Hirotoshi Ishikawa

Shearing and Bending Effects at the Knee Joint at High Speed Lateral Loading

The main objective of this study is to determine the damage tolerance and describe the damage mechanisms of the extended human knee when it is exposed to lateral impact loads in car-pedestrian accidents, particularly those that occur at a low velocity (20 kph), and compare the results with those obtained at a high velocity (40 kph). In-Vitro experiments with human subjects were conducted where only the purest possible shearing deformation or the purest possible bending deformation affected the knee region. When the knee joint was exposed to deformation, the common initial damage mechanism was ligament damage related to ACL (60%). This type of damage occurred when mean values of the peak shearing force and the peak bending moment acting at the knee joint level were 2.4 kN and 418 Nm, and the shearing displacement and bending angle were 16 mm and -2.9 deg (-0.05 rad), respectively. When the knee joint was exposed to deformation, the most common initial damage mechanism (40%) was ligament damage related to MCL. The mean values of the peak shearing force and the peak bending moment calculated when this damage occurred were 1.6 kN and 358 Nm, respectively. This type of initial damage occurred when the knee was bent 12.3 deg (0.22 rad). The initial metaphysics fracture of the femur due to bending deformation of the knee was observed in only 20% of the cases. The mean values of the peak shearing force and the peak bending moment developed at knee joint level that correspond to this damage were 0.9 kN and 205 Nm. This type of damage occurred when the knee was bent 12.3 deg (0.22 rad). The physical values of the shearing force and the bending moment at the time of initial damage for low-speed lateral loading were found to be similar with those from previously performed experiments at high-speed lateral loading. The ratio of bone fracture to ligament damage was 0.3 in the shearing deformation test and 0.5 in the bending deformation test at low speed.

Impact Center and Restitution Coefficients for Accident Reconstruction

Based on a previously presented two-dimensional car-to-car impact model, automobile collision tests were analyzed to understand the relationship of the impact center to the residual vehicle deformation. This is essential for improving the reliability of the impact model. The results from a number of automobile collision tests indicated that the impact centers of the two vehicles at the end of collision were located near the center of the contacting surface when the vehicle deformation is maximized. This leads to a method of defining the impact center from the crush profile at the time of maximum deformation. The relationships of the normal and tangential restitution coefficients to the collision type were also presented, discussed and evaluated to obtain some guidelines on how to choose the restitution coefficients from impact conditions.

Computer simulation of automobile collision: reconstruction of accidents

In analyzing road accidents, it is important to estimate the vehicle behavior and the occupant movement according to the accident site conditions, such as the final vehicle rest position, damage profiles and tire scuffs. For this research, a two-dimensional car-to-car collision model, in which vehicle crash properties and tire forces are considered, has been developed to predict accelerations, deformations, trajectories and tire yawmarks of each vehicle. Further, a two-dimensional occupant model with one mass and three degrees of freedom in consideration of the deformation properties of the human body has been developed and incorporated in the vehicle collision model, in order to analyze the occupant crash victim. In this report, calculation formulas are described, and numerical solutions obtained by the model are compared with those of the crash experiments. It is found that a considerably good agreement exists between both data, and that this model may be used as a computerized accident analysis method.

Development of Simulation Model and Pedestrian Dummy

Honda has been studying ways of improving vehicle design to reduce the severity of pedestrian injury. Full-scale tests using a pedestrian dummy are an important way to assess the aggressiveness of a vehicle to pedestrians. However, from test results, it is concluded that current pedestrian dummies have stiffer characteristics than post mortem human subjects (PMHS). Also, the dummy kinematics during a collision are different from that of a human body. Because of the limitations of current dummies, it was decided to develop a new pedestrian dummy. At the first stage of the project, a computer simulation model that represented the PMHS tests was developed. Joint characteristics obtained from the simulation model were used in building a new pedestrian dummy named Polar I. The advanced frontal crash test dummy, known as Thor, was selected as the base dummy. Modifications were made for the thorax, spine, knee, and other joints. Component tests were conducted to obtain and check the characteristics of each part. An initial series of full-scale tests was conducted, and the kinematics of the dummy were compared with PMHS test results.

Development of computer simulation models for pedestrian subsystem impact tests

The European Enhanced Vehicle-safety Committee (EEVC/WG10 and WG17) proposed three component subsystem tests for cars to assess pedestrian protection. The objective of this study is to develop computer simulation models of the EEVC pedestrian subsystem tests. These models are available to develop a car conforming to the pedestrian subsystem test requirements. The pedestrian subsystem test models were developed and validated in this study. However, some improvements are still needed in these models to make them more reliable in simulating the pedestrian subsystem tests to develop a car conforming to the test requirements.

PEDESTRIAN INJURIES INDUCED BY THE BONNET LEADING EDGE IN CURRENT CAR-PEDESTRIAN ACCIDENTS

The objective of this research is to clarify the significant factors causing AIS 2+ femur or pelvis pedestrian injury and to understand whether the current European Experimental Vehicles Committee (EEVC) upper legform test reflects real world pedestrian accidents. An in-depth case study was conducted using 82 selected pedestrian accident cases from 1987 to 1997 in the database of the Japan Automobile Research Institute and the Institute for Traffic Accident Research and Data Analysis. The results indicate the significant factors were the bonnet leading edge height, the vehicle registration year, and the pedestrian age. The bumper lead was not a significant factor. However, the test condition of the EEVC upper legform test depends on the bumper lead and the bonnet leading edge height. It is recommended that the current test condition of the EEVC upper legform test be reconsidered excluding the bumper lead.

New Biofidelic Corridor and Biofidelity Test Procedure for Pedestrian Legform Impactors

The objectives of this research are to propose a new impact response corridor for the ISO legform impactor and to determine the biofidelity of the current legform impactor with rigid leg and thigh developed by the Transport Research Laboratory (TRL). The latest data obtained from Post Mortem Human Subject (PMHS) knee impact tests were analyzed in connection with the proposal, and biofidelity legform impact tests were conducted using the current rigid legform impactor. New normalized biofidelic corridors of impact force corresponding to adult male 50th percentile (AM50) are proposed. The impact test results indicate the current rigid legform impactor does not have sufficient human knee biofidelity. The present results suggest that human tolerance can not be used directly for the injury reference value of the legform impactor. A conversion method is needed to interpret the data measured by current legform impactors as the injury reference value.