Doctoral Dissertations

Date of Award

5-1996

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Engineering Science

Major Professor

John N. Snider

Committee Members

Jack F. Wasserman, Milt Bailey, John Hungerford

Abstract

The research reported on in this dissertation has been systematically developed through a series of interrelated studies and experiments. The purpose has been to understand and characterize the effects of sever impact loading on the human body that results from accidents involving automobiles, motorcycles, boats, other vehicles, pedestrians, swimmer, et cetera. Previous work in this arena had relied strongly on simulations of human body anatomy, has focused on the microscopic mechanical properties of bone and soft tissue, or has resorted to analytical modeling.

Literature regarding mechanical properties of human tissue is plentiful. The experimental results in comparison among researchers are often quite variable, probably due to the complexity and diversity of the hard and soft materials that compose the human body. The majority of the research involves mechanical properties of human and animal bones and rarely is a full intact bone or specimen used for testing purposes. Instead, small cube samples are usually tested under static conditions. One reason for the widespread use of small cubes is their ease of use in material testing. The mechanical properties, however, of a full intact bone and/or intact specimen are much different than those found in a small cube section of bone or a dissected soft tissue part. This is due to the anisotropic and viscoelastic nature of these materials. When bone is combined with the various soft tissue components (muscles, tendons, ligaments, vessels, nerves, fascia, fat, skin, et cetera), a "black box" complex composite structure is created that needs to be characterized as a "material" of its own.

Hence, more realistic data is needed about impact trauma effect on the human body. This research helps "bridge-the-gap" to this previous research through the use of various intact cadaveric specimens. The approach has been to develop a unique impact biomechanics laboratory, an air bad research laboratory, and various other testing apparatuses. In addition, existing facilities such as a drop tower, standard structural mechanical test equipment, and, in one instance, a specialized marine research facility were used when appropriate.

This research focuses on macroscopic effects of impact loading and includes: comparison of embalmed versus unembalmed specimens, fracture patterns of long bones, impact response of the frontal bone and face, and response of the spine. The study also includes evaluation of the air bad as a protective device and evaluation of a particular cage guard design for boat propellers as a safety device.

Reduction or prevention of impact injury through design of protective devices/safer environments requires certain biomechanical information. This includes a characterization of how the body region of interest responds to impact forces in terms of mechanical parameters such as force-time histories of impact, accelerations/decelerations, and deformations in the tissue structures. Also, mechanisms by which the tissues fail, mechanical parameters by which they respond, and the values of the injury criteria are important results in impact biomechanics research. These "biomechanical behaviors" and "injury characterizations" are the essence of the different parts of this dissertation.

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