Purpose： This study aims to explore the effects of running on different surfaces on the characteristics of in-shoe plantar pressure and tibial acceleration. Methods： Thirteen male recreational runners were required ...Purpose： This study aims to explore the effects of running on different surfaces on the characteristics of in-shoe plantar pressure and tibial acceleration. Methods： Thirteen male recreational runners were required to run at 12 km/h velocity on concrete, synthetic track, natural grass, a normal treadmill, and a treadmill equipped with an ethylene vinyl acetate （EVA） cushioning underlay （treadmill_EVA）, respectively. An in-shoe plantar pressure system and an accelerometer attached to the tibial tuberosity were used to record and analyze the characteristics of plantar pressure and tibial impact during running. Results： The results showed that there were no significant differences in the 1 st and 2nd peak plantar pressures （time of occurrence）, pressure-time integral, and peak pressure distribution for the concrete, synthetic, grass, and normal treadmill surfaces. No significant differences in peak positive acceleration were observed among the five tested surface conditions. Compared to the concrete surface, however, running on treadmillEVA showed a significant decrease in the 1st peak plantar pressure and the pressure time integral for the impact phase （p 〈 0.05）. These can be further ascribed to a reduced peak pressure observed at heel region （p 〈 0.05）. Conclusion： There may not be an inevitable relationship between the surface and the lower-limb impact in runners. It is, however, still noteworthy that the effects of different treadmill surfaces should be considered in the interpretation of plantar pressure performance and translation of such results to overground running.展开更多
A finite element analysis method was used to simulate the stamping process of the blade of a large concrete-mixer truck. The updated Lagrange method and the elasto-plastic constitutive equation were adopted to solve t...A finite element analysis method was used to simulate the stamping process of the blade of a large concrete-mixer truck. The updated Lagrange method and the elasto-plastic constitutive equation were adopted to solve the large strain and displacement deformation of the blade. A modified Coulomb friction model was used to solve the sliding contact between the blade and the dies. The von Mises stress distribution in the blade, the spatial displacement variation and the spring-back of the typical node were investigated in the simulation. The von Mises stress in the blade where the spring-back occurs is lowered from 463.0MPa to 150.0MPa before and after the spring-back. A typical node in the blade has a 3.33mm spring-back in Z direction. The results of the (experiments) agree well with the simulation. The analysis results are valuable for designing optimal tool dies.展开更多
基金supported by the National Natural Science Foundation of China (No. 11302131, No. 11372194, No. 11572202)+4 种基金the Doctoral Fund of Ministry of Education of China (No. 20123156120003)the Innovation Program of Shanghai Municipal Education Commission (No. 14YZ125)the Science and Technology Commission of Shanghai Municipality (No. 14DZ1103500)
文摘Purpose： This study aims to explore the effects of running on different surfaces on the characteristics of in-shoe plantar pressure and tibial acceleration. Methods： Thirteen male recreational runners were required to run at 12 km/h velocity on concrete, synthetic track, natural grass, a normal treadmill, and a treadmill equipped with an ethylene vinyl acetate （EVA） cushioning underlay （treadmill_EVA）, respectively. An in-shoe plantar pressure system and an accelerometer attached to the tibial tuberosity were used to record and analyze the characteristics of plantar pressure and tibial impact during running. Results： The results showed that there were no significant differences in the 1 st and 2nd peak plantar pressures （time of occurrence）, pressure-time integral, and peak pressure distribution for the concrete, synthetic, grass, and normal treadmill surfaces. No significant differences in peak positive acceleration were observed among the five tested surface conditions. Compared to the concrete surface, however, running on treadmillEVA showed a significant decrease in the 1st peak plantar pressure and the pressure time integral for the impact phase （p 〈 0.05）. These can be further ascribed to a reduced peak pressure observed at heel region （p 〈 0.05）. Conclusion： There may not be an inevitable relationship between the surface and the lower-limb impact in runners. It is, however, still noteworthy that the effects of different treadmill surfaces should be considered in the interpretation of plantar pressure performance and translation of such results to overground running.
基金Project(2002A1040703) supported by the Science and Technology Fund of Guangdong Province
文摘A finite element analysis method was used to simulate the stamping process of the blade of a large concrete-mixer truck. The updated Lagrange method and the elasto-plastic constitutive equation were adopted to solve the large strain and displacement deformation of the blade. A modified Coulomb friction model was used to solve the sliding contact between the blade and the dies. The von Mises stress distribution in the blade, the spatial displacement variation and the spring-back of the typical node were investigated in the simulation. The von Mises stress in the blade where the spring-back occurs is lowered from 463.0MPa to 150.0MPa before and after the spring-back. A typical node in the blade has a 3.33mm spring-back in Z direction. The results of the (experiments) agree well with the simulation. The analysis results are valuable for designing optimal tool dies.
