• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.504-514
• /
• 2003

We investigate global bifurcation in the subharmonic motion of a circular plate with one-to-one internal resonance. A system of autonomous equations are obtained from the partial differential equations governing the system by using Galerkin's procedure and the method of multiple scales. A perturbation method developed by Kovacic and Wiggins is used to find Silnikov type homoclinic orbits. The conditions under which the orbits occur are obtained.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.05a
• /
• pp.287-296
• /
• 2003

We investigate global bifurcation in the motion of an harmonically excited circular plate with one-to-one internal resonance. A perturbation method developed by Kovacic and Wiggins is used. Silnikov type homoclinic orbit has been pursued but it has turned out not to exist.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.19 no.5
• /
• pp.75-82
• /
• 2015

An experimental study has been carried out to examine development length effects for high strength headed deformed bars. Current design codes limit the specified yield strength of headed bars to 400 MPa. Such the limit is due to the lack of experimental studies on headed bars made of high strength materials. Thus a test program was planed with headed bars with the yield strength of 600 MPa. The threaded head type with head shapes of round plate and circular cone was selected in this study. The experimental variables were development length, number of bars, and head shape. Specimens were classified into L-type and S-type depending on the development length. The development length of L-type was computed according to the design code without considering the limit. S-type specimens had shorter development lengths than the L-type. Further classification was made depending on the shape of heads. A-types have the head shape of round plate and B-types have the shape of circular cone. Three L-type specimens were fabricated with the variable of number of bars (1, 2, and 3). Four specimens for each of SA and SB types were made with development lengths of 50%, 45%, 40%, and 35% compared with L-type. Pullout tests was carried out with 11 specimens. The test results were compared with computed strengths with the design code equations (Appendix II). Based the current studies, it can be said that high strength headed deformed bars used in this study be able to provide such strengths computed with the current design code without considering the yield strength limit.

• Proceedings of the Korean Institute of Communication Sciences Conference
• /
• 1998.06a
• /
• pp.703-706
• /
• 1998

• Proceedings of the Membrane Society of Korea Conference
• /
• 1999.04a
• /
• pp.123-126
• /
• 1999

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.14 no.10
• /
• pp.1024-1029
• /
• 2003

This paper presents the complex antenna factor of a top-hat EMI monopole antenna for measuring time domain electromagnetic fields. The approach is facilitated by adding a artificial parallel ground plane above the monopole antenna. This allows use of cylindrical harmonic field expansions in each of three subregions enclosed by the two ground plane. The results show that the complex antenna factor of the top-hat monopole antenna does not diverge at low frequencies. When compared with a monopole antenna, the top-hat monopole antenna has broadband characteristics. In order to verify the availability of the mode-matching method, the input impedance of the antenna were compared with experiments.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.5
• /
• pp.1218-1226
• /
• 1993

A method, so called 'successive cracking method,' for measuring residual stresses in a circular disk is proposed. In this method residual stresses are evaluated using a fracture mechanics approach, that is, the strains measured at a point on a edge of the disk as a crack is introduced and extended from the edge are used to deduce the residual stress distribution which existed in the uncracked disk. Through finite element analysis and comparative experiments with generally used sectioning method, the successive cracking method is shown to be valid, simple and effective to measure 2-dimensional residual stress distribution in a circular disk.

• Proceedings of the KAIS Fall Conference
• /
• 2011.05b
• /
• pp.533-536
• /
• 2011

기어는 중요한 핵심 기계요소 중 하나로서 기계적 물성이 강화된 엔지니어링 플라스틱의 개발과 제품의 성능 향상 및 소형화, 경량화, 저소음화 등의 소비자 요구를 만족시키기 위한 노력에 편승하여 정밀도가 높은 플라스틱 기어에 대한 생산 요구가 증대되고 있는 실정이다. 본 논문에서는 시력 측정 장치인 자동굴절검사기용 디스크 기어에 대하여 변형을 최소화하기 위한 성형조건 최적화를 수행하였다. 사출 공정의 주요 공정변수를 사출온도, 충진시간과 보압압력, 금형온도로 정하고 다구치 방법에 의해 성형 해석으로 예측된 변형량을 분석한 결과 사출온도와 보압압력이 원판형 기어의 Z방향 변형에 가장 큰 영향을 미치는 것을 알 수 있었다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1996.04a
• /
• pp.263-270
• /
• 1996

Noise control of a plate structure with multiple disk shaped piezoelectric actuators is studied. The plate is excited by an acoustic pressure field produced by a noise source located below the plate. Finite element modeling is used for the plate structure that supports a combination of three dimensional solid, flat shell and transition elements. The objective function, in the optimization procedure, is to minimize the sound energy radiated onto a hemispherical surface of given radius and the design parameters are the locations and sizes of the piezoelectric actuators as well as the amplitudes of the voltages applied to them. Automatic mesh generation is addressed as part of the modeling procedure. Numerical results for both resonance and off resonance frequencies show remarkable noise reduction and the optimal locations of the actuators are found to be close to the edges of the plate structure. The optimized result is robust such that when the acoustic pressure pattern is changed, reduction of radiated sound is still maintained. The robustness of an optimally designed structure is also tested by changing the frequency of the noise source using only the actuator voltages as design parameters.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.05a
• /
• pp.935-940
• /
• 2005

In this paper, dual rotor disk configuration with a coreless stator is proposed for the Lorentz force type integrated motor bearing system. An experimental compensation for the effects of high order harmonics is performed using the digital controller of the experimental setup. The runout profile and rotor unbalance are also identified by the extended influence coefficient method. The experimental results confirm that this compensation method effectively attenuates the rotor vibration all over the operating range of rotational speed.