水下无人系统学报

2022, 30(3): .

[Abstract](67) [PDF 1503KB](29)

Abstract:

Progress and Prospect of the Acoustic Effects of Underwater Explosions

GUO Rui, YU Yang-hui

2022, 30(3): 266-282. doi: 10.11993/j.issn.2096-3920.2022.03.001

[Abstract](419) [PDF 885KB](111)

Abstract:
Sound sources generated by underwater explosions exhibit the characteristics of high power, wide frequency band, and nondirectivity and are applicable to marine resource detection, hydrological environment inversion, underwater small stealthy target detection, and underwater acoustic countermeasures. Herein, information on the acoustic radiation mechanisms of two features of sound sources, namely, shock waves and ideal bubble pulses, are summarized. Underwater acoustic propagation and reverberation models used to describe the propagation and reverberation effect of the underwater explosion sound sources in the acoustic field model are analyzed; additionally, an overview of typical signal analysis methods and the acoustic characteristics of the sound sources is presented. In addition to the characteristics of the sound sources, typical engineering applications of underwater explosions are introduced. Finally, some future developments of investigations pertaining to the acoustic effects of underwater explosions based on high-explosive materials, the reverberation prediction of explosions, and the engineering applications of sound sources generated by arrays of multipulse explosions are presented. This review can serve as a reference for future studies related to the acoustic effects of underwater explosions.

Characteristic Analysis of Cavitation Load Near Free Surfaces in Underwater Explosions

YU Jun, CHU Dong-yang, WANG Hai-kun, SHEN Chao, SHEN Wen-ni, YU Yang

2022, 30(3): 283-291. doi: 10.11993/j.issn.2096-3920.2022.03.002

[Abstract](249) [PDF 3995KB](51)

Abstract:
Cavitation near free surfaces in underwater explosions has a significant influence on shockwave propagation, explosion bubble movement, and structure impact damage. Currently, the one-fluid model is widely used to analyze cavitation. However, it is difficult to accurately obtain the collapse load during the process of cavitation evolution and characteristics of the flow field in the cavitation domain. In this paper, a four-equation model considering phase transition is introduced. The second-order MUSCL-Hancock reconstruction scheme and HLLC approximate Riemann solver are adopted to solve the homogeneous hyperbolic equation and then the Newton iterative method is used to solve the phase transition equation. The proposed method was preliminarily verified through underwater explosion tests near a free surface, and the typical motion pattern and internal pressure load characteristics in the cavitation domain were captured. The effects of different explosion depths and charge weights on cavitation load characteristics were explored. The results indicate that the pressure in the cavitation domain has a wide distribution that is not maintained near the constant saturated vapor pressure. The results of this paper can provide a reference for further studies on underwater explosions cavitation.

Effects of Water Covering on Impulse Transfer in Shallow Buried Explosions

GAO Wen-bo, ZHAO Zhen-yu, REN Jian-wei, LU Tian-jian

2022, 30(3): 292-299. doi: 10.11993/j.issn.2096-3920.2022.03.003

[Abstract](179) [PDF 1262KB](22)

Abstract:
Shallow buried explosions covered by water are one of the major threats to armored vehicles fighting in tidal flat areas. Based on the influence of both the water layer and sand layer, the impulse transfer characteristics of shallow buried explosions covered by water are significantly different from those of traditional shallow buried explosions. To characterize the influence of water covering on impulse transfer, this study employed a fluid-structure coupling algorithm to simulate shallow buried explosions covered by water using the finite element software AUTODYN. The results demonstrate that the fluid-structure coupling method can effectively simulate shallow buried explosions covered by water. Water covering enhances the impulse transmitted to the target in shallow buried explosions and the impulse increases with an increasing depth of the water layer. The thickness of the cushion layer placed at the bottom of the explosive also affects impulse transfer. The results of this study can provide useful guide-lines for designing high-performance protection structures for armored vehicles used in tidal flat areas.

Overpressure Characteristics of Shock Waves Generated by Underwater Two-point Explosion from Aluminized Explosives

YU Yang-hui, GUO Rui, SONG Pu, GU Xiao-hui, HU Hong-wei

2022, 30(3): 300-307. doi: 10.11993/j.issn.2096-3920.2022.03.004

[Abstract](235) [PDF 1050KB](41)

Abstract:
Multiple-explosion-source shock waves are one of the typical load types in underwater multipoint explosions. However, the associated working conditions often require the use of a large-scale three-dimensional computing domain for simulation, resulting in a significant calculation workload. Based on the existence of bubbles in the explosion products and the secondary energy release process of aluminized explosives, the linear superposition principle cannot accurately describe the laws of multi-point explosion loads. This research focused on the overpressure characteristics of the shock waves generated by the underwater two-point explosions of a typical polymer-bonded aluminized explosive using testing and simulation methods. The results indicate that the time history curves of overpressure obtained using different artificial viscosity values in different time periods are in good agreement with test curves. The error of multi-peak overpressure is typically below 15%. However, the time history curves of overpressure do not exhibit a low-amplitude discontinuous peak after the main shock wave peak. The reasons for this phenomenon are discussed in this paper. Such peaks are thought to be formed by aluminum particles reacting with surrounding material inside a shock wave. Additionally, the time history curves of the shock waves generated by the explosion of a single charge and two charges of the same mass are compared. Finally, the characteristics and differences of the time history curves of overpressure at 0°, 45°,and 90° are analyzed in detail. The research presented in this paper can provide a basis for the subsequent establishment of an underwater multipoint explosion load prediction model.

Experiments of Sympathetic Detonation Performance of Explosives with Shell in Water

HU Hong-wei, WANG Jian, BIAN Yun-long, LU Zhong-bao, YANG Qing

2022, 30(3): 308-313. doi: 10.11993/j.issn.2096-3920.2022.03.005

[Abstract](240) [FullText HTML] (32) [PDF 1304KB](32)

Abstract:
To investigate the safety of ammunition under underwater explosion, underwater sympathetic detonation characteristics of two types of explosives with aluminum shell are investigated via an underwater explosion test. The sympathetic detonation distance and safety distance of the test charges are determined, and the sympathetic reaction degree of the charge is analyzed based on the bubble energy. Results reveal that when the donor charge is a PBX charge with a 1.5 mm aluminum shell and the acceptor charge is an RS211 charge with a 1.0 mm aluminum shell, the sympathetic detonation distance is 60 mm and the safety distance of sympathetic detonation is 120 mm. When the donor and acceptor charges are PBX charges with 1.5 and 1.0 mm aluminum shells, respectively, the sympathetic detonation distance is 10 mm and the safety distance of sympathetic detonation is 30 mm. The reaction rates of completely detonated acceptor charges are only between 86% and 95% owing to a decrease in the bubble period caused by the fusion and collision of two bubbles.

Research Status and Prospects for Coupling Explosion-based Torpedo Warheads

LU Zhong-bao, LI Jun-lin, LU Hai-ling, LI Qin, ZHU Qi-feng, HA Hai-rong

2022, 30(3): 314-320. doi: 10.11993/j.issn.2096-3920.2022.03.006

[Abstract](169) [PDF 2606KB](41)

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Traditional torpedo warheads cannot deliver high efficiency damage to underwater targets based on limitations associated with their charge energy, utilization of charge energy, and damage mode. Therefore, a novel type of torpedo warheads is required. This paper discusses the research status and application prospects of multi-charge coupling explosion-based torpedo warheads and explosive-fuel coupling explosion-based torpedo warheads, as well as related technologies, and discusses the necessity and feasibility of explosive-battery coupling explosion-based torpedo warheads. It is concluded that coupling explosion-based torpedo warheads can deliver high-efficiency damage to underwater targets. Finally, the future study of three coupling explosion-based torpedo warhead technologies is discussed.

Dynamic Response of a Stiffened Cylindrical Shell with a Variable Cross Section Subjected to Shock Wave and Bubble Load

LIU Qi-qi, LIU Liang-tao, WANG Jin-xiang, ZHANG Yi-fan, TANG Kui

2022, 30(3): 321-331. doi: 10.11993/j.issn.2096-3920.2022.03.007

[Abstract](145) [PDF 10245KB](32)

Abstract:
Considering the typical tail of a scaled unmanned undersea vehicle, namely a stiffened cylindrical shell with a variable cross-section, as a research object, its dynamic responses to underwater explosion shock wave and bubble load are simulated using the ALE algorithm in LS-DYNA. The dynamic response of a stiffened cylindrical shell subjected to underwater explosion loads is analyzed and the effects of the impulse factor and explosion orientation on structural damage characteristics are discussed. The results indicate that the damage of shock wave to a stiffened cylindrical shell with a variable cross-section gradually increases with an increase in the impulve factor and that the bubble load further increases the concave deformation and plastic region of the shell. The jet load increases initially and then decreases with an increase in the impulse factor, meaning the jet load is maximized at a specific impulse factor. Explosion orientation has little effect on the damage of shock wave to a stiffened cylindrical shell with a variable cross-section. When the charge is directly above the stiffened cylindrical shell, the jet load is the greatest, resulting in the maximum final damage and deformation of the structure.

Simulations and Experiments on the Damage of Tantalum Alloy EFP to Water-Partitioned Armor

YANG Gui-tao, YU Yang-hui, ZHANG Hong, GUO Rui

2022, 30(3): 332-337. doi: 10.11993/j.issn.2096-3920.2022.03.008

[Abstract](153) [PDF 2159KB](26)

Abstract:
To study the damage effects of tantalum alloy explosively formed projectiles(EFPs) on the water-partitioned armor of submarines with double-layer armor(composed of a non-pressure-resistant hull, pressure-resistant hull, and water interlayer), numerical simulations and experiments were conducted, and the results were compared to numerical damage results for copper EFPs formed using the same charge structure. The results demonstrate that after penetrating a 3 mm non-pressure-resistant hull made of #45 steel and a 680 mm water layer, the tantalum alloy EFP still had residual kinetic energy acting on a 12 mm pressure-resistant shell made of #45 steel, which caused uplift deformation, but failed to penetrate. The copper EFP failed to penetrate the water layer after penetrating the non-pressure-resistant hull. The numerical simulation results are in good agreement with the experimental results, which proves that tantalum alloy is more suitable than copper as a liner material for underwater EFP warheads.

Analysis of Influencing Factors of Underwater EFP Forming Based on Sandwich Charge

FENG Wei, LI Heng, LIU Hai-xiao, ZHAO Jiang, JIAO Jun-jie

2022, 30(3): 338-341. doi: 10.11993/j.issn.2096-3920.2022.03.009

[Abstract](249) [PDF 615KB](30)

Abstract:
To study the influence of a sandwich charge structure on the underwater explosively formed projectile(EFP) forming process, a numerical simulation and analysis of an underwater EFP forming process of different sandwich charge structures were conducted using AUTODYN. With an increase in the air blast height in water, the forming speed and aspect ratio of the composite charge increased, and with an increase in the top width of the outer charge, the crushing speed difference at each Gaussian point of the charge hood decreased and the forming speed dropped gradually. Under the influence of water, the aspect ratio became increasingly smaller. A sandwich charge in water can reduce the influence of water on the EFP forming process and improve the EFP forming speed and posture. This study provides guidance for improving the power of EFPs in water.

Research Progress in Damage and Protection of Surface Ship’s Double-Layer Structure Subjected to Underwater Explosion Load

SUN Yuan-xiang, CHEN Yan-wu

2022, 30(3): 342-353. doi: 10.11993/j.issn.2096-3920.2022.03.010

[Abstract](555) [FullText HTML] (134) [PDF 2428KB](72)

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Research on the damage and protection of surface ship double-layer structures subjected to underwater explosion loads can provide support for the improvement of ship protection capabilities and design of new weapons. Domestic and foreign research progress in terms of experimental research, theoretical research, and numerical simulations is systematically reviewed. The influences of parameters such as the medium and supporting structure between double-layer plates, plate spacing, and plate thickness on damage and protection effects are summarized. Major theoretical research results for double-layer plate damage caused by shock wave transmission and energy absorption are also summarized. Finally, future research directions are discussed.

Study on the Protection Mechanisms of a Polyurea Coating Subjected to Shock Waves and Penetrators

LI Hai-long, WANG Bo, DING Song, ZHANG Zhi-fan

2022, 30(3): 354-363. doi: 10.11993/j.issn.2096-3920.2022.03.011

[Abstract](168) [PDF 906KB](35)

Abstract:
With the widespread use of shaped-charge warheads in underwater weapons, it is of great significance to study the anti-explosion and anti-penetration performance of modern warships. In this study, an underwater explosion model was developed using the AUTODYN finite element software to study the anti-explosion and anti-penetration performance of polyurea protection materials. The protective effects of polyurea coatings in different positions are discussed according to the surface density theory. The results for crevasse, deflection, energy absorption, and velocity reduction characteristics are analyzed comparatively. The optimal position of a polyurea coating is determined to be inside a sandwich of steel plate-polyurea-steel plate. This type of composite structure is optimized. The results demonstrate that with an increase in the thickness of polyuria, its protective effects do not improve and the optimal ratio of steel plate-polyurea-steel plate is 2:10:2. These results provide a theoretical basis and numerical support for ship protection design.

Experiments on Cumulative Damage to Hull Girders Subjected to Multiple Underwater Explosions

TANG Zheng-peng, LI Xiang-yu

2022, 30(3): 364-370. doi: 10.11993/j.issn.2096-3920.2022.03.012

[Abstract](226) [FullText HTML] (120) [PDF 4071KB](42)

Abstract:
For the cumulative damage analysis of hull girders, cumulative damage tests on hull girders subjected to multiple underwater explosions were conducted and the factors affecting cumulative damage were considered, including explosion distance, explosion time, and other parameters. A damage level model for hull girders was established based on the ratio of deflection to the half-length of a hull girder. The results demonstrate that a hull girder does not undergo plastic deformation under the action of medium- and far-field underwater explosion loading. Under the action of near-field explosion loading, a hull girder produces two deformation modes: local plastic deformation of the middle depression and overall plastic bending deformation of the middle arch. With a decrease in the explosion distance, the overall deflection of the hull girder increases. Under the same conditions, the cumulative deflection of a hull girder is approximately linearly correlated with the cumulative loading time of an explosion.

Diffraction Attenuation Distribution of Underwater Explosion Shock Waves on the Surface of a Cylindrical Structure

ZHANG Di-zhou, HE Zhen-hong, HE Xin-yi, LI Ying, LU Jun, CHEN Shuang

2022, 30(3): 371-377. doi: 10.11993/j.issn.2096-3920.2022.03.013

[Abstract](184) [FullText HTML] (93) [PDF 3176KB](37)

Abstract:
When an underwater explosion shock wave acts on the surface of a cylindrical shell, a shock wave forms on the backshock surface in addition to the reflected shock wave. To study the diffraction distribution features of shock wave pressure on the surface of a cylindrical shell, the coupled Eulerian-Lagrangian method in the ABAQUS soft ware is used to simulate the interactions of underwater explosion shock waves and cylindrical shell structures. The pressure field distribution around a cylindrical shell is obtained. The influence of different blast distances and charges of TNT on the diffraction effect of shock wave attenuation is analyzed. The results indicate that the peak pressure and impulse of shock waves decay rapidly in front of the blast surface. With a decrease in blast distance, the angle required for attenuation to 50% decreases and the attenuation speed increases significantly. However, the charge of TNT has little effect on the peak pressure and impulse attenuation of shock waves.

Dimensional Analysis of the Dynamic Responses of Clamped Square Plates under Explosion Loads

WANG Yan-sheng, LI Wei-bing, YU Liang

2022, 30(3): 378-383. doi: 10.11993/j.issn.2096-3920.2022.03.014

[Abstract](83) [PDF 579KB](19)

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The dynamic response of a cabin model under an internal explosion load is explored and the structural responses of clamped square plates under explosion loads are analyzed using dimensional analysis. A dimensionless number for the deflection-thickness ratio of the clamped square plates is proposed and the influence of the explosive energy Qm, thickness H, and yield strength σ₀ of the square plates are considered in the dimensionless number. A dimensionless relationship diagram between the deflection-thickness ratio and dimensionless number is provided. It can be concluded that there is a linear relationship between the deformation of the clamped square plates and Qm/H³σ₀ under explosion loads. The dimensionless number can be applied in dynamic response experiments on cabin structures under explosion loads and used to predict the final plastic deformation of structures.

Review of Testing and Evaluation Methods for Underwater Explosion Power

MAO Zhi-yuan, DUAN Chao-wei, HU Hong-wei, FENG Hai-yun, SONG Pu

2022, 30(3): 384-390. doi: 10.11993/j.issn.2096-3920.2022.03.015

[Abstract](359) [PDF 712KB](69)

Abstract:
Accurate and reasonable evaluation of the underwater explosion power of explosives is very important for underwater warhead design, ship damage assessment, and other tasks. Based on the effector-oriented standard, from the two perspectives of free-field parameter measurement and effector work, this paper summarizes typical experiments conducted for underwater explosion power evaluation, discusses corresponding evaluation methods, and focuses on the explosion bulge testing of a plate structure and its corresponding dimensionless characterization means for deflection. Based on existing research results, we propose: 1) establishing a standardized effector testing method; 2) strengthening research on the relationships among work parameters, explosive detonation parameters, and load parameters; 3) applying the dimensionless deflection used in explosion expansion testing to the evaluation of underwater explosion power.

Study on the Wall Pressure Generated by Detonation Products on the Inner Panel of a Double-layer Structure with a Hole

SHENG Zhen-xin, LIU Jian-hu, MAO Hai-bin, ZHANG Xian-pi, ZHOU Zhang-tao, YANG Jing

2022, 30(3): 391-397. doi: 10.11993/j.issn.2096-3920.2022.03.016

[Abstract](200) [PDF 2674KB](25)

Abstract:
To investigate the characteristics of wall pressure generated by detonation products on the inner panel of a double-layer structure with a hole, we conducted theoretical and experimental studies were conducted. The evolution process of the underwater contact explosion bubble and detonation product jet was divided into three stages: 1) bubble expanding and detonation products entering through the hole, 2) detonation product jet moving in the structure, and 3) detonation product jet impacting the inner panel. Dynamic equations of the detonation products passing through the hole were constructed, the attenuation laws of the velocity and density of detonation products moving in the structure were derived, and a theoretical calculation model for wall pressure on the inner panel of the double-layer structure was established. The effects of charge weight, break radius, and cabin width on bubble motion and wall pressure were analyzed. Additionally, an underwater contact explosion test on a double-layer structure was conducted. The evolution process of the explosion bubble and detonation product jet was photographed using a high-speed camera and the time history of wall pressure on the inner panel was recorded. The results indicate that the deviation in the peak pressure and impulse between the theoretical calculation results and test measurement results were -5.84% and 9.71%, respectively. The accuracy of the theoretical calculation model can meet the requirements of engineering applications, thereby providing a theoretical basis for the damage assessment and shock-resistant design of ship structures.

An Experimental Method for Box Girders Subjected to Underwater Explosions Considering the Initial Bending Moment

ZHENG Jian, LU Fang-yun, LI Xiang-yu, LIANG Wen, CHEN Rong

2022, 30(3): 398-404. doi: 10.11993/j.issn.2096-3920.2022.03.017

[Abstract](146) [FullText HTML] (47) [PDF 1717KB](23)

Abstract:
Box girders are commonly used in underwater explosion experiments on scaled ships. Owing to the challenges associated with materials and welding techniques, the plate thickness of the box girders is always greater than that of a completely geometrically similar model, which leads to increased bending stiffness. Therefore, underwater explosion tests based on these models will underestimate the power of underwater explosions and test results are difficult to map directly to accurate models. To offset the influence of excessive bending stiffness, a method that can easily control the amplitude and distribution of the introduced initial bending moment is proposed. Based on the results of a set of comparative experiments, we determined that the proposed method can reduce the influence of model plate thickness and can be used to study the influence of the bending moment on the underwater explosion responses of box girders. This method can provide a reference for the design of underwater explosion experiments on scaled ships.

Formation Method of Planar Shock Waves in Underwater Explosions Using Small Charges inside a Tube and Its Applications

XU Wei-zheng, HUANG Yu, LI Ye-xun, ZHAO Hong-tao, ZHENG Xian-xu

2022, 30(3): 405-412. doi: 10.11993/j.issn.1673-1948.2022.03.018

[Abstract](95) [FullText HTML] (43) [PDF 2340KB](19)

Abstract:
Shock waves, bubbles, and diffraction effects during underwater explosions, as well as the coupling of these effects, make the investigation of underwater explosion damage complicated. In this paper, an experimental method for forming planar shock waves underwater using small charges inside a tube is presented to decouple these effects. Numerical simulations and theoretical models are used to explore the attenuation rules of planar shock waves in a tube. It is determined that planar shock waves with exponential attenuation forms can be generated by placing the charge at one end of the tube to achieve end-plane detonation. Theoretical results combined with overpressure peak versus distance curves and shock wave location versus time curves coincide well with simulation results. Applications of the proposed experimental method include the analysis of damage effects on typical structures and exploration of fluid-solid coupling mechanisms. The presented results also provide guidance for the damage evaluation of underwater explosions.

2022 Vol. 30, No. 3

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