• Transactions on Electrical and Electronic Materials
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• 제16권4호
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• pp.173-178
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• 2015

In lieu of the excellent radio frequency (RF) performance of microelectromechanical system ( MEMS) switches, these micro switches need higher actuation voltage for their operation. This requirement is secondary to concerns over the swtiches’ reliability. This paper reports high reliability operation of RF MEMS switches with low voltage requirements. The proposed switch is optimised to perform in the Q-band, which results in actuation voltage of just 16.4 V. The mechanical stress gradient in the thin micro membrane is computed by simulating von Mises stress in a multi-physics environment that results in 90.4 MPa stress. The computed spring constant for the membrane is 3.02 N/m. The switch results in excellent RF performance with simulated isolation of above 38 dB, insertion loss of less than 0.35 dB and return loss of above 30 dB in the Q-band.

• 대한치과기공학회지
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• 제21권1호
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• pp.115-121
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• 1999

This investing was carried out to evaluate the alteration of stress distribution on teeth and esthetic crowns. Analyzing the stress distribution by the two-dimensional finite element methods, a model of lower 1st molar according to the porcelain fused metal crown an the porcelain fused glass ceramic core crown and the all glass ceramic crown. 1. The pattern of stress distribution showed no apparent differences. 2. The greatest von Mises values were concentrated around the central fossa of all esthetic crowns. The greatest Maximum principle value were concentrated around the interface between the base of esthetic crown and the abutment tooth. It was found that the apatite glass ceramic could be applicable for use in dental crown prosthesis.

• Structural Engineering and Mechanics
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• 제6권4호
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• pp.395-409
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• 1998

This paper concerns the development and implementation of an orthotropic, stress resultant elasto-plastic finite element model for the collapse load analysis of reinforced concrete plates. The model implements yield line plasticity theory for reinforced concrete. The behaviour of the yield functions are studied, and modifications introduced to ensure a robust finite element model of cases involving bending and twisting stress resultants ($M_x$, $M_y$, $M_{xy}$). Onset of plasticity is always governed by the general yield-line-model (YLM), but in some cases a switch to the stress resultant form of the von Mises function is used to ensure the proper evolution of plastic strains. Case studies are presented, involving isotropic and orthotropic plates, to assess the behaviour of the yield line approach. The YLM function is shown to perform extremely well, in predicting both the collapse loads and failure mechanisms.

• Advances in materials Research
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• 제3권1호
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• pp.271-281
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• 2014

The presence of cavities in the bone cement has a great importance for the transport of antibiotics, but its existence in this material can lead to its weakening by notch effect. The aim of this study allows providing a physical interpretation to the cavities interconnection by cracks observed experimentally. The most important stress of Von Mises is localized at the cement/bone interface near the free edge which is the seat of stress concentration. The presence and interaction of cavities in this site concentrate, by notch effect, stresses which tend to the tensile fracture stress of Bone cement.

• 한국기계가공학회지
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• 제20권5호
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• pp.61-68
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• 2021

Movable weirs with multi-stage control are necessary in many Korean rivers to actively control the water storage level. A mesh dependency test was performed to determine the appropriate number of meshes for structural analysis of movable weirs. The standing angles of movable weirs were set to 60°, 45°, 30°, and 15° for stress analysis. The standing angle of 0° was excluded from the analysis because it was unloaded. Changes in the standing angle led to changes in the water depth, maximum pressure, maximum strain, and maximum stress. The maximum average stress and the structural safety of the multi-stage control movable weir were computed and tested using the Ansys FEA software package.

• 한국기계가공학회지
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• 제15권1호
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• pp.42-49
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• 2016

This study was analyed V-bending in order to analyze the spring-back phenomenon in the roll forming process. The material of forming sheet used in the roll forming process is high tension steel and the product name of sheet material is POSTEN 60. The most important variable is the number of roll passes (3-Pass, 4-Pass, 5-Pass, 6-Pass and 10-Pass) and other roll forming process variables were fixed. To determine the characteristics of the tension and compression, the forming sheet was analyzed by dividing the layer (Upper and Bottom) in the thickness direction from the center line. The results of FEM simulation analysis was derived to von-mises stress equivalent strain, and the spring-back value was calculated according to the final forming shape. The more number of the roll pass, von-mises stress and equivalent strain value of forming sheet were lowed. Also, spring-back values tended to decrease. The results of this study can be utilized for prediction and trend of spring-back value in the roll forming process applied to high tension steel sheet. So, development time and cost of the roll forming process is expected to be reduced.

• 대한기계학회논문집A
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• 제35권11호
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• pp.1399-1406
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• 2011

수처리 공정에는 반드시 교반기 전용 감속기가 사용된다. 본 연구에서는 사용 중의 누유를 방지하고 토크효율 향상을 위한 전용 누유방지형 감속기를 개발하였다. 설계 개선된 감속기 시제품을 개발하는데 있어서, CAD 및 CNC 고속가공기를 사용하여 실물모형(Mock up), 금형 등을 제작하였다. 특히 누유방지 구조인 감속기 시제품의 하부 하우징에 대한 구조적 안전성을 평가하고자 상용 유한요소 해석코드인 ALGOR 을 이용하였다. 해석 결과, 최대 von Mises 응력이 항복응력보다 낮은 123 N/$mm^2$ 으로 안전하였으며, 고유진동수는 650~700 Hz 이었다. 그리고 토크효율은 95.87%로서 이전 연구결과 (88.45%)에 비하여 약 8% 향상되었다. 소음 수준은 75 dB, 사용 중 누유 및 이상 소음은 발생하지 않았다. 따라서 항상된 감속기 시제품을 최적 설계하여 성공적으로 개발하였다.

• 한국가스학회지
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• 제15권1호
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• pp.35-39
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• 2011

본 논문에서는 FEV 차량용 복합소재 연료탱크의 탄소섬유 적층두께에 따라 달라지는 강도안전성에 미치는 기여율의 영향을 해석하고자 한다. 기여율에 의한 영향을 FEM 모델링으로 고찰하기 위해, 복합소재 연료탱크의 알루미늄 라이너와 탄소섬유 적층에 작용하는 von Mises 등가응력을 후프방향과 헤리컬방향에 대하여 각각 계산 하였다. FEM 해석결과에 따르면, 알루미늄 라이너에 작용하는 등가응력 기여율은 후프방향으로는 77.5%, $70^{\circ}C$ 경사진 헤리컬방향으로는 18.11%, $12^{\circ}C$ 경사진 헤리컬방향으로는 4.39%로 각각 작용하는 것으로 나타났다. $12^{\circ}C$ 경사진 탄소섬유의 적층 두께비가 후프방향 적층 두께비의 42% 정도로 높게 유지됨에도 불구하고 알루미늄 라이너 소재에서 보여준 기여율 경향은 탄소섬유 적층의 강도안전성에 대해서도 유사한 것으로 나타났다. 결과적으로, 탄소섬유 연료탱크의 강도안전성은 탄소섬유 적층의 두께보다 와인딩 각도에 의해 더 많은 영향을 받는다는 계산결과를 보여주고 있다.

• Elastomers and Composites
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• 제44권2호
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• pp.98-105
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• 2009

내이의 달팽이관은 기저막(basilar membrane)과 유모세포(hair cells)라는 두 가지 중요한 요소로 이루어져 있다. 기저막은 귀로 들어오는 소리를 주파수에 따라 분리하는 기능을 가지고 있으며, 기저막 위에 있는 유모세포는 생체전기 신호를 발생시키는 기계적 감각 수용기관이다. 인간의 생체청각기구를 모사한 인공와우와 신개념의 인공감각기관을 개발하기 위해서, 본 논문에서는 ZnO 압전 나노필라를 사용하여 인공유모세포(artificial hair cell)를 구현할 수 있는 핵심 기반 기술인 생체모사 기술을 연구하였다. 그 구체적인 방법으로 ZnO 나노필라를 저온성장법으로 유연기판에, 고온성장법으로 실리콘 웨이퍼에 성장시켰다. 유연기판과 실리콘 웨이퍼 위에 ZnO 나노필라를 성장 전에 미리 패턴을 만들었고, 기판에 선택적으로 ZnO 나노필라를 성장시켰다. 또한 ZnO 나노필라의 동적 정적 거동을 이해하기 위해 다중 물리 해석기법을 사용하여 ZnO 나노필라의 electric potential, von Mises stress, 변형량 등을 분석하였다. 본 연구에서는 ZnO 나노필라를 제작 및 패터닝하는 기술과 최적화하는 다중 물리 해석기술을 이용하여 인공 유모세포를 구현하는 핵심기술을 개발하였다.

• Biomaterials and Biomechanics in Bioengineering
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• 제3권2호
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• pp.115-127
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• 2016

Shoulder pain, injury and discomfort are public health and economic issues world-wide. The function of these joints and the stresses developed during their movement is a major concern to the orthopedic surgeon to study precisely the injury mechanisms and thereby analyze the post-operative progress of the injury. Shoulder is one of the most critical joints in the human anatomy with maximum degrees of freedom. It mainly consists of the clavicle, scapula and humerus; the articulations linking them; and the muscles that move them. In order to understand the behavior of individual muscle during abduction arm movement, an attempt has been made to analyze the stresses developed in the shoulder muscles during abduction arm movement during the full range of motion by using the 3D FEM model. 3D scanning (ATOS III scanner) is used for the 3D shoulder joint cad model generation in CATIA V5. Muscles are added and then exported to the ANSYS APDL solver for stress analysis. Sensitivity Analysis is done for stress and strain behavior amongst different shoulder muscles; deltoid, supraspinatus, teres minor, infraspinatus, and subscapularies during adduction arm movement. During the individual deltoid muscle analysis, the von Mises stresses induced in deltoid muscle was maximum (4.2175 MPa) and in group muscle analysis it was (2.4127MPa) compared to other individual four rotor cuff muscles. The study confirmed that deltoid muscle is more sensitive muscle for the abduction arm movement during individual and group muscle analysis. The present work provides in depth information to the researchers and orthopedicians for the better understanding about the shoulder mechanism and the most stressed muscle during the abduction arm movement at different ROM. So during rehabilitation, the orthopedicians should focus on strengthening the deltoid muscles at earliest.