out of accord with the actual conditions of our country have strong antinoise ability of new guardrail products,make the structure crashworthiness and light levels are increased.The main research work carried out and the relevant conclusions are as follows:1)From the structure crashworthiness topology optimization method and the application of the two aspects of the research status at home and abroad were reviewed,based on the method of topology optimization of the structure crashworthiness and application characteristics,this paper compares and analyzes the key problems,in order to make clear the research methods and application scope of this article,and as the basis for this paper introduces the structure and content of each chapter in turn.2)Expounds the structure of the collision analysis theory and guardrail structure collision safety evaluation standard,and discusses the improvement of bi-directional evolutionary algorithm in crashworthiness guardrail structure topology optimization of the process and complete theory,and with China’s current common grade A semi-rigid guardrail,for example,by comparing the PVC material and Q235 material qualitative difference between the mechanics,combining the theory of beam and slab,respectively from two aspects of qualitative and quantitative test based on the finite element model for 10 t passenger vehicle,set up 10 t coach-PVC guardrail topology optimization coupling model,get close to"H" type of new PVC guardrail configuration;Combined with China’s guardrail design code,the new PVC guardrail configuration obtained and the finite element model of a 10T bus were combined to carry out a simulation full-scale verification test.The correctness of the proposed method was verified by analyzing the acceleration value at the center of mass of a l0T bus and the maximum dynamic offset of the guardrail when the collision effect between a 10T bus and the new PVC guardrail.3)The current topology optimization analysis for the crashworthiness of structures is based on a single working condition based on the design specification.However,in actual working conditions,structures often need to bear impact loads in multiple directions,which is a typical multi-objective structural optimization problem,and multi-objective optimization and single-objective optimization belong to the relationship between contradiction and competition.In this paper,based on improved bi-directional evolutionary algorithm,was established by the method of grey correlation weight coefficient of each working condition of the collision,the compromise programming method are used to get the multi-objective optimization function of pareto set function,working condition of each single target collision for the optimal solution of the normalized processing,in order to satisfy a variety of working condition of the collision of crashworthiness multi-objective topology optimization method.Guardrail design code in China,respectively,from two aspects of qualitative and quantitative test was carried out on the 1.5 T car,and in our country is the most common fenders,for example,through the establishment of 1.5 T car-is,side touch,oblique impact,are side,again touch topological coupled finite element model,in order to satisfy different working condition of the collision of new fenders suction box topology optimization configuration;The new type of collision cushion configuration and 1.5T car were used to establish a full-scale simulation and verification test under five collision conditions.The maximum acceleration value at the center of mass of the body after the contact between 1.5T car and the new collision cushion was analyzed to verify the correctness of the proposed method.4)In the structure optimization design are established on the basis of the structural design parameters to determine,but in actual production process measurement error due to the processing technology,equipment,subjective and objective reasons,such as objective reason will have a big impact on the use of the structure function,this paper combines the robustness optimization design with satisfaction function,through determine the range of the design domain and noise factor,combined with the structure design of hope big characteristics,features,hope small features,the multi-objective optimization function normalized processing.Guardrail design code in China,determine the structure noise factors in actual working condition,establish the multi-objective robust optimization mathematical model based on the satisfaction function,and new PVC guardrail configuration in chapter 2,the three chapter new fenders for example combining has 10T test bus and 1.5T car model of the full-scale finite element simulation model is set up,respectively,to the body center of mass of maximum acceleration,guardrail guardrail structure maximum lateral dynamic offset fenders structure body center of mass of energy absorption ratio of the maximum acceleration,fenders,as a multi-objective optimization of the structure of the response,Guardrail and vehicle fenders structure quality,speed,collision Angle,material for uncontrolled factors,multi-objective robust optimization,in order to get on the premise of meet the structure function has stronger antinoise performance of new PVC guardrail configuration,new fenders size parameters of the configuration of the optimal combination;The optimal structural parameters obtained were combined with the 10T bus and 1.5 car model simulation full-scale verification to verify the correctness of the multi-objective robust optimization method extracted in this paper.