Papers by Keyword: Explosive Loading

Abstract: This paper integrates a comprehensive overview of cylindrical shell simulations by means of finite element analysis, focusing on both ductile and brittle fracture behaviors under explosive loading. Special attention is given to high-carbon alloy steels that exhibit pronounced cleavage or quasi-brittle behavior and can produce smaller, higher-velocity fragments under certain conditions. We discuss key numerical approaches for fragmentation modeling and shrapnel kinetic energy calculations, and explore the relevant constitutive equations—particularly the Johnson-Cook law for high strain-rate plasticity and Linear Elastic Fracture Mechanics (LEFM) parameters for cleavage-type fracture. Emphasis is placed on microstructural factors (grain size, carbide distribution) that govern fracture and fragment mass distribution. We incorporate experimental findings on brittle fracture of steels under internal blast, highlighting how microcrack formation, alloy carbides, and high hardness can alter fragmentation and shell initial velocity.

Abstract: The study of the effect of Elongated Cumulative Charges (ECC) on rock formations has an important scientific and practical significance for solving a number of process problems in mining practice. The use of charges with a longitudinal concavity for a directional destruction (presplit blasting, “smoothwall” chipping) involves reducing the explosives consumption, preserving the aquifer rock mass from additional explosion-caused cracks, obtaining a smooth contour and reducing the volume of drilling works. It is noted that one of the options that provides the explosion energy redistribution in a destructible medium is the use of elongated cumulative charges with a damping core. Experimental evidences on the dynamic loading of model blocks by an explosion of an elongated cumulative charge with an inert pad of various acoustic stiffness are reported.

Abstract: In order to further improve the accuracy of the numerical simulation technology in buildings blasting demolition, numerical simulations on seven-story frame structure blasting demolition process were carried out adopting separate common node reinforced concrete model, and two simulation methods between the concrete elements on cut site directly removed and the concrete elements on cut site reserved with explosive loading applied instead were comparative analyzed. Simulation result indicates that, separate common node model can reflect mechanical properties difference of concrete and reinforcement through analysis on their loading process. There would be an upward impact force on the structure at the moment of detonating when the concrete elements on cut site were reserved with explosive loading applied instead, and it made the whole structure collapsed process extend about 0.5 s and structure touchdown vibration increase about 2.39 times. It had a negative impact on blasting vibration control, so the applied explosive blasting on cut site become a factor to be considered on the numerical simulation of structure blasting demolition. Studies suggest that the applied explosive blasting on the numerical simulation of structure blasting demolition can simulate the collapse process of building blasting demolition more real and will be an better aided design of structure blasting, and it has important engineering practical value.

Abstract: Stiffened plate is used widely in ship structure for its high capacity and light weight so studying the limit of deformation of stiffened plates under blast loading has important engineering significance. The blast loading is simplified to triangle with only ascending stage and equivalent stiffness at all directions and every parameter of the stiffened plate are calculated so the maximum deformation can be solved finally. The dynamic response of rectangle stiffened plate under blast loading was simulated by non-linear finite element software and got the maximum deformation of the plate .The simulative results are consistent with the theoretical results. At the same time, the displacement and velocity of all directions at three different points can be got from the simulation and related theoretical derivation is proved correctly by analyzing the simulative results.

Abstract: Stiffened plate is a common structure form in plate and shell structure. There are important theoretical significance and project application value on studying dynamic response of stiffened plate subjected to air explosive loading. The motion equation of orthotropic plate which subjected to explosive loading is established adopting Lagrange’s equation of motion, and the stiffened plate where the stiffener is arranged uniformly is treated as textural orthotropic plate. Then the motion equation of the orthotropic plate is converted into motion equation of the stiffened plate. Therefore the maximum deformation of stiffened plate can be determined.

Abstract: One-dimensional symmetrical explosive loadings are applied to expand structural components: tubular cylinders, spherical shells and rings of 304 stainless steel and double and single walled cylinders of an aluminum alloy, A5052 to fragmentation, and the effects of wall thicknesses, explosive driver diameters and the constant proportionality of the in-plane biaxial stretching rates are investigated on the deformation and fracture behavior of three types of single walled structures and shatterproof behavior for double walled cylinders experimentally and numerically. In the cylinder tests, the driver is a column of high explosive PETN, inserted coaxially into the bore of a cylinder and initiated by exploding a fine wire bundle at the column axis using a discharge current. In case of the ring tests, ring specimens are placed onto a cylinder charged with the PETN as an expansion driver, and for sphere tests, a specimen filled with the PETN is also initiated by exploding a fine copper wire line with small length located at the central point. Observation results of deformation have shown the final maximum in-plane stretching rate order of , and fracture evaluations on recovered fragments are discussed indicating the need of modified fragmentation model for the structural components. In the double walled cylinder tests, only for lowermost amount of the explosive the outer cylinder has almost caught the fragments of inner cylinder, revealing that the damage phenomena are much different from those for single walled ones.

Abstract: A structure of a carbon steel specimen after explosive loading is investigated. The loading was executed by Mach stem, formed in high explosive charge that was preliminary compressed by advanced wave in ceramic bar. In the original condition the specimen had a typical for low carbon steel ferrite-pearlite structure. Metallographic analysis has shown that during the process of the explosive loading the following structural changes took place: formation of numerous deformation twins in both ferrite grains and pearlite colonies (i.e. in two-phase structure); formation of extended bands of localized deformation, which are not crystallographically connected with the original ferrite-pearlite structure; fine grains formation in zones of severe plastic flow. The size of the ferrite grains is by an order of magnitude less than the original grains size. According to the authors’ opinion, above-noted structural peculiarities demonstrate that loading conditions achieved in the current loading scheme differ from common. The phenomenon of non-typical twinning in heterogeneous structure (pearlite) indirectly evidences that extremely high stresses and strain rates took place in the specimen during the loading.

Abstract: By the method of severe plastic deformation at high strain rate of coarse-grained copper under explosively dynamic loading, nanocrystalline copper with the average grain size less than 200 nanometer was fabricated. The mechanism of grain-refining was investigated by means of transmission electron microscopy. Finally, the deformation processes were simulated using Ls-Dyna3d finite element program and the effects of the strain, strain rate as well as temperature rise on grain-refining were analysed systematically. The results show that it is feasible to fabricate nanocrystalline copper by explosively dynamic plastic deformation of coarse-grained copper; twin crystal and dislocation are the main mechanism of grain-refining; higher strain and lower temperature rise are beneficial to the grain refining; the distribution of the grain size is not uniform along the loading direction.

Abstract: By the method of severe plastic deformation at high strain rate of coarse-grained copper under explosively dynamic loading, nanocrystalline(NC) copper was fabricated. The deformation process were simulated recur to Ls-Dyna3d finite element program , the effects of the strain on the degree of grain-refining were analysed. Finally, the dynamic mechanical properties of the NC copper were researched recur to split Hopkinson pressure bar(SHPB). The results show that it is feasible to fabricate nanocrystalline copper by explosively dynamic plastic deformation of coarse-grained copper and the grain size of the NC copper can be controlled less than 100 nanometer; higher strain at high strain rate is beneficial to the grain refining; the distribution of the grain size is not uniform along the loading direction; dynamic yield strength of the NC copper enhences with the decreasing of the average grain size and increasing of the strain rate.

Abstract: The microstructural heterogeneity and stress fluctuation play important roles in the failure process of brittle materials. In this paper, a generalized driven nonlinear threshold model with stress fluctuation is presented to study the effects of microstructural heterogeneity on continuum damage evolution. As an illustration, the failure process of cement material under explosive loading is analyzed using the model. The result agrees well with the experimental one, which proves the efficiency of the model.