• 대한기계학회논문집
• /
• 제16권5호
• /
• pp.838-848
• /
• 1992

본 연구에서는 김성호등의 형상모델인 Fig.1(b)에서 전단하중이 작용하는 경 우에 대한, 복합재료의 탄성층 내부(레진층)에 존재하는 중앙균열의 응력확대계수 산 출을 위하여 균열부위를 제외하고는 섬유층과 레진층이 완전히 접착되었다고 가정한 모델을 다음과 같이 설정 하였다. 접착레진을 주로하는 탄성층(resin rich layer)을 중심으로 상하 각1개의 섬유층(fiber rich layer)과 균질한 특성을 갖는 복합재료의 층으로 단순화하였으며, 복합재료는 레진층이나 섬유층에 비하여 무한히 두꺼우므로 반무한체로 이상화 하였다. 선형탄 이론에 의한 혼합경계조건문제(mixed boundary value problem)로 부터 제2종 Fredholm 적분방정식(fredholm integral equation of a second kind)을 유도하였으며 수치해석적인 방법에 의하여 응력확대계수를 구하였다. 또한, 복합재료의 재료물성 및 균열길이, 섬유두께등이 기하학적 변수에 대하여 응력 확대계수를 산출하였다.

• 한국정밀공학회지
• /
• 제23권8호
• /
• pp.54-63
• /
• 2006

Enhancement methods of sensitivity to in-plane strain measurement by micro-ESPI(Electronic Speckle Pattern Interferometry) technique were proposed using TiN and Au thin films. Micro-tensile strain over the micro-tensile specimens, prepared in micro-scale by those films, was measured by micro-tensile loading system and micro-ESPI system developed in this study. The subsequent measurement of in-plane tensile strain in the micro-sized specimens was introduced using the micro-ESPI technique, and the micro-tensile stress-strain curves for these films were determined. To enhance the sensitivity to measurement of in-plane tensile strain, algorithms of the phase estimation by using curve fitting of inter-fringe and the discrete Fourier Transform with object-induced dynamic phase shifting were developed. Using these two algorithms, the micro-tensile strain-stress curves were generated. It is shown that the algorithms for enhancement of the sensitivity suggested in this study make the sensitivity to measurement of the in-plane tensile strain increase.

• Journal of electromagnetic engineering and science
• /
• 제7권3호
• /
• pp.122-128
• /
• 2007

In this paper, we present the design and measurement of a side-fed circularly-polarized patch antenna with a dielectric loading. The antenna consists of a comer-truncated rectangular patch, an L-shaped ground plane, a dielectric loading material, and a coaxial probe. An antenna operating at the UHF band (910 MHz) for the RFID reader applications is optimized using a commercial software. The size of the patch is reduced by a factor of 1.73 by loading the patch with mono-cast(MC) nylon. Measurements of the fabricated antenna show performance characteristics comparable to those of much larger commercial RFID reader antennas.

• 해양환경안전학회지
• /
• 제20권6호
• /
• pp.738-745
• /
• 2014

본 논문에서는 탄소성 영역 내 패치 로딩 크기에 따른 알루미늄 합금 사각형 판의 초기 처짐 영향을 수치해석방법으로 이용한 탄성 및 탄소성 대변형 시리즈 해석을 수행하였다. 주변 지지조건은 단순지지로 가정하고 초기 처짐 크기(w/t), 종횡비(a/b), 세장비(b/t)를 고려하여 알루미늄 합금 A6082-T6 사각형 판의 임계 탄성 좌굴하중과 좌굴 후 거동을 검토하였다. 탄성 및 탄소성 대변형 시리즈 해석은 상용프로그램을 사용하였다. 초기 처짐 크기가 작을 경우 하중증가와 함께 면내 강성이 처음부터 감소하며 크기가 커질수록 훨씬 두드러지게 발생한다. 종횡비가 커질수록 초기항복강도는 점차 감소하며 판 두께가 두꺼울수록 패치 로딩 크기(l/b) 0.5 이후 초기 항복강도 감소비율은 얇은 두께보다 더 크게 발생한다.

• Composites Research
• /
• 제22권1호
• /
• pp.1-8
• /
• 2009

본 논문에서는 면내하중을 받는 복합적층판의 저속충격거동과 손상을 해석하였다. 초기부터 존재하는 면내변형률을 고려하여 판의 변위장을 새롭게 가정하고, 이 가정된 변위장에 따른 적층판의 구조거동에 대한 유한요소방정식을 유도하였으며, 유한요소해석 프로그램을 코딩하였다. 유한요소해석을 수행하여 참고문헌의 수치해석 결과와 비교하였으며, 충격에너지는 동일하나 충격체의 질량과 속도가 다른 조건에 대해서도 해석하여 초기 면내하중의 영향을 분석하였다. 바닥으로부터 첫 번째 층간면에서의 잠재적인 층간분리 파손영역을 추정하여 초기 인내하중 및 충격조건에 따른 크기의 변화를 고찰하였다.

• 한국지반공학회논문집
• /
• 제22권1호
• /
• pp.5-14
• /
• 2006

본 연구에서는 평면변형률조건하에서 발생 가능한 다양한 응력조건을 보다 자유롭게 구현할 수 있는 간편한 형태의 평면변형률 시험장비를 새롭게 개발하였다. 개발된 시험장비의 적용성은 먼저 이상화된 가정조건하에서 이론적으로 검토되었으며, 실제 점성토시료에 대한. 일련의 평면변형률시험을 통해 실험적으로 확인 검증되었다. 그 결과 개발된 시험장비는 기존의 평면변형률 시험장비들에 비해 광범위한 적용성을 가지고 있음을 확인할 수 있었다. 또한 개발된 시험장비는 일반적인 삼축시험용 재하장치만으로도 다양한 응력조건에 대한 평면변형률시험이 가능하므로, 향후 관련분야에서 그 활용도가 매우 높을 것으로 기대된다.

• 한국지진공학회논문집
• /
• 제23권5호
• /
• pp.239-248
• /
• 2019

In this study, the out-of-plane seismic resistance of lightly-reinforced existing walls strengthened with thick RC jacket was investigated. The thick RC jacket with a thickness of 500 mm was placed at one side of the thin existing wall with a thickness of 150 mm. At the interface between the wall and RC jacket, a tee-shaped steel section with a number of anchor bolts and dowel bars was used as the shear connector. To investigate the connection performance and strengthening effects, the cyclic loading tests of four jacketed wall specimens were performed. The tests showed that the flexural strength of the jacketed walls under out-of-plane loading was significantly increased. During the initial behavior, the tee shear connector transferred forces successfully at the interface without slip. However, as the cracking, spalling, and crushing of the concrete increased in the exiting walls, the connection performance at the interface was significantly degraded and, consequently, the strength of the jacketed walls was significantly decreased. The flexural strength of the jacketed walls with tee shear connector was estimated considering the full and partial composite actions of the tee shear connector.

• 대한족부족관절학회지
• /
• 제26권4호
• /
• pp.157-162
• /
• 2022

Total ankle arthroplasty has become a viable motion-preserving alternative to ankle arthrodesis, especially in the last two decades. Recent improvements have been achieved in the strength of implant design and surgical technique. Nevertheless, addressing preoperative deformities is essential for successful outcomes of total ankle arthroplasty. Residual malalignment can produce instability and edge loading, causing acceleration of polyethylene wear, followed by osteolysis and an increased risk of revision surgery. Therefore, the accompanying deformities and their correction techniques need to be comprehensively elucidated and understood. In this article, we provide a review of the application of total ankle arthroplasty in arthritis with coronal plane varus and valgus deformities.

• Computers and Concrete
• /
• 제7권4호
• /
• pp.317-329
• /
• 2010

The paper describes localization of deformation in a bar under tensile loading. The material of the bar is considered as non-linear viscous elastic and the bar consists of two symmetric halves. It is assumed that the model represents behavior of the quasi-brittle viscous material under uniaxial tension with different loading rates. Besides that, the bar could represent uniaxial stress-strain law on a single plane of a microplane material model. Non-linear material property is taken from the microplane material model and it is coupled with the viscous damper producing non-linear Maxwell material model. Mathematically, the problem is described with a system of two partial differential equations with a non-linear algebraic constraint. In order to obtain solution, the system of differential algebraic equations is transformed into a system of three partial differential equations. System is subjected to loadings of different rate and it is shown that localization occurs only for high loading rates. Mathematically, in such a case two solutions are possible: one without the localization (unstable) and one with the localization (stable one). Furthermore, mass is added to the bar and in that case the problem is described with a system of four differential equations. It is demonstrated that for high enough loading rates, it is the added mass that dominates the response, in contrast to the viscous and elastic material parameters that dominated in the case without mass. This is demonstrated by several numerical examples.

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2001년도 춘계학술대회 논문집
• /
• pp.304-311
• /
• 2001

Unreinforced masonry is widely used as a structural material in residential constructions and known to have poor seismic performance in the out-of-plane rather than in-plane behavior. In countries of lower seismicity such as Korea, it is necessary to check the possibility of the mode of the out-of-plane failure. Though face loading is a major cause of the failure of masonary walls, Korean Seismic Code does not include provision for face-loaded unreinforced masonry walls. This paper briefly reviews the concept of analysis for unreinforced masonry walls subjected to face-load excitation proposed by Priestley, and its applicatility to Korean case.