Research On Crashworthiness Of Car Bumper Based On LS-DYNA

As the increase of automobile possession quantity,the number of traffic accidents has been increasing continuously in recent years,The problem of vehicle safety becomes more and more critical.Beside,safety has been a"green barrier"for exporting the Chinese brand vehicles to Western market.it is urgent and necessary to do some research in this field.The automobile industry mainly divides vehicle safety systems into two types:active safety and passive safety.The main content of vehicle safety systems is passive safety of vehicle.Passive safety,which is also called vehicle crash- worthiness,is how to protect passenger and pedestrian and reduce injury in the event of an accident by vehicle's structural integrity. In the research of passive vehicle safety,crash test is one of the most important elements. Frontal impact,which cause sever injure and death rate to passenger,is one of the normal crash types.So it's worth to do research on frontal crashworthiness of body structure.Bumper car body system is one of the important component of the car,in low-speed crashes,it can absorb low-speed collisions of energy,ease the impact of the outside on the body,it plays the major role in protection to body. In this thesis,through the establishment of the model of Pendulum body and the bumper system,simulating and analysising the collision process,is a basic research in the protection of the body in the conditon of low-speed collisions of Pendulum body and the car bumpers,provide reference value in the design of the bumper system which is based on the protection of body.Below is a brief introduction of the main content of chapters:In the second chapter,first of all,basis on the finite element theory and characteristics,and then introduce the main theoretical equations and algorithms of the crash simulation which is involved in the process of nonlinear finite element.In nonlinear finite element.according the very important position in the simulation of this paper,so it is necessary tohave a detailed introduce of the equation in the law of conservation of mass,momentum equation,energy equation,boundary conditions, contact algorithm,which is the foundation of the research in this thesis.In the third chapter,first of all,used the three-dimensional modeling software CATIA to establish a solid model of bumper systems,then through IGES file formats importe to Hypermesh to form the mesh model,which is form in nodes and finite element.Then detailed analysis the key factors which impact the accuracy of simulation such as: division of Grid,hourglass control,the interface processing method and time step control.In the fourth chapter,firstly brief introduced the collision of bumper simulation system used in finite element software ANSYS / LS-DYNA 3D,and then anslysis the generic processor of former pre-treatment,including the establishment of model definition of material properties,the definition of kind of material and the boundary conditions,solving,as well as for loading.Through the simulation of crash in low- speed frontal bumper,detailed analysis the dynamic response characteristics the low-speed impact of bumper, such as the deformation of the entire bumper system,maximum displacement of node, the changes of the velocity and acceleration of Pendulum in colision.Bumper system through the Pendulum impact dynamic simulation results of the following conclusions:1.In finite element analysis software ANSYS / LS-DANA 3D,analysis and simulation the process the collision in bumper and the Pendulum,formed a valuable simulation curve,thus proved that this simulation analysis method for bumper system crashworthiness provide effective reference value.And the simulation results showed that the largest displacement of the beam of bumper was less than the allowable value of the system in low-speed impact which show the better effect of energy absorption.2.In the course of the collision, plastic deformation of beam is greatly larger then the stent,in order to improve the overall energy absorption effects the bumper system,this paper presents a new design method of bumper system which based in the match of stiffness to increase the effect of energy-absorbing of bumper system.3.through the analysis and simulation of the results which was obtained in the low-speed bumper collision system which in the conditions of power failure mode, developed a low-speed bumper impact of the power failure criterion for bumper system which can provide reference for design and improvement of bumpers.4.Through the simulation and analysis of front bumper in low-speed collision, forming the universal mode of all kinds of model of bumpers,which can be applied to the analysis of other parts.The results show that:In the new stage of development models,make use of the kinds of methods to analysis the performance of bumper system, which can be used to improved and timely evaluation of the impact of the bumper system performance before stereotypes,in order to improve the Crashworthiness of new product effectively,which can improve the blue print and short the development cycle of new product and reduce development costs is of great significance.