• Title/Summary/Keyword: 구형 충격파

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Interactions of Spherical Acoustic Shock Waves with a Spherical Elastic Shell near a Free-Surface (자유표면 근처에서의 구형 셸과 충격파의 비정상 유체-구조물 상호작용 해석)

  • Lee, Min-Hyung;Lee, Beom-Heon;Lee, Seung-Yop
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.6
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    • pp.1143-1148
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    • 2002
  • This paper analyses the transient response of a spherical elastic shell located near fee surface and impinged by spherical step-exponential acoustic shock waves. The problem is solved through extension of a method (Huang, 1969) previously formulated for the excitation in an infinite domain, which employs the classical separation of variables, series solutions, and Laplace transform technique The effect of the free surface reflection is taken into account using the image source method. The reflection of the incident wave has been treated by the same image formulation. If the reflection of the pressure field scattered and radiated by the shell is considered, the problem becomes that of multiple scattering by two spheres. However, this is in general negligible considering errors inherent from other sources and that the scattered and radiated pressure waves emanating from the shell are small. Thus, the problem is reduced to that of a structure immersed in an infinite fluid and impinged upon the origin and the image incident.

Expansion of a Fire-Ball and Subsequent Shock-Wave Propagation due to Underwater TNT Explosion (해저에서 TNT 폭발에 의한 파이어볼의 팽창과 이에 따른 충격파 전파)

  • Kwak, Ho-Young;Kang, Ki-Moon;Ko, Il-Gon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.7
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    • pp.677-683
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    • 2011
  • Until now, several empirical models for assessing the damage due to TNT explosions have been proposed. A set of analytical solutions for the time-dependent radius of an expanding fire-ball after detonation of TNT was obtained by solving the continuity, Euler (momentum), and energy equations with a "polytrope" assumption at the fire-ball center. The shock waves developed from the rapid expansion of a fire-ball under water were obtained by using the KirkwoodBBethe hypothesis. The calculated period of bubble oscillation and the maximum radius of the bubble resulting from the fire-ball due to a violent underwater TNT explosion were in good agreement with the experimental data.

Preparation of the metallic nanopowders by wire explosion in liquid media (액증 전기폭발에 의한 금속 나노분말 제조)

  • Cho, Chu-Hyun;Kim, Byung-Geol;Lee, Hong-Sik;Rim, Geun-Hie
    • Proceedings of the KIEE Conference
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    • 2006.07c
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    • pp.1538-1539
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    • 2006
  • 직경 0.3mm, 길이 40mm의 은 와이어를 증류수 중에서 전기폭발(wire explosion)을 발생시켰다. 전기폭발에 의해서 액체 중에 충격파 발생에 의한 공간의 형성과 더불어 금속 증기 및 플라즈마가 발생하고, 증기의 응축에 의해서 나노분말이 생성되는 것을 확인하였다. 또한 생성된 나노분말은 생성공간의 붕괴와 더불어 액체속으로 자연스럽게 분산되었다. 제조된 은 나노분말은 비교적 잘 분산된 구형의 분말이었으며 비표면적은 $16.2m^2/g$(평균입도 35nm)을 나타내었다.

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Design and Fabrication of a 2-Axis Waveguide Rotary Joint for a Millimeter-wave (Ka-Band) Multi-Mode Seeker with Low VSWR and Insertion Loss (낮은 정재파비와 삽입손실을 갖는 밀리미터파(Ka 밴드) 복합모드 탐색기용 2-축 도파관 로터리 조인트 설계 및 제작)

  • Song, Sung-Chan;Yoo, Sung-Ryong;Lim, Ju-Hyun;Jung, Yong-In
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.30 no.2
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    • pp.173-176
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    • 2019
  • In this study, a Ka-band waveguide rotary joint that can be applied to a millimeter-wave seeker is designed and fabricated. The proposed rotary joint maintains a low standing-wave ratio and low-loss characteristics, and has two rotary axes designed to enable azimuth and elevation rotation. The rotary joint is designed as a ridge-waveguide-type mode converter and a ${\lambda}/4$ choke structure to match the electromagnetic wave propagation mode between the spherical and circular waveguides. A performance test using a network analyzer and a high-power transmitter to assess vibration and shock were conducted. Results showed that the rotary joint had a very low standing-wave ratio of less than the maximum of 1.19:1 and an insertion loss of less than 0.80 dB at $F_C{\pm}500MHz$.