Thoracic Response to Dynamic, Non-Impact Loading from a Hub, Distributed Belt, Diagonal Belt, and Double Diagonal Belts

This paper presents thoracic response corridors developed using fifteen post-mortem human subjects (PMHS) subjected to single and double diagonal belt, distributed, and hub loading on the anterior thorax. We believe this is the first study to quantify the force-deflection response of the same thorax to different loading conditions using dynamic, non-impact, restraint-like loading. Subjects were positioned supine on a table and a hydraulic master-slave cylinder arrangement was used with a high-speed materials testing machine to provide controlled chest deflection at a rate similar to that experienced by restrained PMHS in a 48-km/h sled test. All loading conditions were tested at a nominally non-injurious level initially. When the battery of non-injurious tests was completed, a single loading condition was used for a final, injurious test (nominal 40% chest deflection). To minimize the influence of repeated testing, all subjects were preconditioned prior to each loading condition using 10 cycles of a 1-Hz sine wave, and the order in which the loading conditions were tested was varied across subjects. Thoracic response was characterized using the deflection at the midline of the sternum and a load cell mounted between the subject and the loading table. Responses were defined by cross-plotting the mid-sternal deflection (normalized to 50th male) and the posterior force (scaled to a 45-year-old, 50th male based on size and modulus) and then forming a ±1-standard-deviation corridor that considered the variance in both force and deflection. Corridors were developed to a deflection level of 20% of the 50th percentile male’s external chest depth. The distributed loading condition generated the stiffest response (3.33 kN at 4.6 cm), followed by the double diagonal belt condition (3.18 kN at 4.6 cm), the single diagonal belt (2.28 kN at 4.6 cm) and the hub (1.14 kN at 4.6 cm).