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The paper presents the results of computer simulations of the transient heat flow in the barrel wall of a 35 mm caliber cannon for a single shot and a sequence of seven shots for a selected 30HN2MFA barrel steel. It was assumed that the inner surface of the barrel does not have a protective layer of chromium or nitride. When calculating heat transfer in a barrel, constant and temperature variable values of thermal conductivity, specific heat and density (in the range from RT (Room Temperature) up to 1000) in the 30HN2MFA steel were assumed. The test results were compared for both cases. A barrel with a total length of 3150 mm was divided into 6 zones (i = 1,, 6) and in each of them, the heat flux density was calculated as a function of the time q _i (t) on the inner surface of the barrel. In each zone, the heat transfer coefficient, as a function of the time hi(t) and bore gas temperature as a function of the time Tg(t) to the cannon barrel for given ammunition parameters, was developed. A calculating time equaling 100 ms per single shot was assumed. The results of the calculations were obtained using FEM implemented in COMSOL Multiphysics ver. 5.6 software.

A physical model and specificity of a two-stage light gas gun propulsion system are presented in this paper. For the considered system, a mathematical model of phenomena inside a combustion chamber, a light gas filled chamber, and a barrel was worked out. A numerical solution of the proposed model for the considered propulsion system gives pressures of powder gases, pressure of light gas, and motion parameters of a piston and a projectile. On the basis of the results of the accomplished calculations, influence of system structural parameters on the maximum pressure inside a compression chamber and a muzzle velocity of a projectile has been analysed. The final results of this work were used for development of the first in Poland a laboratory station with two-stage light gas gun intended for experimental investigation in the field of terminal ballistics of objects moving at hypersonic velocities.

This paper presents the results of numerical simulations of heat transfer in a tube with a protective chromium layer on the inner surface made of steel, with different shrinkage temperatures. Shrinkage in the steel is an unfavorable phenomenon because it causes cracks in the chrome coating. The cracks contribute to the peeling of the protective material on the inner surface of the tube. Wear and damage to the chrome layer significantly shortens the tube’s service life. The influence of the type of steel with medium carbon content on heat transfer for a sequence of ten, thirty, and sixty heat impulses was examined. Simulations were carried out for two selected steels with clearly different shrinkage temperatures, i.e., 30HN2MFA and X37CrMoV5-1 (1.2343). In 30HN2MFA steel, the shrinkage effect occurred at a temperature of approx. 750 °C, while in X37CrMoV5-1 steel it occurred at a temperature of approx. 870 °C. In the computational model, 30 cross-sections of the three-meter-long tube were analyzed. A time-dependent heat transfer coefficient was calculated in each zone. Heat transfer simulations were carried out using COMSOL version 6.1 software. This paper shows that for X37CrMoV5-1 steel, the shrinkage temperature on the inner surface of the tube was reached after approx. 60 heat impulses, while for 30HN2MFA steel, it was reached after approx. 30. The greatest differences in the number of impulses occurred for a pipe with a 200 µm thick chrome layer.

Mathematical models for the simulation of the operation of various projectile-throwing systems are continuously modified, simultaneously with the development of propellants. For these models, properly determined values of energetic ballistic characteristics of propellants are very important. This paper presents an original test and the results of closed vessel comparative investigations. The study analyses specific combustion characteristics of single-base propellants using conventional black powder ignition, plasma ignition, and gas ignition. The results of the study indicate the need to take into account—in the calculation of the burning rate—not only the dynamics of gas pressure changes but also the real (experimental) form function, which differs from the theoretical one resulting from the assumed geometric burning model. The obtained results allow for a critical analysis of the existing methods used for the determination of values of ballistic characteristics of propellants. Further, it will allow for creating pyrostatic test conditions that would reflect the condition of instantaneous ignition of propellant grains over their entire surface in the most realistic way.

This paper presents the results of numerical calculations of heat transfer in the steel wall of a tube with different chromium layer thicknesses on the inner surface for a single and a sequence of heat impulses. In modeling the thermal phenomenon, the tube material was assumed to be homogeneous, and the inner surface of the tube had a protective chromium layer. The calculations were performed for temperature-dependent parameters of the 30HN2MFA steel and chromium. The tube was divided into 30 zones. The time varying the heat transfer coefficient and the heat flux density on the inner surface of the tube in each zone were calculated. The numerical simulations of heat transfer in the tube wall were performed using the FEM implemented in COMSOL Multiphysics software. On account of the high thermal conductivity of chromium, after the first and subsequent heat impulses, as the thickness of the chrome layer increases, the highest peak temperature drops, while the temperature inside the steel wall of the tube increases. After the first heat impulse, the temperature of the wall at a depth 0.5 mm below the inner surface is twice as high for a tube with a 200 µm thick chrome coating compared to a tube without this coating. This paper showed that, after seven heat impulses, the temperature of the steel tube substrate does not exceed 750 °C, at which the shrinkage of the material occurs, causing cracks in the chrome coating.

In theoretical simulations of internal ballistics phenomena, the value of pressure generated by the ignition system is required. Typically, the ignition pressure value is assumed to be 3 - 5 MPa. The work presents a measurement stand using a “micro closed vessel”, designed to determine the ignition pressure for 9 mm pistol ammunition. Pressure measurements were made for two types of ammunition, differing in the construction of the ignition system. The results of measurements indicate that the value of the ignition pressure is twice as high as usually assumed. In addition, the mass of the ignition charge was determined, which is used in selected models of internal ballistics. The mass value was at the level of 0.02 g.

The combustible cartridge case has become an integral part of many modern weapons systems. The energetic and burning characteristics of the combustible case can have a significant impact on shot parameters. This paper describes Closed Vessel Tests (CVTs) performed on combustible cartridge case material and presents a method of determining the physical burning law and the linear burning rate of the tested material. The method was verified on the basis of the results of CVT of the felted combustible cartridge case material of a 120 mm tank round. It is shown that, in the case of porous combustible materials, the standard methods of determining the burning rate fail. The porosity of combustible materials greatly increases the burning surface and heat feedback from the burning zone to the unburned structure. These effects significantly increase the burning rate of porous materials. The results of analysis show the strong dependence of the burning rate on pressure. The results of this study can be applied in the modeling of gun propellant systems that contain combustible case elements.

This paper presents the results of a comparative investigation into the effects of the ignition method on the ballistic properties of a single-base gun propellant, as determined via closed vessel tests. Conventional gunpowder ignition and plasma jet ignition methods were used, and differences in the ignition time were analysed. The influence of the ignition method on the dynamic vivacity is discussed. It is shown that this influence is significant in the first phase of the combustion process, and with respect to the low values of the loading density. In the second phase of the combustion process, and for large values of the loading density, the dynamic vivacity plots for the two ignition methods converge. Regarding the burning law, close values of the exponent were obtained for the two ignition methods. The dynamic vivacity plots determined for plasma ignition reveal stronger dependence on the loading density than those determined for gunpowder ignition. The conclusion is that plasma ignition is not a solution to the problems inherent to the process of determining the ballistic properties of propellants, which results in deviation of the burning process from the geometric burning law. Keywords: Closed vessel test, Gun propellant, Gunpowder ignition, Plasma ignition

The paper presents an attempt to determine the dynamic vivacity functions of propellants with taking into account a parallel burning of the black powder igniter and the tested propellant. The approach is based on presented results of closed vessel tests, proving that the burning of the tested propellant starts before complete burning of the black powder igniter. Basing on closed vessel tests results for black powder, its dynamic vivacity function was determined. It was used for a prediction of the partial pressure of black powder combustion products in the case when black powder was used as an igniter. Dynamic vivacity curves are compared with the dynamic vivacity curves calculated at the assumption that the combustion of the main charge starts after the complete burning of the igniter. Obtained results show that the considered approach fails due to a very complex interaction between the igniter and the tested propellant.

The development of the interior ballistics general model of gun propellant systems by taking into account the specificity of the recoilless propellant system is presented in this paper. The presented expanded physical and mathematical model makes possible the simulation of classical and nonclassical gun systems: two-chamber, mortar, and the considered recoilless one. To solve the system of equations associated with the mathematical model, a computer programme was developed. An analysis was made for two configurations of a recoilless system, differing in the way of arrangement of a propellant charge, i.e., with the propellant charge moving together with a projectile and with the propellant charge burning in a cartridge chamber. The obtained calculation results showed that the system, in which the propellant charge moves together with a projectile, has the maximum pressure and the muzzle velocity higher in comparison with the system with the propellant charge burning in a cartridge chamber. Influence of a way of placement of the propellant charge is the stronger, the higher is the ratio of its mass to the projectile mass. The results of the accomplished calculations, especially the pressure inside the barrel as well as motion parameters of the projectile make the grounds for projecting and construction optimization of the recoilless gun systems.

This paper presents the method of determining the burning rate of fine-grained propellants based on the results of closed vessel tests. It is shown that in the case of fine-grained propellants, the standard methods of determining the burning rate fail. There are two reasons for this: imperfections of the grain shapes and the prolonged process of ignition due to a more developed surface than that of coarse grains at the same mass of the propellant. The value of the exponent in the burning law is estimated by the use of the so-called experimental form–function. The upper and lower limits of the value of the coefficient in the burning law are estimated. The accuracy of the proposed method is analyzed. Its validity is assessed by comparing the results of closed vessel tests analysis with accessible literature data.

The results of numerical simulations of transient heat transfer in the barrel wall of a 35 mm caliber cannon for a single shot and the sequences of seven shots and sixty shots for chosen barrel steels are presented. It was assumed that the cannon barrel was made of one of the three types of steel: 38HMJ (1.8509), 30HN2MFA and DUPLEX (1.4462). To model the thermal phenomena in the barrel, the barrel wall material was assumed to be homogeneous and the inner surface of the barrel had no protective chromium or nitride layer. The calculations were made for temperature-dependent thermophysical parameters, i.e., thermal conductivity, specific heat and thermal expansion (in the range from RT up to 1000 °C) of the selected barrel steels. A barrel with a total length of 3150 mm was divided into 6 zones (i = 1, …, 6) and in each of them, the heat flux density was calculated as a function of time q˙i(t) on the inner surface of the barrel. Using lumped parameter methods, an internal ballistic code was developed to compute in each zone the heat transfer coefficient as a function of time hi(t) and bore gas temperature as a function of time Tg(t) to the cannon barrel for given ammunition parameters. A calculation time equaling 100 ms per single shot was assumed. The results of the calculations were obtained using FEM implemented in COMSOL Multiphysics ver. 5.6 software.

This paper presents the results of numerical simulations of non-stationary heat transfer in a 35 mm anti-air gun barrel cover made of composite materials. The cover protects the gun against weather conditions, including sea water effects, and serves as a protection against mechanical damage. It was assumed that heat coercion in this problem will be the heat condition reached by the material of the barrel with the cover removed, after firing three bursts of 7 shells each, 120 s after opening fire. It was assumed, that in the second 120, the gun crew installs the gun cover and at this point, the heating process begins, followed by cooling of the cover material. The problem of initial and boundary value in the barrel with a cover installed system was solved as a three-dimensional initial and boundary problem. The initial and boundary value model adopted for the coverless barrel and the calculation results for the first burst of seven shells was presented in paper [7]. To obtain the heat condition of the barrel in the second 120, it was necessary to perform calculations for the second and third bursts, and for the barrel cooling processes starting in the second 120. The calculations were performed with a finite element method in the COSMOS/M software [9]. The cover material temperature values obtained during the numerical simulation are well below the temperature of 387K, which could form the upper limit of the composite applicability temperature range.

One direction of modern artillery ammunition development is to reduce its vulnerability to the effects of mechanical and thermal factors during transport, storage and operation. For LOVA, the reduced vulnerability of propellant explosives intended for loading into this ammunition is usually connected with a higher thermal ignition impulse threshold and reduced burning rate under low propellant gas pressure. Since 2016, work has been under way at the Military University of Technology (Warsaw, Poland), intended to develop a Polish low-vulnerability gun propellant for 120 mm tank ammunition. It was established during the initial stage of research and analysis, that the JA-2 gun propellant (more specifically, its energy and ballistics characteristics and geometrical dimensions of grains) will be the reference propellant for the low-vulnerability propellant in development. To this end, the authors performed closed vessel tests with JA-2 propellant (with seven-perforated grains designated LO5460). This paper contains comparative (with the JA-2 propellant) results of closed vessel tests of several propellant blends developed by the MUT Faculty of New Technologies and Chemistry research team. Closed vessel tests of these propellant blends were performed in the Ballistics Laboratory of the MUT Institute of Armament Technology using a manometric chamber with a volume W0 = 200 cm3. Experimental tests and theoretical analyses were performed based on provisions of the standardisation agreement STANAG 4115 [6], American military standard MIL-STD 286C [7] and original test procedures developed based on [8, 9]. The tests focused mainly on the issue of correlation between the chemical composition of the given propellant blend with the expected values of energy and ballistics characteristics in connection with the required shape of propellant grains.

Results of investigations of ballistic characteristics of the single-based N340 propellant are presented. A novel approach, proposed in an earlier authors’ work, was applied. Basing on pressure records, obtained in closed vessel tests the burning law and the dynamic vivacity function were determined. High value of the exponent in the burning law was obtained (1.25). This effect can be attributed to the process of infiltration of hot gases into propellant pores, enhanced by the increase in the pressure. The dynamic vivacity function was proved to be dependent on the value of the loading density. A simple analytical approximation of the averaged vivacity function was proposed. It describes the ballistic properties of the propellant much better than the geometric law of combustion. An effect of heat losses on the vivacity function was estimated, showing relatively small influence of the losses on the vivacity function. The obtained results confirmed applicability of the novel approach to the characterization of ballistic properties of fined-grained propellants.

This paper presents the results of a comparative investigation into the effects of the ignition method on the ballistic properties of three types of propellants: a single-base propellant, a double-base propellant and a low vulnerability (LOVA) propellant, as determined via closed vessel tests (CVT). Conventional gunpowder ignition and plasma jet ignition methods were used. The influence of the ignition method on the values of the propellant characteristics obtained in CVT was analysed. It was found that the method of ignition has an influence on the values of propellant characteristics, determined in CVT. An analysis of the experimental form functions showed that plasma ignition is not a solution to the problems inherent to the process of determining the ballistic properties of propellants in which the burning process deviates from the geometric burning law.

This paper presents a selection of the deliverables for a research project intended to develop a technology demonstrator for a smart counterprojectile forming part of an active protection system. Given the required activation of the active protection system within a distance of ten or so metres from the protected facility, a solid-propellant rocket engine was used, which has the characteristics of a booster rocket. For the determined configuration of the rocket engine, the elements of the counterprojectile and missile launcher were designed, based on homogeneous rocket propellant of Polish origin. To confirm the validity of the adopted concept for the propulsion system solution, preliminary testing of the rocket engine was conducted using an engine test bed, and included the measurement of gas pressure and engine thrust for different masses of ignition charge. To ultimately verify the operation of the design, field testing of the counterprojectile propulsion system was carried out, based on which the parameters of projectile motion inside the missile launcher and along the initial flight path length were determined.

This paper presents a selection of deliverables of a research project intended to develop a technology demonstrator for an active protection system smart counterprojectile. Numerical simulations were completed to analyse the effects of geometry and weight of the counterprojectile warhead on the counterprojectile flight (motion) parameters. This paper investigates four variants of the counterprojectile warhead shape and three variants of the counterprojectile warhead weight. Given the investigated geometric and weight variants, the PRODAS software environment was used to develop geometric models of the counterprojectile warhead, followed by the determination of the model aerodynamic characteristics. The final deliverable of this work are the results of the numerical simulation of the counterprojectile motion along the initial flight path length. Given the required activation of the active protection system in direct proximity of the protected object, the analyses of counterprojectile motion parameters were restricted to a distance of ten-odd metres from the counterprojectile launching system.

In the presented paper, kinematic characteristics of movable parts of investigated pistols have been experimentally determined with application of high speed camera and appropriate software TEMA motion. Results of measurements can be useful in validation of various theoretical models and can reveal the influence of some technical solutions on parameters of motion of selected parts. Obtained curves presenting dependence of slide velocity versus time, allowed for rough estimation of average value of interaction force between slide and frame of the investigated construction. The results of study highlights advantage of HK USP pistol design. The achieved results are from reduction of the value of the mentioned interaction force (approximately 50%) due to elongation of the most intensive phase of slide motion damping process.

The paper presents the results of computer simulations of unidentified transient heat transfer in the wall of a 35 mm cannon barrel for a single shot and for a sequence of seven shots with a subsequent firing break. The cannon barrel was made of 32CrMoV12-28 steel. For the phenomenon modelling, it was assumed that the material of the barrel wall is uniform and the barrel’s inner surface does not feature a protective coating of galvanic chrome or a nitrided casing. Calculations were performed for two input data variants: (i) for constant values of thermophysical parameters and (ii) for a temperature-dependent specific heat. The barrel with an overall length of 3150 mm was divided into 6 zones. On the inner surface of the barrel in each zone there were assumed various values of heat flux density expressed as rectangular functions in the range from 0 to 10 ms (with the start of ti of the function shifted in the subsequent zones). The calculation time for a single shot was assumed as equal to 100 ms. The calculations were performed with a finite element method in COSMOS/M software.

In this study, high strength steel plates made of 30PM steel were subjected to 7.62 Armour Piercing projectiles at the ordnance velocity. Several experiments differing considerably in conditions of interaction between projectiles and plates were performed. Selected parameters were measured before, during, and after ballistic tests, and both projectile and plate were subjected to detailed examination. It is foreseen to use the obtained results in two ways. Protection performance of steel plates will be determined and experimental data will be used as a reference for analyzing various models and numerical techniques, accessible in commercially available hydrocodes. The authors present the methodology, the experimental set-up configuration, and the results of laboratory experiments.

The geometric burning law of gun propellants is widely used in computer codes used for the simulations of the internal ballistics of guns. However, the results of closed vessel tests prove that the burning process of some propellants deviates from the geometric law. Validation of the hypothesis that observed deviations can be attributed to the cracking of propellant grains was the aim of this work. In order to verify the hypothesis, three types of gun propellants were chosen with considerably differing mechanical strengths: a single-base propellant, a double-base propellant, and a composite propellant. The mechanical properties of the gun propellants were tested using a quasi-static compression method with strain rate values of the order of 0.001 s−1 and the Split Hopkinson Pressure Bar technique with the strain rate in the range of 1000–6000 s−1. The mechanical responses of the propellants were assessed on the basis of the true stress–strain curves obtained and from the point of view of the occurrence of cracks in the propellant grains specimens. Moreover, closed vessel tests were performed to determine experimental shape functions for the considered gun propellants. Juxtaposition of the stress‒strain curves with the experimental shape functions proved that the observed deviations from the geometrical burning law can be attributed mainly to the cracking of propellant grains. The results obtained showed that the rheological properties of propellants are important not only from the point of view of logistical issues but also for the properly controlled burning process of propellants during the shot.

The results of field tests of 120 mm mortar have been presented in this paper. Tests were conducted with using the mortar projectile type OF-483A. The main task of investigations was experimental determination of muzzle velocity and throwing angle, which are initial conditions for numerical simulation of the mortar projectile flight. Muzzle velocity and throwing angle were determined on the basis of accomplished results of motion the projectile as well as the mortar. The high-speed camera Phantom v12 was used during the field tests. The projectile velocity and the movement of the mortar barrel were calculated by means of TEMA Motion program.