Fall from height in a stairwell--mechanics and simulation analysis.
The range of problems considered in the biomechanical analysis of a fall from height has been presented. A complicated case of a fall in a stairwell was investigated, the analysis of which demonstrates the research scale and aspect multitude. The scope of the article was restricted to the analysis of biomechanical problems and the simulation analysis of the event. A virtual 3D model of the stairwell was built using sketches, photographs and photogrammetric techniques. A dummy created according to the victim's data was parameterised. Using the PC-Crash biomechanical module a series of several hundred simulations were run following the adopted research plan, allowing for pre-formulated boundary conditions. The region of the stairwell where the accident was likely to originate and the victim's initial configuration were identified. It was proved that biomechanical simulation can bring invaluable benefits in exposing the mechanism of an event and verification of various hypotheses. Despite general similarities, each fall has its own specificity, which, making the use of methodological generalisations difficult, increases the significance of casuistry. The presented analysis can prove very useful in providing guidelines on investigating other cases.
An Evaluation of Rectified Bitmap 2D Photogrammetry with PC-Rect
Without good-quality measurements taken at the time of an accident the analyst is faced with the need to extract measurement data from incident scene photographs. This paper discusses the history and development of the mathematical model for two-dimensional (2D) single exposure analytical photogrammetry, presents the PC-Rect software, and compares the analytical results obtained with PC-Rect to survey results. The sensitivity of the analytical results to the variation in such parameters as subject distance, camera height, digital photograph resolution, and bitmap density is discussed.The concept of using the directly rectified scanned photograph in the reconstruction task is introduced, and the utility of performing the dynamic simulation directly on the rectified photograph is discussed. (A) For the covering abstract of the conference see IRRD 899758.
Biomechanics of skull fracture.
This study was conducted to determine the biomechanics of the human head under quasistatic and dynamic loads. Twelve unembalmed intact human cadaver heads were tested to failure using an electrohydraulic testing device. Quasistatic loading was done at a rate of 2.5 mm/s. Impact loading tests were conducted at a rate of 7.1 to 8.0 m/s. Vertex, parietal, temporal, frontal, and occipital regions were selected as the loading sites. Pathological alterations were determined by pretest and posttest radiography, close-up computed tomography (CT) images, macroscopic evaluation, and defleshing techniques. Biomechanical force-deflection response, stiffness, and energy-absorbing characteristics were obtained. Results indicated the skull to have nonlinear structural response. The failure loads, deflections, stiffness, and energies ranged from 4.5 to 14.1 kN, 3.4 to 16.6 mm, 467 to 5867 N/mm, and 14.1 to 68.5 J, respectively. The overall mean values of these parameters for quasistatic and dynamic loads were 6.4 kN (+/- 1.1), 12.0 mm (+/- 1.6), 812 N/mm (+/- 139), 33.5 J (+/- 8.5), and 11.9 kN (+/-0.9), 5.8 mm (+/- 1.0), 4023 N/mm (+/- 541), 28.0 J (+/- 5.1), respectively. It should be emphasized that these values do not account for the individual variations in the anatomical locations on the cranium of the specimens. While the X-rays and CT scans identified the fracture, the precise direction and location of the impact on the skull were not apparent in these images. Fracture widths were consistently wider at sites remote from the loading region. Consequently, based on retrospective images, it may not be appropriate to extrapolate the anatomical region that sustained the impact forces. The quantified biomechanical response parameters will assist in the development and validation of finite element models of head injury.