• Title/Summary/Keyword: Vibration of structures underwater

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Analysis of the Phase Change of a Laser Beam in a Laser Doppler Vibrometer Due To the Sound Field Radiated From Structures Vibrating Underwater (수중에서 진동하는 구조물로부터 방사되는 음에 기인한 레이저 도플러 진동측정기 광선의 위상변화에 대한 분석)

  • Kil, Hyun-Gwon;Jarzynski, Jacek
    • The Journal of the Acoustical Society of Korea
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    • v.27 no.4
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    • pp.178-182
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    • 2008
  • In measurements of the vibration of structures underwater with a laser Doppler vibrometer, the surface vibration is measured by means of detecting the phase change of the laser beam due to the structural vibration. The laser beam passes through the sound field radiated from the vibrating structures underwater. It experiences an additional phase change due to the change in refractive index in the radiated sound field. This phase change due to the sound field may cause the error in surface vibration measurements. In this paper, this phase change due to the radiated sound filed has been analyzed. The numerical simulation has been peformed to evaluate the phase change in sound field radiated from an infinite cylindrical structure vibrating underwater.

A Study on Dynamic Strength Analysis of Submarine Considering Underwater Explosion (내충격 성능을 고려한 수중함 동적 강도 설계에 관한 연구)

  • Son, Sung-Wan;Choi, Su-Hyun;Kim, Kuk-Su
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.1185-1191
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    • 2000
  • In general, the strength of hull structures can be estimated from stress evaluation considering static and hydro-dynamic load due to sea-wave. However, war ships such as submarine, have frequently experienced the underwater explosion and local structures of ship as well as hull girder can be damaged by the dynamic response excited from underwater non-contact explosion. When explosion happens at underwater, shock wave is radiated In early short time, then gas bubbles are generated, and expansion and contraction are repeated as they float to the surface. The shock wave causes the damage of equipment and its supporting structures, on the other hand, the hull girder strength can be lost by resonance between bubble pulsation and lowest ship natural vibration period. In this paper, the hydro-Impulse force due to bubble was calculated. Based on these results the hull girder strength of submarine was estimated from transient response analysis by using NASTRAN. Also, shock analysis for some equipment supporting structures was carried out by using DDAM. In order to evaluate the strength of these local structures due to shock wave.

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Active Vibration Control of Smart Hull Structure in Underwater Using Micro-Fiber Composite Actuators (MFC 작동기를 이용한 수중 Hull 구조물의 능동 진동 제어)

  • Kwon, Oh-Cheol;Sohn, Jung-Woo;Choi, Seung-Bok
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.11a
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    • pp.466-471
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    • 2008
  • Structural vibration and noise are hot issues in underwater vehicles such as submarines for their survivability. Therefore, active vibration and noise control of submarine, which can be modeled as hull structure, have been conducted by the use of piezoelectric materials. Traditional piezoelectric materials are too brittle and not suitable to curved geometry such as hull structures. Therefore, advanced anisotropic piezoceramic actuator named as Macro-Fiber Composite (MFC), which can provide great flexibility, large induced strain and directional actuating force is adopted for this research. In this study, dynamic model of the smart hull structure is established and active vibration control performance of the smart hull structure is evaluated using optimally placed MFC. Actuating performance of MFC is evaluated by finite element analysis and dynamic modeling of the smart hull structure is derived by finite element method considering underwater condition. In order to suppress the vibration of hull structure, Linear-Quadratic-Gaussian (LQG) algorithm is adopted. After then active vibration control performance of the proposed smart hull structure is evaluated with computer simulation and experimental investigation in underwater. Structural vibration of the hull structure is decreased effectively by applying proper control voltages to the MFC actuators.

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Active Vibration Control of Underwater Hull Structure Using Macro-Fiber Composite Actuators (MFC 작동기를 이용한 수중 Hull 구조물의 능동 진동 제어)

  • Kwon, Oh-Cheol;Sohn, Jung-Woo;Choi, Seung-Bok
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.19 no.2
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    • pp.138-145
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    • 2009
  • Structural vibration and noise are hot issues in underwater vehicles such as submarines for their survivability. Therefore, active vibration and noise control of submarine, which can be modeled as hull structure, have been conducted by the use of piezoelectric materials. Traditional piezoelectric materials are too brittle and not suitable to curved geometry such as hull structures. Therefore, advanced anisotropic piezocomposite actuator named as Macro-Fiber Composite(MFC), which can provide great flexibility, large induced strain and directional actuating force is adopted for this research. In this study, dynamic model of the smart hull structure is established and active vibration control performance of the smart hull structure is evaluated using optimally placed MFC. Actuating performance of MFC is evaluated by finite element analysis and dynamic modeling of the smart hull structure is derived by finite element method considering underwater condition. In order to suppress the vibration of hull structure, Linear Quadratic Gaussian(LQG) algorithm is adopted. After then active vibration control performance of the proposed smart hull structure is evaluated with computer simulation and experimental investigation in underwater. Structural vibration of the hull structure is decreased effectively by applying proper control voltages to the MFC actuators.

An Experimental Study on Ground Vibration Equations by Underwater Blasting at Construction Site (수중발파 현장에서의 진동추정식에 관한 실험적 연구)

  • Park, Yeon-Soo;Kang, Sung-Hoo;Jeon, Yang-Bae;Gong, Gang-Joo;Park, Sun-Joon
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.16 no.7 s.112
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    • pp.777-783
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    • 2006
  • In this study, quantitative ground vibration values and damping coefficient produced by underwater blasting were measured and analyzed. Also, hydrospace noise in aquafarm and noise in atmosphere as well as ground vibrations were measured, and maximum values of these results were 86,8 dB(A), 147,8dB(A), 0.244 cm/s, respectively, With these results, vibration influence about snakehead (channa argus) and structures were examined. the damage of those was proved that is not. Equations of vibration ($V_{50%}=1.507SD^{-0.536},\;V_{95%}=2,171SD^{-0.536}$) and hydrospace noise ($SL=293.2SD^{-0.164}$) were presented from quantitative experiment results. respectively. The results of the study may be applied for the evaluation of the influence on aquafarm as a basic data before having main underwater blasting at construction sites.

An Analysis on the Underwater Radiated Noise of the Submerged Cylindrical Shell (몰수체의 방사소음 해석)

  • Jeon, Jae-Jin;Ryu, Jeong-Suh
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.825-830
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    • 2000
  • In this article, the underwater radiated noise of the submerged cylindrical shell model is investigated using hull transfer functions which were defined in accordance with structureborne and airborne noise propagation paths. This method is very useful tool as the prediction of radiated noise from submerged structures in design stage. This approach is verified by experimental model and its measurement results.

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Shock response analysis to underwater explosion using Hydrocode (Hydrocode를 이용한 수중폭발 충격응답 해석)

  • Lee, Sang-Gab;Park, Chung-Kyu;Kweon, Jung-Il;Jeong, Sung-Min
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.1174-1179
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    • 2000
  • In recent years, the structural shock response to underwater explosion has been studied as much, or more, through numerical simulations than through testing for several reasons. Very high costs and sensitive environmental concerns have kept destructive underwater explosion testing to a minimum. Increase of simulation capabilities and sophisticated simulation tools has made numerical simulations more efficient analysis methods as well as more reliable testing aids. For the simulation of underwater explosions against, surface ships or submerged structures one has to include the effects of the explosive shock wave, the motion of the gaseous reactive products, the local cavitation collapse, the different nonlinear structural properties and the complex fluid-structure interaction phenomena. In this study, as benchmark step for the validation of hydrocode LS/DYNA3D and of technology of fluid-structure interaction problems, two kinds of cavitation problems are analyzed and structural shock response of floating ship model are compared with experimental result.

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A Study on Design of Underwater Acoustic Transducers Using the Electro-mechanical Coupling Analysis Code ATILA (전기-기계 연성해석 코드 ATILA를 이용한 수중 음향 트랜스듀서 설계)

  • Lee, Jeong-min;Cho, Yo-han;Kim, Jung-suk
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.10 s.103
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    • pp.1211-1216
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    • 2005
  • Underwater acoustic transducers are widely used for SONAR application, whose important design parameters are shapes. materials, dimensions and supporting structures. Practical design method of transducers consists of manufacturing, experiments and modifications so that it requires much time and expenses. In this study, an analytical method was developed for the Tonpilz type transducers using the commercial finite element analysis code ATILA which can solve the electro-mechanical coupling problems. A finite element model was established including the transducer elements such as ceramic stack, head mass, tail mass, tensile bolt, and molding layers. The proposed model was verified and modified by comparing the in-air and in-water test results of prototypes. The developed analysis method will be effectively used for the sensitivity analysis of design parameters in transducer design process.

Tonpilz Type Underwater Acoustic Transducers Design using Finite Element Method (유한요소법을 이용한 Tonpilz형 수중 음향 트랜스듀서 설계)

  • Cho, Yo-Han;Kim, Jung-Suk;Lee, Jeong-Min
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.11a
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    • pp.247-250
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    • 2005
  • Underwater acoustic transducers are widely used for SONAR application, whose important design parameters are shapes, materials, dimensions and supporting structures. Practical design method of transducers consists of manufacturing, experiments and modifications so that It requires much time and expenses. In this study, an analytical method was developed for the Tonpilz type transducers using the commercial finite element analysis code ATILA which can solve the electro-mechanical coupling Problems. A finite element model was established including the transducer elements such as ceramic stack, head mass, tall mass, tensile bolt, and molding layers. The proposed model was verified and modified by comparing the in-air and in-water test results of prototypes. The developed analysis method will be effectively used for the sensitivity analysis of design parameters in transducer design process.

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Stress Wave Reduction of Structures Using MR Inserts (MR Insert를 이용한 구조물의 응력파 저감)

  • 강병우;김재환;최승복;김경수
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.11 no.4
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    • pp.71-77
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    • 2001
  • In this paper, stress wave propagation characteristics of MR(Magneto-rheological) inserts are experimentally investigated. Generally, stress waves of structures such as warships or submarines are induced by shock waves from underwater explosion. Their fatal effects on the shipboard equipments or structures damage the performance of warships. But, such a problem can be solved by controlling the stress waves propagating through structures by means of MR inserts. MR insert consists of two aluminum layers and MR fluid filled in between. Two piezoceramic disks are embedded on the host plate as a transmitter and a receiver of stress waves. Pulse waves are generated by the transmitter and they reach to the receiver through the MR insert. Permanent magnet and magnetic coil are used to produce magnetic field at the MR insert. In the presence of magnetic field, MR particles are arranged in chains parallel to the magnetic field such that the transmitted stress waves are reduced. Attenuation of stress waves is experimentally investigated.

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