Cylindrical Charge Research Articles

Experimental Study on Blasting Funnel under Cylindrical Uncoupled Charge

According to the Livingston blasting funnel theory, a series of single-hole blasting funnel tests were performed at the May Fourth Square Station. The relationship curve between blasting funnel volume and drug embedding depth was plotted, and the variation curves of blasting funnel depth, vibration speed and noise with burial depth were obtained. The MATLAB software was used to perform four-term regression on the test data, and the parameters such as the optimal burial depth, critical burial depth, and optimal explosive consumption of the blasting funnel were calculated.

Study on the influence of rigid wall surface on the bubble characteristics of underwater explosion

In order to investigate the influence of rigid wall surface on the bubble characteristics of underwater explosion, the underwater explosion experiment under the boundary conditions of free surface and rigid wall surface was carried out on 2.5g cylindrical charge TNT in a 2×2×2m tank. The time history curves of shock wave and bubble pulsation were obtained by underwater pressure sensor, and the bubble pulsation process was observed by high-speed photography. The experimental results show that compared with the free surface underwater explosion, the shock wave peak pressure and the bubble pulse peak pressure in rigid wall surface underwater explosion are increased, and a large cavitation area appeared at the junction of rigid wall and water surface. After the bubbles contacted the rigid wall surface, the bubble morphology changed significantly, the first bubble pulsation period and the maximum radius of bubble expansion became larger. After the first bubble pulsation, the bubble partially collapsed and split into two parts, bubbles continued to pulsate in the direction of the rigid wall and the bottom of the water. Finally, combined with the experimental data of rigid wall surface at different explosion depths, the relationship between the first bubble pulsation period, the maximum bubble expansion radius and the explosion depth of 2.5gTNT under rigid wall conditions is given.

Creation and Verification of Numerical Model of Explosive Charge Blast in The Ansys Software System, for the Purpose of Substantiating the Optimal Parameters of Drilling and Blasting Operations

The purpose of this paper was to create a numerical model of explosive destruction of a rock slab by exploding a cylindrical explosive charge. The paper considers the features of solving the problem of explosive charge using the finite element method in a three-dimensional setting. The equations of state of materials used for calculations are given. The results of the laboratory experiment carried out on the basis of the laboratory: “Physical and technological processes of rock destruction” and “Physics of rock destruction by explosive energy” of the Department of Blasting works of the Mining University are presented. The comparison of the results of the laboratory experiment and the numerical modeling performed using the ANSYS software system is presented. Experimental research has shown that having clarified the constants in the polynomial equation of state of the material and the Johnson–Holmquist strength model, the results of numerical modeling, in general, are similar to the experimental ones. The obtained and verified numerical model of the cylindrical explosive charge blast is considered as the basis for choosing the optimal parameters of drilling and blasting works.

Study of the cylindrical wave propagation across a single rock joint with nonlinear normal deformation

ABSTRACT Rock joints, usually with nonlinear deformation, widely exist in many natural rock masses, which greatly affect stress wave propagation. In practical engineering, the generated stress wave is taken as a cylindrical wave when an explosion with cylindrical charge or a tunneling explosion occurs. The cylindrical wave propagation in jointed rock mass is a great concern of underground structure safety. In this paper, the time-domain recursive method (TDRM) is extended to investigate cylindrical stress wave propagation through a rock joint with nonlinear normal deformation. Based on the conservation of momentum at the wave fronts and the displacement discontinuity method, a quantitative analysis for the interaction between wave and the joint is carried out and the wave propagation equation is accordingly deduced by considering the attenuation. Verification of the TDRM-based results is conducted by comparison with the simulated results from UDEC code. Finally, parametric studies are carried out, which include the influences of joint stiffness, the maximum allowable closure of joint and the frequency of the incident wave on the transmission and reflection coefficients.

Dynamic response of cylindrical explosion containment vessels subjected to internal blast loading

This paper presents an experimental investigation into a self-designed single-layer cylindrical explosion containment vessel (CECV) and a new multi-layer CECV composed of single-layer CECV and aluminum foam sacrificial inner lining subjected to non-uniformly distributed internal blast loading. Based on the experimental results, the characteristics of the blast loading acting on the inner wall of the vessel and the strain response of the vessel shell are analyzed through theoretical analysis and numerical simulation. The analysis results show that the pole of the ellipsoidal end cap is the most dangerous position of the vessel when subjected to internal blast loading produced by a cylindrical charge at the geometric center of the vessel. At the same time, the analysis results confirm the possibility of nonlinear modal coupling to cause strain growth in a CECV. For the multi-layer CECV composed of single-layer CECV and aluminum foam sacrificial inner lining, analysis results demonstrate that the inner lining has a certain protective effect on the CECV as a whole, but may play a counteraction on the cylindrical shell portion of the vessel. This study can guide the design and safety assessment of explosion containment vessels.

Behaviour of explosively welded impedance-graded multi-metal composite plates under near-field blast loads

This paper presents a comprehensive analysis of the blast response of functionally graded composite metallic plates, fabricated using explosive welding. Explosive welding is a solid-state welding technique, which has previously shown capabilities in bonding metals that have different chemical and mechanical properties. Impedance, which is the product of volumetric mass density and wave propagation velocity for a given material, was chosen as the function when designing the graded composite plates. The performance of two composite plate configurations, namely, Steel-Titanium-Aluminium and Steel-Brass-Aluminium were compared with a monolithic steel configuration of equal overall plate dimensions. The plates were subjected to highly intensive blast loads produced by detonation of the 250 g cylindrical Composition-B charges at standoff distances between 20–65 mm and spherical 1 kg Nitromethane charges at standoff distances of 200 mm and 250 mm. Detailed numerical models of near-field loading of the monolithic and composite plates were developed using the non-linear finite element analysis software LS-DYNA and validated using the experimental deformation measurements. Experimental evaluation of the impedance-graded explosively- welded composite plates has been carried out for the first time and herein lies the novelty of the work presented in the paper. It was observed that the impedance graded composite plates, which were lighter in density than the monolithic plates, resisted the highly intensive blast loads through their enhanced ductility.

Flash Radiographic Study of Detonation Propagation in Semi-Ring Charges of TATB

Flash radiography was used to study the propagation of detonation in semi-ring charges of plastic bonded TATB with an inner steel shell when initiating normal detonation along a line on the outer surface of the charge. The shape of the detonation wave front at different times was determined. The shape of the front was found to be influenced by a layer of RDX based plastic bonded explosive placed on the surface of the main charge and having a detonation velocity ≈10% higher than that of TATB. It is shown that the position and shape of the detonation wave front in a cylindrical TATB charge is not described by the laws of geometric optics (Huygens principle) due to the features of detonation initiation in the initial section and the presence of the steel shell.

Method of gas flows calculation in solid propellant rocket engines taking into account the combustion of solid fuel charge

The paper presents a method for calculating the local and integral characteristics of the flow in the axisymmetric gas-dynamic paths of solid propellant rocket motors, taking into account the combustion of a charge of solid fuel. The numerical method of calculation is based on the use of the Godunov scheme, formulated for moving computational grids. The speed of movement of the combustion surface is defined locally on the edge of each calculation boundary cell. This approach allows us to take into account the uneven distribution of the pressure of the combustion products in the free volume of the combustion chamber. In test calculations, the power law of burning rate is used. Calculations of the gas flow in the solid propellant combustion chamber with cylindrical charge of solid fuel are carried out. Unsteady pressure curve in the combustion chamber is obtained. The method allows to determine all integral characteristics of the developed solid propellant rocket motors as a function of the engine running time.

Experimental studies of explosion energy output with different igniter mass

For study the energy output law of cylindrical charge with shell induced by different input energies, four different black powder masses were selected to ignite the main charge. Fragmentation degree of the shell was qualitatively analyzed by the area of holes on the witness plate and the recovered fragments mass. Through theoretical analysis, established the functional relationship between the average mass of fragments and the relative energy output of warhead, obtained how the relative energy output of charge changed with different initial energy input. The results showed that the change of input energy could lead to obvious variation in fragment characteristics, and could also control the output of charge. When the igniter mass increases from 1.55 g to 5.00 g, the relative energy output of the charge increases by 26.28%. Excessive initial input energy will destroy the shell confine in advance, resulting in a decrease in the relative energy output of charge.

A novel method for prediction of the critical diameter of solid pure and composite high explosives to assess their explosion safety in an industrial setting

ABSTRACTFor the explosion safety assessment in an industrial setting, the knowledge of critical diameter of high explosives provides important information on the sensitivity and conditions whereby detonations are likely to occur. The critical diameter or failure diameter is the minimum diameter of a cylindrical charge of high explosive which sustains a high order steady-state detonation. Available predictive methods require complex models, which are based on complicated variables such as the shock adiabat, and the generalized kinetic characteristic of decomposition of a high-explosive charge under shock-wave compression. For the first time, this paper describes a novel simple method for assessment of the critical diameter of pure and composite CHNO high explosives. The new model is based on the contribution of the number of nitrogen and oxygen atoms as well as some conditions, which are based on shock sensitivity, impact sensitivity and the negative values for core critical diameter of the desired explosives under certain situations. Experimental data of 42 high explosives have been used to derive and test the new model. The predicted critical diameters for building the model (29 explosives) and the test set (13 explosives), under the unconfined condition of these explosives, have the values of root-mean-square deviation (RMSD) of 5.14 and 3.96 mm, respectively.

Numerical modelling of steady detonations with the CREST reactive burn model

Watt et al. [J Eng Math 75(1):1–14, 2012] have shown that one can obtain good results for the propagation of detonation waves in cylindrical charges by assuming that the post-shock streamlines are straight. In this paper, we compare this Straight Streamline Approximation (SSA) to high-resolution Direct Numerical Simulations (DNS) for different models of explosives. We find that the SSA is less accurate for realistic explosion models than it is for polytropic equations of state with power-law reaction rates.

Shock Initiation of Nano‐TATB Explosives under Short‐Duration Pulses

AbstractBecause of the potential of nano‐TATB as a charge in slapper detonator, the shock initiation threshold of nano‐TATB explosive was studied over short pulse durations (down to 0.017 μs) and high pressure ranges (up to 17 GPa). The pulses were produced by the impact of thin plastic flyer plates, which were accelerated by electrically exploded metal foils. Nano‐TATB powders with a mean particle size of 60 nm were prepared and pressed into cylindrical sample charges with three densities (1.56, 1.64 and 1.74 g/cm3). The flyer impact velocity data versus charging voltages was measured with different flyer thicknesses. Together with the Hugoniot relationships of flyer and samples, the impact pressures and pulse durations were calculated. By using Langlie method, the threshold pressures for shock initiation were determined. In case of the identical flyer plate, the threshold pressure increases with increasing density. In case of the identical explosive density, the threshold pressure increases as the thickness of the flyer decreases (i. e. the pulse duration decreases) except for the highest tested density. These data are represented well by a constant P2τ initiation criterion for the short, high‐pressure pulses and deviate from the P2τ behavior at lower pressures. Finally, nano‐TATB is proved to be a little more sensitive to short‐duration pulses than superfine TATB, but much more sensitive than production grade TATB.

Analysis of the Cavity Formation Mechanism of Wedge Cut Blasting in Hard Rock

The basic process of cut blasting is to break rock, throw fragments, and form a cavity. Based on the characteristics of cut blasting and the combined effect of stress waves and detonation gas, the evolution process of wedge cut blasting is divided into two stages, and a theoretical model is proposed to investigate the cavity formation mechanism by theoretical analysis and field tests. In phase one, rock breaking is caused by stress waves. By considering the dynamic strength of the rock, a computational model is built for the rock failure zone derived from the coupled cylindrical charge explosion. In phase two, the driving force of the detonation gas overcomes the total resistance of the surrounding rock mass, accelerates fragments, and then throws fragments to form a cavity. The criterion of cavity formation is established on the basis of the quasi‐static loading of the detonation gas. The theoretical model provides an overall interpretation of the cavity formation mechanism, in which stress waves break rock and detonation gas throws fragments. A specific case indicates that the range of the failure zone is approximately 18 times the borehole radius in granite and that the hole‐bottom spacing of the wedge cut can be designed as 50 cm; in addition, detonation gas is sufficient to overcome the total resistance, accelerate rock fragments, throw fragments, and form a cavity. Field tests present favourable blasting results, with a high utilization rate of boreholes and uniform fragment sizes. Therefore, the model could provide theoretical support and technical guidance for wedge cut blasting in hard rock.

Effect of Initiation Location within Blasthole on Blast Vibration Field and Its Mechanism

In drill and blast, the explosive filled in each blasthole is cylindrically shaped and generally initiated by the detonator. Thus, the effect of the initiation location must be addressed, as it determines the detonation direction along the entire column explosive. In this paper, the effect of the initiation location on blast vibration field and its acting mechanism were comprehensively investigated through the theoretical, computational, and experimental approaches. The results indicate that the initiation location plays an important role in the blast vibration filed of the cylindrical charge. The underlying effect of the initiation location can be regarded as the combined results of the energy distribution and phase delay effects of the column explosive source. The behavior of the rock mass in the single‐hole blasting experiment demonstrates that the explosion energy is preferentially transmitted to the forward direction of the detonation wave. The seed wave‐based computation model verifies that owing to the phase delay effect, the blast vibration field of the cylindrical charge is not uniformly distributed and is strengthened at the forward direction of the detonation wave. The production blasting experiment indicates that the ground PPV under bottom initiation is 61.3%∼211.7% larger than that under top initiation. In addition, the effect of the initiation location is sensitive to the charge length L and the denotation velocity D. Meanwhile, the effect of the initiation location vanishes with distance. The present study provides valuable reference for understanding the effect of the initiation location on blast vibration in drill and blast.

Установление связи критических условий распространения детонации со средними скоростями разложения взрывчатых веществ в детонационнных волнах

The study introduces a model of steady propagation of non-ideal detonation of open cylindrical charges with diameters close to critical ones. The model was obtained in the quasi-one-dimensional approximation with the use of analytical methods. We found a solution for the model’s closing equation, which directly relates the average decomposition rate in the detonation front, determined by the parameters of the formal kinetics equation and dependent on the detonation rate, the gas-dynamic parameters of the initial explosive and its reaction products (isentropic exponents), the duration of the chemical peak and ideal detonation velocity, and also the ratio of the charge diameter to the duration of the chemical peak of the ideal detonation. We obtained an equation which reflects the dependence of the non-ideal detonation velocity on the charge diameter. The critical diameter is determined as the range boundary of the charge diameter values at which this equation still has a solution. The study shows that the expression for the fundamental characteristics of the detonation process, i.e. the ratio of the spread time and the reaction time of the explosive, differs from the expression used in the Khariton principle when taking into account the divergence of the reacting flow in the curved detonation front. As for the critical value of this ratio, in general it is different from the unity and is a variable value depending on the characteristics of the kinetics of decomposition of a substance in shock waves. Based on the calculations, we draw a conclusion that changes in the microstructure of the explosive charge of the same composition, displayed by changes in the parameters of the formal kinetics equation, are accompanied by relative changes in the critical diameter, many times greater than the relative changes in the duration of the chemical peak of ideal detonation

Analytical treatment of the wakefields driven by transversely shaped beams in a planar slow-wave structure

The suppression of transverse wakefield effects using transversely elliptical drive beams in a planar structure is studied with a simple analytical model that unveils the geometric nature of this phenomenon. By analyzing the suggested model we derive scaling laws for the amplitude of the longitudinal and transverse wake potentials as a function of the Gaussian beam ellipticity - $\sigma_x/a$. We explicitly show that in a wakefield accelerator application it is beneficial to use highly elliptical beams for mitigating transverse forces while maintaining the accelerating field. We consider two scaling strategies: 1) aperture scaling, where we keep a constant charge to have the same accelerating gradient as in a cylindrical structure and 2) charge scaling, where aperture is the same as in the cylindrical structure and charge is increased to match the gradient.

Wyznaczenie pola obciążeń generowanych wybuchem wydłużonych ładunków cylindrycznych

Dynamic load field generated in the rock mass by detonation of elongated cylindrical charges is determined. In practical blasting operations charges of dozen and more meters long are employed. Therefore, in the ambient medium around of the hole in which the charge detonates, a stationary field of stress and displacements is established. In the paper a stationary solution is presented which estimates the fields of pressure as well as of radial and axial velocity generated by a moving load propagating with constant velocity along the cylindrical hole cut in an infinite medium. The loaded medium is described by a one-wave model in which the small displacements speed is determined by the magnitude of the bulk modulus. The solution is estimated using integral transformations. A sample solution is provided, or a constant-value moving load acting on the internal surface of the hole for a given interval of time.

Nonlinear dynamics of relativistically intense cylindrical and spherical plasma waves

Spatio-temporal evolution and breaking of relativistically intense cylindrical and spherical space charge oscillations in a homogeneous cold plasma are studied analytically and numerically using the Dawson Sheet Model [J. M. Dawson, Phys. Rev. 113, 383 (1959)]. It is found that cylindrical and spherical space charge oscillations break via the process of phase mixing at an arbitrarily small amplitude due to anharmonicity introduced by geometry and relativistic mass variation effects. A general expression for phase mixing time (wave breaking time) has been derived and it is shown that for both cases, it scales inversely with the cube of the initial wave amplitude. Finally, this analytically obtained scaling is verified by using a numerical code based on the Dawson Sheet Model.

Experimental Research about the Effect of Particle Sizes on the Melt-through Effects of Al-MnO2 Flame Jet Thermite

The method of ultrasonic dispersion was adopted to prepare reactive materials of Al-MnO2 flame jet thermite with different components, which was aimed at experimental research about factors on the melt-through effects of Al-MnO2 flame jet thermite. Based on the single factor experiment, the disposal experiment of the steel plates with 3mm thickness had been carried out. According to the phenomena of experiments, there were many advantages with the form of powder cylindrical charge such as better ignition performance, faster burning rate and firmer combustion process. The charge with the 40um particle size of Al powder and 30-40um particle size of MnO2 had the best melt-through ability which could penetrate the steel plates with ranging from 1.5cm to 3cm aperture by contrasting and analyzing melt-through effects and molten zones. By contrasting and analyzing melt-through effects and molten zones, it was significant to analyze the accounts for the better performances, with the purpose of providing references for the selections of formula in the future experiments and applications.

Determination of Lee‐Tarver Model Parameters of JO‐11C Explosive

AbstractIn order to determine the Lee‐Tarver model parameters of JO‐11C when the density is 1.707 g/cm3, the detonation propagation of cylindrical charge with different diameters is modelling by AUTODYN software. The output performance parameters such as critical dimension, detonation velocity, detonation pressure and reaction time of different charge diameters through simulation are consistent with the experimental results by fixing and adjusting material model parameters of the JO‐11C explosive .The results show that the critical dimension is between 0.4 mm and 0.5 mm, the detonation velocity and pressure increase with the charge diameter increasing and the rule of reaction time is opposite. According to the determined parameters of the Lee‐Tarver model, the detonation pressure attenuation of JO‐11C charge with different diameter bearing on different steel gap were simulated and compared with the test. The simulation results are in good agreement with the experimental results when charge diameter is greater than 2 mm, which the error is less than 10 %. In smaller charge diameter, the error is also not more than 20 %.