DEVELOPMENT OF A MECHANICAL NECK FOR A 6-YEAR-OLD PEDESTRIAN DUMMY. EVALUATION IN CRASH TESTS AND SIMULATIONS

The objective of this study was to develop an omni-directional mechanical neck for a 6-year old (6YO) pedestrian dummy. The dummy has been developed in co-operation between Autoliv Research and Chalmers University of Technology based on a 6YO Hybrid III dummy equipped with a standard neck originally designed for frontal impact tests. The intention of the current research was to provide higher biofidelity to the neck primarily in lateral bending. The reason for developing such a dummy neck is the high involvement of child pedestrians in car-to-pedestrian impacts. Severe head injuries are frequently observed, and the neck affects notably the head kinetics and kinematics. Thus, more accurate reproduction of the head impact responses under these circumstances is needed. A prototype of 6YO neck was designed and manufactured based on available biomechanical data. Results of pediatric related studies as well as data scaled down from adult properties were used to set the mechanical characteristics of the neck. The design consists of three rubber segments providing bending stiffness whereas rotational stiffness is controlled by rubber straps. Response of both necks was obtained by static and pendulum tests. The prototype performance was compared with the response of the standard neck and with human data for evaluation. Impact responses of the mechanical dummy obtained from full scale tests were compared with results of mathematical simulations. The static stiffness of the prototype neck satisfied human data in flexion, extension and lateral bending with a significant improvement. Pendulum tests emphasised the different dynamic response of the two different necks and confirmed the higher flexibility of the prototype. In terms of WAD, full scale tests showed that the prototype neck is more sensitive to impact speed than the standard neck and the mathematical model. Also, tests with the prototype neck gave higher head impact velocities relative to the car. Head acceleration amplitudes given by the prototype were more similar to results from simulations than those given by the standard neck. As a result, the prototype neck works in every direction and is more flexible than the standard version. It can then be used to predict impact response of the infant head and to assess more accurately new safety devices. Further evaluation and validation of the prototype would be required to guarantee a more biofidelic model. (A)