Biofidelity of test devices and validity of injury criteria for evaluating knee injuries to pedestrians

Takahashi, Yukou; Kikuchi, Yuji

In the current test procedure proposed by the European Enhanced Vehicle-safety Committee (EEVC) /WG17 for evaluating leg injuries to pedestrians, a legform impactor with a rigid bony structure is used. The risk of damages to knee ligaments is evaluated with the shearing displacement and the bending angle at the knee joint. A recent study has focused on evaluating biofidelity of the legform. However, it was not possible to obtain a local deformation at the knee joint from published experiments with Post Mortem Human Subjects (PMHSs). In addition, past PMHS experiments have suggested that the height of a bumper significantly affects the risk of ligamentous damages.

In this study, three kinds of finite element models were used in order to investigate the relationship between the bumper height and the shearing displacement / bending angle of the knee; 1) a legform impactor with a rigid bony structure, 2) a recently developed pedestrian dummy (Polar) with both a flexible tibia and a biofidelic knee joint structure, 3) a human lower limb. By utilizing the human model, a local deformation at the knee joint could be obtained. The model for the legform impactor and the pedestrian dummy have been validated against experiments with an actual car and in component level, respectively. The human lower limb model has been validated against published PMHS experiments. The result of a parameter study with these models in a range of bumper heights showed that the dynamic response of the dummy model is quite similar to that of the human model. In addition, it was found that the mass of the upper body significantly affects the bending angle of the knee. A geometric analysis of the knee joint was also performed to obtain tensile strains of four principal knee ligaments as a function of both the shearing displacement and the bending angle. The result suggested that the shearing displacement and the bending angle should be considered in combination when developing an injury criteria for knee ligaments.

Year

Entry

1988

Cesari D, Cavallero C, Cassan F, Moffatt C. Interaction between human leg and car bumper in pedestrian tests. In: Proceedings of the 1988 International IRCOBI Conference on the Biomechanics of Impact. September 14-16, 1988; Bergisch-Gladbach, West Germany.259-269.

2000

Artis M, McDonald J, White R, Huang TJ, Shams T, Rangarajan N, Akiyama A, Okamoto M, Yoshizawa R, Ishikawa H. Development of a new biofidelic leg for use with a pedestrian dummy. In: Proceedings of the 2000 International IRCOBI Conference on the Biomechanics of Impact. September 20-22, 2000; Montpellier, France.41-52.

1998

EEVC Working Group 17 Report: Improved Test Methods to Evaluate Pedestrian Protection Afforded by Passenger Cars. European Enhanced Vehicle-Safety Committee (EEVC); 1998.

1996

Cesari D, Fontaine H, Lassare S. The validity of the proposed European pedestrian protection procedure and its expected benefits. In: Proceedings of the 15th International Technical Conference on the Enhanced Safety of Vehicles (ESV). May 13-16, 1996; Melbourne, Australia.1102-1106.

1991

Cesari D, Alonzo F, Matyjewski M. Subsystem test for pedestrian lower leg and knee protection. In: Proceedings of the 13th International Technical Conference on Experimental Safety Vehicles (ESV). November 4-7, 1991; Paris, France.310-317.