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

EXPERIMENTAL AND NUMERICAL INVESTIGATION ON THE PERFORMANCES OF A SMALL WEAPON BARREL DURING ITS LIFECYCLE

The paper presents experimental and numerical investigations on the performances of a small caliber rifle barrel during its lifecycle. Two 7.62 mm rifle barrels were used, the first was considered as a standard barrel, the second barrel was subjected to an accelerated life cycle test. Measurements of the muzzle velocity, the rate of fire and the firearm accuracy and precision were carried out. The paper presents the correlation between the measured parameters and the total number of shots fired. After the durability tests, longitudinal cross sections were made by cutting the tested and the standard barrels. 3D scanning was employed to perform a comparison between the tested and the standard bore surfaces. ANSYS Explicit dynamic analyses were performed based on the obtained surface scans. The numerical analyses results of the tested and the standard barrels showed good agreement with the experimental and the numerical internal ballistic model results

Numerical investigations of thermal spray coating processes: combustion, supersonic flow, droplet injection, and substrate impingement phenomena

The aim of this thesis is to apply CFD methods to investigate the system characteristics of high speed thermal spray coating processes in order facilitate technological development. Supersonic flow phenomena, combustion, discrete droplet and particle migration with heating, phase change and disintegration, and particle impingement phenomena at the substrate are studied. Each published set of results provide an individual understanding of the underlying physics which control different aspects of thermal spray systems.A wide range of parametric studies have been carried out for HVOF, warm spray, and cold spay systems in order to build a better understanding of process design requirements. These parameters include: nozzle cross-section shape, particle size, processing gas type, nozzle throat diameter, and combustion chamber size. Detailed descriptions of the gas phase characteristics through liquid fuelled HVOF, warm spray, and cold spray systems are built and the interrelations between the gas and powder particle phases are discussed. A further study looks in detail at the disintegration of discrete phase water droplets, providing a new insight to the mechanisms which control droplet disintegration, and serves as a fundamental reference for future developments of liquid feedstock devices.In parallel with these gas-particle-droplet simulations, the impingement of molten and semi-molten powder droplets at the substrate is investigated and the models applied simulate the impingement, spreading and solidification. The results obtained shed light on the break-up phenomena on impact and describe in detail how the solidification process varies with an increasing impact velocity. The results obtained also visually describe the freezing induced break-up phenomenon at the splat periphery

Theoretical and experimental techniques in the design of CRT deflection systems

This investigation considers the design methodologies associated with the development and optimization of a magnetic deflection system for Cathode Ray Tube (CRT) Display Systems. The development of a magnetic deflection system and the calculations necessary to determine the associated performance are both complex tasks. Their complexity arises from the detailed geometry involved in deflection unit designs, the wide range of product types and sizes, and variability in product performance specifications. The large variations of these issues compound the difficulty in realising an acceptable product design. Software simulation techniques which are able to accurately manipulate data and perform iterative calculations greatly aid this process. This work introduces a simulation technique used within the Philips organisation, called DUCAD (Deflection Unit Computer Aided Design), which is used to analytically and numerically model the deflection system, with the objective of assessing and speedily realising a design. The simulation technique allows magnetic deflection product designs to be synthesized by simulating the magnetic field generated by the deflection system. Approximate solutions can be iteratively investigated leading to a greater understanding of the problem domain. To gain a degree of confidence with the simulation results the software design proposal is thereafter replicated in hardware allowing a full validation of the DUCAD. Extensive simulation studies and practical prototyping experiments are presented to support the theoretical development. Comparing the calculated theoretical performance and the actual measured values, conclusions are drawn as to the quality of the simulation tool in deriving the intrinsic magnetic deflection characteristics of the generated product design. The level of agreement of theoretical prediction and experimental results are defined, and the design methodologies required to yield a slot based deflection system are assessed

Construction and Characterization of a Single Stage Dual Diaphragm Gas Gun

In the interest of studying the propagation of shock waves, this work sets out to design, construct, and characterize a pneumatic accelerator that performs high-velocity flyer plate impact tests. A single stage gas gun with a dual diaphragm breach allows for a non-volatile, reliable experimental testing platform for shock phenomena. This remotely operated gas gun utilizes compressed nitrogen to launch projectiles down a 14 foot long, 2 inch diameter bore barrel, which subsequently impacts a target material of interest. A dual diaphragm firing mechanism allows the 4.5 liter breech to reach a total pressure differential of 10ksi before accelerating projectiles to velocities as high as 1,000 m/s (1570-2240 mph). The projectile’s velocity is measured using a series of break pin circuits. The target response can be measured with Photon Doppler Velocimetry (PDV) and/or stress gauge system. A vacuum system eliminates the need for pressure relief in front of the projectile, while additionally allowing the system to remain closed over the entire firing cycle. Characterization of the system will allow for projectile speed to be estimated prior to launching based on initial breach pressure

Experimental investigation of contamination prevention techniques to cryogenic surfaces on board orbiting spacecraft

Within the simulation limitations of on-orbit conditions, it was demonstrated that a helium purge system could be an effective method for reducing the incoming flux of contaminant species. Although a generalized purge system was employed in conjunction with basic telescope components, the simulation provided data that could be used for further modeling and design of a specific helium injection system. Experimental telescope pressures required for 90% attenuation appeared to be slightly higher (factor of 2 to 5). Cooling the helium purge gas and telescope components from 300 to 140 K had no measurable effect on stopping efficiency of a given mass flow of helium from the diffuse injector

Advanced Hypervelocity Aerophysics Facility Workshop

The primary objective of the workshop was to obtain a critical assessment of a concept for a large, advanced hypervelocity ballistic range test facility powered by an electromagnetic launcher, which was proposed by the Langley Research Center. It was concluded that the subject large-scale facility was feasible and would provide the required ground-based capability for performing tests at entry flight conditions (velocity and density) on large, complex, instrumented models. It was also concluded that advances in remote measurement techniques and particularly onboard model instrumentation, light-weight model construction techniques, and model electromagnetic launcher (EML) systems must be made before any commitment for the construction of such a facility can be made

Public-Private Partnerships (PPPs) and the Road to Self- Reliance in Defence: A Perspective

The Industrial Policy Resolution of 1956, under Schedule A, reserved 17 industries including arms and ammunition for the public sector. Accordingly, the defence sector remained solely the domain of defence Public Sector Undertakings (PSUs), Ordnance Factory Board (OFB), and Defence Research and Development Organisation (DRDO) till 2001. However, the country had to resort to the import of ammunition for the Bofors artillery guns during the Kargil War from South Africa, amongst others, even though the country already had a large industrial base consisting of nine defence PSUs, 39 Ordnance Factories (OFs) and 52 laboratories of DRDO. The armed forces stared at the perils of dependence on imports during the war. On a positive note, post the Kargil War, the government decided to open the doors to the defence sector to the private industry. Thus, in May 2001, the government permitted 100 per cent participation by the Indian private sector, subject to licensing, with the aim to galvanise the country's defence industrial base for achieving self-reliance and indigenisation

Fuzzy Method for in Control Acetaldehyde Generation in Resin Pet in the Process of Packaging Pre-Forms of Plastic Injection

In order to control the drying temperature of the PET resin in the silo of the plastic injection molding machine, during the plastic injection process in the industries producing preforms for the manufacture of beverage bottles, care is taken in the ideal temperature regulation for the better performance in controlling the generation of Acetaldehyde (AA), which alters the taste of carbonated or non-carbonated drinks, providing a citrus nuance to the palate and questioning the quality of the packaged products The objective of this work is to develop a tool based on Fuzzy logic to support the control of the drying temperature of PET resin, allowing specialists to make the ideal temperature control decisions necessary to control the generation of Acetaldehyde (AA). For the development of the proposed Fuzzy inference model, we used the Matlab Fuzzy toolbox tool, where the input variables, the fuzzyfication rules and the output variable were implemented based on the data collected from the preform injection process. From the inference model, we obtained a more precise management of the variables that influence the generation of AA, estimating a reduction of $ 240,044.00 in annual costs in the production of preforms

Evaluation of capacitors for space propulsion applications final progress report

Low inductance energy storage capacitors for space propulsion application