• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.700-703
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• 2003

The test method of ASTM E 756 and KS D 0076 to estimate vibration-damping properties is compared. Comparison method depending on specimen support, exciting method and calculation method for loss factor is used. Half-power bandwidth method and vibration decay method is used in the calculation method for loss factor, and Young's modulus is decided by geometric character and density for specimen and resonance frequency. Vibration measurement sensor is compared by using non-contact displacement detector, velocity detector and accelerometer. This paper is also presented the matter which is able to cause error in the measurement

• 터널과지하공간
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• 제8권2호
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• pp.139-145
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• 1998

The reliable estimation of the system parameters and the accurate prediction of the system behavior are important to design underground structures safely and economically. Especially, the elastic modulus and the in-situ stresses are very important parameters in predicting the behavior of the underground structure. Therefore, the back analysis using the field measurement data is developed to determine accurately the elastic modulus and the in-situ stresses of the underground structural system in this study. A back analysis using the combined finite and boundary element is developed. It can consider the far field boundary condition and is efficient in computation. In this study, a back analysis is performed to predict behaviors of underground structures for the real construction site. The comparison between the results of the back analysis with field measurement data and the obtained material properties from the field test shows good agreement for the real construction site.

• 한국방재학회 논문집
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• 제8권2호
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• pp.39-43
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• 2008

Determination of strain associated with shear modulus and damping ratio during torsional test is complicated. This is due to nonuniform stress-strain variation occurring linearly with radius in a soil specimen in torsion. A conventional equivalent radius approach proposed by Chen and Stokoe appears to be adequate for evaluating strain associated with shear modulus at low to intermediate strain levels. This approach is less accurate for damping measurement, particularly at high strain. Modified equivalent radius approach was used to account for the nonuniform stress-strain effect more precisely. The modified equivalent radius approach was applied for hyperbolic, modified hyperbolic, and Ramberg-Osgood models. The results illustrate the usefulness of the modified equivalent radius approach and suggest that using a single value of equivalent radius ratio to calculate strains is not appropriate.

• 반도체디스플레이기술학회지
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• 제3권2호
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• pp.23-26
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• 2004

Thin film is one of the most general structures used in micro-electro-mechanical systems (MEMS). To measure the mechanical properties of SU-8 film, tensile testing was adopted which offers not only elastic modulus but also yield strength and plastic deformation by load-displacement curve. Tensile testing system was constructed with linear guided servo motor for actuation, load cell for force measurement and dual microscope for strain measurement.

• 한국산학기술학회논문지
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• 제17권12호
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• pp.98-106
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• 2016

본 연구는 공업용 응용이 많은 알루미늄 또는 구리와 같은 재료를 나노 압입 시험기에 의하여 탄생계수 및 경도 값을 얻을 때 파일-업(pile-up) 현상이 생기는 경우 계측 값을 교정할 수 있는 방법에 대해 다룬다. 나노 압입 시험기에 의해 얻어지는 탄성계수와 경도의 측정치는 접촉면적의 피팅 (fitting) 식에 의존하게 되는데 이는 오로지 싱크-인(sink-in) 재료에만 유효하다. 그러므로 싱크-인이 아닌 파일-업인 많은 무른 공학재료들에 있어서는 그 접촉면적이 실제보다 적게 계산되고 따라서 탄성계수와 경도는 높게 계산된다. 본 연구에서는 이미 탄생계수를 알고 있는 파일-업 거동을 보이는 재료의 경우에 경도 값을 교정하는 방법을 제안한다. 이 방법을 경금속인 Al 6061 T6와 C 12200에 적용하기 위해 인장시험, 나노 압입시험, 압입자국 측정, 그리고 유한요소해석을 수행하였다. 압입 자국 측정과 유한요소해석을 흥하여 두 재료 모두 파일-업 거동이 발생하는 것을 알 수 있었다. 제안한 교정 방법은 싱크-인 접촉면적 값을 파일-업 접촉면적 값으로 늘려 주었고 경도 측정값을 낮추어 주었다. 교정된 경도 값은 별도의 연구에서 다룬 변형률 구배 소성을 고려한 유한요소해석 결과와 잘 일치하였다.

• 대한기계학회논문집
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• 제7권2호
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• pp.161-167
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• 1983

In this study the phenomenon of cutting stress which arises on cutting tools and work pieces in cutting process is investigated by rake angle of cutting tools and feed for this measurement, P$_{s}$-1 (high modulus, photolastic Inc.) was used as a cutting tool, P$_{s}$-3 (medium modulus, photolastic Inc.) was used as work piece and reduction apparatus was attached to the head stock, and orthogonal cutting was adapted as a cutting method and transparent glass was used to block the strain in the orientation of thickness. The followings are the results of this study. (1) Photoelastic experimental equipments have made it possible to make dynamic measurement and analyze stress distribution in cutting tool and work piece surface which has hitherto been conducted only in static measurement and analyzing method. (2) The maximum stress arising at tools and work pieces in cutting process is on the tool edge tip, and the maximum stress arising on the tip of cutting tools is equal to that on the contacting area of work pieces in values. (3) The distributions of maximum shear stress on certain parts of the cutting tools and work pieces are as follows; for cutting tools, .alpha.=12.deg., .alpha.=0.deg., .alpha.=-12.deg. in order, and for work pieces, .alpha.=-12.deg., .alpha.=0.deg., .alpha.=12.deg. in opposite order.der.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.42-45
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• 2003

Nondestructive damage sensing and mechanical properties for acid-treated carbon nanotube (CNT) and nanofiber (CNF)/epoxy composites were investigated using electro-micromechanical technique and acoustic emission (AE). Carbon black (CB) was used to compare to CNT and CNF. The results were compared to the untreated case. The fracture of carbon fiber was detected by nondestructive acoustic emission (AE) relating to electrical resistivity under double-matrix composites test. Sensing for fiber tension was performed by electro-pullout test under uniform cyclic strain. The sensitivity for fiber damage such as fiber fracture and fiber tension was the highest for CNT/epoxy composites. Reinforcing effect of CNT obtained from apparent modulus measurement was the highest in the same content. For surface treatment case, the damage sensitivity and reinforcing effect were higher than those of the untreated case. The results obtained from sensing fiber damage were correlated with the morphological observation of nano-scale structure using FE-SEM. The information on fiber damage and matrix deformation and reinforcing effect of carbon nanocomposites could be obtained from electrical resistivity measurement as a new concept of nondestructive evaluation.

• 대한조선학회논문집
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• 제45권1호
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• pp.73-80
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• 2008

An improved method to measure the dynamic viscoelastic properties of elastomers is proposed. The method is based on the analysis of forced oscillation of a cylindrical sample loaded with inertial mass. No special equipment or instrumentation other than the ordinary vibration measurement apparatus is required. Typical measurement of the viscoelastic properties of a silicone rubber $Silastic^{(R)}$ S2 were measured over the wide frequency range from 10 Hz to 3 kHz under the action of wide region of deformation from $10^{-4}%$ to 5%. It was shown that modulus of elasticity and loss tangent fall on the single curves when the ratio of load mass to sample mass changed from 1 to 20.

• Korea-Australia Rheology Journal
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• 제14권3호
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• pp.107-114
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• 2002

Residual stress distribution in injection molded short fiber composites is determined by using the layer-removal method. Polystyrene is mixed with carbon fibers of 3% volume fraction (4.5% weight fraction) in an extruder and the tensile specimen is injection-molded. The layer-removal process, in which removing successive thin uniform layers of the material from the surface of the specimen by a milling machine, is employed and the resulting curvature is acquired by means of an image processing. The isotropic elastic analysis proposed by Treuting and Read which assumes a constant Yaung’s modulus in the thickness direction is one of the most frequently used methods to determine residual stresses. However, injection molded short fiber composites experience complex fiber orientation during molding and variation of Yaung’s modulus distribution occurs in the specimen. In this study, variation of Yaung’s modulus with respect to the thickness direction is considered for calculation of the residual stresses as proposed by White and the result is compared with that by assuming constant modulus. Residual stress distribution obtained from this study shows a typical stress profile of injection-molded products as reported in many literatures. Young’s modulus distribution is predicted by using numerical methods instead of experimental results. For the numerical analysis of injection molding process, a hybrid FEM/FDM method is used in order to predict velocity, temperature field, fiber orientation, and resulting mechanical properties of the specimen at the end of molding.

• 한국세라믹학회지
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• 제35권8호
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• pp.813-818
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• 1998

A simple method to measure the elastic modulus E and Poisson's ratio v of diamod-like carbon (DLC) films deposited on Si wafer was suggested. Using the anisotropic etching technique of Si we could make the edge of DLC overhang free from constraint of Si substrate. DLC film is chemically so inert that we could not on-serve any surface damage after the etching process. The edge of DLC overhang free from constraint of Si substrate exhibited periodic sinusoidal shape. By measuring the amplitude and the wavelength of the sinu-soidal edge we could determine the stain of the film required to adhere to the substrate. Since the residual stress of film can be determine independently by measurement of the curvature of film-substrate com-posite we could calculated the biaxial elastic modulus E/(1-v) using stress-strain relation of thin films. By comparing the biaxial elastic modulus with the plane-strain modulus E/(1-{{{{ { v}^{2 } }}) measured by nano-in-dentation we could further determine the elastic modulus and Poisson's ratio independently. This method was employed to measure the mechanical properties of DLC films deposited by {{{{ { {C }_{6 }H }_{6 } }} rf glow discharge. The was elastic modulus E increased from 94 to 169 GPa as the {{{{ { V}_{ b} / SQRT { P} }} increased from 127 to 221 V/{{{{ {mTorr }^{1/2 } }} Poisson's ratio was estimated to be abou 0.16∼0.22 in this {{{{ { V}_{ b} / SQRT { P} }} range. For the {{{{ { V}_{ b} / SQRT { P} }} less than 127V/{{{{ {mTorr }^{1/2 } }} where the plastic deformation can occur by the substrate etching process however the present method could not be applied.