本研究旨在利用有限元素法模擬3D列印腕護具之靜態與動態分析，由手持式3D掃描器取得病人手腕與前臂數位模型，並匯入有限元素模型中。本研究選用PLA為護具之材料，其楊氏係數可由拉伸試驗求得,其值約為1 GP。本文之有限元素分析可分為三部分，第一部分為靜態分析，可解出護具在手腕各種動作下之應力分布，分析結果顯示,在各種幾何參數中，厚度對應力影響最大，建議需至少大於2 mm以保證護具之強度。第二部分為動態分析，藉以模擬護具受到直徑4 cm、質量為0.3768 kg的鋼球，以初始速度5 m/s撞擊護具，分析結果顯示，撞擊位置會顯著影響撞擊後護具之塑性變形。最後則以有限元素分析護具與手腕皮膚之間的接觸壓力分佈，在護具設計中，護具與皮膚之間必須有一間隙，若間隙太小會導致穿戴不舒服甚至引發壓瘡，太大之間隙則無法提供足夠之固定性。有限元素分析結果顯示，間隙若小於0.2 mm，某些皮膚受到過高的壓力而增加壓瘡的風險。本研究之結果可提供準則，使3D客製化護具同時具有高強度、舒適性以及固定性。

In this study, the static and dynamic analyses were conducted for 3D printed customized wrist brace (or wrist orthosis) by finite element method (FEM). The brace is designed to fit the profile of a patient’s wrist, which can be recorded by an optical 3D scanner. The material used for the brace was PLA. Based on the tensile testing data, the Young’s modulus of PLA was determined experimentally to be about 1 GPa. The finite element simulation of this study is divided into three parts. In the first part, the static analysis was conducted to obtain responses of the wrist brace under the various types of actions of the wrist. The simulation results showed that, among various geometric design factors, the thickness of the brace is the most significant one that affects the strength of the brace. It is recommended the thickness should be greater than 2 mm in order to ensure the strength of the brace. In the second part, the dynamic analysis was conducted to simulate the brace impacted by a steel ball with a diameter of 4 cm and a mass of 0.3768 kg. The impact velocity is 5 m/s. It was concluded that the impact location is a key parameter that influences the plastic deformation after the impact. In the final part, the contact pressure between wrist and brace was simulated by the FEM. In the brace design, a gap exists between the brace and the wrist skin. Small gap can result in uncomfortable wearing and large contact pressure that the skin ulceration could occur. In contrast, the fixity of the brace reduces if large gap is used. The FEM simulations reveal that a gap less than 0.2 mm is unacceptable because contact pressure is higher than the threshold in some locations. The present study gives a guideline to design a brace with enough strength, comfortability and fixity.

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