正常足部之三維準靜態有限元素分析

Three-Dimensional Quasi-StaticFinite Element Analysis of a Normal Foot

莊舜弘(Shueen-Hong Juang)

指導教授 ： 陳文斌

中原大學/工學院/醫學工程研究所/碩士(2001年)

https://doi.org/10.6840/cycu200100471

摘要

本研究建立出一細分所有關節之正常左足三維有限元素模型，並已完成收斂測試，分析結果已經由臨床實驗值驗證，包括：關節接觸壓力、足底壓力與剪應力。
幾何外型資料得自CT影像，受測者為無足部病史之24歲男性。利用影像輪廓擷取軟體自動取得骨骼與軟組織之外輪廓，由CAD軟體（SolidWorks 99）建立實體模型，以CAE軟體（Mentat 2000與MARC 2000）建立四面體有限元素模型並分析之。材料性質假設為線性彈性，限制小腿上端橫截面所有節點之三軸位移自由度，準靜態分析中，一足底剛性平面以控制位移方式，朝足部或鞋底移動12個分析瞬間、共推擠12 mm，並計算出每一分析瞬間之限制端反作用力。
分析結果方面，由於模型中關節接觸面積大於真實關節，造成關節接觸壓力分析值遠低於臨床實驗值。裸足站立之足底壓力與剪應力分析值與文獻實驗結果比較過，趨勢與數值皆符合臨床觀測。穿著簡易鞋具站立之分析結果則與裸足結果比較，穿著平面式、全觸式鞋內墊簡易鞋具單腳站立時，分別可降低足跟區壓力61.39%、90.71%。目前研究所建立之三維足部模型，可供將來模擬其他足部條件。本模型能觀察足部內部之應力分佈、用於鞋具設計，亦可用來研究不正常足部運動之生物力學行為模式。

關鍵字

正常足部 ； 鞋具 ； 生物力學 ； 有限元素分析 ； 鞋內墊

並列摘要

The purpose of this study was to develop a three-dimensional finite element model of a normal left foot which comprising most joints of the foot. The validity of this model was verified by comparing analysis results with experimentally measured joint contact pressures, plantar normal pressures and plantar shear stresses.
The geometry of the left foot was acquired from a 24 year male without any foot pathology by computed tomography scan. The outer contours of the bone and soft tissue were determined by an automatic contouring program, and used to generate the solid models by a CAD program (SolidWorks 99). The 4-node tetrahedral models were created and analyzed using a CAE program (Mentat 2000 and MARC 2000). The material properties were assumed to be linear elastic. A quasi-static loading scheme was employed. All nodes on the upper cross-sectional area of the shank were constrained, and a rigid plane under the foot or footwear was moving towards the foot by using 12 displacement increment control from 0 to 12 mm at 1 mm interval. The reaction forces on the constrained nodes were recovered at each increment.
The joint contact pressures obtained from the finite element analysis were found to be much lower than the experimentally measured results. This is due to the fact that the larger contact areas assumed in the finite element model. The plantar normal pressures and plantar shear stresses were compared with experimentally measured results from literature and similar trends and pressure ranges were found. When wearing flat insole or total contact insole, the plantar pressure at the heel region can be reduced 61.39% and 90.71%, respectively.
The current study proposed a validated three-dimensional foot model which can be modified to simulate other foot conditions in the future. This foot model can be useful in observing stress distributions inside the foot, and in designing footwear, and the investigation of other biomechanical behavior of the foot subjected to different ambulatory movements.

並列關鍵字

footwear ； insole ； finite element analysis ； normal foot ； biomechanics

參考文獻

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