Abstract

In this thesis, absorbed power during exposure to vertical whole-body vibration is considered as a potential indicator of the physical stress affecting human health. The amount of vibration energy, either absorbed or exchanged between the source and body, may be a good measure of the physical stress on the body since it takes into consideration the interaction between the vibrating structure and the body as well as the relative motion between the vibrating body parts. Moreover, energy is a scalar quantity that makes it easy to add up contributions from all directions and all body segments to a single value. In order to study the energy content of the vibration transmitted to the whole body and to the different body segments, a four-degree-of-freedom linear biodynamic model used in earlier studies is chosen to represent the body. The local absorbed powers and the total power absorption under different excitations ( e.g. sinusoidal excitation, random excitation, and transient excitation) are derived. On the basis of the model and of the guidance provided in ISO 2631-1 (1997) to relate vibration exposure with the risks of health effects, health guidance caution zones are established based on absorbed power. The eigenvalues and natural frequencies, damping ratios and damping ratio matrix, the vertical transmissibilities from seat to different body segments, and driving-point mechanical impedance for the 4-DOF biodynamic model are also computed.