Selecting Material Properties for Maximizing Gun Firing Power

2014 ◽  
Author(s):  
J. Perry ◽  
M. Perl
Keyword(s):  
Detailed Analysis ◽  
Yield Stress ◽  
Bauschinger Effect ◽  
Strain Curve ◽  
Residual Stress Field ◽  
Transition Range ◽  
Effect Factor ◽  
Gun Barrel ◽  
Zero Offset ◽  
Gun Firing

The design of gun barrels aims at maximizing its firing power determined by its SMP — the maximal allowed firing pressure, which is considerably enhanced by inducing a favorable residual stress field through the barrel’s wall commonly by the autofrettage process. Presently, there are two distinct processes: hydrostatic and swage autofrettage. In both processes the barrel’s material is fully or partially plastically deformed. Recently, a 3-D code was developed, which finally enables a realistic simulation of both swage and hydraulic autofrettage, using the experimentally measured stress-strain curve, and incorporating the Bauschinger effect. This code enables a detailed analysis of all the factors involving the final SMP of a barrel, and it can be used to establish the optimal process for any gun barrel design. A major outcome of this analysis was the fact that the SMP of an autofrettaged barrel is dictated by the detailed plastic characteristics on the barrel’s material. The main five plastic parameters of the material that have been identified are: the exact (zero offset) value of the yield stress, the universal plastic curve in tension and in compression, the Bauschinger Effect Factor (BEF) curve, and the Elastic-Plastic Transition Range (EPTR). A detailed analysis of these three materials points to the fact that the major parameter determining the barrel’s SMP is the yield stress of the material and that the best way to determine it is by the newly developed “zero offset” method. All these four parameters have a greater influence on the SMP of an hydraulically autofrettaged barrel than on a swaged one.

The Effects of the Material's Exact Yield Point and Its Plastic Properties on the Safe Maximum Pressure of Gun Barrels

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
J. Perry ◽  
M. Perl
Keyword(s):  
Yield Stress ◽  
Bauschinger Effect ◽  
Strain Curve ◽  
Detailed Comparison ◽  
Maximum Pressure ◽  
Residual Stress Field ◽  
Transition Range ◽  
Plastic Properties ◽  
Gun Barrel ◽  
Zero Offset

The design of a gun barrel aims at maximizing its firing power, determined by its safe maximum pressure (SMP)—the maximal allowed firing pressure—which is considerably enhanced by inducing a favorable residual stress field through the barrel's wall commonly by the autofrettage process. Presently, there are two distinct processes: hydrostatic and swage autofrettage. In both processes, the barrel's material is fully or partially plastically deformed. Recently, a 3D computer code has been developed, which finally enables a realistic simulation of both swage and hydraulic autofrettage processes, using the experimentally measured stress–strain curve and incorporating the Bauschinger effect. This code enables a detailed analysis of all the factors relating to the final SMP of a barrel and can be used to establish the optimal process for any gun-barrel design. A major outcome of this analysis was the fact that the SMP of an autofrettaged barrel is dictated by the detailed plastic characteristics on the barrel's material. The main five plastic parameters of the material that have been identified are: the exact (zero offset) value of the yield stress, the universal plastic curve in both tension and compression, the Bauschinger effect factor (BEF) curve, and the elastic–plastic transition range (EPTR). A detailed comparison between three similar barrel materials points to the fact that the major parameter determining the barrel's SMP is the yield stress of the material and that the best way to determine it is by the newly developed “zero offset” method. All other four parameters are found to have a greater influence on the SMP of a hydraulically autofrettaged barrel than on a swaged one. The simplicity of determining the zero offset yield stress will enable its use in any common elastic and elastoplastic problem instead of the present 0.1% or 0.2% yield stress methods.

The Evaluation of the 3-D Residual Stress Field Due to Hydraulic Autofrettage in a Finite Length Cylinder Incorporating the Bauschinger Effect Factor Based on the “Zero Offset Yield Stress”

2008 ◽  
Author(s):  
J. Perry ◽  
M. Perl
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Yield Stress ◽  
Yield Point ◽  
Finite Length ◽  
Bauschinger Effect ◽  
Residual Stress Field ◽  
Tangential Strain ◽  
Effect Factor ◽  
Zero Offset

The autofrettage process increases the ability of a pressurized cylinder to withstand higher pressure values prior to the onset of yielding. The yield-pressure of an autofrettaged cylinder is strongly affected by the Bauschinger Effect (BE) that results in a reduction of the yield stress in compression. This reduction, which is measured by the Bauschinger Effect Factor (BEF), highly depends on the exact determination of the yield point. The present analysis suggests a new 3-D axisymmetric model for solving the residual stress field in a hydraulically autofrettaged finite-length cylinder including the BEF curve evaluated by using the newly proposed concept of the “zero offset” yield point definition. The numerical model is validated experimentally using axial and tangential strain gauges attached to a thick walled cylinder undergoing hydraulic pressurization. The experimental set-up enables continuous strain measurements vs. the increasing pressure. The calculated strains and displacements as well as the initial yield-pressure were found to be in very good agreement with the measured values.

The Influence of the Bauschinger Effect on the Yield Stress, Young’s Modulus, and Poisson’s Ratio of a Gun Barrel Steel

2005 ◽  
Vol 128 (2) ◽  
pp. 179-184 ◽  
Author(s):  
J. Perry ◽  
M. Perl ◽  
R. Shneck ◽  
S. Haroush
Keyword(s):  
Plastic Deformation ◽  
Yield Stress ◽  
Young’S Modulus ◽  
Poisson’S Ratio ◽  
Bauschinger Effect ◽  
Young's Modulus ◽  
Poisson's Ratio ◽  
Compression Tests ◽  
Residual Stress Field ◽  
Gun Barrel

The Bauschinger effect (BE) was originally defined as the phenomenon whereby plastic deformation causes a loss of yield strength restraining in the opposite direction. The Bauschinger effect factor (BEF), defined as the ratio of the yield stress on reverse loading to the initial yield stress, is a measure of the magnitude of the BE. The aim of the present work is to quantitatively evaluate the influence of plastic deformation on other material properties such as Young’s modulus and Poisson’s ratio for gun barrel steel, thus extending the definition of the Bauschinger effect. In order to investigate the change in this material’s properties resulting from plastic deformation, several uniaxial tension and compression tests were performed. The yield stress and Young’s modulus were found to be strongly affected by plastic strain, while Poisson’s ratio was not affected at all. An additional result of these tests is an exact zero offset yield point definition enabling a simple evaluation of the BEF. A simple, triphase test sufficient to characterize the entire elastoplastic behavior is suggested. The obtained experimental information is readily useful for autofrettage residual stress field calculations.

The Beneficial Influence of Bauschinger Effect Mitigation on the Barrel's Safe Maximum Pressure

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
M. Perl ◽  
J. Perry
Keyword(s):  
Heat Treatment ◽  
Low Temperature ◽  
Bauschinger Effect ◽  
Computer Code ◽  
Maximum Pressure ◽  
Residual Stress Field ◽  
Gun Barrel ◽  
First Case ◽  
Temperature Heat ◽  
Temperature Heat Treatment

The favorable residual stress field generated by the autofrettage process is increasing the barrel's capacity to withstand pressure during firing—defined as the reloading phase. There are two principal autofrettage processes: swage autofrettage and hydraulic autofrettage. While the theoretical solution for hydraulic autofrettage has been available and accessible for a long time, the available models for swage autofrettage have been quite limited. Both processes include two successive stages of pressure loading and unloading followed by an additional reloading during firing. Reyielding during the firing phase of an autofrettaged barrel is strongly affected by the secondary Bauschinger effect (BE) that involves a reduction of the yield stress in tension due to previous plastic deformation in compression, occurring in the unloading phase of the autofrettage process. The secondary Bauschinger effect can be completely mitigated by introducing a low temperature heat treatment (LTHT) immediately after the autofrettage process, thus increasing the barrel's safe maximum pressure (SMP). The aim of the present work is to quantitatively analyze the effect of low temperature heat treatment on the safe maximum pressure of a gun barrel. Two extreme cases are considered: In the first case, it is assumed that low temperature heat treatment was applied to the barrel, and that it completely mitigated the secondary Bauschinger effect, while in the second case it is assumed that no low temperature heat treatment was applied to the barrel. Both the swage and the hydraulic autofrettage processes are numerically analyzed using a newly developed 3D computer code. The numerical results confirm that a low temperature heat treatment, which fully eliminates the influence of the secondary Bauschinger effect, increases the barrel's safe maximum pressure especially in the case of hydraulic autofrettage.

Changes in the Bauschinger Effect Level Post the Autofrettage Process

2009 ◽  
Author(s):  
M. Perl ◽  
J. Perry
Keyword(s):  
Heat Treatment ◽  
Low Temperature ◽  
Yield Stress ◽  
Bauschinger Effect ◽  
Computer Code ◽  
Maximum Pressure ◽  
Residual Stress Field ◽  
Temperature Heat ◽  
Effect Level ◽  
Temperature Heat Treatment

The favorable residual stress field generated by the autofrettage process is increasing the barrel’s capacity to withstand pressure during firing — defined as the re-loading phase. There are two principal autofrettage processes: swage autofrettage and hydraulic autofrettage. Both processes include two successive stages of loading and unloading followed by an additional reloading during firing. Reyielding during the firing phase of an autofrettaged barrel is strongly affected by the secondary Bauschinger effect that involves a reduction of the yield stress in tension due to previous plastic deformation in compression, occurring in the unloading phase of the autofrettage process. The level of the secondary Bauschinger effect can be reduced by introducing a low temperature heat treatment (LTHT) immediately after the autofrettage process, thus increasing the barrel’s safe maximum pressure (SMP). In the utmost case, the yield stress in tension may regain its initial value prior to the autofrettage process. The aim of the present work is to quantitatively analyze the effect of different levels of the yield stress in tension post the autofrettage process, on a gun barrel’s SMP, resulting from a low temperature heat treatment. The two autofrettage processes, the swage and the hydraulic, are numerically analyzed using the newly developed 3-D computer code. For the hydraulic autofrettage case five different Bauschinger effect levels were analyzed while for the swage autofrettage case, only two limiting cases were considered. The numerical results are indicating that the thermal treatment might partially or fully eliminate the influence of the secondary Bauschinger effect thus, increasing the barrel’s SMP. The swage autofrettage SMP, which is higher than the hydraulic one, is less sensitive to the LTHT thus, increasing barrel’s reliability.

The overstrain of Thick-Walled cylinders considering the bauschinger effect factor (BEF)

2003 ◽  
Vol 17 (4) ◽  
pp. 477-483 ◽  
Author(s):  
A. Ghorbanpour ◽  
A. Loghman ◽  
H. Khademizadeh ◽  
M. Moradi
Keyword(s):  
Bauschinger Effect ◽  
Effect Factor

Dynamic Tensile Properties of Magnesium Nanocomposite

2012 ◽  
Vol 706-709 ◽  
pp. 780-785 ◽  
Author(s):  
Y.B. Guo ◽  
V.P.W. Shim ◽  
B. W. F. Tan
Keyword(s):  
Yield Stress ◽  
Strain Curve ◽  
Absorption Capacity ◽  
Tensile Behaviour ◽  
Al Alloy ◽  
Compression Tests ◽  
Energy Absorption Capacity ◽  
Dynamic Tension ◽  
Melt Deposition ◽  
Tension Compression Asymmetry

In this study, a Mg-6wt%Al alloy and its composite containing 0.22vol% Al2O3 nanoparticles are fabricated using a disintegrated melt deposition technique, and samples are subjected to quasi-static and dynamic tension. Compared to quasi-static loading, both materials exhibit significantly higher yield stresses and tensile strengths, much better ductility, and thus a higher energy absorption capacity under dynamic tension. In terms of nanoparticle addition, its influence on the mechanical properties are not notable; enhancement of the elastic modulus, yield stress and tensile strength are negligible, and there is a small reduction in ductility. The tensile behaviour obtained in this investigation was compared with results of previous compression tests, and significant tension-compression asymmetry in the response is observed. The tensile yield stress is noticeably larger than that in compression, and the profile of the stress-strain curve for tension differs from that for compression – it is convex upwards for tension, but concave upwards for compression. A possible reason for this asymmetry is the occurrence of twinning in compression and its absence in tension.

Advanced Gun System Gun and Projectile Dynamic Model Results and Correlation to Test Data

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
J. Edward Alexander
Keyword(s):  
Test Data ◽  
Development Program ◽  
Element Model ◽  
Dynamic Finite Element ◽  
Firing Test ◽  
Gun Barrel ◽  
Angular Velocities ◽  
Gun Firing ◽  
Explicit Dynamic ◽  
Abaqus Model

BAE Systems is currently developing and testing a 155 mm advanced gun system (AGS) and a long range land attack projectile (LRLAP) as a part of the DDG-1000 ship development program. For this development, it is important to understand the barrel and projectile dynamics, including the interaction of the barrel and the projectile in the bore as well as the projectile tip-off parameters at exit. An abaqus explicit dynamic finite element model has been developed to compare results with test data that were taken on June 18, 2003, at the BAE Systems site at the Alliant Techsystems Proving Ground (ATPG) during AGS propellant testing. The abaqus model includes the gun barrel, the projectile used for propellant testing (a steel slug), the M110 gun mount, and the recoil system. Features of the model incorporate settling of the barrel due to gravity, gun recoil, in-bore interaction of the projectile and the barrel using contact surfaces, and the initial flight of the projectile after bore exit. The abaqus model results have been compared with gun firing test data acquired during propellant testing at Elk River, MN. These comparisons include barrel and projectile displacements, angular velocities, and axial accelerations. The abaqus model results are also compared to similar models of the test conditions with the simulation of barrel dynamics (simbad) gun dynamics code and the ibhvg2 interior ballistics code.

Crystal Plasticity Simulation of the Bauschinger Effect of Polycrystalline AA7075 through a Texture-Based Representative Volume Element Model

2014 ◽  
Vol 553 ◽  
pp. 22-27
Author(s):  
Ling Li ◽  
Lu Ming Shen ◽  
Gwénaëlle Proust
Keyword(s):  
Finite Element ◽  
Representative Volume Element ◽  
Crystal Plasticity ◽  
Bauschinger Effect ◽  
Voronoi Tessellation ◽  
Strain Curve ◽  
Element Model ◽  
Volume Element ◽  
Model Parameters ◽  
Representative Volume

A texture-based representative volume element (TBRVE) model is developed for the three-dimensional crystal plasticity (CP) finite element simulations of the Bauschinger effect (BE) of polycrystalline aluminium alloy 7075 (AA7075). In the simulations, the grain morphology is created using the Voronoi tessellation method with the material texture systematically discretised from experiment. A modified CP constitutive model, which takes into account the backstress, is used to simulate the BE during cyclic loading. The model parameters are calibrated using the first cycle stress-strain curve and used to predict the mechanical response to the cyclic saturation of AA7075. The results indicate that the proposed TBRVE CP finite element model can effectively capture the BE at the grain level.

Elasto-Plastic Stresses in Thick Walled Cylinders

2003 ◽  
Vol 125 (3) ◽  
pp. 248-252 ◽  
Author(s):  
Joseph Perry ◽  
Jacob Aboudi
Keyword(s):  
Residual Stress ◽  
Yield Criterion ◽  
Plastic Region ◽  
Weight Ratio ◽  
Theoretical Development ◽  
Cylinder Wall ◽  
Residual Stress Field ◽  
Gun Barrel ◽  
Von Mises ◽  
Made In

In the optimal design of a modern gun barrel, there are two main objectives to be achieved: increasing its strength-weight ratio and extending its fatigue life. This can be carried out by generating a residual stress field in the barrel wall, a process known as autofrettage. It is often necessary to machine the autofrettaged cylinder to its final configuration, an operation that will remove some of the desired residual stresses. In order to achieve a residual stress distribution which is as close as possible to the practical one, the following assumptions have been made in the present research on barrel analysis: A von Mises yield criterion, isotropic strain hardening in the plastic region in conjunction with the Prandtl-Reuss theory, pressure release taking into consideration the Bauschinger effect and plane stress conditions. The stresses are calculated incrementally by using the finite difference method, whereby the cylinder wall is divided into N-rings at a distance Δr apart. Machining is simulated by removing rings from both sides of the cylindrical surfaces bringing the cylinder to its final shape. After a theoretical development of the procedure and writing a suitable computer program, calculations were performed and a good correlation with the experimental results was found. The numerical results were also compared with other analytical and experimental solutions and a very good correlation in shape and magnitude has been obtained.

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