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훅조인트로 연결된 축계의 비선형 비틀림 진동의 분기해석
장서일 한국소음진동공학회 2003 한국소음진동공학회 논문집 Vol.13 No.4
Torsional oscillations of a system incorporating a Hooke's joint are investigated by adopting a nonlinear 2-degree-of-freedom model. Linear and Van der Pol transformations are applied to obtain the equations of motion to which the method of averaging can be readily applied. Various subharmonic and combination resonances are identified with the conditions of their occurrences. Applying the method of averaging leads to the reduced amplitude- and phase-equations of motion, of which constant and periodic solutions are obtained numerically. The periodic solution which emerges from Hopf bifurcation point experiences period doubling bifurcation leading to infinite solution rather than chaotic solution.
에어컨 실내기의 방사소음과 실외기의 투과소음에 의한 환경소음 예측
장서일,최진권,손진희,모진용,구형모 한국소음진동공학회 2003 한국소음진동공학회 논문집 Vol.13 No.1
This study was conducted to determine the sound paths and transmitted sound level in house. An air-conditioner system was selected a typical sound source. The measured transmission loss data shows that the apertures have an significant effect on the transmitted noise and comparable with the existing theoretical data. Therefore the complex aperture was substitute to quantitative apertures approximately. An effective simulation method, ray tracing and mirror image source method, was employed in the prediction of transmitted sound level. The measured results were efficiently reflected on the simulated results. So it is important that measuring the acoustic parameter prior to the prediction of the transmitted sound level in the house.
장서일,송덕근,최진권 한국소음진동공학회 2002 한국소음진동공학회 논문집 Vol.12 No.1
Three kinds of viscoelastic damper model, which has a non-linear spring as an element is studied analytically and numerically The behavior of the damper model shows non-linear hysteresis curves which is qualitatively similar to those of real viscoelastic materials. The motion is governed by a non-linear constitutive equation and an additional equation of motion. Harmonic balance method is applied to get analytical solutions of the system. The frequency-response curves sallow that multiple solutions co-exist and that the jump phenomena can occur. In addition, it is shown that separate solution branch exists and that it can merge with the primary response curve. Saddle-node bifurcation sets explain the occurrences of such non-linear Phenomena.