• International Journal of Naval Architecture and Ocean Engineering
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• 제10권6호
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• pp.762-781
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• 2018

This paper presents the ballistic armor performance examination and thickness estimation for the latest naval ship structure materials in the Republic of Korea. Up to date, research regarding methods of ballistic experiments establishing database on the latest hull structure materials as well as a precise method of estimating required thickness of armor against specific projectiles have been rarely researched. In order to build a database and estimate proper thicknesses of structure materials, this study used four structure materials that have been widely applied in naval ships such as AH36 steel, AL5083, AL5086, and Fiber Reinforced Plastics (FRP). A $7.62{\times}39mm$ mild steel core bullet normally fired by AK-47 gun was considered as a threat due to its representativeness. Tate and Alekseevskii's penetration algorithm was also used to calculate a correction factor (${\alpha}$) and then estimate the armor thickness of naval ship hull structure materials with a given impact velocity. Through live fire experiments, the proposed method performance difference was measured to be 0.6% in AH36, 0.4% in AL5083, 0.0% in AL5086, and 8.0% in FRP compared with the experiment results.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.75-85
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• 2021

The broadband noise can be dominant or important for total characteristics for marine propeller noise representing the minimum base of self-noise. Accurate prediction of such noise is crucial for survivability of underwater military vessels. While the FW-H Formulation 1B can be used to predict broadband trailing edge noise, the method required experiment measurements of surface pressure correlations, showing its limitations in generality. Therefore, in this study, the methods are developed to utilize wall pressure spectrum models to overcome those limitations. Chase model is adopted to represent surface pressure along with the developed formulations to reproduce pressure statistics. Newly developed method is validated with the experiments of airfoils at different velocities. Thereafter, with its feasibility and generality, the procedure incorporating computational fluid dynamics is established and performed for a propeller behind submarine hull. The results are compared with the experiments conducted at Large Cavitation Tunnel, thus showing its usability and robustness.

• Structural Engineering and Mechanics
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• 제65권3호
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• pp.243-250
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• 2018

The use of blast hardened bulkheads (BHBs) is an effective vulnerability hardening technique for improving the survivability of naval warships when internal explosions occur due to being shot by an anti-surface missile. In this paper, a new concept of BHBs reinforced by aluminum (Al) foam is proposed. The new concept can significantly reduce the blast pressures transferred to bulkheads and, unlike conventional BHBs, can be easily installed to operating naval warships. Chamber model blast tests were performed to demonstrate the effectiveness of the Al-foam BHBs and the results are further supported by numerical simulations. Finally, a practical preliminary is proposed for the Al-foam BHBs.

• 대한조선학회논문집
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• 제33권2호
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• pp.75-84
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• 1996

수중폭발에 의한 선체충격응답의 이론적 해석은 충격파를 전달하는 유체와 구조와의 복잡한 상호작용 문제로 귀착되나, 함정 내충격 설계의 측면에서 주요 관심사가 되는 선체의 충격운동은 폭발의 초기에 발생하므로 충격응답의 해석을 폭발의 초기로만 한정할 경우에는 매우 단순화된 구조동역학적 방법에 의해 충격응답을 근사적으로 산정할 수 있다. 이에 따라, 본 논문에서는 충격파에 의해 가속되는 선체 몰수부 단면에 해당하는 물기둥에 전달되는 운동량을 이상화하고, 이를 이용하여 선체거더의 충격응답을 근사 해석할 수 있는 기법을 제시하였다. 또한 이를 토대로 개발한 전산 프로그램을 이용하여 상자형의 단순모델에 적용하여 본 방법의 실용성을 검증하고 여러 가지의 구조특성 및 폭발 조건에 따른 충격응답을 해석하여 그 특성을 분석하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제41권2호
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• pp.171-175
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• 2017

The high-tech large warships are minimal and they are always monitored by opponents, and become primary targets when conflicts occur. The improvement in reducing susceptibility has significant importance because it is difficult for a ship to maintain mission capability and functionality once it is damaged. Ordinary decoys are effective only under the premise that the ship has already been exposed. Traditionally, for naval vessels, techniques related to the radar have been used in military stealth techniques to ensure confidentiality. The corner reflector, on the other hand, can produce rather large radar cross sections. Continued use of deceptive systems such as chaff during operations will help to improve survivability of naval ships. From this viewpoint, corner reflector was considered for making radar countermeasures and deception technology. This paper reviews the current status of corner reflector basis decoys and the technical feasibility of corner reflectors for developing structural decoys.

• 대한조선학회논문집
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• 제56권5호
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• pp.383-388
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• 2019

It is essential to reduce the Infra-red signature for increasing ship's survivability in ship design stage. However the ship's IR signature is quite sensitive to the maritime and atmosphere. Therefore, it is very important to select the marine meteorological data to be applied to the signature analysis. In this study, we selected the three meteorological sample sets from the population of the Korea Meteorological Administration's marine environment data in 2017. These samples were selected through the two-dimensional stratified sampling method, taking into account the geopolitical threats of the Korean peninsula and the effective area of the buoy. These sample sets were applied to three naval ships classified by their tonnage, and then the IR signature analysis was performed to derive the Contrast Radiant Intensity (CRI) values. Based on the CRI values, the validity of each sample set was determined by comparing Cumulative Distribution Function (CDF), and Probability Density Function (PDF). Also, we checked the degree of scattering in each sample set and determined the efficiency of analysis time and cost according to marine meteorological sample sets to confirm the possibility of a probabilistic method. Through this process, we selected the standard for optimization of marine meteorological sample for ship IR signature analysis. Based on this optimization sample, by applying probabilistic method to the management of IR signature for naval ships, the robust design is possible.

• 한국해양공학회지
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• 제23권6호
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• pp.77-81
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• 2009

The radar cross section (RCS) of a warship is one of the most important design features in terms of her survivability in hostile environments. Ocean waves continuously changes the attitude of an objective warship to hostile radar and distorts the RCS as a result. This paper presents a dynamic RCS analysis technique and procedure that considers temporal ship motion. First, data sets are prepared for ship motions in 6 degrees of freedom, which are numerically simulated for an objective warship via frequency to time domain conversion with response amplitude operators and specified ocean wave spectra. Second, a series of RCS analysis models are transformed geometrically by referring to ship motion data sets. Finally, temporal RCS analyses are carried out with the RCS simulation code, SYSCOS. As an example, RCS analysis results are given for a virtual warship, which show that ship motions temporally change RCS values and cause RCS reduction compared with static value in terms of mean values.

• 대한조선학회논문집
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• 제44권5호
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• pp.526-533
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• 2007

It should be primarily aimed to increase survivability consisting of susceptibility, vulnerability and recoverability of naval vessels including ship hull, armament system as well as crews from the design stage to practical operations. With this in mind, swift and efficient actions should be executed on the basis of accurate calculations for the recoverability of damaged vessels. In this paper, it is established how the damage control system of naval vessels is embodied through step-by-step processes intending to cope with various damaged situations that may possibly occur during real operations. It is validated that this system has the applicability to naval vessels through the case study of the battle ship which has been damaged during the operation.

• 대한조선학회논문집
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• 제60권1호
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• pp.10-19
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• 2023

Blast Hardened Bulkhead (BHB) is an important measure that can increase the ship's survivability as well as protect the lives of the crew by mitigating the damage extent caused by an internal explosion in the ship. In particular, both the pressure and the shock impulse should be considered when designing the BHB against reflected shock waves having a high pressure with a short duration. This study proposes a design method for BHB that considers both the pressure and the shock impulse generated during the internal explosion. In addition, analysis and design concepts for accident loads such as explosion, fire, and collision of NORSOK and DNVGL, one of the international design guidelines for the curtain plate type blast hardened bulkhead type applied by the Korean Navy, are utilized. If this method is applied, it is expected that it can be used as a design concept for the pressure as well as the shock impulse of the explosion load of the curtain plate.

• 대한조선학회논문집
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• 제43권1호
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• pp.1-14
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• 2006

To improve maritime safety, it is very important not only to make safer design and operation but also to do proper response in case of maritime casualty. The large-scaled casualties will be caused by loss of structural strength and stability due to the progressive flooding and enlargement of damage by the effect of waves and wind. To prevent foundering and structural failure, the prediction of ship motion behavior of damaged ship in wave is necessary. This paper describes the motion behavior of damaged ship in waves through theoretical and experimental studies. A time domain theoretical model of damaged ship motions and accidental flooding, which can be applied to any type of ship or arrangement and considers the effects of flooding of compartments, has been developed. The model tests have been carried out in regular and irregular waves with different wave heights and directions in ship motion basin. Those were performed for three different damaged conditions such as engine room bottom damage, side shell damage and bow visor damage of a Ro-Ro ship. Comparison of theoretical and experimental results was performed.