• Title/Summary/Keyword: underwater structure

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Performance Evaluation of the Underwater Structure which used a Epoxy Panel (에폭시 섬유판넬을 이용한 수중구조물의 단면보수시스템에 대한 성능평가)

  • 박준명;홍성남;박선규
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.11a
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    • pp.343-346
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    • 2003
  • Confirmation of a damage degree and repair about a damage part are very hard for an underwater structure. And quality control of a construction is very complicated even if repair work is carried out on a damaged structure because repair work is carried out in water. If repair work is carried out while a defect part of the structure which there is in water keeps dry state, a efficient of repair is maximized. However, as for the repair technology about an underwater structure, a systematic researcher is not enough because of the environmental trouble. And, as for the effect about repair method to be applied to a currently underwater structure, it is not certainly proved. In this study The repair work of an underwater structure damaged applied the method that used a fiber panel form work. And a efficient of structure repaired was evaluated.

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Multi-objective geometry optimization of composite sandwich shielding structure subjected to underwater shock waves

  • Zhou, Hao;Guo, Rui;Jiang, Wei;Liu, Rongzhong;Song, Pu
    • Steel and Composite Structures
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    • v.44 no.2
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    • pp.211-224
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    • 2022
  • Multi-objective optimization was conducted to obtain the optimal configuration of a composite sandwich structure with honeycomb-foam hybrid core subjected to underwater shock waves, which can fulfill the demand for light weight and energy efficient design of structures against underwater blast. Effects of structural parameters on the dynamic response of the sandwich structures subjected to underwater shock waves were analyzed numerically, from which the correlations of different parameters to the dynamic response were determined. Multi-objective optimization of the structure subjected to underwater shock waves of which the initial pressure is 30 MPa was conducted based on surrogate modelling method and genetic algorithm. Moreover, optimization results of the sandwich structure subjected to underwater shock waves with different initial pressures were compared. The research can guide the optimal design of composite sandwich structures subjected to underwater shock waves.

A Basic Study of ROV System Design for Underwater Structure Inspection (수중 구조물 검사를 위한 ROV 시스템 설계 연구)

  • Ryu, Jedoo;Nam, Keonseok;Ha, Kyoungnam
    • Journal of the Korean Society of Industry Convergence
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    • v.23 no.3
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    • pp.463-471
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    • 2020
  • Recently, various tries to apply ROV (Remotely Operated Vehicle) into underwater are being developed. However, due to underwater environment uniqueness, the additional problem must be taken into account when designing an ROV for the inspection of the underwater structure. This is because a GPS-based information method cannot be applied, and the obtainable image is also dependent on the turbidity. Also, it is necessary to be able to satisfy waterproof and operating speeds in consideration of most practical application environments. This paper describes the design results of the ROV system for underwater structure inspection considering the above problems. The designed system applied INS / DVL for location recognition and was configured to support 3D mapping and stereo camera-based image information using sonar depending on visibility. To satisfy the waterproof, a pressure vessel using a composite material was applied. And over-actuated system using eight thrusters to maintain a stable posture and operating speed was applied also. The designed system was verified by structural analysis and flow analysis also.

Extended Kalman Filter-based Localization with Kinematic Relationship of Underwater Structure Inspection Robots (수중 구조물 검사로봇의 기구학적 관계를 이용한 확장 칼만 필터 기반의 위치추정)

  • Heo, Young-Jin;Lee, Gi-Hyeon;Kim, Jinhyun
    • Journal of Institute of Control, Robotics and Systems
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    • v.19 no.4
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    • pp.372-378
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    • 2013
  • In this paper, we research the localization problem of the crawler-type inspection robot for underwater structure which travels an outer wall of underwater structure. Since various factors of the underwater environment affect an encoder odometer, it is hard to localize robot itself using only on-board sensors. So in this research we used a depth sensor and an IMU to compensate odometer which has extreme error in the underwater environment through using Extended Kalman Filter(EKF) which is normally used in mobile robotics. To acquire valid measurements, we implemented precision sensor modeling after assuming specific situation that robot travels underwater structure. The depth sensor acquires a vertical position of robot and compensates one of the robot pose, and IMU is used to compensate a bearing. But horizontal position of robot can't be compensated by using only on-board sensors. So we proposed a localization algorithm which makes horizontal direction error bounded by using kinematics relationship. Also we implemented computer simulations and experiments in underwater environment to verify the algorithm performance.

Mechanical and Durability Characteristics of Latex Modified Repair Mortar for Agricultural Underwater Concrete Structure (수중에 노출된 농업용 콘크리트 구조물 보수용 라텍스개질 모르타르의 역학적 특성 및 내구성능 평가)

  • Won, Jong-Pil;Lee, Jae-Young;Park, Chan-Gi;Sung, Sang-Kyung;Kim, Wan-Young
    • Journal of The Korean Society of Agricultural Engineers
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    • v.49 no.4
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    • pp.35-41
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    • 2007
  • The most agricultural concrete structures for the irrigation and drainage are exposed to the underwater condition at the irrigation period and they take the influence on very severe cold in the winter. Therefore, it is impossible to use repair materials used to the general concrete structures. The research need the development of the repair material for a performance enhance of the agricultural underwater concrete structures. This research evaluated the mechanical and durability performance of the latex modified repair mortar for underwater concrete structures which peformed the repair in the underwater according to the characteristic of the agricultural concrete structure. The latex modified repair mortar is a material that minimize the effect of the ecosystem, environment and the segregation. In this research, the construction condition of the latex modified repair mortar for agricultural concrete structures was considered and the test specimens made in the underwater condition. Test results was then compared with target performance and commercial repair mortar. Experimental test results indicated that the mechanical and durability performance of latex modified repair mortar for agricultural underwater concrete structure satisfied all target performance. Also, the latex modified repair mortar resulted in better repair performance than the commercial repair mortar.

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.

Image Mosaicking Considering Pairwise Registrability in Structure Inspection with Underwater Robots (수중 로봇을 이용한 구조물 검사에서의 상호 정합도를 고려한 영상 모자이킹)

  • Hong, Seonghun
    • The Journal of Korea Robotics Society
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    • v.16 no.3
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    • pp.238-244
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    • 2021
  • Image mosaicking is a common and useful technique to visualize a global map by stitching a large number of local images obtained from visual surveys in underwater environments. In particular, visual inspection of underwater structures using underwater robots can be a potential application for image mosaicking. Feature-based pairwise image registration is a commonly employed process in most image mosaicking algorithms to estimate visual odometry information between compared images. However, visual features are not always uniformly distributed on the surface of underwater structures, and thus the performance of image registration can vary significantly, which results in unnecessary computations in image matching for poor-conditioned image pairs. This study proposes a pairwise registrability measure to select informative image pairs and to improve the overall computational efficiency of underwater image mosaicking algorithms. The validity and effectiveness of the image mosaicking algorithm considering the pairwise registrability are demonstrated using an experimental dataset obtained with a full-scale ship in a real sea environment.

Underwater Radiated Noise Analysis for An Unmanned Underwater Vehicle Using Power Flow Analysis (파워흐름해석법을 이용한 무인잠수정의 수중방사소음해석)

  • Kwon, Hyun-Wung;Hong, Suk-Yoon;Lee, Sang-Young;Hwang, A-Rom;Song, Jee-Hun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.22 no.4
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    • pp.328-334
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    • 2012
  • Power flow finite element method(PFFEM) combining power flow analysis(PFA) with finite element method is efficient for vibration analysis of a built-up structure, and power flow boundary element method(PFBEM) combining PFA with boundary element method is useful for predicting the noise level of a vibrating complex structure. In this paper, the coupled PFFE/PFBE method is used to investigate the vibration and radiated noise of the unmanned underwater vehicle(UUV) in water. PFFEM is employed to analyze the vibrational responses of the UUV, and PFBEM is applied to analyze the underwater radiation noise. The vibrational energy of the structure is treated as an acoustic intensity boundary condition of PFBEM to calculate underwater radiation noise. Numerical simulations are presented for the UUV in water, and reliable results have been obtained.

APPLICATION OF AN IMMERSED BOUNDARY METHOD TO SIMULATING FLOW AROUND TWO NEIGHBORING UNDERWATER VEHICLES IN PROXIMITY (인접한 두 수중운동체 주위의 유동 해석을 위한 가상경계법의 적용)

  • Lee, K.;Yang, K.S.
    • Journal of computational fluids engineering
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    • v.18 no.1
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    • pp.49-57
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    • 2013
  • Analysis of fluid-structure interaction for two nearby underwater vehicles immersed in the sea is quite challenging because simulation of flow around them is very difficult due to the complexity of underwater vehicle shapes. The conventional approach using body-fitted or unstructured grids demands much time in dynamic grid generation, and yields slow convergence of solution. Since an analysis of fluid-structure interaction must be based on accurate simulation results, a more efficient way of simulating flow around underwater vehicles, without sacrificing accuracy, is desirable. An immersed boundary method facilitates implementation of complicated underwater-vehicle shapes on a Cartesian grid system. An LES modeling is also incorporated to resolve turbulent eddies. In this paper, we will demonstrate the effectiveness of the immersed boundary method we adopted, by presenting the simulation results on the flow around a modeled high-speed underwater vehicle interacting with a modeled low-speed one.