맞춤형 폴리프로필렌 단하지보조기의 잔류응력측정 및 제거 방법

• 영문명: The Method for Measuring and Removing Residual Stress in the Customized Polypropylene Ankle Foot Orthosis
• 발행기관: 한국지체.중복.건강장애교육학회
• 저자명: 최영철(Choi Young Chul) 이근민(Rhee Kun Min)
• 간행물 정보: 『지체.중복.건강장애연구』제49권, 243~260쪽, 전체 18쪽
• 주제분류: 사회과학 > 교육학
• 파일형태: PDF
• 발행일자: 2007.01.30

국문 초록

단하지보조기(ankle foot orthosis)는 보행동작이 비정상적인사람의 족관절 기능을 대체 혹은 보완해줄 수 있는 보행보조 장치이다. 단하지보조기 재료로는 폴리프로필렌(polypropylene)이 가장 많이 사용되고 있다. 이 재료를 사용하여 단하지보조기를 설계제작하기위해서는 가공 공정에 따른 잔류응력과 보행 시 지면반력에 의한 동적응력 및 두 응력간의 상호 작용(interaction)에 대한 이해가 중요하다. 본연구의 목적은 맞춤형 폴리프로필렌 단하지보조기에 내재된 잔류응력을 측정하고 이를 제거하는 풀림공정(annealing cycle)을 개발하는 것이다. 잔류응력을 측정하기위하여 동일인을 대상으로 동일한 방법으로 제작된 5개의 폴리프로필렌 단하지보조기를 대상으로 스트레인 게이지(strain gage)와 절단법(cutting method)을 이용한 잔류응력측정방법을 수행하였다. 이중 2개의 단하지보조기는 잔류응력제거를 위한 풀림공정을 추가로 거친 후 잔류응력을 측정하였다. 실험결과, 허용응력의 20-10%에 해당하는 응력이 보조기 주요부에 존재하는 것으로 나타났다. 이러한 잔류응력은 보조기 품질의 균질성 및 신뢰성 확보에 부정적 영향을 끼치므로 마땅히 제거하여야한다. 본 연구에서 개발된 풀림공정을 거친 보조기의 잔류응력을 측정한 결과 허용응력의 0.9-0.05%에 해당되는 미소한 잔류응력만이 존재하는 것으로 나타났다. 따라서 본 연구에서 제시한 잔류응력 제거방법은 보조기 제작과정에 유효하게 활용될 수 있다.

영문 초록

An ankle-foot orthosis (AFO) is a brace for persons with gait disabilities to support or replace the function of ankle joint. Thermoplastic materials such as polypropylene are commonly used to make ankle foot orthoses. Quantifying dynamic stress levels in the AFO during gait and evaluating the effect of residual stress on stress fields are crucial for designing a light-weight AFO with suitable strength. The main objective of this study was to evaluate the effect of residual stress on the stress distribution in the customized ankle foot orthoses during gait and to develop the Annealing Cycle for getting rid of this. Strain gages were attached on five polypropylene AFO s, and the sectioning method was used to measure residual stress introduced during manufacturing procedure. Two of these five AFO s underwent additional thermal stress relief process, and the reduction of residual stress was investigated. The experimental results showed that tensile residual stresses existed around main part of the AFO. The magnitude of tensile stress was about 10% to 20% of allowable stress. Such residual stresses are to be removed get the homogeneity and reliability. By measuring residual stresses of the AFO developed through the this process, there were as little as 0.9-0.05%. The conclusion is that the process of removing residual stress suggested in this study is greatly effective for the AFO manufacturing. An ankle-foot orthosis (AFO) is a brace for persons with gait disabilities to support or replace the function of ankle joint. Thermoplastic materials such as polypropylene are commonly used to make ankle foot orthoses. Quantifying dynamic stress levels in the AFO during gait and evaluating the effect of residual stress on stress fields are crucial for designing a light-weight AFO with suitable strength. The main objective of this study was to evaluate the effect of residual stress on the stress distribution in the customized ankle foot orthoses during gait and to develop the Annealing Cycle for getting rid of this. Strain gages were attached on five polypropylene AFO s, and the sectioning method was used to measure residual stress introduced during manufacturing procedure. Two of these five AFO s underwent additional thermal stress relief process, and the reduction of residual stress was investigated. The experimental results showed that tensile residual stresses existed around main part of the AFO. The magnitude of tensile stress was about 10% to 20% of allowable stress. Such residual stresses are to be removed get the homogeneity and reliability. By measuring residual stresses of the AFO developed through the this process, there were as little as 0.9-0.05%. The conclusion is that the process of removing residual stress suggested in this study is greatly effective for the AFO manufacturing.

목차

Ⅰ. 서론

Ⅱ. 실험

Ⅲ. 실험결과 및 고찰

Ⅳ. 결론

키워드

단하지보조기 잔류응력 풀림공정 Ankle Foot Orthosis Residual Stress Annealing Cycle