Effects of strain rate on the mechanical properties of plantar soft tissues of foot.

• Main Authors: HuYiHua, 何奕樺
• Other Authors: Shua YW
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/72738585639933582120

碩士 === 國立臺灣大學 === 應用力學研究所 === 89 === Loading-unloading apparatus that combined clinical ultrasound and load cell was built to investigate the effects of strain rate on the plantar soft tissue. A 5-12 MHZ linear array transducer was used to compress the soft tissues up to 19.6N/cm2, and three loading velocities 3.75±0.2cm/s, 6.23±0.4cm/s, 14.64±0.2cm/s was adopted. The changes in soft-tissue thickness and the compression force were recorded simultaneously, and the stress-strain could be derived directly. Young subjects (five females and seven males) with no apparent foot diseases were enrolled in the study. The mechanical properties were based on their compressive index (CI), stiffness (Ep), and energy dissipation of ratio (EDR). For young subjects, the increase in loading velocity caused the stress-strain curve at the loading phase to shift upward. However, the unloading phase was not affected. This resulted an increase in the EDR. The EDR for fore foot (metatarsal heads) were about 38.29±9.07%, 43.42±8.31% and 54.59±7.44% that corresponding to increasing frequencies. The EDR for the heel pad were 32.56±3.89%, 36.08±6.04% and 49.65±5.65% respectively. Higher strain rate resulted in a larger EDR. The loading velocity had little influence on the CI. The metatarsal heads of the fore foot except the first toe (61.78±2.73%) have similar CI values (55.26 ±6.28%). The CI of the heel pad is smaller than that of the fore foot. No direct correlation was found between the Ep and the loading velocity.