• 대한의용생체공학회:의공학회지
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• 제19권2호
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• pp.183-188
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• 1998

동맥과 PTFE 재료로 된 대체혈관이 혈관폐색이 생긴 부위를 우회하기 위하여 단측문합이 되었을 때 문합각의 변화에 의한 영향을 살펴보기 위하여 두 혈관의 직경비를 0.5로 고정하고 문합각을 30$^{\circ}$에서 90$^{\circ}$까지 $10^{\circ}$간격으로 변화시켜 컴플라이언스와 응력의 분포형태를 살펴보고 또한 직경비의 영향도 살펴보기 위하여 문합각을 45$^{\circ}$로 고정하고 직경비를 0.1에서 1까지 0.1간격으로 변화시켜 컴플라이언스와 응력의 변화를 살펴보았다. 단측문합비에 사용된 모델은 20-24mm, 내경 4mm, 두께 0.5mm의 동맥과 길이 10mm, 내경 2mm, 두께 0.2mm의 PTFE 대체혈관이 사용되었으며 문합각이 작아지거나 직경비가 커질수록 예각 문합부의 컴플라이언스가 점점 더 커진다는 것을 알았다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 추계학술대회
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• pp.337-346
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• 1996

Debonding of cement-femoral stem interface has been suggested as a initial focus of loosening mechanism in many previous studies of cemented total hip replacement. The purpose of this study was to investigate the effect of debonding of cement-femoral stem interface to the bone-cement interface by using three-dimensional non-liner finite element analysis. Three cases of partial debonded, full debonded, full bonded cement-bone interface were modelled with partial bonding of distal 70mm from the tip of femoral stem. Each situation was studied under loading stimulating one-leg stanced gait of 68kg patient. The results showed that under partial and full debonded cement-stem interface condition the peak von Mises stress(3.1 MPa) were observed at the cement of bone-cement interface just under the calcar of proximal medial of femur, and sudden high peak stresses(3.5MPa) were developed at the distal tip of femoral stem at the lateral bone-cement interface in all 3 cases of bonding. The stresses were transfered very little to the cement of upper lateral bone-cement interface in partial and full debonded cases. Thus, once partial or full debonded cement-femoral stem interface occured, 3 times higher stress concentration were developed on the cement of proximal medial bone-cement interface than full bonded interface, and these could cause loosening of cemented total hip replacement. Clinically, preservation of more rigid cement-femoral stem interface may be important factor to prevent loosening of femoral stem.

• 한국산학기술학회논문지
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• 제16권2호
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• pp.963-969
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• 2015

자전거는 환경공해 능력과 웰빙에 대한 관심증가 때문에 가장 유망한 미래 교통수단 중의 하나이다. 실제 자전거에 적용될 무단변속기를 제작하기 전에 신뢰성이 확보된 시뮬레이션 프로그램을 통하여 문제점을 초기에 확인하고, 각 링크의 소재 및 두께 등의 설계인자 최적화와 능력을 평가할 필요가 있다. 이 같은 과정을 통하여 무단 변속기 시스템 설계 과정에서의 소요비용을 줄일 수 있다. 본 논문에서는 설계인자를 확정하기 위해 응력해석을 수행되었으며. 전체 모델링 중에서 각 링크와 조인트 부분을 주요 설계인자로 가정하고 각각의 링크 및 조인트의 영향도 및 작동 시 받은 응력들을 CAE를 통해 확인하였다. 또한, 해석 영역에 대하여 적절한 수학적 모델링을 통해 맥동 현상을 계산할 수 있는 전용 code를 개발하였으며, 이를 Matlab에 적용하여 해석 결과를 graphic화하여 분석하였다.

• 한국가스학회지
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• 제18권5호
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• pp.6-11
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• 2014

차량용 LNG 연료 용기의 내진동 단열 지지구조 최적화 설계 개발을 위하여 종래의 해외특허구조 설계를 기본으로 한 특성요인도 분석으로 용기의 내조 및 외조 지지부 구조설계의 주요 설계 인자를 도출하였다. 도출된 설계인자 중에서 우선적으로 지지 봉재의 직경과 단열 격판 연결부 곡률을 대상으로 하여 최적화를 수행하였다. 차량용 LNG 연료 용기 설계안에 대한 평가를 위해 설계안을 MSC/MARC 상용유한 요소해석 패키지를 활용하여 유한요소 모델링하여 진동모드해석과 열전달 및 열응력해석을 수행하였다. 최적화 설계 결과를 통하여 도출된 설계안은 고유진동해석을 통한 1차 모드 고유진동수(1st Mode Natural Frequency), 열전달해석을 통한 초저온 용기 내조 외조간 지지부를 통한 총전열량 및 열응력해석을 통한 최대 Von-Mises 응력이 모두 설계 목표치를 만족하였으며, 개발된 설계안에 따라 차량용 LNG 연료 용기의 제작하여 3차원 진동 시험과 단열성능 시험을 통해 설계를 검증하였다.

• 한국가스학회지
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• 제17권5호
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• pp.37-41
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• 2013

본 연구에서는 안전모 쉘 구조물의 정상부에 돌출부를 설치한 경우와 설치하지 않은 경우에 대해, 안전모의 두께를 변수로 응력과 변위거동 안전성을 유한요소법으로 해석하였다. 안전모는 오랫동안 착용해도 안전성을 높여주고, 충격에너지를 흡수하여 착용상의 불편함을 줄여주며, 머리와 목 부분을 보호할 수 있어야 한다. 응력해석결과에 의하면, 4,540N의 충격력이 안전모의 정상부 표면에 가해졌을 때 기존의 안전모에서는 3.7mm, 수정된 새로운 안전모에서는 3.2mm의 두께를 확보해야 안전하다는 것을 보여주고 있다. 변형거동 해석에 기초한 FEM 해석결과에 의하면, 기존의 안전모에서는 3.2mm, 수정된 새로운 안전모에서는 2.0mm의 두께를 유지해야 안전한 것으로 나타났다. 따라서, 안전모를 안전하게 설계하기 위해서는 안전모의 정상부에 돌출 구조물을 설치하는 것이 좀 더 안전하다할 수 있다.

• Asian Spine Journal
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• 제12권6호
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• pp.1092-1099
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• 2018

Study Design: In-vitro biomechanical investigation. Purpose: To evaluate the biomechanical effects of the degeneration of the biodegradable cervical plates developed for anterior cervical discectomy and fusion (ACDF) on fusion and adjacent levels. Overview of Literature: Biodegradable implants have been recently introduced for cervical spine surgery. However, their effectiveness and safety remains unclear. Methods: A linear three-dimensional finite element (FE) model of the lower cervical spine, comprising the C4-C6 vertebrae was developed using computed tomography images of a 46-year-old woman. The model was validated by comparison with previous reports. Four models of ACDF were analyzed and compared: (1) a titanium plate and bone block (Tita), (2) strong biodegradable plate and bone block (PLA-4G) that represents the early state of the biodegradable plate with full strength, (3) weak biodegradable plate and bone block (PLA-1G) that represents the late state of the biodegradable plate with decreased strength, and (4) stand-alone bone block (Bloc). FE analysis was performed to investigate the relative motion and intervertebral disc stress at the surgical (C5-C6 segment) and adjacent (C4-C5 segment) levels. Results: The Tita and PLA-4G models were superior to the other models in terms of higher segment stiffness, smaller relative motion, and lower bone stress at the surgical level. However, the maximal von Mises stress at the intervertebral disc at the adjacent level was significantly higher in the Tita and PLA-4G models than in the other models. The relative motion at the adjacent level was significantly lower in the PLA-1G and Bloc models than in the other models. Conclusions: The use of biodegradable plates will enhance spinal fusion in the initial stronger period and prevent adjacent segment degeneration in the later, weaker period.

• Coupled systems mechanics
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• 제8권4호
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• pp.315-338
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• 2019

The numerical investigations have been carried out on reinforced concrete slab against blast loading to demonstrate the accuracy and effectiveness of the finite element based numerical models using commercial package ABAQUS. The response of reinforced concrete slab have been studied against the influence of weight of TNT, standoff distance, boundary conditions, influence of air blast and surface blast. The results thus obtained from simulations were compared with the experiments available in literature. The inelastic behavior of concrete and steel reinforcement bar has been incorporated through concrete damage plasticity model and Johnson-cook models available in ABAQUS were presented. The predicted results through numerical simulations of the present study were found in close agreement with the experimental results. The damage mechanism and stress response of target were assessed based on the intensity of deformations, impulse velocity, von-Mises stresses and damage index in concrete. The results indicate that the standoff distance has great influence on the survivability of RC slab against blast loading. It is concluded that the velocity of impulse wave was found to be decreased from 17 to 11 m/s when the mass of TNT is reduced from 12 to 6 kg. It is observed that the maximum stress in the concrete was found to be in the range of 15 to $20N/mm^2$ and is almost constant for given charge weight. The slab with two short edge discontinuous end condition was found better and it may be utilised in designing important structures. Also it is observed that the deflection in slab by air blast was found decreased by 60% as compared to surface blast.

• 구강회복응용과학지
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• 제28권2호
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• pp.147-161
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• 2012

본 연구에서는 유한요소해석 방법을 사용하여 임플란트 지지 3본 고정성 가공 의치에 수평적인 부적합이 존재할 때 그 정도가 임플란트 인접골 응력 발생에 미치는 영향에 대해 조사하였다. 3본 고정성 가공의치, 임플란트/악골 복합체로 구성된 해석 모델은 3차원으로 연구되었다. 3본 고정성 가공의치의 체결 간격은 하악 제2 소구치와 제2 대구치에 17.9mm 거리로 식립된 임플란트 간격에 비해 0.1mm 짧거나(17.8mm), 0.1mm 길게(18.0mm) 모델링하였다. 3본 고정성 가공의치와 임플란트 지대주 간의 체결은 총 6단계로 모사되었고 각 단계별로 가공의치가 하방으로 0.1mm 씩 변위되었다. 유한요소해석에는 PC용으로 출시된 DEFORM$^{TM}$ 3D 프로그램(ver 6.1, SFTC, Columbus, OH, USA)을 사용하였다. 3본 고정성 가공의치와 임플란트 사이의 응력은 von-Mises 응력, 최대 압축 응력, 필요한 경우 방사상 응력을 평가하였다. d=18.0mm인 모델에서는 가공의치와 지대주간의 체결이 이루어지지 않은 반면, d=17.8mm 인 모델에서는 성공적으로 체결이 가능했다. 체결 여부를 떠나 과도하게 높은 응력이 체결과정과 그 이후에 발생되었는데, 17.8mm 모델의 경우 체결완료 후에도 임플란트 주위 변연골에서 잔류하는 인장 및 압축 응력이 각각 최대 186.9MPa과 114.1MPa이었다. 이 경우 임플란트로부터 2mm 떨어진 부분까지 압축 응력이 골개조 장애 임계 응력인 55MPa($4,000{\mu}{\varepsilon}$과 같은 크기)보다 크게 측정되었다. 3본 고정성 가공의치의 0.1mm 크기의 수평적 부적합은 체결 과정뿐만 아니라 완료 후에도 인접 변연골에 높은 응력을 발생시킬 수 있다.

• 구강회복응용과학지
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• 제18권4호
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• pp.277-288
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• 2002

Seven finite element models were constructed in mandible having single screw-type implant fixture connected to the premolar superstructure, in order to evaluate how the length, diameter and platform shape of a screw-type fixture influence the stress in the supporting tissue around fixtures. Each finite element model was varied in terms of length, diameter, and platform shape of the fixture. In each model, 250N of vertical load was placed on the central pit of an occlusal plane and 250N of oblique load placed on the buccal cusp. The stress distribution in the supporting tissue and the other components was analysed using 2-dimensional finite element analysis and the maximum von Mises stress in each reference area was compared. Under lateral loading, the stress was larger at the abutment/fixture interface, and in the crestal bone, compared to the stress pattern under vertical loading. The amount of stress at the superstructure was similar regardless of the length, diameter and platform shape of a fixture. Around the longer fixture, the stress was decreased at the bone crest and subjacent cancellous bone and increased in the cancellous bone area apical to the fixture. Around the wider fixture, the stress was decreased at the abutment/fixture interface, and the bone crest and increased in the cancellous bone area apical to the fixture. Around the fixture having wider platform, less stress was produced at the abutment/fixture interface and the upper part of the cortical bone, compared to the fixture having standard platform. In conclusion, the stress distribution of the supporting tissue was affected by length, diameter, and platform shape of a fixture, and the fixture which was larger in diameter and length could reduce the stress in the supporting tissues at the bone-fixture interface and bone crest area.

• The Journal of Advanced Prosthodontics
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• 제9권5호
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• pp.371-380
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• 2017

PURPOSE. The aim of this study is to evaluate and compare the stress distribution in Locator attachments in mandibular two-implant overdentures according to implant locations and different loading conditions. MATERIALS AND METHODS. Four three-dimensional finite element models were created, simulating two osseointegrated implants in the mandible to support two Locator attachments and an overdenture. The models simulated an overdenture with implants located in the position of the level of lateral incisors, canines, second premolars, and crossed implant. A 150 N vertical unilateral and bilateral load was applied at different locations and 40 N was also applied when combined with anterior load at the midline. Data for von Mises stresses in the abutment (matrix) of the attachment and the plastic insert (patrix) of the attachment were produced numerically, color-coded, and compared between the models for attachments and loading conditions. RESULTS. Regardless of the load, the greatest stress values were recorded in the overdenture attachments with implants at lateral incisor locations. In all models and load conditions, the attachment abutment (matrix) withstood a much greater stress than the insert plastic (patrix). Regardless of the model, when a unilateral load was applied, the load side Locator attachments recorded a much higher stress compared to the contralateral side. However, with load bilateral posterior alone or combined at midline load, the stress distribution was more symmetrical. The stress is distributed primarily in the occlusal and lateral surface of the insert plastic patrix and threadless area of the abutment (matrix). CONCLUSION. The overdenture model with lateral incisor level implants is the worst design in terms of biomechanical environment for the attachment components. The bilateral load in general favors a more uniform stress distribution in both attachments compared to a much greater stress registered with unilateral load in the load side attachments. Regardless of the implant positions and the occlusal load application site, the stress transferred to the insert plastic is much lower than that registered in the abutment.