• Journal of the Korean Wood Science and Technology
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• 제31권2호
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• pp.84-91
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• 2003

본 연구에서는 3 수종(이태리 포플러, 소나무, 굴참나무재)을 공차별(0, 0.15, 0.3, 0.45 mm)로 초산비닐 수지와 레소시놀-페놀 공축합 수지를 이용하여 접합 제작하였다. 휨시험에서 핑거공차에 따라서 검출되는 AE와 휨강도성능 특성을 살펴본 결과는 다음과 같았다. 레소시놀재의 AE파 발생시기가 초산재보다 빨랐으며, 레소시놀재의 AE파 사상총수는 하중의 증가와 함께 계속적으로 증가하였으며 총발생 사상총수도 초산재보다 휠씬 많이 나타났다. 또한, 레소시놀재의 AE파 사상총수는 낮은 하중에서도 많은 개수가 발생하였다. 비례한도 내에서도 레소시놀 접착제를 사용한 경우에는 많은 AE파가 검출되었다. 따라서 레소시놀 접착제로 접착한 핑거 접합재의 휨시험으로부터 얻은 AE 신호는 핑거공차에 따른 접합재의 강도 예측이나 보증에 이용 가능할 것으로 판단되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.35-40
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• 2001

The exact solution of strength of reinforced concrete RC columns subjected to axial compression combined with biaxial bending needs trial and adjustment procedure to find the depth and inclination of the neutral axis. Thus, approximate methods of analysis and design for biaxial bending are used in practice. Load contour interprets the relation of biaxial bending and equivalent uniaxial bending by u factor which is related to material properties and column shapes. The purpose of this study is to investigate the behavior of high strength RC columns subjected to the combined axial compression and biaxial bending. Fifteen test specimens with dimensions of 200mm$\times$200mm and 4-Dl3 longitudinal steel were examined. The variable of the test is compressive strength of concrete (350, 585, 650kgf/$cm^{2}$), compression load ratio (0.2$P_{o}}$, 0.35$P_{o}}$, 0.5$P_{o}}$), and inclination of loading ($\theta$=0, 22.5, $45^{\circ}$). Test results of coefficient $\alpha$ depending on the compressive strength of concrete are compared with ACI code.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.60-65
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• 2007

Local buckling behaviors of aluminum square tube beams reinforced by aluminum plates under three point bending loads have been analyzed using experimental tests combined with theoretical and finite element analyses. For this analysis true stresses were determined from applied loads and cross-sectional area records of a tensile specimen with a rectangular cross-section by real-time photographing. True strains were also obtained from in-situ local elongation measurements of the specimen gage portion by the multi-point scanning laser extensometer. Six kinds of aluminum tube beam specimens reinforced by aluminum plates were employed for the bending test. The bending deformation behaviors up to the maximum load analyzed by the numerical simulation agreed well with experimental ones. After passing the maximum load, reinforcing plate hindering the local buckling of the tube beam was debonded from the aluminum tube beam. An aluminum tube beam strengthened by aluminum plate on the upper web showed the most excellent bending capacity, which could be explained on the basis of the neutral axis shift and the local buckling deformation range.

• 대한화장품학회:학술대회논문집
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• 대한화장품학회 2003년도 IFSCC Conference Proceeding Book I
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• pp.1-12
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• 2003

Instead of sensory evaluation, we designed an evaluation method of the setting function of hairstyling products, based on an original theory focusing on changes in bending stress observed when a load with continuous bending is applied to human hair. Specifically, we developed a device to measure bending stress to quickly and objectively evaluate the condition of human hair, particularly its dynamic properties such as the setting function, following the application of hairstyling products. This device generates a load with continuous bending while applying a pendulum motion to a hair tress, one end of which is anchored. The setting function and holding power of resins of various molecular weight and ionic properties were evaluated using this device. The results demonstrated a close correlation with those obtained by experts' sensory evaluation. The evaluation results of bending stress and holding rate confirmed that the combined use of two different resins could improve the function of setting preparations. Evaluation using this device was able to substitute for sensory evaluation, and offers quick objective evaluation and detection of changes in the holding power of hairstyling products over time. We conclude that evaluation using this device is a promising new method.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.117-118
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• 2006

The objective of this paper is to investigate into bending and failure characteristics of ISB panel with dimple shapes as inner structures. Through three-points bending test, the force-displacement curve and the failure shape are obtained to examine the deformation pattern, characteristic data including maximum load and displacement at the maximum load and failure pattern for the ISB panel. In addition, the influence of design parameters for ISB panel on the bending stiffness and failure mode has been found. From the results of the experiments, it has been shown that bending and failure characteristics of the ISB panel can be controlled by the ratio of radius and the direction of the material.

• Steel and Composite Structures
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• 재36권6호
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• pp.671-687
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• 2020

The aim of this research is to analyze buckling and bending behavior of a sandwich Reddy beam with porous core and composite face sheets reinforced by boron nitride nanotubes (BNNTs) and shape memory alloy (SMA) wires resting on Vlasov's foundation. To this end, first, displacement field's equations are written based on the higher-order shear deformation theory (HSDT). And also, to model the SMA wire properties, constitutive equation of Brinson is used. Then, by utilizing the principle of minimum potential energy, the governing equations are derived and also, Navier's analytical solution is applied to solve the governing equations of the sandwich beam. The effect of some important parameters such as SMA temperature, the volume fraction of SMA, the coefficient of porosity, different patterns of BNNTs and porous distributions on the behavior of buckling and bending of the sandwich beam are investigated. The obtained results show that when SMA wires are in martensite phase, the maximum deflection of the sandwich beam decreases and the critical buckling load increases significantly. Furthermore, the porosity coefficient plays an important role in the maximum deflection and the critical buckling load. It is concluded that increasing porosity coefficient, regardless of porous distribution, leads to an increase in the critical buckling load and a decrease in the maximum deflection of the sandwich beam.

• 대한기계학회논문집A
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• 제27권1호
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• pp.8-17
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• 2003

Fracture behaviors of pipes with local wall thinning are very important for the integrity of nuclear Power Plant. In Pipes of energy Plants, sometimes, the local wall thinning may result from severe erosion-corrosion (E/C) damage. However, the effects of local wall thinning on strength and fracture behaviors of piping system were not well studied. In this paper, the monotonic bending tests were performed of full-scale carbon steel pipes with local wall thinning. A monotonic bending load was applied to straight pipe specimens by four-point loading at ambient temperature without internal pressure. From the tests, fracture behaviors and fracture strength of locally thinned pipe were manifested systematically. The observed failure modes were divided into four types; ovalization. crack initiation/growth after ovalization, local buckling and crack initiation/growth after local buckling. Also, the strength and the allowable limit of piping system with local wall thinning were evaluated.

• Steel and Composite Structures
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• 제31권5호
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• pp.469-488
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• 2019

We in this paper study nonlinear bending of a functionally graded porous nanobeam subjected to multiple physical load based on the nonlocal strain gradient theory. For more reasonable analysis of nanobeams made of porous functionally graded magneto-thermo-electro-elastic materials (PFGMTEEMs), both constituent materials and the porosity appear gradient distribution in the present expression of effective material properties, which is much more suitable to the actual compared with the conventional expression of effective material properties. Besides the displacement function regarding physical neutral surface is introduced to analyze mechanical behaviors of beams made of FGMs. Then we derive nonlinear governing equations of PFGMTEEMs beams using the principle of Hamilton. To obtain analytical solutions, a two-step perturbation method is developed in nonuniform electric field and magnetic field, and then we use it to solve nonlinear equations. Finally, the analytical solutions are utilized to perform a parametric analysis, where the effect of various physical parameters on static bending deformation of nanobeams are studied in detail, such as the nonlocal parameter, strain gradient parameter, the ratio of nonlocal parameter to strain gradient parameter, porosity volume fraction, material volume fraction index, temperature, initial magnetic potentials and external electric potentials.

• 대한치과교정학회지
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• 제36권5호
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• pp.349-359
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• 2006

니켈-티타늄 합금은 높은 spring-back성질, 초탄성 효과, 형상기억 효과 등의 장점을 가지고 있으나 성형이 어렵다는 단점을 가지고 있다. 본 연구에서는 니켈-티타늄 와이어의 굴곡을 위한 열처리 시에 나타나는 부하-변위 곡선의 변화 및 상전이 온도 변화와 같은 물성 변화 양상을 조사하고자 하였다. 수종의 니켈-티타늄 와이어를 열처리를 시행하지 않은 군, 전기저항 열처리 장치를 이용하여 와이어 단면적에 따라 제조회사에서 권장하는 전류를 기초로 하여 $00.016"\;{\times}\;00.022"$ (5 A, 7 sec), $0.018"\;{\times}\;0.025"$ (6 A, 7 sec) 그리고 $0.0215"\;{\times}\;0.028"$ (7 A, 8 sec) 와이어를 열처리만 시행한 실험군, 열처리를 시행하여 굴곡을 부여한 실험군 그리고 열처리 시간을 1초 증가시켜 굴곡을 부여한 실험군으로 분류하여 3점 굴곡 실험과 시차주사열량측정을 하여 다음과 같은 결과를 얻었다. $0.016"\;{\times}\;0.022"$, $0.018"\;{\times}\;0.025"$ 그리고 $0.0215"\;{\times}\;0.028"$ 니켈-티타늄 와이어에서 굴곡을 부여하지 않고 열처리만 시행한 실험군이 열처리를 시행하지 않은 대조군에 비해 부하-변위 곡선이 상방 이동되어 초탄성 현상에 의한 평탄역(loading and unloading plateau)의 힘이 더 증가되었다. $0.016"\;{\times}\;0.022"$, $0.018"\;{\times}\;0.025"$ 그리고 $0.0215"\;{\times}\;0.028"$ 와이어에서 열처리만 시행한 실험군이 열처리를 시행하지 않은 군보다 더 낮은 austenite finish ($A_f$) 온도를 보였다. $0.018"\;{\times}\;0.025"$ 및 $0.0215"0.028"$ 와이어에서 열처리를 시행하여 굴곡을 부여한 실험군은 열처리만 시행한 실험군과 열처리를 시행하지 않은 대조군에 비해 부하-변위 곡선이 상방 이동되었으며, 열처리 시간을 1초 증가시켜 굴곡을 부여한 실험군에서 가장 높은 부하-변위 곡선을 나타냈다. $0.018"\;{\times}\;0.025"$ 그리고 $0.0215"\;{\times}\;0.028"$ 와이어에서 $A_f$ 온도는 열처리 시간을 1초 증가시켜 굴곡을 부여한 실험군에서 가장 낮게 관찰되었고 열처리를 시행하여 굴곡을 부여한 실험군, 열처리만 시행한 실험군 그리고 열처리를 시행하지 않은 대조군 순으로 높게 관찰되었다. 이상의 결과를 종합할 때, 임상에서 니켈-티타늄 합금 와이어에 굴곡을 부여하기 위해 열처리하는 경우 초탄성 특성은 유지될 수 있으나, 부하-변위 곡선의 상방 증가가 나타나므로, 와이어에 의한 교정력이 증가될 수 있음에 유의하여야 한다.

• 자동차안전학회지
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• 제11권1호
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• pp.40-47
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• 2019

First, three point bending analysis for the inclined press door impact beam was carried out to investigate inclination angle effect on the maximum strength with varying support distance. Next, for the system model with spring elements representing body stiffness at door mounting area, the bending structural behavior of impact beam mounted on vehicle was estimated. The mounting distance and inclination angle were changed and the beam bending buckling strength was presumed at the head displacement below which spring stiffness change has little effect on the load. Finally strength ratio to predict the bending buckling strength of impact beam mounted on vehicle from three point bending maximum strength of fixed support distance was suggested.