• Tribology and Lubricants
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• 제20권4호
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• pp.197-203
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• 2004

As the rotational speed and the track density are increased, the vibration of disk/spindle system becomes critical issue in order to reduce the track mis-registration. In this work, we propose a simple inclined air bearing (20${\times}$20 mm) system which is located very near to the rotating poly-carbonate disk, and investigate suppressing effect for the disk vibration mode (0,0) both experimentally and numerically. We find dynamic stiffness and damping coefficients of air bearing and then apply those values to the disk vibration analysis. Numerical results show about 10 percent difference comparing to the experimental results. Also we investigate the reduction of disk vibration and power consumption with two different kinds of inclined bearing for the normal disk drive system experimentally. We find inclined air bearing can reduce about 30 percents of the transverse disk vibration.

• 한국자동차공학회논문집
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• 제6권1호
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• pp.122-133
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• 1998

This paper presents the static analysis, the modal analysis and the forced vibration analysis on engine structures to find out the structure-borne noise sources by finite element method. The deformation of engine structures under the maximum combu- stion gas force was calculated through the static analysis, and the resonance possibilities were predicted by the modal analysis which ascertains mode shapes and the corresponding frequencies of engine global and its major noise sources in engine surfaces were investigated with the forced vibration analysis by means of finding the transfer mobilities on engine surfaces due to the piston impact and the velocity levels due to the combustion in consideration of oil film stiffness and damping coefficients. Finally, the direction of engine structure-borne noise reduction can be estabilished by the above-mentioned analysis procedure and the reduction effect of cost on proto-type engine build-up is expected.

• 대한기계학회논문집A
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• 제24권8호
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• pp.2022-2031
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• 2000

Since the surface roughness of adherends affects much the strength of adhesivelybonded joints, the effect of surface roughness on the fatigue life of adhesively bonded tubular single lap joints was investigated analytically and experimentally by fatigue torsion test. The stiffness of the interfacial layer between adherends and adhesive was modeled as a normal statistical distribution function of surface roughness of adherends. From the investigation, it was found that the optimum surface roughness of adherends for the fatigue strength of tubular single lap joints was dependent on bondthickness and applied load.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1450-1454
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• 2000

In order to understand dynamic characteristics of centrifugal compressor supported foil bearing, of which normal operating speed is about 20,000 ${\sim}$ 50,000 rpm, the rotor whirl is measured using gap sensors. Not only critical speeds of rotor system but also stability of rotor whirl, which are main concerns of the turbo compressor system, are measured using gap sensors by varying the rotating speed the rotor. The stiffness characteristics of bearing system is shown to be almost invariant according to speed variation by the measurement of eccentricity. In addition, from the directional power spectral density function of the measured vibration signal, the isotropy stiffness characteristics of foil bearing system is discussed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.393-398
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• 2002

Rubber isolator has properties that can adjust easily stiffness and can be formed various shape. Also, it has high damping and is effective about structure-borne noise at high frequency range, So, rubber mount has widely used to isolate vibration at industrial equipment and construction field. However, rubber material is nonlinear and require enough consideration about shape factor whenever it is designed. The purpose of this paper is to develop conical rubber mount using compression and shear elasticity. The first, the dimension of mount is calculated by theoretical analysis considering design condition and static characteristics have been analyzed by FEM method. In addition, the fatigue test of rubber mount is performed to get reliability for product life and dynamic stiffness test is executed to get dynamic magnification factor. Finally, transmissibility test of vibration isolator has been carried out to suggest normal quantity data about vibration isolation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.439-442
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• 2005

Steel encased composite columns are widely used due to their excellent structural performance in terms of stiffness, strength, and ductility. However, these columns were usually utilized for building structures and had higher steel ratio for small sections. For bridge pier applications, it is necessary to design the SRC columns having low steel ratio, which is nearly the same steel ratio as the normal RC columns. In this study, the evaluation of the composite columns with a core steel in term of the stiffness and the strength was investigated using experimental results. The effects of the steel ratio was also estimated using design provisions. The calculation of steel encased composite columns with multiple steel sections were performed and compared with RC columns.

• Journal of Welding and Joining
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• 제16권1호
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• pp.63-69
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• 1998

The stress intensity factor has been calculated theoretically for the cracked plate subjected to remote normal stress and reinforced with a sheet by symmetric seam welding. The singular integral equation was derived based on displacement compatibility condition between the cracked sheet and the reinforcement plate, and solved by means of Erdogran and Gupta's method. The results from the derived equation for stress intensity factor were compared with FEM solutions and seems to be reasonable. The reinforcement effect gets better as welding line is closer to the crack and the stiffness ratio of the cracked plate and the reinforcement sheet becomes larger.

• Steel and Composite Structures
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• 제51권5호
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• pp.575-586
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• 2024

Steel arch supports are used in mines and underground structures to provide stability. Most of the supports are made up of overlapping arches. They can behave either yieldingly or unyieldingly. If the normal force at any point of overlapping equals the slip resistance, the slide occurs. This paper presents a solution procedure for determining the load-carrying capacity of steel arch supports in the yielding implementation. This solution considers the effects of several significant elements, including differing materials and the number of clamps in yielding friction joints. The direct stiffness method is applied. The solution contains geometric, physical, and structural nonlinearity. The results obtained from numerical modeling using the provided procedure are compared to laboratory tests conducted at GIG Katowice in 2012. They show a good correlation with previously collected data from equivalent laboratory conditions.

• 한국터널지하공간학회 논문집
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• 제21권6호
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• pp.861-874
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• 2019

최근 발생한 포항과 경주 지진 이후 공동구와 같은 소단면 터널 구조물에 대한 내진 성능 평가에 대한 관심이 증가하고 있다. 이 연구에서는 유한 차분법 기반의 FLAC3D를 사용하여 지진 하중에 대한 수직구와 수평 터널 구조물에 대한 3차원 동적 해석을 수행하였다. 특히 지반과 구조물 사이 경계면 특성을 고려한 지반-구조물 상호 해석 시 중요 인자인 경계면 강성 계수의 영향을 분석하기 위한 매개변수 해석을 수행하였다. 매개변수 해석을 통해 경계면 강성 계수는 지하 구조물의 전체 동적 거동에는 큰 영향을 미치지 않지만 접속부의 국부적인 변위 거동에는 큰 영향을 미치는 것을 확인 할 수 있었다. 경계면 강성계수의 크기는 접속부에서의 변위와 반비례하는 경향을 보였으며, 수직 응력 및 전단 응력에 대해서는 비례하는 경향을 확인하였다. 연구 결과 수치 해석에서 주로 사용되고 있는 경계면 강성 계수에 대한 경험적 식의 한계를 제시할 수 있었으며, 새로운 경계면 강성 계수 모델 개발의 필요성을 확인하였다.

• Journal of Oral Medicine and Pain
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• 제32권3호
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• pp.319-328
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• 2007

본 연구는 근육의 경도와 탄성도를 측정하여 교근 피로에 대한 물리치료의 효과를 정량적으로 평가하고자 하였으며, 측두하악장애 치료에 가장 흔히 사용되는 물리치료이면서 작용기전은 서로 다른 세 가지 치료법인 전기침자극치료(EAST), 극초단파(Microwave diathermy), 저수준레이저치료(LLLT)의 효과를 비교하였다. 실험을 위하여 건강한 20대 지원자 10명을 선정하여, 교근의 전부와 하부의 근육 경도와 탄성도를 촉각센서로 측정하였다. 실험적으로 교근 피로를 유발하기 위해 피검자가 VAS (0 to 10) 5 이상의 통증을 느낄 때까지 껌을 씹게 하여 근육 변화를 조사하였으며 치료 없이 15분간의 휴식을 준 다음 다시 검사하여 물리치료 후의 효과 비교를 위한 대조군으로 사용하였다. 하루 간격으로 사흘에 걸쳐 동일한 시간 동안 껌을 씹게 한 다음, 물리치료 한 가지씩을 매일 시행하였으며 3가지 물리치료법의 적용 순서는 무작위로 하였다. 껌 저작 전, 직후, 15분 후, 각각의 물리치료 시행 후에 근육 경도와 탄성도 측정과 함께 피검자들이 느끼는 근육의 피로도를 VAS로 평가 하도록 조사하였다. 실험 결과, 저작측에서만 껌 저작 직후와 15분 후에 근육경도의 증가와 탄성도의 감소가 관찰되었으며 (p<0.05) 비저작측에서는 유의한 차이가 없었으나 VAS는 저작측과 비저작측 모두에서 증가하였다(p<0.05). 껌 저작으로 인해 변화되었던 근육경도와 탄성도는 전기침자극치료나 극초단파 치료 후에 효과적으로 회복되고 VAS가 감소했으나(p<0.05) 저수준레이저 치료 후에는 유의한 변화를 보여주지 않았다. 이상의 결과로 보아, 편측 저작은 저작측 근육의 경도를 증가시키고 탄성도는 감소시키는 반면, 비저작측에서는 변화가 없는 것을 알 수 있다. 또한 전기침자극치료와 극초단파치료는 모두 근육의 경도를 감소시키고 탄성도를 증가시켜 근육의 피로를 감소시키는데 효과적인 치료법인데 반해 저수준레이저치료의 효과는 미약한 것으로 판단된다.