No abstract

An accurate modeling of gun barrel temperature variation over time is important to assess wear and the number of shot fires needed to reach cook-off. Using lumped parameter methods, an internal ballistics code was developed to compute heat transfer to the gun barrel for given ammunition parameters. Subsequently the finite element method was employed to model gun barrel temperature history (temperature variation over time). Simulations were performed for a burst of nine shots and the results were found to match satisfactorily to the corresponding experimental measurements. Wear or erosion of the barrel during a gun fire is very sensitive toward the maximum bore surface temperature. The proposed scheme can accurately simulate gun barrel temperature history; hence improved wear calculations can be made with it. An important and unique advantage of the developed scheme is that it easily couples internal ballistics simulations with the finite element methods.

No abstract

The purpose of solid propellants is to generate gas, which expands to accelerate (and spin, in the case of rifled barrels) a gun projectile so that it achieves the desired launch velocity at the muzzle. Some of the important properties of a propellant are the burning rate and vivacity, both of which strongly influence gun performance and projectile range. However, nitrate ester propellants undergo physical and chemical degradation during storage and this can change the burning rate and/or vivacity, either reducing the propulsive efficiency or increasing the safety risk to the operator during transportation and handling. Here we report the effect of aging on the burning rate and vivacity of spherical doublebase propellants containing diphenylamine (DPA) as the main stabilizer. We tested three sets of propellants that were artificially aged at 80 ºC for 5.3, 10.6 and 21.6 days, equivalent to 5, 10 or 20 years of aging at 25ºC according to STANAG 4582. It was found that DPA was progressively lost from the propellants during aging, with the greatest loss observed in propellants aged for the longest time. The DPA was able to fulfil its stabilisation role of propellant when NG was up to 14%, however, failed to stabilize when the nitroglycerin content was nearer to 20%. Aging caused changes in the burning rate and vivacity compared to the unaged propellant batch. The burning rate of propellant containing~20% nitroglycerin exceeds the burning rates of samples containing 12-14% nitroglycerin. The limited role of DPA as a stabilizer for double-base propellants is discussed. The DPA stabilized double base propellant may undergo significant changes during storage, making them unsuitable for their designated use.

This paper reports on the design requirements and a range of specific concepts for optical fiber-based sensor protection systems that can be used in concrete structures. The designs range from sensor protection systems that are manufactured involving stainless steel, fiber reinforced composites and concrete. The feasibility of manufacturing the sensor protection systems using these materials is also demonstrated. A detailed finite element analysis was carried out to optimise the stainless steel-based sensor protection system for concrete. Experimental results involving the sensor protection system will be presented in Part 2 of this series of papers.

No abstract

Shaped charges are designed to produce high-velocity jets for penetration. During jet formation, the liner collapses and converges at a point source also known as the virtual origin (VO), along the distancetime plane. The location of the VO must be known to allow the development of penetration analytical models. Here we determined the VO position using the ANSYS ® Autodyn 2D shaped charge jetting technique. Jetting analysis was conducted for two shaped charges of 18 and 32 mm diameter. The explosive and casing were represented by Eulerian two-dimensional finite difference grids whereas the liner was modelled using a shell formulation. The summary/history of the jetting analysis was used to determine the location of the VO of the shaped charges. Interpolating the point of intersection between the jet velocity (U-Jet) and the cumulative jet mass, on the liner, revealed the location of the VO at a distance equivalent to approximately two-thirds of the inner cone diameter of the shaped charges in agreement with earlier studies using

No abstract