• International Journal of High-Rise Buildings
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• v.1 no.1
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• pp.1-13
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• 2012

The importance of appropriate use of damping evaluation techniques and points to note for accurate evaluation of damping are first discussed. Then, the variation of damping ratio with amplitude is discussed, especially in the amplitude range relevant to wind-resistant design of buildings, i.e. within the elastic limit. The general belief is that damping increases with amplitude, but it is emphasized that there is no evidence of increasing damping ratio in the very high amplitude range within the elastic limit of main frames, unless there is damage to secondary members or architectural finishings. The damping ratio rather decreases with amplitude from a certain tip drift ratio defined as "critical tip drift ratio," after all friction surfaces between primary/structural and secondary/non-structural members have been mobilized.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.1009-1014
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• 1997

The small material removal rate of elastic emission machinong (EEM) becomes a serious problem due to using fine powder particles for obtaining finished of high quality. If a cylindrical polyurethane-wheel is used as a tool for accelerating powder particles, the efficiency of machining may be increased through enlarging the machining regionand increasing the surface velocity of the wheel. If these analyicl results are compared with experimental ones, characteristics of EEM using polyurethan-wheel can be clarified. In this study, effects of EEM using cylindrical polyurethane-wheel on the surface roughness and the material removal rate were verified through polishing of the brittle material under various conditions. The high-efficient polishing of silicon wafer has been also carried out using this method.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.513-518
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• 1999

The objective of this experiment is to observe the elastic and inelastic behaviors of high-rise reinforced concrete frame with infilled masonry. To do this a building frame designed according to Korean seismic code and detailed in the Korean conventional manner was selected. An 1:12 scale plane masonry-infilled frame model was manufactured according to similitude law. Push-over test were performed under the roof displacement control. To simulate the earthquake effect, the lateral force distribution was maintained to be an inversed triangular by using whiffle tree. From the tests, story displacements, lateral story forces, local plastic rotations and the relations between inter-story drift versus story shear are obtained. Based on the test results, conclusions on the characteristics of the elastic and inelastic behaviors of a high-rise reinforced concrete frame with infilled masonry are drawn.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.7
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• pp.1014-1020
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• 2004

The present work complies the elastic stress concentration factor for a pipe with local wall thinning, based on detailed three-dimensional elastic FE analysis. To cover practically interesting cases, a wide range of pipe and defect geometries are considered, and both internal pressure and global bending are considered. Resulting values of stress concentration factors are tabulated for practical use, and the effect of relevant parameters such as pipe and defect geometries on stress concentration factors are discussed. The present results would provide valuable information to estimate fatigue damage of the pipe with local wall thinning under high cycle fatigue.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1306-1309
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• 2003

In the present paper, finite element analyses were carried out to evaluate the most important feature of a stent, that is. high radial strength and flexibility. Palmaz-Schatz 154 stent and two new models(stent A, stent B) were selected because they are the most representatives of tubular stents. Finite element analyses for the stent system were performed using ABAQUS/Explicit code. As a result, Palmaz-Schatz 154 stent shows sufficient radial strength but it needs some improvement in general properties such as high flexibility, low elastic recoil, low longitudinal contraction and low metal coverage area. Other two models show that sufficient flexibility, foreshortening and longitudinal recoil.

• Journal of the Korean Society for Nondestructive Testing
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• v.9 no.2
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• pp.18-24
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• 1989

Computer-aided high frequency ultrasonic is applied to aluminum oxide(85w%, 94w%, 96w%, and 99w%) MOR(modulus of rupture) samples to evaluate mechanical properties such as density variation, pore content, elastic modulus, shear modulus, and poisson's ratio. Ultrasonic wave velocity and attenuation measurement techniques were used as an evaluator of such properties. Pulse-echo C-Scan images with different fate setting method using 50MHz center frequency 1 inch focal length transducer allows evaluation of density variation and pore content. Elastic modulus calculated with the relation of density and ultrasonic velocity. It shows good reliability as compared with resonance method. Sintered density variation of $0.025g/cm^{3}$, that is 0.6% of theoretical density in $Al_{2}O_{3}$ samples can be observed by ultrasonic velocity measurement. Attenuation measurement method qualitatively agree with 4-point fracture testing result concerning of porosity content.

• Journal of Welding and Joining
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• v.31 no.5
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• pp.1-6
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• 2013

In carrying out the elastic-plastic analysis, four conditions (equilibrium equation, constitutive equation, condition of compatibility and yield condition) should be satisfied. In welding, the temperature largely changed from a melting temperature to a room temperature. So, yield stress of materials largely changed, too. In particular, yield stress becomes about zero over $700^{\circ}C$. The analysis should be carried out under the condition that equivalent stress generated in temperature increment ${\Delta}T$ did not exceed yield stress of materials at high temperature over $700^{\circ}C$. It should be sufficiently recognized that the obtained results were not reliable if this condition was not satisfied.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.285-288
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• 2007

In the recent years the using of low-density material such as high-strength Al alloy on the various industries is becoming light-weight. High strength and hollow Al alloy is good material for stiffness and recycling. Therefore the advanced manufacturing technology with Al alloy is continuously required in many industrial fields. In this study simplified hallow rectangular section of Al alloy is analyzed by FE analysis. Bending stress is affected punching and rotating of wing-die. The analysis of press bending is preformed at first. The elastic recovery value of component and stress distribution acting from the result of the bending angle of three types were obtained. The designed precesses were analyzed by the commercial FE code, Deform-3D. Forming dies for each process were designed and prototypes were manufactured by the verified forming process. Some of the important features of design parameters in the press bending were reviewed.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.239-244
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• 1996

The aim of this study is to present the elastic modulus equation that suits to a domestic situation to coincide the improved mechanical properties of high-strength concrete. For this purpose, this study collected the laboratory data more than 400 connected with the modulus of elasticity that performed in this country and also compared with the existing equations compressive strength of investigated concrete ranged from 400 to 1, 400kg/$\textrm{cm}^2$. As a result, it could confirm that the existing equations which were proposed by the ACI 363R. CEB-FIP, NS 3473, and New-RC have a tendency to the overestimation in general.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.669-672
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• 1999

In this paper, we studied the properties of small-size disk-type ultrasonic motor using travelling wave for the application to the precise control robotic joint motor and fabricated it. The diameter of the ultrasonic motor fabricated was 13mm. Also, the piezoelectric vibrator was constructed by piezoelectric ceramic and elastic material. The piezoelectric ceramic was composed to PZ-PT-PMN which was shown the high electromechanical stability under high vibration level and stainless steel was used as the elastic material in which configuration was disk-type. To conform the capability of application to robotic motor, we measured the change of rotational speed according to applied voltage and applied frequency. As the results, the small-size disk-type ultrasonic motor was able to fabricate, and the revolution speed was 350 (rpm) when input voltage was 55 (Vrms) and applied frequency 160.4 IkHz] under pre-load.