A Model for Shaped Charge Warhead Design

A model for shaped charge warhead design was developed. The model is incorporated in the computer code - CUMUL. The code includes detonation wave profile estimation, liner collapse, arrival of collapsed liner to the centerline of shaped charge, jet creation and jet breakup. The penetration phenomena are discussed and governing equations are presented. Two cases dealing with the target type are included: homogenous and non-homogeneous targets. For the purpose of verifying CUMUL, a set of 20 specimens of shaped charges was tested. The tests were directed to investigate the effect of cone apex angle and stand-off distance on the performance of shaped charge. From the comparison between experiments and CUMUL results, it was concluded that CUMUL program shows a good agreement with the experiments. That enables it to be a powerful tool for shaped charge warhead design

Modeling of gas parameters in the cylinder of the automatic gun during firing

The change of gas parameters in the cylinder of the automatic gun has a great influence on the dynamics of the gun. Many factors have an influence on the gas parameters in the gas cylinder such as the diameter and position of the gas port, the initial volume of the gas cylinder, the gap between the piston and the cylinder, initial temperature of the cylinder parts, etc. The analytical model was made to analyze the parameters on which depends gas piston dynamics. The numerical simulation with CFD software ANSYS Fluent was performed to analyze the change of the thermodynamic properties of the gases in the cylinder, temperature change of the cylinder parts and dynamics of the gas piston. The experiment was performed to provide pressures in the barrel and the gas cylinder and velocity of the gas piston. The comprehensive comparisons between results obtained by the analytical model, the numerical simulation and experiments have been performed and good agreements were observed

Experimental and numerical analysis of thermo-chemical erosion in gun steel

Various factors of thermo-chemical erosion process in gun steel were analysed. The factors are mainly related to the thermal load of gun barrel inside surface, characteristics of barrel surface and chemical interactions between propellant combustion products and barrel surface. The experimental simulation of conditions in gun barrel was carried out by vented vessel firings in the device based on modification of 37 mm M39 gun. The nozzle mass loss during firing was the measure of gun steel erosion. The main thermal factor of erosion is maximum nozzle inner surface temperature. This temperature was determined experimentally by micro thermocouples measurements at specified distance away from the inner surface and by numerical analysis of the inverse heat conduction problem. Modelling of two-phase flow of propellant combustion products and unburned propellant grains in the vented vessel and heat transfer to the nozzle were conducted using developed 1-D interior ballistic code and CFD simulation in FLUENT. Influence of different propellants, TiO2/wax wear reducing liner and tungsten-disulfide nanoparticles layer on nozzle erosion was analysed. Good agreement between experimental and computational results was achieved

Experimental and numerical analysis of thermo-chemical erosion in gun steel

Various factors of thermo-chemical erosion process in gun steel were analysed. The factors are mainly related to the thermal load of gun barrel inside surface, characteristics of barrel surface and chemical interactions between propellant combustion products and barrel surface. The experimental simulation of conditions in gun barrel was carried out by vented vessel firings in the device based on modification of 37 mm M39 gun. The nozzle mass loss during firing was the measure of gun steel erosion. The main thermal factor of erosion is maximum nozzle inner surface temperature. This temperature was determined experimentally by micro thermocouples measurements at specified distance away from the inner surface and by numerical analysis of the inverse heat conduction problem. Modelling of two-phase flow of propellant combustion products and unburned propellant grains in the vented vessel and heat transfer to the nozzle were conducted using developed 1-D interior ballistic code and CFD simulation in FLUENT. Influence of different propellants, TiO2/wax wear reducing liner and tungsten-disulfide nanoparticles layer on nozzle erosion was analysed. Good agreement between experimental and computational results was achieved

Determination of detonation products equation of state from cylinder test: analytical model and numerical analysis

Contemporary research in the field of explosive applications implies utilization of hydrocode simulations. Validity of these simulations strongly depends on parameters used in the equation of state for high explosives considered. A new analytical model for determination of Jones-Wilkins-Lee equation of state parameters based on the cylinder test is proposed. The model relies on analysis of the metal cylinder expansion by detonation products. Available cylinder test data for five high explosives are used for the calculation of Jones-Wilkins-Lee parameters. Good agreement between results of the model and the literature data is observed, justifying the suggested analytical approach. Numerical finite element model of the cylinder test is created in Abaqus in order to validate the proposed model. Using the analytical model results as the input, it was shown that numerical simulation of the cylinder test accurately reproduces experimental results for all considered high explosives. Therefore, both the analytical method for calculation of Jones-Wilkins-Lee equation of state parameters and numerical Abaqus model of the cylinder test are validated

Modeling of gas parameters in the cylinder of the automatic gun during firing

The change of gas parameters in the cylinder of the automatic gun has a great influence on the dynamics of the gun. Many factors have an influence on the gas parameters in the gas cylinder such as the diameter and position of the gas port, the initial volume of the gas cylinder, the gap between the piston and the cylinder, initial temperature of the cylinder parts, etc. The analytical model was made to analyze the parameters on which depends gas piston dynamics. The numerical simulation with CFD software ANSYS Fluent was performed to analyze the change of the thermodynamic properties of the gases in the cylinder, temperature change of the cylinder parts and dynamics of the gas piston. The experiment was performed to provide pressures in the barrel and the gas cylinder and velocity of the gas piston. The comprehensive comparisons between results obtained by the analytical model, the numerical simulation and experiments have been performed and good agreements were observed

Determination of detonation products equation of state from cylinder test: analytical model and numerical analysis

Contemporary research in the field of explosive applications implies utilization of hydrocode simulations. Validity of these simulations strongly depends on parameters used in the equation of state for high explosives considered. A new analytical model for determination of Jones-Wilkins-Lee equation of state parameters based on the cylinder test is proposed. The model relies on analysis of the metal cylinder expansion by detonation products. Available cylinder test data for five high explosives are used for the calculation of Jones-Wilkins-Lee parameters. Good agreement between results of the model and the literature data is observed, justifying the suggested analytical approach. Numerical finite element model of the cylinder test is created in Abaqus in order to validate the proposed model. Using the analytical model results as the input, it was shown that numerical simulation of the cylinder test accurately reproduces experimental results for all considered high explosives. Therefore, both the analytical method for calculation of Jones-Wilkins-Lee equation of state parameters and numerical Abaqus model of the cylinder test are validated

Two-stage model of explosive propulsion of metal cylinder

The paper considers acceleration of cylindrical metal liner by expanding detonation products. A new analytical model of liner motion is developed for the cases of axisymmetric (head-on) and grazing (side-on) detonation of the explosive charge. Suggested model relies on the two-stage regime of cylinder motion: (i) the first stage is the consequence of detonation wave-metallic liner interaction; as the result initial velocity is imparted to the liner, (ii) the second stage is gas-dynamic push of the liner governed by detonation product expansion, similarly to the Gurney approach. Results of the analytical model are validated by comparison with available experimental data

Perforation of multi-layered metallic targets by kinetic penetrators

In the paper it is considered problem of perforation of multi-layered metallic targets by deformable cylindrical flat-ended penetrators. Analytical model for perforation of multilayered targets is created on the basis of complex, multiphase, phenomenological model of deformation waves. Two variants of model involve cases of spaced and jointed layers of target. Computer program based on developed model enables determination of residual penetrator’s velocity as well as ballistic limit velocity. Double-layered target with constant total thickness is specially investigated in order to define optimal ratio of layers’ thickness that provides maximum target resistance. Results of analytical model are in good correspondence to experimental data. These results also enable formulation of few conclusions that can have practical importance

Fragment shape distribution in explosively driven fragmentation

The paper considers the shape distribution of fragments generated by detonation of a fragmentation warhead. Determination of the fragment shape distribution is very important for analysis of fragment ballistics and then for treatment of fragment interaction with a target. Morphology of metal fragments originating from casings of high-explosive projectiles is examined. Subsequently, the idealized fragment geometry and shape parameters are defined. Two theoretical models of fragment shape distribution are presented: (a) the model based on Mott’s two-dimensional fragmentation approach, and (b) the Curran’s “slot machine” model. The results of both models are transformed into previously defined shape parameters. Theoretical results are shown to be in good agreement with available experimental data