Uddin Kazi Zahir, Youssef George, Trkov Mitja, Seyyedhosseinzadeh Hamid, Koohbor Behrad
Department of Mechanical Engineering, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, USA.
Experimental Mechanics Laboratory, Department of Mechanical Engineering, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA.
J Biomech. 2020 Aug 26;109:109950. doi: 10.1016/j.jbiomech.2020.109950. Epub 2020 Jul 15.
Several sports-related injuries and orthopedic treatments need the necessity of corrective shoes that can assuage the excessive pressure on sensitive locations of the foot. In the present work, we study the mechanical and energy absorption characteristics of density-graded foams designed for shoe midsoles. The stress-strain responses of polyurea foams with relative densities (nominal density of foam divided by the density of water) of 0.095, 0.23, and 0.35 are obtained experimentally and used as input to a semi-analytical model. Using this model, three-layered foam laminates with various gradients are designed and characterized in terms of their weight, strength, and energy absorption properties. We show that, in comparison with monolithic foams, significant improvement in strength and energy absorption performance can be achieved through density gradation. Our findings also suggest that there is not a single gradient that offers a superior combination of strength, energy absorption, and weight. Rather, an optimal gradient depends on the plantar location and pressure. Depending on the magnitude of the local plantar pressure, density gradients that lead to the highest specific energy absorption are identified for normal walking and running conditions.
几种与运动相关的损伤以及骨科治疗都需要矫正鞋，以缓解脚部敏感部位的过度压力。在本研究中，我们研究了专为鞋底夹层设计的密度渐变泡沫材料的力学性能和能量吸收特性。通过实验获得了相对密度（泡沫的标称密度除以水的密度）分别为0.095、0.23和0.35的聚脲泡沫材料的应力-应变响应，并将其用作半解析模型的输入。利用该模型，设计了具有不同梯度的三层泡沫层压板，并对其重量、强度和能量吸收性能进行了表征。我们表明，与整体泡沫相比，通过密度渐变可以显著提高强度和能量吸收性能。我们的研究结果还表明，不存在一种能同时提供强度、能量吸收和重量最佳组合的单一梯度。相反，最佳梯度取决于足底位置和压力。根据局部足底压力的大小，确定了正常行走和跑步条件下能实现最高比能量吸收的密度梯度。
