• Title, Summary, Keyword: shock structure

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Experimental Study on the Shock Response of a Cylindrical Structure with the Bolted Joint (조인트를 가진 원통형 구조물의 충격 응답에 관한 실험적 연구)

  • Jeon, Ho-Chan;Song, Ohseop
    • Journal of the Korea Institute of Military Science and Technology
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    • v.22 no.5
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    • pp.581-589
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    • 2019
  • Guided missiles assembled with the bolted joint are subjected to various shock loading conditions while flying in the air and operating on the ground or platform. Especially, It is important to analyze the effect of the shock load on the structure because it affects the structure for a short duration time while its acceleration magnitude is quite large. In this study, mechanical shock tests on the structure with the bolted joint have been carried out to measure the acceleration changes of the structure against external shock loads by electrical exciter. Variation of dynamic characteristics of a structure with fastening methods and fastening forces has been investigated through Shock Response Spectrum analysis.

Optimal Arrangement of Resilient Mount installed on Frame Support Structure at Shipboard Equipment under Shock Load (충격하중하의 탑재장비 프레임 지지구조의 탄성마운트 배치 최적화에 관한 연구)

  • Ji, Yong Jin;Kwak, Jeong Seok;Lee, Hyun Yup;Kim, Sung Chan
    • Journal of the Society of Naval Architects of Korea
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    • v.52 no.4
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    • pp.298-304
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    • 2015
  • Shipboard equipment in naval ships should be designed to be safe under the shock load. Very high stress due to the shock load can be effectively reduced by the resilient mounts considering the mount capacity and dynamic characteristics. An optimum arrangement of resilient mount installed to absorb the shock energy is addressed to assess the safety of ship structure and shipboard equipment subjected to the shock load. Structural responses are analyzed for both frame structure supporting the shipboard equipment subject to the shock load with and without the resilient mounts. The shock absorbability of the resilient mount is evaluated by the results of structural response analysis; meanwhile, several types of shock analyses considering the arrangement of resilient mounts are carried out and the shock responses are compared to verify the effect of the arrangement. Thereafter, optimum arrangements are obtained by means of Genetic algorithm (GA) considering the different capacities of resilient mount. Stress, deformation and dynamic feature at the frame structure supporting the shipboard equipment under the shock load are also discussed in order to meet the capacity of resilient mount.

Finite Element Vibration/Shock Analysis of Double Stage Elastic Mounting System with Viscoelastically Damped Foundation Structure (유한용소법을 이용한 점탄성 감쇠구조물이 포함된 2단 탄성마운트 시스템의 진동/충격응답 해석)

  • 정우진;류정수;배수룡;함일배
    • Journal of KSNVE
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    • v.10 no.3
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    • pp.508-516
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    • 2000
  • To study the possibility of F.E.M application to vibration and shock response of double stage elastic mounting system with complicated damped foundation structure like common-bed or raft in ships foundation structure model which has complicated damped sandwich cross-section is analyzed first. And then vibration responses experimental results and shock response of double stage elastic mounting system with complicated damped foundation structure like common-bed or raft in ships foundation structure model which adopts the above damped structure as intermediate foundation were compared. As a result it is found that F.E.M could be effectively used in analyzing the vibration and shock response of double and multi-stage elastic mounting system with complicated damped foundation structures.

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COSMIC RAYS ACCELERATED AT SHOCK WAVES IN LARGE SCALE STRUCTURE

  • RYU DONGSU;KANG HYESUNG
    • Journal of The Korean Astronomical Society
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    • v.37 no.5
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    • pp.477-482
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    • 2004
  • Shock waves form in the intergalactic space as an ubiquitous consequence of cosmic structure formation. Using N-body/hydrodynamic simulation data of a ACDM universe, we examined the properties of cosmological shock waves including their morphological distribution. Adopting a diffusive shock acceleration model, we then calculated the amount of cosmic ray energy as well as that of gas thermal energy dissipated at the shocks. Finally, the dynamical consequence of those cosmic rays on cluster properties is discussed.

Study of the Shock Structure of Supersonic, Dual, Coaxial, Jets (초음속 이중 동축 제트유동에서 발생하는 충격파 구조에 관한 연구)

  • Lee, K.H.;Lee, J.H.;Kim, H.D.
    • Proceedings of the KSME Conference
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    • pp.417-422
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    • 2001
  • The shock structure of supersonic, dual, coaxial jet is experimentally investigated. Eight different kinds of coaxial, dual nozzles are employed to observe the major features of the near field shock structure of the supersonic, coaxial, dual jets. Four convergent-divergent supersonic nozzles having the Mach number of 2.0 and 3.0, and are used to compare the coaxial jet flows discharging from two sonic nozzles. The primary pressure ratio is changed in the range between 4.0 and 10.0 and the assistant jet pressure ratio from 1.0 to 4.0. The results obtained show that the impinging angle, nozzle geometry and pressure ratio significantly affect the near field shock structure, Mach disk location and Mach disk diameter. The annular shock system is found depending the assistant and primary jet pressure ratios.

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Analysis of the Structural Robustness of Cabinet Structure Equipped with Military Vehicles (군용 차량 탑재 캐비닛 구조물의 구조건전성 분석)

  • Son, Dong-Hun;Kang, Kwang-Hee;Choi, Ji-Ho;Park, Do-Hoon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.273-276
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    • 2014
  • The development of a vehicle-mounted radar to detect the location of enemy artillery is mainly mounted during operation to the mobility of the equipment and efficiency of utilization range. It is equipped with an electronic device responsible for the operation of the radar system. Electronic equipments is performed functionality imparted without an error-specific in spite of disturbances such as vibration / shock caused by vehicle movement. Therefore, vibration / shock resistance is held to prevent damaging from vibration / shock generated from the outside environment during operation. In addition, a standardized and specified cabinet structure equipped with electronic equipment is placed in shelter to ensure additional safety for vibration / shock. In this study, it is evaluated by analytical method with vibration / shock resistance of the cabinet structures for ensuring structural safety factor is applied to the aluminum. It is verified the reliability of the structure and structural dynamics to verify by calculated natural frequencies adding the weight of the cabinet structure and the structural displacement and stress results confirmed with vibration / shock caused by the vehicle movement.

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ER Smart Structures for Shock Wave Reduction (충격파 저감을 위한 ER 지능구조물)

  • 김재환;김지선;최승복;김경수
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.13 no.9
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    • pp.679-687
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    • 2003
  • Shock wave reduction in electrorheological(ER) smart structures is studied. ER insert is a composite structure comprising two elastic outer layers between which is sandwiched layer of ER fluid. When a voltage is applied across the outer layers. the shear modulus and the loss factor of the ER fluid are enabled, and thus the dynamic properties of the composite structure is altered. For the shock wave reduction in a hull mount of a submerged structure, ER inserts are made on the hull mount structure. To investigate the ER insert shape. many types of ER insert pattern are considered. Modal test of ER insert structures is performed to obtain the mode shapes, natural frequencies and the acceleration transmissibility. The acceleration transmissibility is reduced at such a frequency region when an electric field is applied. It is observed that the natural frequencies and mode shapes can be tunable by applying electric field. The ER-inserted hull mount is installed in an integrated system and the overall performance of shock wave reduction is tested. The possibility of shock wave reduction in the hull mount is demonstrated.

Investigation of the shock structural formation of the supersonic nozzle jet with longitudinal variation of coaxial pipe location

  • Roh, Sung-Cheoul;Park, Jun-Young;Kim, Soo-Yong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.784-788
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    • 2004
  • A visualization study of shock formation of the supersonic jet nozzle using a Shadowgraph Method (SM) was carried out to investigate the effect of the longitudinal variation of coaxial pipe end tip position inside the supersonic nozzle. The experiment was performed for the Mach number range from 1.1 to 1.2 at nozzle exit. The well known shock cell structure was shown with the pipe end located deep inside the nozzle for the studied Mach number. With the pipe end approaches nozzle exit, it was found that the shock cell structure disappeared and turned into complex formation. In order to understand the mechanism of the shock structural change, computational simulation was carried out using the Navier-Stokes solver, FLUENT. Topological sketch was added with an aid of the visualization and the numerical simulation.

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Visualization of Underexpanded Jet Structure from Square Nozzle

  • Tsutsumi, Seiji;Yamaguchi, Kazuo;Teramoto, Susumu
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.408-413
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    • 2004
  • Numerical and experimental investigation were car-ried out to clarify the flow structure of underexpanded jet from a square nozzle. The square nozzle rep-resents one of the clustered combustors of a linear aerospike engine. From the numerical results, the three-dimensional shock wave of the underexpanded square jet was found to be composed of two shocks. One is the intercepting shock which corresponds to the shock observed in two-dimensional planar jet. The other is the recompression shock divided into two types. The expansion fans coming from the nozzle edges interact with each other at the comers of the nozzle exit, and overexpanded regions are generated. Therefore one of the two recompression shocks is formed at the comers of the nozzle exit behind the overexpanded regions. As the jet goes downstream, the overexpanded regions grow larger to coalesce at the symmetry planes. Then, the other type of the recompression shock is generated. The three-dimensional shock structure formed by the intercepting shock and the recompression shocks dominates the expansion of the jet boundary. The shock detection algorithm us-ing CFD results was developed to reveal the relation between the shock waves and the jet boundary, and it was found that the cross-sectional jet shape becomes cross-shape. The key features observed in the numerical investigation were verified by the experimental results. The shock structure at the diagonal plane was in good agreement with the experimental schlieren images. Moreover, the cross-sections visualized by the Mie scattering method confirmed that the cross-section of the jet becomes cross-shape.

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3-Dimensional Underwater Explosion Shock Response Analysis of a Floating Structure considering Cavitation Effects (캐비테이션을 고려한 부유구조물의 3차원 수중폭발 충격응답 해석)

  • 이상갑;권정일;정정훈
    • Journal of the Society of Naval Architects of Korea
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    • v.40 no.6
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    • pp.1-11
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    • 2003
  • For an accurate shock response analysis of a floating structure such as a naval surface ship subjected to an UNDEX(UNDerwater Explosion), the cavitation effects due to reflected wave at free surface and wetted structural surface should be considered. In this study, for the consideration of cavitation effects an effective method using LS-DYNA/USA and its theoretical background were presented. Through the application of the analysis of bulk cavitation phenomena in the free field, it could be confirmed that almost the same results were obtained between LS-DYNA/USA code and the analytical method. for the investigation of cavitation effects from the structural shock response characteristics, three dimensional UNDEX shock response analysis of an idealized ship model was also carried out It could be found that the cavitation Phenomena gave significant effects on the structural shock response characteristics, and especially that the shock loadings calculated at the installed location of shipboard equipment were underestimated in the case of no consideration of the cavitation effects, which might cause the severe mistake in its shock-resistance design.