The U.S. Army has recently developed cutting edge designs for gun barrels, projectiles, and propellants that require testing. This includes measuring the internal pressure during fire. There are concerns with the current method of drilling to mount pressure transducers near the breech and chamber of the gun barrel where pressure is highest. An alternative, non-intrusive strain measurement method is introduced and discussed in the present work. This focuses on determining the feasibility and accuracy of relating tangential strain along the sidewall of a gun barrel to the drastic internal pressure rise created during combustion. A transient structural, numerical modal was created using ANSYS of a 155 mm gun barrel. The pressure gradient was derived using a method outline in IBHVG2 (Interior Ballistics of High Velocity Guns, version 2), and the model was validated using published experimental tangential strain testing data from a gun of the same caliber. The model was used to demonstrate the ideal location for strain measurement along the sidewall of the chamber. Furthermore, three different pressure ranges were simulated in the model. The behavior of the tangential strain in each case indicates a similar trend to the internal pressure rise and has oscillation due to a dominant frequency of the barrel. A method to predict internal pressure from external tangential strain was developed. The internal pressure predicted is within 4% of the pressure applied in the model. A sensitivity study was performed to determine the primary factors affecting tangential strain. The study specifically looked at material properties and geometry of the gun barrel. The thickness and elastic modulus of the gun barrel were determined the most relevant. Overall, the present work helps to understand tangential strain behavior on the sidewall of a large caliber gun barrel and provides preliminary work to establish an accurate prediction of internal pressure from external tangential strain. / Master of Science / Innovative technology for large gun systems require testing to evaluate safety and performance. The most recent designs from the U.S. Army for long range artillery require higher pressures. Currently, large gun barrels are drilled to mount pressure transducers for internal pressure testing, but the new generation of weapons require a way to measure internal pressure of the gun without introducing these high stress locations. External strain offers a means to measure displacement of the barrel caused by the internal pressure change with minimal alteration to the gun barrel. The present work focuses on modelling a large gun barrel using finite elements to understand the behavior of strain on the external surface due to internal pressure during fire. Measurements were taken near the chamber of the gun barrel model. The strain behavior is comprised of two components, a linear change due to a pressure increase and vibrations introduced due to the sharp pressure increase over a short amount of time. Three cases were evaluated at different pressure ranges and a method was developed to predict internal pressure from the tangential strain with a maximum error of 4% for all cases studied. The model also indicates that the strain results are most sensitive to a change in thickness and the elastic modulus of the gun barrel material.

Synthetic HRTEM images are simulated using Jems® simulation software with a model specimen consisting of a film of strained silicon on top of a relaxed Si0.82Ge0.18 alloy substrate in the [110] zone axis, where biaxial tensile strain exists in the strained silicon layer. Two simulated models are created: one with a sudden change in lattice constant (strained Si on a “fat” Si substrate) and another with a sudden change in atomic number (strained Si on a Cl substrate) in order to separate the effects of strain discontinuities from atomic number discontinuities measuring strain using Geometric Phase Analysis (GPA). The simulated models are subjected to image processing using GPA software developed by Chung. Two dimensional strain maps are reconstructed and the local strain is determined. Further, an analysis is done to evaluate the best imaging conditions for strain measurement using GPA at heteroepitaxial interfaces. In addition, the behavior of GPA across a step function in strain or atomic number is examined for information about (a) spatial resolution, (b) the effects of a sudden change in atomic number, (c) instrument parameters, and (d) specimen thickness for a 300KeV TEM. / text

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The evolution of the physical sciences and engineering has involved a detailed and quantified understanding of the properties of metals. In particular, it is necessary to know how metals deform and the stresses that are involved which, in turn, are affected by the rate at which strain is applied. The nature and layout of this work is outlined. The history of the pressure bar transducer is summarised. The original concept of Hopkinson in 1914 was to use a long metal bar to study the propagation of wave pulses. During the Second World War, Davies refined the instrumentation and studied the shape of such pulses as modified by dispersion. Kolsky in 1949 adapted the technique to investigate the dynamic plasticity of specimens wedged between two instrumented pressure bars. Subsequent workers have used variants of this apparatus to make measurements at strain rates up to 10<SUP>5</SUP> s<SUP>-1</SUP>, whilst others have considered the effects of friction and inertia on the specimen. After an explanation of the particular design requirements, a description is given of the high strain rate apparatus that forms the basis for the research reported in this dissertation. The components that make up the system are described separately and the experimental procedures are outlined. The accuracy of components critical to the experimental technique is investigated. The effects of friction at the specimen interfaces, inertia during deformation and wave dispersion in the pressure bar are discussed. Bar calibration is described. Experiments have been carried out on copper in five different microstructural states at average strain rates of 6 x 10<SUP>4</SUP> s<SUP>-1</SUP> and 5 x 10<SUP>-2</SUP> s<SUP>-1</SUP> and their behaviour compared. The metal has been specially worked to induce anisotropy in the form of texture. Special techniques have been developed to prepare specimens of known orientation from the bulk of the raw material. The results show correlations between the texture severity and the anisotropy of stress-strain properties. A dynamic work hardening effect is observed. There is evidence that the Petch relationship holds at high strain rates. The high strain rate deformation of uranium alloyed with titanium or molybdenum is investigated. Specimens often display evidence of macroscopic localised shear bands whose adiabatic formation is accompanied by a sharp fall in the materials' dynamic strength. Metallographic sections reveal the morphology of these bands and the relative motion of microstructural features during deformation. Results are presented on a eutectoid zinc-22% aluminium alloy in a lamellar and superplastic microstructural state and a gun steel. The high strain rate deformation of titanium-6% aluminium-4% vanadium alloy is compared with uranium-0.75% titanium alloy regarding their tendency to form macroscopic shear bands. The dynamic behaviour of copper is contrasted with that of uranium alloy. In conclusion, the current work is viewed in the context of the historical development of the miniaturised Hopkinson pressure bar. Some comments are made about the application of the technique, and the scope for further research.

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