Application of HyperWorks in Vehicle and Pedestrian Leg Collision Simulation
1 Overview This article refers to the address: http:// About 65% of traffic accident injuries are vulnerable road users. Pedestrians, as a vulnerable group of road users, are high-risk groups in traffic accidents and have extremely high mortality rates. In the collision between a vehicle and a pedestrian, the injured part of the human body can cover the whole body, and the probability of injury to the head and lower limbs of the pedestrian is the greatest. Studies have shown that pedestrian head and lower limb injuries account for about 30% of the damage caused by car and pedestrian collisions. Although the damage to the human leg and knee joint is generally not life-threatening, it often results in a person's lifetime disability or incapacity. This paper takes the calf impactor as the simulation object, uses HyperWorks' pre-processing software HyperMesh to establish the finite element model of the impactor and the whole vehicle, computer simulation of the calf and car collision process, and analyzes the simulation results through the post-processing software HyperView. Compare the simulation results with the test results to verify the reliability of the simulation model and results. 2 Establishment of finite element model Both the calf impactor and the vehicle model were built in HyperWorks, a pre-processing software from HyperWorks. HyperMesh is a high-performance CAE and CFD pre-processor that provides the widest range of CAD, CAE and CFD software interfaces for seamless integration with any simulation environment, providing direct interface to a wide range of CAD data formats. Data loss caused by data format conversion, widely used in automotive, aerospace and other industries. 2.1 Meshing The finite element model and structure of the leg impactor are shown in Figure 1. The leg impactor consists of two rigid sections covered with foam. The total length of the impactor is 926mm and the mass is 13.4kg. The accelerometer is mounted on the non-impact side of the calf and is located 66mm below the center of the knee. In order to improve the calculation speed, considering the collision process between the car and the pedestrian, the pedestrian's leg will only affect the front structure such as the car bumper. Therefore, in the established simulation model, only the part before the A-pillar of the car is taken and simplified. For example, the parts that have less influence on the collision result, such as the front lamp and the fog lamp, are omitted. The cell grid size is about 8mm, the maximum mesh size is no more than 15mm, and the minimum is not less than 5mm. The total number of nodes is 221852, the total number of units is 214847, and the total number of components is 174. The unit warpage and the angular extent of the angles in the quadrilateral and triangular elements are strictly controlled. The bolt connection in the whole vehicle is simulated by RBE2, and the coating method is realized by a hexahedral element with adhesive material characteristics, and other welding is simulated by bolt and cweld. The final finite element model of the car for pedestrian protection analysis. 2.2 Constraints The model used in this paper is not the whole vehicle model, but the part before the A-pillar is selected, so a full constraint is imposed on the suspension, the A-pillar and the sill beam, and the six degrees of freedom are constrained, as shown in Fig. 3. This simulation not only loses its authenticity, but also increases the speed of operation. 2.3 Collision conditions In this paper, the simulation analysis is carried out according to the impact test requirements of the GTR regulations. According to the regulations, the speed of the leg impactor is defined as 40km/h and the collision angle is 0°. The collision location takes the license plate center of the car. The simulation model is calculated in LS-DYNA with a calculation time of 40ms. 3 Simulation results analysis In this paper, the simulation results are post-processed using HyperView software. HyperView is a powerful and comprehensive CAE simulation and experimental post-processing visualization environment with an intuitive, high-performance graphical interface that significantly reduces the time and cost of engineering analysis. HyperView can directly output the parameters examined by the regulations, namely tibia acceleration, knee joint shear displacement and knee joint bending angle. By comparison, the simulation results are in good agreement with the experimental data, and the errors between the parameters are 4.69%, 9.91%, and 1.64%, respectively, as shown in the figure. The above analysis results show that the computer simulation can better reflect the collision process between the leg impactor and the car, and can correctly predict the damage degree of the leg and knee joint. 4 Conclusion It can be seen from the above analysis that HyperWorks has played a significant role in the simulation analysis of car and pedestrian leg collisions. In this paper, with the support of its software, the finite element method and computer simulation technology are applied to simulate the collision process between the leg impactor and the car. The simulation results are in good agreement with the experimental data, which provides a more effective and economically feasible method for the study of the collision process between automobiles and pedestrians. In the new car development and design stage, it can correctly predict the pedestrian protection safety performance of the vehicle and provide a reference for its performance optimization.
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