Thermal Study of 155 mm Gun Barrel

Thermal analysis of 155 Gun barrel is an important aspect of designing the gun barrel and deciding the maximum firing rate. The performance of any artillery depends upon the thermal behaviour of the gun barrel among various factors, and its availability for continuous firing depends on the maximum bore temperature and cook-off time of the barrel. In this paper, the effect of maximum bore temperature, cook-off, active cooling is reviewed. Heat transfer to the gun barrel surface is calculated using analytical analysis with given ammunition parameters. Analytical and finite element analysis of maximum bore temperature and cook-off time is also included. Finite element analysis of external Jacket water cooling of the barrel shows that the gun can fire continuously at three rounds per minute without reaching cook-off temperature

Numerical and Experimental Analysis of Sound Suppressor for a 5.56 mm Calibre

A sound suppressor is an internal or external device coupled to the barrel of a firearm. Its development has been historically related to the negative effects produced by the noise. This article presents the numerical and experimental analysis of a sound suppressor for a 5.56 mm caliber rifle. It was designed, manufactured, and tested inside a shooting tunnel for 911 m/s and 344 m/s velocities. Three geometric configurations with curved deflectors, conical deflectors, and finally with a reactive spiral capable of dissipating the acoustic wave were compared considering reactive and dissipative systems. The attenuation of the sound inside the silencer depends directly on the reduction of the projectile wave velocity and the deflagration of the gases at the instant of firing. Then the MIL-STD-1474E standard was used to carry out the experiments. The results in the computational numerical simulation show an average value of 143 dB for the considered three models, the Sound Pressure Level in the reactive core model decreased by 25% with respect to other proposals, which have an average value of 141 dB. These results can be useful to improve in the design of sound suppressors based on the needs of the users and under the specific characteristics of each weapon ballistic.&nbsp

An investigation into the effect of the gilding jacket on 12.7 mm armour-piercing projectile penetration of armour materials

© Cranfield University, 2018The influence of both the bullet jacket and projectile core hardness for 12.7-mm armour piercing (AP) rounds has been investigated using a variety of different experiments with the aim of optimising projectile performance. The research was designed to elucidate the role of these two elements in the penetration process, building on work elsewhere in the literature. A combination of forwards and reverse (target impacting stationary projectile) investigations provided insight into both penetration efficiency and resultant target failure modes. The results of these experiments, backed by a pressure-gauge based impact technique, were validated via numerical modelling. It was observed that the jacket appears to serve three inter-linked functions: pre-damage of the target; cushioning of the AP core and confinement of the core. Modifying the core hardness showed that penetration efficiency was maximised when this hardness was greater than / overmatched that of the target (Armox Advance) plate. This behaviour was more pronounced when a thicker (9 rather than 5-mm thick) target plate was employed, suggesting that projectile / target interaction time was of particular importance (a potential confinement effect). However, for the 9-mm target plates where overmatch did not occur, reduced penetration / a ‘ceramic-like’ response was observed. In a similar manner, the presence of a jacket had the greatest effect for thicker plates. However, this confinement effect was complemented by pressure gauge results which suggested that the presence of the jacket enhanced energy coupling into the target (and, in corollary, that the jacket prevented premature and excessive loading of the core). In turn, numerical simulations provided further evidence that the jacket appeared to be protecting (cushioning) the core on impact. However, these also highlighted the extent of pre-damage caused by the jacket

Simplified Interior Ballistics Analysis of a Tube Launched UAV Prototype

Structural analysis is a critical aspect in the successful design of tube launched projectiles, such as mortar rounds. Ongoing research conducted at West Virginia University has focused on a tube-launched, folding-wing UAV design inspired by mortars. This has driven the necessity of a structural analysis of the prototype design to provide vital feedback to designers to ensure that the UAV is likely to survive the act of launching. Due to the extreme accelerations during the launching phase, a typical mortar round experiences dramatic impulse loads for an extremely brief duration of time. Such loads are the result of the propellant combustion process. Thermodynamic-based interior ballistic computations have been formulated and were used to solve the dynamic equations of motion that govern the system. Modern ballistic programs solve these equations by modeling the combustion of the propellant. However, mathematical procedures for such analyses require complex models to attain accurate results. Consequently, the objective of this research is to create a ballistics program that can evaluate interior ballistics by using archived pressure-time data without having to simulate the propellant combustion in order to minimize the computational effort required. A program routine created for this purpose reduces the complexity of calculations to be performed, while maintaining a reasonable degree of accuracy for the motion dynamics results (temporal displacement, velocity, acceleration of the projectile) and thermodynamic results (combustion gas pressure and volume). Additionally, the program routine was used to produce a mathematical model describing the pressure as a function of time. Advanced simulations could then be conducted via explicit-dynamic finite element solvers such as ANSYS LS-DYNA using the ballistics code outputs as loading conditions to simulate the transient response and stress wave propagation of the prototype and individual payload components. Such simulations remove uncertainties related to the transient loads needed to assess the structural integrity of the projectile and its components. Results obtained from the simulations were compared for verification purposes to review the accuracy of the solutions. The program provided researchers with an effective design tool that may be used in the optimization of a successful structural design. The results obtained from the simulations will be examined in the context of this thesis

Analysis of Steel Made Leaf Spring using FEA Tool ANSYS

Mathematical and computer modelling have been playing an increasingly important role in the Computer Aided Engineering (CAE) process of many products in the last 60 years. Simulation offers great advantages in the development and analysis phase of products and offers a faster, better and more cost effective way than using physical prototypes alone. This paper analyses the mechanics characteristic of a composite leaf spring made from glass fibre reinforced plastics using the ANSYS software. Considering interleaf contact, the stress distribution and deformation are obtained. Taking the single spring as an example, comparison between the performance of the GFRP and the steel spring is presented. The comparison results show that the composite spring has lower stresses and much lower weight. Then the automotive dead weight is reduced observably

Pounding response of buildings under earthquake motions

Simulation of structural pounding using impact element models has attracted researcher’s attention for many years. This study aims at developing an impact element model which can represent the elasto-plastic pounding behaviour of buildings during earthquake. This impact element model will be appropriate for modelling impact between two flat surfaces. For this purpose, Hopkinson Pressure Bar (HPB) experimental tests and non-linear finite element (FE) analysis are first conducted to investigate the contact response of different structural materials at variable loading rates. Then, existing impact element models have been applied to predict the response of experimental and numerical models. The performance of the existing impact element models particularly the linear viscoelastic model has been compared against the HPB experimental results of steel/steel impact. The results indicated that providing suitable contact parameters, the impact element models can predict the impact response of materials realistically

Effects of Tank Gun Structural Components on the First Shot Hit Probability

Fire power for a main battle tank is one of the most important performance parameters like survivability and mobility. Fire power effectiveness is directly related to the first shot hit probability, performance of main gun, second armament, gun and turret drive system, fire control system, automatic target tracker, commander and gunner sight etc. First shot hit probability (a measure of cumulative effects of errors) is affected by the variations of the projectile parameters, the main gun structure uncertainties, fire control system errors, interaction between the projectile and the gun barrel and the unpredictable environmental changes. These errors and variations can be eliminated or minimised by understanding and simulating the firing event properly, manufacturing the related parts in high precision, using advanced fire control algorithms, and accurate sensors. In this review study, the effects of main gun structural components on the first shot hit probability are investigated taking into account all of the associated error sources. In order for a main battle tank to have both high and repetitive first shot hit probability under all battlefield conditions the gun structure should respond in a similar manner in successive firings without causing any abrupt change in performance. In this study, first the dynamic behaviour of gun/projectile system is discussed and then the design recommendations for the main gun components such as bearings, gun barrel, recoil system etc. to achieve higher first shot hit probability are reviewed

A review of composite structures subjected to dynamic loading

The following review of composite impact work summarises key research interests and provides a brief overview for the development of theoretical, experimental and numerical methods for low, high, and hyper velocity impact. Particular attention is given to experimental apparatus and techniques used for the different impact velocity regimes, and the implementation of failure criteria in finite element (FE) modelling methods which predict material behaviour. Areas are then identified for which limited research has been currently undertaken and suggestions are made for possible future research topics

Magneto-Rheological Fluid Device as Artificial Feel Force System on Aircraft Control Stick

The conventional feel system in any aircraft occupies large space in the cockpit and has complicated designs. The primary objective of this research is to develop an artificial feel force system that can overcome some drawbacks of the current feel force system. A novel feel system using magneto-rheological (MR) fluid is constructed to precisely control the shear stress under the magnetic field. To validate the functionality of the MR artificial feel system, the final system is fabricated and multiple tests are performed to acquire force-velocity characteristics that are compared to the mathematical model derived. In addition, the reference model of the force feedback control is simulated for the feel force application. Both experimental and simulation results are compared to validate the derived system model. The system response time and the sampling rates are evaluated and compared to the conventional system at the end. It is concluded from the research that the developed artificial feel system can precisely control and acts as a fail proof system when incorporated with a modern fly-by-wire aircraft system

Effects of Projectile and Gun Parameters on the Dispersion

 Main battle tanks constitute one of the most powerful fire powers for the armoured land forces. To use this very high fire power efficiently, the dispersion of shot impacts becomes crucial. Dispersion is affected by the aerodynamic factors, gun-projectile interactions, projectile and gun dependent factors, manufacturing tolerances and environmental factors. The change in aerodynamic factors and environmental conditions varies the aerodynamic forces applied on the projectile and this affects the dispersion characteristics of the projectile. In this study, the effects of the changes in recoil stiffness, gun support stiffness, projectile muzzle velocity and manufacturing tolerances of projectile forward/rear bourrelet diameters on the dispersion for 120 mm L44 and L55 calibre guns are investigated. Armour piercing fin stabilised discarding sabot type projectile is used in the analysis. Statistical dispersion analyses including interior ballistic, in-bore balloting and exterior ballistic analyses are conducted using PRODAS ballistic software. According to the results, it is determined that the decrease in projectile/bore clearance (forward/rear bourrelet diameter) results in improved dispersion of ammunition. The 10% changes from the nominal recoil stiffness and the vertical support stiffness values have negligible effects on the dispersion. In addition, the results show that muzzle velocity variations influence the dispersion in vertical direction substantially. Using the procedure applied in this study, it is shown that different clearance conditions can be analysed and most suitable tolerances may be determined taking into consideration of both the gun system performance and manufacturability