For women of reproductive age, automobile crashes are the leading cause of death worldwide. It has been estimated that 40,000 women in the second half of pregnancy are involved in motor-vehicle crashes each year. It has been estimated that between 300 to 3800 will experience a fetal loss. Placental abruption has been shown to account for 50% to 70% of fetal losses in motor vehicle crashes. While there is a growing database of medical case studies and retrospective studies describing the outcome of motor vehicle accidents involving pregnant occupants, as well as the effect of seatbelts on fetal survival, previous research has not produced a tool for engineers to use to improve the safety of a pregnant occupant in a motor vehicle. The goal of this project was to develop a model that can quantify the stresses and strains on the uterus of a pregnant woman in order to predict the risk of injury. A finite element uterine model of a 7-month pregnant female was created and integrated into a multi-body human model. Unrestrained, 3-pt belt, and 3-pt belt plus airbag tests were simulated at speeds ranging from 13 kph to 55 kph. Peak uterine strain was found to be a good predictor of fetal outcome. The uterine strain sufficient to cause placental abruption was seen in simulations known to have greater than 75% risk of adverse fetal outcome. Head injury criteria (HIC) and viscous criterion (V*C) were examined as a check of overall occupant protection. The 3-pt belt plus airbag restraint provided the greatest amount of protection to the mother. The model proved successful at predicting risk of fetal demise from placental abruption and verified experimental findings noting the importance of proper restraint use for the pregnant occupant. / Master of Science

Work has been done to develop the computer laboratory portion of a course in biodynamic modeling, with particular emphasis towards applications in forensic engineering. Three course modules have been developed which explore the whiplash injury mechanism, pilot ejection and windblast, and gait analysis. These case studies make use of software entitled MADYMO (MAthematical DYnamic MOdeling). Each case study provides the scene, outcome, details, and instructions for setup of the biodynamic model. An "In-House" User's Manual has also been written so that students without previous MADYMO or UNIX experience can become proficient at using the program. Through the case studies presented within this thesis, students will gain insight into injury mechanisms and learn valuable biomechanical modeling tools. / Master of Science

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Lower back disorders due to whole-body vibration (WBV) are the most common injuries reported by professional drivers. Such injuries often have long-term complications leading to significant personal and societal costs. An improved mathematical model of the whole human body would contribute to a better understanding of the mechanisms of lower back injury and be valuable in injury prevention research. Current biodynamic human models reported in the literature lack detailed information for predicting the non-linearity due to vibration amplitude of transmission of vibration from seat to a human. Therefore, one of the primary objectives of this research has been to develop and validate a detailed threedimensional biodynamic human model, with special attention given to the incorporation of active trunk muscles with non-linear stiffness properties. These muscles have been incorporated into an existing spine and neck model of a MADYMO 50th percentile male occupant model. A detailed multi-body human model has been developed, called MODEL ONE. This thesis shows that incorporating non-linear stiffness functions and energy dissipation using hysteresis or damping into a human model is appropriate for predicting non-linear biodynamic responses in arbitrary excitation functions. A major advantage of MODEL ONE compared to other multi-body models and lumped mass models is its ability to predict nonlinear seat-to-human transmissibility. However MADYMO 50th male occupant models use simplified geometry and rigid bodies to represent the lower lumbar spine. These simplified spinal models have no ability to simulate the internal stresses and deformations of soft tissues, even if these are the apparent cause of lower back pain (LBP). Therefore a detailed finite element human lower lumbar spine model - with appropriate material properties and capable of simulating internal stresses⎯is necessary, in order to better understand spinal injuries under WBV. A three-dimensional finite element model of a lower lumbar spine motion segment - called MODEL TWO - has thus been developed for the present study. MODEL TWO comprises a detailed geometric description of vertebrae, nucleus pulposus, endplates, and intervertebral discs. The intervertebral discs lump together the annulus fibrosus, ground substance and ligaments. The vertebrae have been assumed to be rigid. The material properties of the intervertebral discs of MODEL TWO were obtained from test matrices and from various parameter data reported in the literature. MODEL TWO has been validated against cadaveric experiments reported in the literature. The mechanical behaviour and stress distribution within the MODEL TWO intervertebral disc agree reasonably well with the cadaveric experiments. MODEL TWO was integrated into MODEL ONE to form a new human model, called MODEL THREE, which was subsequently dynamically validated against volunteers� responses to WBV reported in the literature. MODEL THREE, as presented in this thesis, consists of a multi-body human model with detailed representation of a finite element (FE) lower lumbar spine. As far as the author is aware, MODEL THREE is the first model with detailed representation of a FE lower lumbar spine to successfully demonstrate that it is capable of simulating the stress profile of the entire intervertebral disc and endplate region due to WBV. The simulated results revealed abnormal stress concentrations in both the posterior and xviii the posterolateral annulus. The stresses increased most in the posterolateral intervertebral discs region during WBV, suggesting a possible mechanism for disc mechanical overload leading to fatigue fracture and degeneration. The results from MODEL THREE are promising and lead to a more comprehensive understanding of the behaviour of the intervertebral disc under WBV. MODEL THREE has also provided a good foundation for the development of a bio-fidelity human model. However, implementation of currently unavailable and/or inadequate in vitro and in vivo experimental studies is needed to further validate and develop MODEL THREE. A better understanding of injury mechanisms and the clinical significance of LBP will ultimately be arrived at using a combination of analytical models with in vitro and in vivo experimental data.

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