Experimental study on the side impact of the hotte

Automotive side impact test research

Abstract: with the continuous development of automotive safety research in China and the improvement of domestic automotive impact test water, which mainly tests the fatigue performance of production materials, regulations on automotive side impact safety have also begun to be promulgated and implemented. According to the regulations on the certification of motor vehicle side impact occupant protection (CMVDR 295) compiled by the Bureau of machinery industry in 1998, the automobile crash Laboratory of Tsinghua University has carried out a lot of research work on side impact. The software and hardware equipment in the test have met the requirements of side impact test. At the same time, through the research on the mechanical properties of standard aluminum honeycomb and a variety of energy absorbing materials, The energy absorbing structure that meets the requirements of vehicle side impact test regulations is obtained

keyword: side impact; Image motion analysis; Aluminum honeycomb

Research of vehicle side impact test

Jin Xin, Li Zhenping, Zhang Jinhuan, Huang Shilin

State Key Lab of automotive safety and energy, Tsinghua University

[abstract] with the development of vehicle passive safety research and the improvement of the vehicle impact test methods, the side impact regulation will be broke into effect soon in china Based on the China Motor Vehicle Design Regulation (CMVDR295), a lot of research of side impact test has been carried out in automobile collision test laboratory in Tsinghua University. In these tests, the instruments and the procession fulfilled the request of the regulation. In addition, this paper introduces the research based on the mechanical character of the aluminum honeycomb which is used in the side impact test, putting forward the blue print of a new energy absorbing structure for vehicle side impact tests.

key words: side impact analysis of image motivation aluminum honeycomb

1 Introduction

vehicle side impact accidents are traffic accidents with high frequency and a large number of serious injuries in China. Statistics show that in 1998, the incidence of side impact accidents accounted for 31.56% of the total traffic accidents, and the number of serious injuries accounted for 30.15%, which exceeded the corresponding data of frontal collision accidents. Therefore, it is necessary to improve the protection performance of passengers in side impact. The automobile side impact test has just been carried out in China. According to the regulations on the certification of passenger protection in side impact of motor vehicles (CMVDR295) compiled by the Bureau of machinery industry in 1998, the automobile side impact test room of Tsinghua University has carried out several automobile side impact tests, and has carried out some research work on the automobile side impact test and the side impact energy absorbing materials

2 research on energy absorbing materials for side impact test

an energy absorbing material with honeycomb structure is placed in front of the moving wall in the side impact regulations to simulate the front stiffness of the impact vehicle in the side impact accident of two vehicles. The characteristic values (mass, shape and stiffness) of mobile deformable barrier (MDB) are simulated according to the vehicle characteristics of various countries, and the regulations on MDB in European and American regulatory systems are also very different. At present, the draft of side impact regulations in China is prepared according to ECE R95, and the characteristics of energy absorbing materials are also consistent with European regulations

the standard energy absorbing materials necessary for the vehicle side impact test are consumable materials, which can only be obtained through import at present. The price is relatively expensive and the procurement cycle is long. In order to carry out the research of side impact successfully in China, the source of standard deformed materials must be solved. Based on the source of materials in China, the automobile collision Laboratory of Tsinghua University has carried out extensive experimental research on a large number of possible alternative materials, and proposed an energy absorbing structure composed of a variety of materials. The experimental results show that the energy absorbing structure has met the regulatory requirements, greatly reduced the cost, and achieved good results

2.1 side impact test regulations on the impact barrier

the automobile side impact regulations have detailed regulations on the standard energy absorption structure used in the test: the impact material is aluminum honeycomb structure, and the impact wall is composed of six independent blocks. The regulations not only stipulate that the overall energy absorption characteristics of the impact wall can be distinguished according to the appearance of the extruded material, but also provide the force deformation characteristics of each block. However, the regulations also indicate that other materials that meet the characteristics requirements can also be used in the side impact regulations after being approved by the relevant institutions. Therefore, the development of energy absorbing structure in this paper mainly focuses on the selection of different domestic materials or specifications

2.2 test of alternative materials and analysis of results

in the process of research, static compression tests were carried out on various materials, including foamed plastic, foam aluminum, aramid paper honeycomb of various specifications, aluminum honeycomb, and paper honeycomb materials, to investigate their force deformation characteristics, and to determine the materials and combinations that can be used in vehicle side impact tests

the material properties required in the regulations are roughly manifested in three stages: the pressure increases linearly to the compressive limit - the pressure drops to a more stable compressive strength - the pressure begins to increase after deformation

through the test, it is found that the adhesive of aramid paper material shows obvious non-uniformity, which leads to the continuous increase of pressure during the deformation process. Figure 1 shows the characteristic curve of aromatic paper honeycomb. The non-uniformity of this material structure will increase the uncertainty of the test results, and it is difficult to be used as the material of standard collision energy absorption structure. The ideal foam aluminum has good impact response characteristics, but due to the limitation of the current production process level of foam aluminum, its foaming process and foaming size are difficult to control, and the pressure of foam aluminum selected in the test continues to rise in the stable stage of static compression characteristics due to the non-uniformity of the process. Although foamed plastics have a certain guarantee for its processability, the static pressure characteristics also show that the pressure deformation characteristic curve increases continuously throughout the compression stage, and the increase range is large, so it is difficult to achieve the compression response characteristics required by the regulations

Figure 1 aromatic paper honeycomb characteristic curve figure 2 aluminum honeycomb static pressure characteristic

through test screening, the static compression characteristics of paper honeycomb and aluminum honeycomb materials are relatively ideal, as shown in Figure 2. In the stable fold buckling stage, the static compression load deformation curve shows good characteristics, and can be used as an alternative material for the standard energy absorbing material structure. The standard energy absorbing structures commonly used in the world also use aluminum honeycomb materials. The purpose of domestic aluminum honeycomb is mainly to strengthen the stiffness, and its specifications and models are not many, which increases the difficulty of forming a standard energy absorbing structure that meets the regulations

through a large number of tests on the materials that may be used, the materials that form the energy absorbing structure for side impact are selected, and the combination scheme is proposed according to the load characteristic requirements of the regulations, and the required structure is composed of different materials. Taking the second energy absorbing structure as an example, figure 3 shows the energy absorbing material composed of paper honeycomb and aluminum honeycomb of different specifications, and Figure 4 shows the comparison between the static pressure test results of the side impact energy absorbing structure and the characteristics required by the regulations. It can be seen that the static compression load deformation curve with fast energy absorption shows good mechanical properties, and can be used as an alternative material for the standard energy absorbing material structure. Moreover, the cost of new materials is lower than that of imported materials, which reduces the test cost and lays a foundation for the localization of side impact standard energy absorbing materials

3 research on vehicle side impact test method

3.1 kinematics analysis and test site layout of side impact

domestic vehicle frontal collision was carried out relatively early, and some vehicle collision test sites are planned based on a common level of tensile testing machine. With the continuous improvement of vehicle safety regulations, the research on vehicle side impact test has also been developed. The automobile crash Laboratory of Tsinghua University has done a lot of work on the research of side impact according to the regulations on the certification of passenger protection in side impact of motor vehicles (CMVDR 295) compiled by the Bureau of machinery industry in 1998. The hardware and software facilities meet the requirements of side impact test

this side impact test is carried out on the basis of the front impact test bench. Some planning has been made on the original site according to the side impact regulations. Figure 5 is the layout diagram of the laboratory site. During the test, the guide device is separated from the moving wall after braking with a buffer, so that the moving wall impacts the tested vehicle at the speed of (50 ± 1) km/h, and there can be no secondary collision with the tested vehicle. During the test, the position of the tested vehicle shall be appropriate to avoid the guide device affecting the collision process

before the test, the dynamic analysis of the vehicle side impact process is carried out to discuss whether it meets the site conditions of the laboratory, so as to cooperate with the layout of lights and camera equipment in the site. Figure 6 is a simplified side impact dynamic model. The moving wall impacts the vehicle under test at a certain speed, and the kinetic energy of the moving wall is finally converted into three parts of energy: the energy absorption material at the head of the moving wall and the deformation energy absorption of the door of the vehicle under test, as well as the energy loss of friction

Figure 5 Schematic diagram of laboratory site layout

Figure 6 side impact dynamic model

for the convenience of research, assuming that the moving wall has a completely inelastic collision with the vehicle under test, a simple kinematic analysis of this model can estimate the displacement of the vehicle under test after the collision. Suppose that the mass of the moving wall is M1 and the velocity at the time of collision is V1, we can see that the total kinetic energy of the system is

the characteristic curve of moving wall energy absorbing material is shown in Figure 7

Figure 7 energy absorbing material characteristic curve

according to the deformation limit of the energy absorbing material in the collision process in the regulations, set its compression to 350mm, and simplify the integration to obtain the absorbed energy E absorption

the rest of the energy is the total kinetic energy of the whole plane moving rigid system

in addition, the regulations require that the mobile deformable barrier and the vehicle under test will not have a secondary collision. According to the analysis and research of side impact, the moving wall is braked 200ms after the collision, and the collision deformation process ends

coefficient of sliding friction between tire and ground measured by experiment μ， The sliding distance S1 between the moving wall and the vehicle under test 200ms after the collision is calculated according to the resistance F of the moving wall

after the moving wall is braked, the tested vehicle stops under the action of ground sliding resistance. If the sliding distance is

then the total moving distance of the tested vehicle during the collision is s = S1 + S2. The energy loss caused by door deformation and the kinetic energy of the tested vehicle rotation are not considered in the analysis, so the calculation result is too large, and the actual sliding distance of the tested vehicle should not be greater than 3.2m

the above calculation results in the movement of the vehicle centroid. The measured vehicle will rotate during the collision, and the rotation of the vehicle body should also be considered in the site planning. The average torque of the tested car

where f is the average force of the moving wall on the tested car, which can be obtained from the stress deformation curve. F and fr are the sliding friction between the front and rear wheels and the ground respectively, where

the rotation angle of the tested vehicle is θ， IC is the moment of inertia of the vehicle under test. By solving the differential equation, the rotation angle of the tested vehicle after collision can be estimated θ= 28°。

3.2 calibration of ES-2 side impact dummy

after the crash test dummy was initially put into use and used for a period of time, in order to verify its bionic simulation performance, the dummy must be calibrated. As the ES-2 dummy is a new international unified side impact dummy, the calibration method of the ES-2 dummy is studied and designed in this paper. ECE R95 takes the eurosid-1 dummy as an example, for the side impact test