Research On Crashworthiness Structure And Its Energy Absorption Characteristics Matching Of Bus

With the rapid development of the economic society,the number of floating people has increased dramatically.As an important public transport for long-distance transportation,highway passenger buses are essential for long-distance travel.China is a country with a large territory and a large floating population.It is the largest country in terms of passenger bus production,sales,and ownership.However,the fatality rate of passenger bus accidents in China is far higher than that in developed countries in Europe and the United States.Therefore,research on passenger bus crash safety is of great significance.Compared with passenger cars,highway passenger buses are mostly flat-headed structures.Drivers are extremely vulnerable to injuries during frontal collisions.At present,there are no mandatory regulations at home and abroad for large highway passenger bus frontal collisions,and related research is lagging behind.This article is based on a school-enterprise cooperation project,combined with two authorized patents: a simple three-segment sleeve-type liquid-filled energy-absorbing element and an extendable and retractable bumper to study the front-collision energy-absorbing structure of highway passenger buses.The bus body skeleton is a space truss structure welded by thin-walled rods of different cross-section sizes and materials.In a collision accident,the collision energy is mainly absorbed by the crushing deformation of the rods.This article has processed rectangular beam energy absorbing elements of five kinds of common body materials and the simple sleeve-type liquid-filled energy-absorbing element.And the drop weight impact experiments were carried out to compare the crushing stiffness characteristics of different energy absorbing elements in terms of impact force and crushing distance.Compared with the rectangular beam energy absorbing elements,the liquid-filled energy-absorbing element can achieve constant pressure control during the energy absorption process and obtain a more ideal collision acceleration waveform,which represents a uniform energy absorption process and avoids excessively high concentrated peak acceleration.According to the flat head structure of highway passenger buses,the liquid-filled energy-absorbing element can maximize the energy absorption in a limited crush space,which has a simple structure and can be reused after crushing so as to effectively reduce the cost of collision maintenance.In order to carry out further research on the energy absorption structure in frontal collision of passenger buses,this paper adopts a method of experiment and simulation combination.The paper establishes an entire bus CAE model based on the parameters provided by the enterprise,conducts a finite element simulation analysis,and compares the simulation results with the enterprise's real vehicle frontal impact experiment to verify the validity of the model.At the same time,in order to improve the calculation efficiency in the research of the frontal energy absorption structure,the main deformation structure of the passenger bus is extracted.The front end of the body underframe is used as a substructure.Parameter design and energy absorption characteristics matching research are based on the substructure,and the optimal results were brought into the full bus model for verification.In the middle and low speed collision conditions,the energy absorption element absorbs most of the collision energy,the truss structure is nearly not deformed,and the collision acceleration is reduced,which effectively improve the safety performance of passenger buses in the low and medium speed collision conditions and reduce maintenance costs.The parameters of the sleeve and the relief valve were finally determined according to the optimal level of the element collision force.In view of the problem that the liquid-filled energy-absorbing element cannot fully absorb the collision energy even fully compressed under high-speed collision conditions,which results in the deformation of the front truss structure and the reduction of the collision safety indexes,this paper proposes an extendable and retractable impact energy absorption system.The design of the bumper energy absorption structure and the research of the system energy absorption characteristics matching were carried out based on substructure in different high-speed collision conditions.The overall size and material of the bumper were initially designed,the corrugated energy absorption block and energy absorption box were chosen as the energy absorption area of the longitudinal beam of the bumper,and then the collision simulation analysis was performed based on the substructure.Energy absorption box structure was finally chosen as the energy absorption area of the longitudinal beam.Three kinds of high-speed collision conditions are selected,and the thickness and length parameters of the energy absorption box are designed based on the optimized substructure of the liquid-filled element.The optimal parameters level combination of the energy absorption box is obtained through orthogonal experiment and range analysis method.The system's energy absorption characteristics are matched with the entire body at different collision speeds,and the optimal parameters level combination of the energy absorption box is brought into the full bus model for verification.The extendable and retractable impact energy absorption system is in the contracted state under medium and low speed conditions.The liquid-filled energy-absorption element and the front fixed part of the longitudinal beam of the bumper absorb most of the collision energy,and the body truss structure is nearly not deformed.The bumper is extended under high-speed conditions,the energy absorption of the system is increased by increasing the crushing distance in the front of the passenger bus and the impact on the driver and occupants in bus is obviously reduced.In this paper,through the design and research of the extendable and retractable impact energy absorption system,the front truss structure deformation in the frontal collision is effectively reduced,the energy absorption of the anti-collision structure is improved,the driver's injury is reduced,and the frontal collision safety performance of the bus gets effectively promoted.