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This study was performed as a part of the research on the ultrasonic measurement of bone porosity, bone density, and Young's modulus. It was found that the bone porosity estimated by Biot's theory agrees within 5% of the actual porosity. The bone's structure factor involved in the Biot's theory was determined experimentally to have a value of 2. It was also found that the use of the propagation velocity of the fast wave is more advantageous than using the slow wave in estimating bone porosity. The estimated bone density obtained by the use of Biot's theory is within ±5% of the measured value obtained by the use of Archimedes' principle. Bone density as well as Young's modulus can be estimated precisely by using the proposed ultrasonic wave method.

Tension-compression and rotating bending fatigue tests were carried out using aluminum alloy 2024-T3 in 3% sodium chloride solution. During corrosion fatigue process, many corrosion pits were initiated at the early stage, and cracks were initiated from the pits. The characteristics of the pit growth were investigated in detail. The critical condition for crack initiation from the corrosion pit was also studied. Crack initiation periods during corrosion fatigue were evaluated on the basis of the corrosion pit growth law.

This study was performed as a part of the research on the ultrasonic measurement in vivo of bone porosity, density, Young modulus and hardness. It was clarified that the bone porosity estimated by Biot's theory agrees well with the actual porosity within an accuracy of 5%. In the estimation the structure factor involved in the Biot's theory was determined as a value of 2. In this evaluation, an use of the propagation velocity of the fast wave is more advantageous to estimate the bone porosity than using the one of the slow wave. The estimated bone density by Biot's theory yields only ±5% differences from the measured value by the Archimedes method. Therefore, bone density can be estimated precisely by using the proposed ultrasonic wave method.