Biomechanical Evaluation of Additive-Manufactured Midsoles during Stance Phase of Gait – a Dynamic Finite Element Analysis

• Main Authors: CHEN, LIANG-YU, 陳亮宇
• Other Authors: CHEN, WENG-PIN
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/9jpje3

碩士 === 國立臺北科技大學 === 製造科技研究所 === 107 === The foot and the ground produce repeated impact when the heel strikes the ground. During this process, the lower limbs are responsible for absorbing these impact forces, and excessive impact forces may cause damage to the foot. For the sake of protecting foot, proper footwear is an important consideration, and the midsole of the footwear can provide impact absorbing function. As additive manufacturing technology advances, many processing technologies that can not be achieved by traditional manufacturing methods are developed. In recent years, such technology has also been applied to the production of commercially available honeycomb-structured shoes, such as Adidas Futurecraft 4D (FC4D) shoes, and they emphasize on better shock absorbing capability. At the same time, some literatures have pointed out that a negative poisson's ratio (NPR) can be applied to impact attenuation devices such as automobile bumpers and packaging materials. Therefore, the purpose of this study is to use dynamic finite element analysis to assess the relationship between the biomechanical benefits of the foot and the energy absorbing efficacies of the midsoles for the Adidas Futurecraft 4D and NPR midsoles. In this study, two honeycomb structures with different internal geometries were established and made according to the standard specifications, and the porosity of the test blocks were defined as 65% (Adidas FC4D) and 67% (NPR). The finite element model of the midsole was simplified by using equivalent element method, and the elemental triaxial compression analysis was performed to verify that the element has the equivalent anisotropic material property of the detailed honeycomb structure. To simulate the change in the plantar pressure when wearing two footwears with different midsole structures during the stance phase. Biomechanical evaluation was performed by using a three-dimensional finite element model of the foot, and the kinematic parameters obtained from gait analysis were brought into the foot model. From the analysis results, the plantar pressure under the calcaneus and the third metatarsal region of the forefoot were compared and the energy absorption of the midsole during stance phase was observed. The results showed that the midsoles of the Adidas FC4D shoes are more effective in plantar pressure reduction than the NPR midsole under the calcaneus and the third metatarsal region. For the percentage of plantar pressure reduction in the calcaneus area, Adidas FC4D midsole is 54% and the NPR shoe midsole is 33%, as compared to the barefoot condition. As for the third metatarsal area, Adidas FC4D midsole is 50% and the NPR midsole is 38%. The energy absorption results of the two hollow midsoles showed that the adidas FC4D midsole is better than that of the NPR midsole during the heel strike and push-off phases, Adidas FC4D midsole can absorb 903 joules of energy and the NPR shoe midsole can absorb 875 joules during heel strike, while the Adidas FC4D midsole can absorb 1368 joules and the NPR midsole can absorb 1200 joules during push-off. When comparing the plantar pressure reduction effects of the midsole and the energy absorption effect, the adidas FC4D midsole is better than the NPR midsole during the stance phase. Therefore, it can absorb more impact energy and decrease the plantar pressure of the foot. This study simplified the finite element model of the honeycomb structured shoes with equivalent elements. This can significantly reduce the number of elements for the honeycomb structure and can shorten the time required for analysis. The finite element model established in this study can be used as a preliminary evaluation tool for new shoes by eliminating unnecessary waste of experimental resources.