Displacement Measurements in the Hybrid III Chest

This paper presents an analysis of the displacement measurement of the Hybrid III 50^th percentile male dummy chest in quasistatic and dynamic loading environments. In this dummy, the sternal chest deformation is typically characterized using a sliding chest potentiometer, originally designed to measure inward deflection in the central axis of the dummy chest. Loading environments that include other modes of deformation, such as lateral translations or rotations, can create a displacement vector that is not aligned with this sensitive axis. To demonstrate this, the dummy chest was loaded quasistatically and dynamically in a series of tests. A string potentiometer array, with the capability to monitor additional deflection modes, was used to supplement the measurement of the chest slider. Results indicated that the Hybrid III chest behaved in a rigid manner in frontal crash environments, but in a less rigid manner when denuded of its skin and subjected to highly localized quasistatic deflections. Chest slider measurements deviated from those of the supplemental instrumentation in loading environments where the upper chest received the maximum deflection. This indicates that the chest slider may not accurately characterize the motion of the sternum when lateral translations and rotations occur, and therefore its data cannot be interpreted correctly. Further, the differences in local and sternal slider measurements are discussed for typical air bag and seat belt thoracic loading for both drivers and passengers in automobile crashes.