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HHT와 연속스캐닝 진동계를 이용한 구조물의 모드 형상 복원
경용수(Yongsoo Kyong),김대성(Daesung Kim),Jedol Dayou,박기환(Kyihwan Park),왕세명(Semyung Wang) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.6
For CSLDV, the Chebyshev demodulation (or polynomial) technique and Hilbert transform approach have been used for mode shape reconstruction with harmonic excitation. In this paper, the Hilbert-Huang transform approach was applied as an alternative to impact excitation cases in terms of a numerical approach. The vibration of the tested structure is modeled using impulse response functions. In order to verify this technique, a simply supported beam was chosen as the test rig. With additional innovative steps which are the ideal-band pass filter and the nodal point determination, Hilbert-Huang transformation can be used for a good mode shape reconstruction even in the impact excitation case.
LSV 측정 정보를 이용한 ODS와 OMA의 동시분석 방법
이종서(Jongsuh Lee),경용수(Yongsoo Kyong),왕세명(Semyung Wang) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
It is important not only modal parameters of the structure such as natural frequency, mode shape and damping ratio but also a deflection shape of the structure when it is operating condition to reduce noise and vibration of a system. In case of deflection shape at operating condition, the Operating Deflection Shape (ODS) is will ing used. The dynamic properties of a system can be estimated by a method called Operational Modal Analysis (OMA) during operating condition of the system. However, both techniques are not used at the same model in spite of the same experimental set up. Because OMA technique is only applicable under the assumption that the force causing vibration of the system should be White Noise, OMA is limited to use for huge buildings such as large vessel. In this paper, it extends the application of OMA by using a signal processing technique and it shows experimental convenience because a data obtained by single experiment can be applied to ODS and OMA at the same time
이종서(Jongsuh Lee),경용수(Yongsoo Kyong),왕세명(Semyung Wang) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
It is important to know modal parameters of the structure such as natural frequency, mode shape and damping ratio when it is operating condition to reduce noise and vibration of a system. The dynamic properties of a system can be estimated by the Operational Modal Analysis (OMA) during operating condition of the system. However, this technique is not used generally. Because OMA technique is only applicable under the assumption that the force causing vibration of the system should be White Noise, OMA is limited to use for huge buildings such as large vessel. In this paper, it extends the application of OMA by using a signal processing technique and it shows experimental convenience because a data obtained by single experiment with Laser Scanning Vibrometer.
왕세명(Semyung Wang),배원기(Wonki Bae),경용수(Yongsoo Kyong),박기환(Kyi-hwan Park),Jedol Dayou 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.6
It is important to figure out the dynamic characteristics of the mechanical system in terms of the safe design. The most widely used method to grasp the inherent dynamic characteristics is Modal Analysis which gives us information of modal parameters, such as natural frequency, damping ratio and mode shape vector. However, as mechanical systems get larger and more complicated, difficulties how to set boundary and excitation conditions arise to Modal Analysis. Surely, the actual vibration of mechanical systems varies with surrounding conditions, which are temperature, rpm, air flow, pressure, load and so on; for example, the vibration of an indoor machine would be different from that of the machine at different location if outside is very cold and windy. Therefore, another method known as Operating Deflection Shape (ODS) is needed to deal with these situations that Modal Analysis cannot do. Practical ways to reduce the problem of vibration and noise might be proposed on the condition that the shape and quantity of deflections at certain operating conditions are measurable. Also, the rapid measurement not influencing dynamic characteristics of the structure is required for ODS. It is desirable to use Laser Scanning Vibrometer (LSV) which is untouchable to the structure. For that reason, ODS program is developed using LSV and Damage Detection is introduced through this program.