• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2001년도 춘계학술대회 논문집
• /
• pp.226-230
• /
• 2001

Electronic Speckle Pattern Interferometry (ESPI) has been recently developed and widely used because it has advantage to be able to measure surface deformations of engineering components and materials in industrial areas with non-contact. The spekle patterns to be formed with interference phenomena of scattering phenomena measure the out-of-plane deformations, together with the use of digital image equipment to process the informations included in the speckle patterns and the display consequent interferogram on a computer monitor. In this study, the experimental results of a canti-levered plate using ESPI were compared with those obtained from the simple beam theory. The ESPI results of the canti-levered plate analyzed by 4-step phase shifting method are close to the theoretical expectation. Also, out-0of-plane displacements of a spot welded canti-levered plate were measured by ESPI with 4-step phase shifting technique. The phase map of the spot welded canti-levered plate is quite different from that of the canti-levered plate without spot welding.

• Steel and Composite Structures
• /
• 제38권4호
• /
• pp.463-476
• /
• 2021

The concept of using Steel-concrete (SC) composite walls as retaining walls has recently been introduced by the authors and their effectiveness of resisting out-of-plane loads has also been demonstrated. In this paper, an improved analytical formulation based on partial interaction theory, which has previously been developed by the authors, is presented. The improved formulation considers a new loading condition and also accounts for cracking in concrete to simulate the real conditions. Due to a limited number of test specimens, further finite element (FE)simulations are performed in order to verify the analytical procedure in more detail. It is observed that the results from the improved analytical procedure are in excellent agreement with both experimental and numerical results. Moreover, a detailed parametric study is conducted using the developed FE model to investigate effects of different parameters, such as distance between shear connectors, shear connector length, concrete strength, steel plate thickness, concrete cover thickness, wall's width to thickness ratio, and wall's height to thickness ratio, on the behavior of SC composite walls subjected to out-of-plane loads.

• 한국강구조학회 논문집
• /
• 제24권2호
• /
• pp.137-147
• /
• 2012

본 연구는 L형, I형 실험체에 강판 콘크리트 구조와 철근콘크리트 구조를 적용하여 이질접합부를 만들고, 실험체에 반복하중을 파괴 시 까지 가력하여 면외 휨 내력 및 면내 전단 내력을 평가하고 구조특성을 검토하기 위해서 실험연구를 수행하였다.본 연구에서 면외 휨 성능실험은 접합부에서 정착부 수직철근이 인발되면서 파괴되었고, 면내 전단성능실험은 기초부에서의 휨 균열이 발생하여 파괴되었으며, 이론식과의 비교결과 최대 내력이 실험값/이론값의 결과가 면외 휨성능실험은 96%, 면내 전단성능실험은 82%의 값을 나타내었다.

• 한국강구조학회 논문집
• /
• 제19권1호
• /
• pp.129-137
• /
• 2007

본 연구에서는 X-브레이싱 접합부의 경계조건에 따른 탄성 면외 좌굴하중 및 유효 좌굴길이 계수에 관한 연구를 수행하였다. X-브레이싱의 접합부는 연결방법에 따라 강접합 혹은 단순 연결로 가정할 수 있으며, 이러한 접합부의 경계 조건은 X-브레이싱의 좌굴하중에 영향을 미친다. 본 연구에서는 접합부의 경계 조건에 따른 X-브레이싱의 면외 유효 좌굴길이 계수들을 유도 하였으며, 면외 유효 좌굴계수들은 압축부재와 인장부재의 길이비 $L_P$/$L_T$, 인장력과 압축력의 비 T/P, 및 인장부재와 압축부재의 Euler 좌굴하중의 비 $P_{ET}$/$P_{EP}$의 함수로 나타났다. 이러한 연구결과는 기존 연구자들 및 유한요소해석결과와 비교 분석하여 그 타당성과 적용성을 검증하였다. 마지막으로 유도된 면외 유효 좌굴길이 계수들을 비교하여 접합부의 경계 조건이 X-브레이싱의 면외 좌굴하중에 미치는 영향을 분석하였다.

• 한국광학회지
• /
• 제16권3호
• /
• pp.239-247
• /
• 2005

본 연구에서는 물체의 내부 결함 측정을 위해서 레이저 스페클에 바탕을 둔 dual-beam shearography 기술을 이용하였다. 층 밀림을 만들기 위해서는 여러 가지 간섭계 중에서 마이켈슨 층 밀림 간섭계를 사용하였다. 열전도도가 낮은 아크릴 판 내부에 인위적인 결함을 만들어서 시료로 사용하였다. 시료에 레이저 beam을 조사하여 산란된 빛을 마이켈슨 층 밀림 간섭계를 통하여 스페클 간섭무의를 얻었으며, 위상이동기술을 통하여 위상도를 얻었다. 단일 beam을 시료에 조사할 경우, 물체의 변형의 in-plane과 out-of-plane 성분이 혼합된 상태로 측정되기 때문에 결함에 대한 정확한 분석이 불가능하다. 따라서 두 성분을 분리하기 위해서 dual-beam shearography 기술을 도입하였다. 내부 결함이 있는 시료에 이중 beam을 조사하여 변형 전의 간섭 스페클을 얻고, 약간의 전기 열을 가하여 미세한 변형을 가한 후의 간섭스페클을 얻은 후 의 위상도를 얻은 후 LS filtering과 unwrapping 처리를 통하여 내부 결함 부위를 쉽게 알아볼 수 있도록 하였을 뿐 아니라, 외력에 의한 물체의 미세 변형에 따른 결함 부위에서의 in-plane과 out-of-plane 변형성분의 위상도와 대략적인 변형 정도를 알아낼 수 있었다. 전기 열에 의한 내부결함이 있는 아크릴 판의 변형은 주로 z 방향(out-of-plane)으로 일어났으며 이것은 낮은 열전도도 때문이라는 예측과 잘 일치하였다.

• Structural Engineering and Mechanics
• /
• 제43권6호
• /
• pp.739-759
• /
• 2012

The tailoring optimization technique recently developed by the author for improving structural response and energy absorption of composites is extended to sandwich shells using a previously developed zig-zag shell model with hierarchic representation of displacements. The in-plane variation of the stiffness properties of plies and the through-the thickness variation of the core properties are determined solving the Euler-Lagrange equations of an extremal problem in which the strain energy due to out-of-plane strains and stresses is minimised, while that due to their in-plane counterparts is maximised. In this way, the energy stored by unwanted out-of-plane modes involving weak properties is transferred to acceptable in-plane modes. As shown by the numerical applications, the critical interlaminar stress concentrations at the interfaces with the core are consistently reduced without any bending stiffness loss and the strength to debonding of faces from the core is improved. The structural model was recently developed by the author to accurately describe strain energy and interlaminar stresses from the constitutive equations. It a priori fulfills the displacement and stress contact conditions at the interfaces, considers a second order expansion of Lame's coefficients and a hierarchic representation that adapts to the variation of solutions. Its functional d.o.f. are the traditional mid-plane displacements and the shear rotations, so refinement implies no increase of the number of functional d.o.f. Sandwich shells are represented as multilayered shells made of layers with different thickness and material properties, the core being treated as a thick intermediate layer.

• 한국소음진동공학회논문집
• /
• 제15권10호
• /
• pp.1186-1194
• /
• 2005

In this paper, we have systematically formulated the equations concerned to the in-plane and out-of-plane motions and deformations of a thick circular beam by using the kinetic and strain energies in order to analyse natural frequencies of a thick ring. The effects of variation of radius of curvature across the cross-section and also the effects of bending shear, extension and twist are considered. The equations of motion for natural vibration analysis of a ring are obtained utilizing the cyclic symmetry of vibration modes of the ring. The frequencies calculated using thick ring model and thin ring model are compared and discussed with the ones obtained from finite element analysis using the method of cyclic symmetry with 20-node hexahedral solid elements for rings with the different ratio of radial thickness to mean radius.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1997년도 춘계학술대회 논문집
• /
• pp.987-992
• /
• 1997

Burrs always come out with the machining of ducterial with small size. Though the size of burrs is small, burrs dominate deterioration of the accuracy of the micro grooves. So the burr generation model especially side burr generation model was investigated to predict the size of the burrs at the given cutting conditions. The side shear plane is introduced to build the burr generation model and the width of side shear plane nomalized with cutting depth is defined with the shear angle. From the theoretical observation, the width of side shear plane can vary up 40% of the cutting depth. To determine the size of burr and stiffness, single groovings were carried out and it was found that there exist a critical depth of cut that the size or stiffness of the burr vary.

• 한국소음진동공학회논문집
• /
• 제14권1호
• /
• pp.64-72
• /
• 2004

In this paper. we analyse and present electro-mechanical dynamic characteristics of a micro-machined vibrating silicon ring gyroscope which can measure angular velocities about three orthogonal axes. The ring gyroscope has a ring connected to the gyroscope main body by support-ligaments which are arranged with cyclic symmetry. The natural modes of its vibration can be distinguished into the in-plane motion and the out-of-plane motion which are coupled by the gyro-effect due to the rotation of the gyroscope main body. The motions of the ring are electro-statically derived. sensed and balanced by electrodes. The equations of motion are formulated. The measuring method of angular velocities by force-to-rebalance is presented. The dynamic characteristics of a ring gyroscope are calculated and compared.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2005년도 춘계학술대회 논문집
• /
• pp.1803-1807
• /
• 2005

The pipe which it uses from the nuclear power plant or factory by a long period use and a corrosive action the inside defect occurs on the inside. abstract here. The ESPI method is in order to investigate the laser light in the measurement object it will be able to measure the wide territory whole in once, does not receive an effect in direction of defect not to be, has the strong point it will be able to measure a change of place arrowhead real-time defect. It measured a inside defect of pressure vessel by using Out of plane ESPI and In plane of ESPI. It compared a each method result.