摘要 :
The shock wave propagation characteristics of underwater explosion have been of great interest to researchers. While the physical processes during an underwater explosion near boundaries are extremely complex, which involve lots o...
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The shock wave propagation characteristics of underwater explosion have been of great interest to researchers. While the physical processes during an underwater explosion near boundaries are extremely complex, which involve lots of complex issues such as the explosion, shock wave propagation, water-air or water-structure interaction, etc. After the underwater detonation of an explosive, the shock wave may approach two main types of boundaries: the free surface of the water and the fluid-structure interface. The presence of these boundaries will significantly affect the wave propagation phenomena, and lead to bulk cavitation near the free surface or the structure surface. This paper deals with the behavior of shock wave propagation and cavitation from underwater explosion near different boundaries. A coupled numerical approach with combined Lagrangian and Eulerian methods is used to simulate the water-air interface and shock wave-structure interaction. A numerical model of free-field explosion in water is established, and the results have been compared with the published empirical formulas to verify the results of numerical solutions. The shock wave propagation characteristics from explosions in water near different boundaries are simulated and compared. In addition, the unsteady cavitations just near the free surface and the structure surface are described and captured. The water-air and water-structure interaction effects are examined. The results show that the free surface and structure surface boundaries have significant influence on the shock wave propagation characteristics.
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摘要 :
The response of dam structures subjected to explosion shock loading is a key element in assessments for the dam antiknock safety and antiterrorism applications. The physical processes during an explosive detonated in underwater/ai...
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The response of dam structures subjected to explosion shock loading is a key element in assessments for the dam antiknock safety and antiterrorism applications. The physical processes during an explosive detonated in underwater/air and the subsequent response of structures are extremely complex, involving many complex issues such as the explosion, shock wave propagation, shock wave-structure interaction, and structural response. In addition, there exists a significant contrast in wave propagation phenomena in the water and the air medium due to their different physical properties and interface phenomena. In this paper, a fully coupled numerical approach with combined Lagrangian and Eulerian methods is used to simulate the dynamic responses of a concrete gravity dam subjected to underwater and air explosions. The shock wave propagation characteristics from explosions in water and air are simulated and compared. The damage profiles of concrete gravity dams subjected to underwater and air explosions are discussed. The influence of the blast loading from explosions in water and air on the dynamic response and the damage of the dam is also investigated. The analysis results show that a submerged explosion causes significantly more damage to the dam in water than the same mass of explosive in air. (C) 2014 American Society of Civil Engineers.
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摘要 :
The response of E-Glass/Vinyl ester curved composite panels subjected to underwater explosive loading has been studied. Three laminate constructions have been investigated to determine their relative performance when subjected to ...
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The response of E-Glass/Vinyl ester curved composite panels subjected to underwater explosive loading has been studied. Three laminate constructions have been investigated to determine their relative performance when subjected to shock loading. These constructions are: (1) a baseline 0°/90° biaxial layup, (2) a 0/90 biaxial layup that includes a thin glass veil between plies, and (3) a 0°/90 biaxial layup that has a coating of polyurea applied to the back face. The work consists of experimental work utilizing a water filled, conical shock tube facility. The samples are round panels with curved midsections, and are approximately 2.54 mm in thickness. The transient response of the plates is measured using a three-dimensional (3D) Digital Image Correlation (DIC) system, including high speed photography. This ultra high speed system records full field shape and displacement profiles in real time. The results show that the performance of the baseline laminate is improved when coated with the polyurea material, but conversely, is degraded by the inclusion of the glass veils between plies.
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摘要 :
The general features of an isolated underwater explosion have been extensively studied and are considered to be reasonably well understood. However, our understanding of the interaction which ensues when an explosion occurs in the...
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The general features of an isolated underwater explosion have been extensively studied and are considered to be reasonably well understood. However, our understanding of the interaction which ensues when an explosion occurs in the immediate vicinity of a floating or submerged structure is considerably less well developed.
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摘要 :
The high temperature and high pressure gas produced by propellant deburning has strong thermal effect,which will produce strong thermal damage effect on the target. In this study, an improved closed explosive device was used to si...
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The high temperature and high pressure gas produced by propellant deburning has strong thermal effect,which will produce strong thermal damage effect on the target. In this study, an improved closed explosive device was used to simulate the thermal shock loading of 5/7 single base propellant with a charge mass of 17.4 g, and the change law of heat flow density of propellant in the process of deflagration in a closed environment was tested. The experimental results show that the temperature rises rapidly during the deflagration of the 5/7 single-base propellant, and the maximum heat flow density can reach 17.68 MW/ m2 . The curves obtained from the three tests have good consistency in the change trend, which proves the engineering practicability of the improved closed explosive device in the study.
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摘要 :
Deformation twinning resulting from high explosive-driven shock and associated plasticity was investigated in high-purity b.c.c. tantalum. Post mortem characterization of samples shocked at relatively higher and lower pressures sh...
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Deformation twinning resulting from high explosive-driven shock and associated plasticity was investigated in high-purity b.c.c. tantalum. Post mortem characterization of samples shocked at relatively higher and lower pressures showed significant {112}< 111 > twin activity. Further analysis of the lower shock pressure sample showed twins to be spatially clustered at the mesoscale, indicating the role of twin termination at grain boundaries to produce requisite twin initiation stresses in neighbor grains. In addition, analysis of electron backscatter diffraction data suggests that twin propagation across boundaries does not require minimal misorientations between the active variants of the twins in adjacent parent grains. A minimum threshold grain size of approximately 25 urn was determined for both samples, below which twinning was suppressed. Finally, the observation of spall voids at twin intersections implied that twinning increases the density of preferred damage initiation sites during the shock deformation process. Overall, twinning was shown to play a significant role in the deformation and damage evolution of shock-loaded tantalum.
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摘要 :
The response of E-Glass/Vinyl ester curved composite panels subjected to underwater explosive loading has been studied. The work consists of experimental testing utilizing a water filled conical shock tube facility and computation...
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The response of E-Glass/Vinyl ester curved composite panels subjected to underwater explosive loading has been studied. The work consists of experimental testing utilizing a water filled conical shock tube facility and computational simulations with the commercially available Ls-Dyna finite element code. The composite specimens are 0/90 biaxial laminates with a thickness of approximately 1.3 mm. The samples are round panels with curved midsections. The transient response of the plates is measured using a three-dimensional (3D) Digital Image Correlation (D1C) system, along with high speed photography. This ultra high speed system records full field shape and displacement profiles in real time. The DIC data and the computational results show a high level of correlation using the Russell error measure.
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摘要 :
In this study, systematic centrifuge experiments and numerical studies are conducted to investigate the effect of shock loads due to an underwater explosion on the dynamic responses of an air-backed steel plate. Numerical simulati...
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In this study, systematic centrifuge experiments and numerical studies are conducted to investigate the effect of shock loads due to an underwater explosion on the dynamic responses of an air-backed steel plate. Numerical simulations with three different models of pressure time history generated by underwater explosion were carried out. The first model of pressure time history was measured in test. The second model to predict the time history of shock wave pressure from an underwater explosion was created by Cole in 1948. Coefficients of Cole's formulas are determined experimentally. The third model was developed by Zamyshlyaev and Yakovlev in 1973. All of them are implemented into the numerical model to calculate the shock responses of the plate. Simulated peak strains obtained from the three models are compared with the experimental results, yielding average relative differences of 21.39%, 45.73%, and 13.92%, respectively. The Russell error technique is used to quantitatively analyze the correlation between the numerical and experimental results. Quantitative analysis shows that the simulated strains for most measurement points on the steel plate are acceptable. By changing the scaled distances, different shock impulses were obtained and exerted on the steel plate. Systematic numerical studies are performed to investigate the effect of the accumulated shock impulse on the peak strains. The numerical and experimental results suggest that the peak strains are strongly dependent on the accumulated shock impulse.
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摘要 :
When using the explicit finite element method to solve explosion problems at engineering sites, high-density meshes are usually adopted near the explosion source to calculate the high-frequency components of the explosion response...
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When using the explicit finite element method to solve explosion problems at engineering sites, high-density meshes are usually adopted near the explosion source to calculate the high-frequency components of the explosion response. However, the critical time step in an explicit algorithm is usually controlled by the minimum mesh size. The resulting poor computational efficiency will restrain the application of the overall explosion source-engineering site model in explosion problems for large-scale numerical systems, especially in 3D conditions. In this study, a 3D multiscale analysis method based on the substructure of explosion sources is proposed. This method computationally separates the process of explosion initiation and the propagation of shock waves by dividing the model of engineering sites under explosion loads into a small-scale near-source model and a largescale site-structure model, and the substructure of explosion source is used as an approach for explosion action transmission and mesh transition between different models, thereby progressively completing the explosion analysis of the entire explosion source-site-structure system from the near-source region to the far-field region. The proposed multiscale method adopts appropriate mesh sizes and numerical techniques in different calculation stages and avoids the use of irregularly shaped elements that are employed in traditional mesh transition methods, thereby reducing the calculation cost and modeling difficulties while ensuring accuracy. In addition, the proposed method provides a convenient approach for calculating standard explosion loads for a given explosion equivalent, which can be further applied in multiload-case explosion response analyses of large-scale complex site-structure systems.
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An anisotropic elastoviscoplasticity constitutive model for
β
‐cyclotetramethylene tetranitramine (
β
‐HMX) and
α
‐cyclotrimethylene trinitramine single crystals (
α
‐RDX) is developed to analyze the thermomechanical responses under shock loading. The model considers nonlinear, pressure and temperature dependent elasticity, and dislocation‐based plasticity which incorporate regenerative multiplication and heterogeneous nucleation mechanisms. The proposed model is calibrated against experimental wave profiles of (011), (010), (100),
(1￣11)
,
(011￣)
and
(111￣)
orientations of HMX single crystals and (210), (100),
(111￣)
,
(21￣0)
and (111) orientations of RDX single crystals. The model can well capture elastoplastic double wave structure, stress relaxation after the Hugoniot elastic limit as well as the arrival of plastic wave. Moreover, pressure, accumulated shear strain, and temperature contours of both HMX and RDX show obvious anisotropy and non‐uniform spatial distribution, which is explained by analyzing dislocation activity with corresponding resolved shear stress on slip systems. Results provide insights into understanding ignition mechanisms and predicting ignition sensitivity of explosive single crystals as well as polymer bonded explosives at the mesoscale.
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