Impact Response of the Human Thorax

Abstract

Part I — Biomechanics Response Data — Thoracic impact response data for unembalmed human cadavers previously published by three of the authors are reviewed. These data are then “averaged,” adjusted to reflect an estimate for muscle tensing, and used as the basis for recommended force-deflection corridors to serve as dummy design guidelines. A volunteer study of muscle tensing, as related to thoracic stiffness at low force and deflection levels, is discussed, and comments are made concerning additional response data recently acquired by other investigators. Finally, consideration is given to possible “second order” refinements for future generations of a high fidelity dummy thorax.

Part II — Response of Current Dummy Chests —The chest structures of five currently available dummies were evaluated for blunt impact force-deflection response. Testing was conducted in essentially the same manner as was used to acquire the cadaver data of Part I. The resulting force-deflection characteristics were then compared with the GMR recommended performance corridors. In all cases, the existing structures were found to develop excessive resisting forces at deflection levels beyond 3/4 inch, clearly indicating the need for an improved design.

Part III — Mathematical Model for Thoracic Impact —A mathematical model has been developed which simulates the dynamic force-deflection response of the human thorax under blunt impact. The model consists of four differential equations derived from a mechanical thoracic analog formed from springs, masses, and dashpots. Equation parameters were adjusted to give desired responses. It was found that when parameters were set to give responses correlating closely with cadaver data previously published by three of the authors, the model response also correlated well with The University of Michigan HSRI cadaver data when the proper impact conditions were used. The model was used to show the relationship between various types of blunt thoracic impact and for dummy thorax design.