The Validity of the Physiological Cost Index at Short Distances

Background and purpose. The Physiological Cost Index (PCI) was developed as a tool using heart rate and walking speed to measure energy expenditure during walking. This tool was developed using long distances, therefore, its validity at short distances is unknown. The purpose of this study was to determine the validity of the PCI at short distances.; Subjects. Forty-six subjects aged 20-30 years old were tested. Methods. Subjects walked 600 meters around a 40 meter oval track. Heart rate and walking speed were monitored at various intervals. Results. No strong correlation between short and long distances was found until 80 meters (r =.84). An r-value above.9 was not obtained until 160 meters. Conclusion and discussion. In order to obtain a valid PCI measurement, subjects must walk a minimum of 80 meters. For a strong correlation subjects must walk a minimum of 160 meters

On the crashworthiness of foam-filled ultralight automotive structures

grantor: University of TorontoIn this thesis, a novel 'layered' model for simulating the quasi-static and dynamic collapse of foam-filled ultralight aluminium structures using three-dimensional elasto-plastic finite element analysis is presented. Specifically, the quasi-static and dynamic axial collapse of foam-filled box columns is investigated. The column was modelled using shell elements, while the filler foam was modelled as a series of solid layers with a shear-stress failure criterion, which ties the layers together. This method enabled the simulation of the shear rupture of the foam, as observed in the extensive mechanical testing carried out in support of this study. The interface between the filler and the tube was modelled using an automatic contact algorithm, which incorporates the penalty method. The finite element analysis consisted of two investigations. In the first, aluminium columns of varying dimensions filled with aluminium foam of varying densities undergoing quasi-static axial crushing were examined. The effect of foam density, wall thickness and width of the column on energy absorption was evaluated and discussed. In the second, the same geometry was explored under dynamic impact loading. (Abstract shortened by UMI.)M.A.Sc