Experimental study on side impact safety of the ho

2022-07-29
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Experimental study on the safety of car side impact

Abstract: in China's road traffic environment, road intersections are mainly level crossings. The traffic accident statistics show that the number of side impact accidents accounts for about 34.4%, ranking first. The research on the safety of automobile side impact is of positive significance to improve the road traffic safety in China. This paper introduces the development of side impact test capability in China and the side impact test results of three domestic cars, and analyzes the problems existing in the side impact safety performance of these three cars

key words: automobile side impact test

safety, emission, energy saving and anti-theft of automobiles are listed as mandatory inspection items of the government in China's automobile product type certification. In October, 1999, CMVDR294 "design rules on frontal collision occupant protection" was issued. In 2000, the frontal collision of vehicles was included in 40 mandatory inspection items. It is required that the newly produced M1 passenger bus meet the frontal collision occupant protection requirements after April 1, 2000, and the M1 passenger bus meet the requirements of CMVDR294 before July 1, 2002

in Europe, the United States, Japan and other developed countries in the automotive industry, common accident forms such as frontal collision, side collision and rear end collision have been included in the safety regulation system. China's national automobile Standardization Committee also takes 300 joints of the same type in each floor as a batch. The drafting of side impact standards has been included in the 2002 work plan, and China's side impact occupant protection standards have been drafted with reference to version ecer95.01. The automobile crash safety technology involves two key technologies, the safe body and the occupant restraint system. At present, the domestic research on the side impact safety of the automobile body and the side impact airbag technology are blank, and the technical preparation needs a long period. In particular, the improvement of the anti-collision ability of the automobile body needs to change the body structure, which is very difficult

the formulation of China's automobile side impact regulations and the improvement of the side impact safety of car models by automobile enterprises need the support that all side impact additives that can meet the requirements of the regulations can not add too many test capabilities and the technical guidance of the side impact safety improvement measures. Therefore, in 2002, we began to develop the side impact test capability of ECE R95 regulation, and learned about the side impact safety performance of Chinese car models through the side impact tests of some domestic car models in production

1 development of ECE R95 side impact test capability

the side impact test in this paper is based on the European ECE R95 test method. The test site shall be flat, dry and clean. The side impact dummy shall be placed on the driver's seat, and the impacted vehicle shall be parked at the specified position perpendicular to the traction rail, as shown in Figure 1. During the test, the movement stops repeatedly measuring a certain parameter, and the deformable barrier impacts the driver's side of the vehicle at a speed of (50 ± 1) km/h. A speed measuring device is set at 0.5m from the impact position, and the decoupling device ensures that the moving deformable barrier is in a free motion state when 1m from the crashed vehicle. It is required to ensure that the deviation of MDB is less than 25mm

Figure 1 test vehicle status before the test

1.1 development of MDB

in the side impact test, the moving deformable barrier, as an "average vehicle", impacts the tested vehicle. As shown in Figure 2, it consists of a moving trolley, a deformable energy absorbing block and a braking system. The design of the mobile deformable barrier has strict requirements on the quality and center of gravity position, and the energy absorbing block adopts multi-layer honeycomb aluminum structure

Figure 2 Mobile deformable barrier

energy absorbing block is installed with mobile trolley through ventilation device. The structure of ventilation device is shown in Figure 3. When installing the energy absorbing block, first fix the energy absorbing block and the ventilation device with iron wire, and then connect the ventilation device with the front fixing plate of the mobile trolley with bolts. During installation, it should be noted that the ground on which the trolley is parked should be horizontal. Check whether the tyre pressure of the trolley is consistent, and ensure that the gap between the lower surface of the energy absorbing block and the ground is (300 ± 5) mm

Figure 3 ventilation device

the mobile deformable barrier requires braking after collision to prevent secondary collision, so the braking system must also be installed on the mobile trolley. The whole braking system is centrally controlled by a single chip microcomputer: a strip switch is used to trigger the solenoid valve to ensure that the braking system is started after a period of time after the collision. The solenoid valve controls the high-pressure gas in the air reservoir to push the hydraulic brake master cylinder to work, so that each wheel brake works. In order to ensure no deviation during braking, it is necessary to conduct braking test, adjust the clearance of each brake, and keep the braking force of each wheel as consistent as possible

1.2 positioning of impact position and measurement of MDB deviation during the impact test, the distance between the left and right symmetry planes of the moving deformable barrier and the cross section of the vehicle passing through the H-point of the front seat on the impact side must be within ± 25mm, as shown in Figure 4. Before the test, mark the position of H point on the door on the struck side, and draw the impact reference line in the vertical direction through the H point. At the parking position of the test vehicle, ensure that the test vehicle is perpendicular to the traction track, and align the impact reference line with the symmetrical center line of the moving deformable barrier by adjusting the mutual position of the test vehicle and the moving deformable barrier, so as to determine the position of the test vehicle. Before departure, draw a watercolor line on the center line of the MDB. The center line of the MDB will be printed on the body of the test vehicle during the collision, so as to measure the deviation of the MDB in the side impact test

Figure 4 impact benchmark

2 analysis of side impact test results of three domestic car models

a is a domestic medium-sized car with a weight of 1100kg, B is a large car with a weight of 1400KG, and C is a compact car with a weight of 900kg. The initial collision speed is 50.5km/h. Table 1 shows the test results. The waveform of X-axial impact acceleration on MDB is shown in Figure 5, and the waveform of lateral impact acceleration measured on the vehicle central channel is shown in Figure 6

Figure 5 waveform of X-axial impact acceleration on MDB Figure 6 waveform of lateral acceleration in the central channel of vehicle Table 1 collision test results

2.1 compliance analysis of regulatory requirements

it can be seen from the test results in Table 1 that the three vehicle models do not comply with regulatory requirements

(1) model a: the door lock system is completely locked in the collision. After the collision, all doors cannot be opened. Put your hand into the vehicle. Only the right door that has not been impacted can be opened after the central lock is opened, which does not meet the regulatory requirements

(2) vehicle type B: the direct cause of non-compliance with the regulatory requirements is the failure of the safety belt. After the collision, the door in which the dummy was seriously invaded was squeezed out of the driver's seat, the fixing point on the safety belt fell off, and the dummy fell on the co driver's seat after the test

(3) model C: there is no problem with the body and restraint system, but the chest injury index of the dummy exceeds the limit

2.2 characteristic analysis of side impact test results of various vehicle types

integrate the impact acceleration waveform of MDB and test vehicle, and calculate the speed change curve and intrusion change curve of test vehicle and MDB during the collision process. As shown in Figures 7, 8 and 9, the side impact speed change curves of models a, B and C are shown. Figure 10 shows the MDB intrusion curve of three models. Table 2 lists the relationship between the weight of three vehicle types A, B and C, the maximum speed of the test vehicle in the collision and the maximum amount of MDB intrusion

Figure 7 A-type collision speed curve figure 8 B-type collision speed curve

Figure 9 C-type collision speed curve figure 10 MDB intrusion curve of three models

Table 2 maximum speed and maximum intrusion of three models (collision speed 50.5 km/h)

from the above calculation results, the following characteristics can be summarized:

(1) the speed of the test vehicle in the collision is inversely proportional to the mass of the test vehicle. After the MDB collision representing the "average vehicle", The greater the mass of the test vehicle, the smaller the speed after collision. Heavier vehicles suffer less impact in side impacts

(2) the amount of MDB intrusion in a collision mainly depends on the body side wall stiffness. A. Among the three models B and C, the intrusion amount of model C is the smallest, and the side structure of model B collapses in the collision, with the largest intrusion amount. Model C is a relatively new compact car. Although its mass is small, its intrusion is the smallest among the three models due to its large side stiffness; Model B has the oldest body structure among the three models. There are defects in the side beam system structure. During the side impact, the body floor and top beam at the B-pillar position buckle and cannot resist the side impact

(3) the HIC value of dummy head injury index is directly related to the contact speed, and the HIC of C model with small weight is the largest; The HIC of heavy a and B models is small. From the three tests, the HIC of dummy head injury will not exceed the standard in the side impact of ECE R95 regulation

(4) the dummy's chest injury index is related to the contact speed between the vehicle's side wall and the dummy. Although model C has a small amount of intrusion, the B-pillar has a plastic hinge at the waist line of the body, and the intrusion speed of the door inner panel at the dummy's chest is the largest. Because model C has a small mass and the test vehicle has a large speed in the collision, the chest injury value exceeds the standard. The lower rigid part of model a is small, and a large amount of intrusion deformation is concentrated below the waist of the dummy, so the chest injury is small

(5) the pubic joint force index at the waist and pelvis of the dummy does not exceed the standard in the side impact of ECE R95 regulation. However, the lower rigid part of model a is small, and a large amount of intrusion deformation is concentrated below the dummy waist. The impact force at the pelvis is large, and the pubic joint force is close to the regulatory limit

2.3 analysis of side impact safety defects of three models

body structure defects: the problem of model B is that there are serious defects in the body structure. The side impact safety requirements are completely not considered in the body beam structure design. There is no complete side beam structure on the body. In case of a side impact, the body floor and top beam under the B pillar are crushed and deformed, and the MBD intrudes into the passenger compartment and squeezes the driver's seat. The driver's seat of model B was deformed greatly before and after the collision. During the collision, the side of the seat was squeezed, and the deformation of the seat cushion position reached 260mm. After the collision, the width of the driver's seat was only 280mm, which could not safely accommodate the driver. According to the size of the human body, the width of the seat after collision shall not be less than 400mm, so that the passengers in the vehicle can be safely accommodated from crushing injury

structural defect of door lock: the problem of model a is the linkage of the central lock structure. The side door on the struck side has a large amount of deformation, and the linkage mechanism of door lock is located in the door inner plate. When analyzing the car lock linkage mechanism, it must be ensured that the door linkage locking cannot occur in the side impact. The dummy's chest injury exceeds the standard. 6. The pressure testing machine has many different fixing screws: the problem of model C is that the dummy's chest injury exceeds the standard. There are three main reasons: ① the vehicle with small mass has a higher speed after being impacted in side impact; ② The stiffness distribution of the side wall is unreasonable, and the plastic hinge is generated at the waist line of the B pillar, resulting in the maximum intrusion speed of the door inner panel at the dummy's chest; ③ The door inner panel is not softened well. If the contact part between the door and the dummy is softened sufficiently to absorb part of the impact energy, the injury to the dummy's chest can also be mitigated

3 analysis of improvement measures

c model is a typical side impact safety defect. For small cars, due to their small vehicle weight, the kinetic energy transferred from MDB to the test vehicle in the collision is large. This model has the possibility that the dummy injury value exceeds the standard. This category

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