• 대한기계학회논문집A
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• 제30권1호
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• pp.60-65
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• 2006

The present paper provides experimental J estimation equation for the circumferential through-wall cracked pipe under four-point bending, based on the load-crack opening displacement (COD) record. Based on the limit analysis and the kinematically admissible rigid-body rotation field, the plastic ${\eta}$-factor for the load-COD record is derived and is compared with that for the load-load line displacement record. Comparison with the J results from detailed elastic-plastic finite element (FE) analysis shows that the proposed method based on the load-COD record provides reliable J estimates even for shallow cracks, whereas the conventional approach based on the load-load line displacement record gives erroneous results for shallow cracks. Thus, the proposed J estimation method could be recommended for testing the circumferential through-wall cracked pipe, particularly with shallow cracks.

• 대한기계학회논문집A
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• 제34권6호
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• pp.725-730
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• 2010

부정정계 배관의 두께 관통 후 파단전누설 거동과 균열개구변위는 정정계 배관과 비교하여 연구 하였다. 부정정 배관은 균열 발생으로 인한 최대 강도의 감소가 비교적 적었다. 부정정 배관계의 파단 전누설 거동은 정정계 배관보다 더 안전 하였다. 균열개구변위는 미관통균열을 가지는 배관에서 균열 관통 후 평가하기 위하여 제안된 소성힌지를 사용하여 평가하였다.

• Macromolecular Research
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• 제14권6호
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• pp.624-629
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• 2006

The cellulose-based, Electroactive Paper (EAPap) has recently been reported as a smart material with the advantages of lightweight, dry condition, biodegradability, sustainability, large displacement output and low actuation voltage. However, it requires high humidity.. This paper introduces an EAPap made with a cellulose solution and lithium chloride (LiCl), which can be actuated in room humidity condition. The fabrication process, performance test and effect of LiCl content of the EAPap actuator are illustrated. The bending displacement of the EAPap actuators was evaluated with actuation voltage, frequency, humidity and LiCl content changes. At a LiCl/ cellulose content of 3:10, the displacement output was maximized at a room humidity condition. Even though the displacement output was less than that of a high humidity EAPap actuator, the mechanical power output was not reduced due to the increased resonance frequency, which is promising for developing EAPap actuators that are less sensitive to humidity.

• 한국소음진동공학회논문집
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• 제15권9호
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• pp.1077-1083
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• 2005

Electro-Active Paper (EAPap) is one of attractive electro-active polymer (EAP) materials for artificial muscles due to its many advantages such as light weight, biologically degradable, low cost, large displacement output, low actuation voltage and low power consumption. However, drawbacks of EAPap actuators include low force output and humidity dependence. To enhance the performance of EAPap, conductive polymer (PPy) and SWNT/conductive polymer (PANI) are coated on EAPap PPy as conductive polymer is coated on cellulose EAPap by means of electrochemical deposition. Two different dopants are used in PPy through conducting polymer processing. SWNTS are mixed with PANI in emeraldine base along with different dopants. The compound materials are coated on cellulose EAPap using spin coating system. The performance of PPy/EAPap and SWNT/PANI/EAPap are evaluated in terms of bending displacement, blocked force, and the effects of dopants, humidity, coaling time, voltage and frequency are investigated. Comparing with EAPap actuators, SWNT/PANI/EAPap actuators show $200\%$ improvement of bending displacement and $300\%$ increment of blocked force.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 춘계학술대회 논문집
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• pp.33-36
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• 1998

This paper is a study on a linear ultrasonic motor with a first longitudinal$(L_1)$ and fourth bending $(B_4)$ double-mode rectangular plate. The stator vibrator is composed of an elastic material plate and of a piezo-ceramic element having a motion by electrical excitation. Each strain vector differs by $90^{\circ}$ generate travelling wave with the elliptical displacement motion of a point on the surface. To magnify displacement of longitudinal direction in elliptical displacement motion, the motor has a mechanism of the.displacement enlargement. In this paper, the vibration shape of the stator is simulated using the finite element method. A detailed model considered of the piezoelectric effect and of the exact geometry of the stator is used to calculate the displacement. The position of displacement mechanism is decided by the maximum displacement.

• 대한기계학회논문집
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• 제16권5호
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• pp.864-872
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• 1992

본 연구에서는 이중노출 홀로그래피 간섭계의 원리를 이용하여 임의의 2차원 적 변형에 있어서 면외 변위와 면변위(in-plane displacement) 각각에 대한 홀로그램 을 제작하고 이를 컴퓨터에 입력하여 간섭무늬를 해석함으로써 변위와 변형률의 정량 화를 시도하였다.

• 한국항공우주학회지
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• 제47권2호
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• pp.98-106
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• 2019

인간동력항공기의 날개는 고세장비의 형상을 가지고 있어 큰 굽힘변위가 발생한다. 본 논문에서는 고세장비 형상의 날개가 가지는 구조적인 한계를 붙임각을 변경함으로써 개선하고자 하였다. 날개의 익형 및 단면형상을 고정시킨 후 동일 수준의 양력 발생을 만족시킨다는 전제하에 붙임각의 변경에 따른 날개 끝단의 굽힘변위 변화 경향을 관측하였다. 이를 위해 유한날개의 양력, 항력, 모멘트 하중을 날개의 각 섹션에 분포시켰다. 그리고 EDISON의 "geometrically exact beam (GEB)" 프로그램과 "Variational Asymptotic Beam Sectional Analysis (VABS)" 단면해석 프로그램을 사용하여 변경된 설계안의 구조 안전도를 평가하였다. 또한, 다물체 동역학 해석 프로그램 DYMORE를 이용하여 본 논문에서 예측한 날개의 끝단 변위 예측값을 비교 검증하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.276-279
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• 2004

Concrete is one of the principal materials for the structure and it is widely used all over the world. but it shows extremely brittle failure under bending and tensile load. Recently to improve such a poor property. High Performance Fiber Reinforced Cementitious Composites (HPFRCC) have been developed. and it are defined by an ultimate strength higher than their first cracking strength and the formation of multiple cracking during the inelastic deformation process. This study is to develop the hybrid HPFRCC with high ductility and strain capacity in bending and tensile load. and the three-point bending test on hybrid HPRFCC reinforced with micro and macro fibers is carried out in this paper. As the results of the bending tests. hybrid HPFRCCs reinforced with PVA40+SF and PVA100+PVA660 showed the high ultimate bending stress, multiple cracks and displacement hardening under bending load.

• Structural Engineering and Mechanics
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• 제33권4호
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• pp.485-502
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• 2009

A new 8-node serendipity quadrilateral plate bending element (MQP8) based on the Mindlin-Reissner theory for the analysis of thin and moderately thick plate bending problems using Integrated Force Method is presented in this paper. The performance of this new element (MQP8) is studied for accuracy and convergence by analyzing many standard benchmark plate bending problems. This new element MQP8 performs excellent in both thin and moderately thick plate bending situations. And also this element is free from spurious/zero energy modes and free from shear locking problem.

• Journal of the Korean Wood Science and Technology
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• 제26권1호
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• pp.87-96
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• 1998

The bending performances were evaluated at the radiata pine plywood through veneer compositions encompassing veneer quality, ply-numbers and overlays of the high density- or medium density-phenol resin impregnated sheets (hereafter abbreviated as resin sheets) on the raw plywood. In addition, a prediction on the bending MOE of veneers and plywoods was carried out by the nondestructive testing with stresswave timer. The summarized results were as follows: I. Bending strength and bending MOE of resin sheets-overlaid plywoods in parallel surface grain direction through 5 and 7ply were increased by 13 to 45% and 17 to 34%, respectively. Resin sheets-overlay occurred an increasing effect of the strength efficiency i.e. strength perpendicular-to-grain direction versus that parallel-to-grain direction, showing the phenomenon that the plywood strength becomes greater at the perpendicular-to-grain direction of 7ply than at that of 5ply. Displacement at bending failure had a greater trend at 7ply than at 5ply, and was decreased by resin sheets-overlay. 2. After the nondestructive bending MOEs were measured for individual veneers, these veneers were rearranged in plywood-manufacture. In these plywoods, including resin sheets-overlay, the actual MOE was predictable with feasibility of $R^2$=0.53, and also the nondestructively-evaluated MOE was lower by 20% in raw plywood, and higher 20% in LVL than actual bending MOEs.