Strain Rate Insensitivity of Damage-Induced Surface Area in M30 and JA2 gun propellants

1996 ◽  
Vol 21 (6) ◽  
pp. 307-316 ◽  
Author(s):  
George A. Gazonas ◽  
Arpad A. Juhasz ◽  
James C. Ford
Keyword(s):  
Strain Rate ◽  
Surface Area ◽  
Gun Propellants

scholarly journals On Influence of Mechanical Properties of Gun Propellants on Their Ballistic Characteristics Determined in Closed Vessel Tests

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3243
Author(s):  
Radosław Trębiński ◽  
Jacek Janiszewski ◽  
Zbigniew Leciejewski ◽  
Zbigniew Surma ◽  
Kinga Kamińska
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Point Of View ◽  
Closed Vessel ◽  
Shape Functions ◽  
Stress Strain ◽  
Static Compression ◽  
Burning Process ◽  
Double Base ◽  
Gun Propellants

The geometric burning law of gun propellants is widely used in computer codes used for the simulations of the internal ballistics of guns. However, the results of closed vessel tests prove that the burning process of some propellants deviates from the geometric law. Validation of the hypothesis that observed deviations can be attributed to the cracking of propellant grains was the aim of this work. In order to verify the hypothesis, three types of gun propellants were chosen with considerably differing mechanical strengths: a single-base propellant, a double-base propellant, and a composite propellant. The mechanical properties of the gun propellants were tested using a quasi-static compression method with strain rate values of the order of 0.001 s−1 and the Split Hopkinson Pressure Bar technique with the strain rate in the range of 1000–6000 s−1. The mechanical responses of the propellants were assessed on the basis of the true stress–strain curves obtained and from the point of view of the occurrence of cracks in the propellant grains specimens. Moreover, closed vessel tests were performed to determine experimental shape functions for the considered gun propellants. Juxtaposition of the stress‒strain curves with the experimental shape functions proved that the observed deviations from the geometrical burning law can be attributed mainly to the cracking of propellant grains. The results obtained showed that the rheological properties of propellants are important not only from the point of view of logistical issues but also for the properly controlled burning process of propellants during the shot.

Chemisorptive electron emission as a probe of plastic deformation in reactive metals

1994 ◽  
Vol 9 (5) ◽  
pp. 1156-1165 ◽  
Author(s):  
J.T. Dickinson ◽  
L.C. Jensen ◽  
S.C. Langford ◽  
R.G. Hoagland
Keyword(s):  
Plastic Deformation ◽  
Strain Rate ◽  
Surface Area ◽  
Electron Emission ◽  
Tensile Deformation ◽  
Constant Strain Rate ◽  
Total Surface Area ◽  
Unit Surface Area ◽  
Deformation And Fracture ◽  
Reactive Metals

The surface area created during tensile deformation and fracture of the reactive metals Ti, Zr, Mg, and Al is probed by real-time measurements of chemisorptive electron emission (CSE) due to oxygen adsorption. CSE is sensitive to the number of fresh metal atoms exposed at the surface as a consequence of plastic deformation. At constant strain rate, Ti, Zr, and Mg all display exponential increases in CSE intensities during loading, reflecting exponential increases in surface area prior to fracture. In Ti and Zr, CSE begins at the onset of unstable necking. In contrast, CSE intensities from Al reflect a nearly constant rate of surface area production during deformation at constant strain rate. Calibration of the Ti CSE intensities per unit surface area allowed determination of the total surface area produced during deformation and fracture. Atomic force microscopy of the necked region in strained Ti samples shows dramatic increases in surface roughness, in near agreement with the CSE results. A model is presented to account for these observations. The utility of CSE measurements as a probe of deformation and ductile fracture is discussed.

Development and Validation of Novel FE Models for 3D Analysis of Peening of Strain-Rate Sensitive Materials

2006 ◽  
Vol 129 (2) ◽  
pp. 271-283 ◽  
Author(s):  
S. A. Meguid ◽  
G. Shagal ◽  
J. C. Stranart
Keyword(s):  
Residual Stresses ◽  
Strain Rate ◽  
Surface Area ◽  
Shot Peening ◽  
Cell Model ◽  
Target Surface ◽  
Separation Distance ◽  
Hole Drilling ◽  
3D Analysis ◽  
Element Analysis

In this paper, we provide two different symmetry cells to describe the shot-peening process. In this multiple impingement model, we study the dynamic behavior of TI-6Al-4V targets subjected to a large number of shots. Three-dimensional elastoplastic finite element analysis (FEA) of the process was conducted using these two symmetry cells for strain-rate sensitive targets and rigid shots. The basic symmetry cell is assigned a target surface area C×C, where C is one half of separation distance between adjacent shots. The second “enhanced” symmetry cell is assigned a target surface area 2C×2C thus allowing higher density of impact point locations. Average residual stresses inside the target predicted by FEA were compared with experimental measurements using the hole-drilling technique. In order to do this, a new averaged technique was developed to obtain the stress distribution inside the symmetry cell. The results reveal that both symmetry cell models could be used for shot-peening modeling. However, the use of the enhanced symmetry cell leads to a better agreement with the measured residual stresses. In addition, the enhanced symmetry cell model allowed us to overcome some of the shortcomings of the basic symmetry cell for cases involving high peening velocity and intensity.

Dislocation Substructures Produced During Tensile, Creep, and Fatigue Deformation of Ti3Al at 700°C

1977 ◽  
Vol 35 ◽  
pp. 272-273
Author(s):  
S. M. L. Sastry
Keyword(s):  
Intermetallic Compound ◽  
Strain Rate ◽  
Tensile Creep ◽  
Slip Systems ◽  
Slip Vector ◽  
Superlattice Structure ◽  
Slip Activity ◽  
Dislocation Arrangement ◽  
Ordered Intermetallic ◽  
Tangled Dislocation

Ti3Al is an ordered intermetallic compound having the DO19-type superlattice structure. The compound exhibits very limited ductility in tension below 700°C because of a pronounced planarity of slip and the absence of a sufficient number of independent slip systems. Significant differences in slip behavior in the compound as a result of differences in strain rate and mode of deformation are reported here.Figure 1 is a comparison of dislocation substructures in polycrystalline Ti3Al specimens deformed in tension, creep, and fatigue. Slip activity on both the basal and prism planes is observed for each mode of deformation. The dominant slip vector in unidirectional deformation is the a-type (b) = <1120>) (Fig. la). The dislocations are straight, occur for the most part in a screw orientation, and are arranged in planar bands. In contrast, the dislocation distribution in specimens crept at 700°C (Fig. lb) is characterized by a much reduced planarity of slip, a tangled dislocation arrangement instead of planar bands, and an increased incidence of nonbasal slip vectors.

Quantitative analysis of in situ straining experiments in the case of strong frictional forces

1978 ◽  
Vol 36 (1) ◽  
pp. 570-571
Author(s):  
F. Louchet ◽  
L.P. Kubin
Keyword(s):  
Strain Rate ◽  
Radiation Effects ◽  
Dislocation Line ◽  
Critical Length ◽  
Local Strain ◽  
Local Flow ◽  
Double Kink ◽  
Dislocation Densities ◽  
Frictional Forces ◽  
Local Strain Rate

Investigation of frictional forces -Experimental techniques and working conditions in the high voltage electron microscope have already been described (1). Care has been taken in order to minimize both surface and radiation effects under deformation conditions.Dislocation densities and velocities are measured on the records of the deformation. It can be noticed that mobile dislocation densities can be far below the total dislocation density in the operative system. The local strain-rate can be deduced from these measurements. The local flow stresses are deduced from the curvature radii of the dislocations when the local strain-rate reaches the values of ∿ 10-4 s-1.For a straight screw segment of length L moving by double-kink nucleation between two pinning points, the velocity is :where ΔG(τ) is the activation energy and lc the critical length for double-kink nucleation. The term L/lc takes into account the number of simultaneous attempts for double-kink nucleation on the dislocation line.

Preparation and characterisation of vanadium pentoxide supported rhodium catalyst

1988 ◽  
Vol 46 ◽  
pp. 946-947
Author(s):  
A. Legrouri
Keyword(s):  
Aqueous Solution ◽  
Thermal Decomposition ◽  
Physicochemical Properties ◽  
Surface Area ◽  
Vanadium Pentoxide ◽  
High Purity ◽  
Gas Adsorption ◽  
Rhodium Catalyst ◽  
Optical Methods ◽  
Reducible Oxides

The industrial importance of metal catalysts supported on reducible oxides has stimulated considerable interest during the last few years. This presentation reports on the study of the physicochemical properties of metallic rhodium supported on vanadium pentoxide (Rh/V2O5). Electron optical methods, in conjunction with other techniques, were used to characterise the catalyst before its use in the hydrogenolysis of butane; a reaction for which Rh metal is known to be among the most active catalysts.V2O5 powder was prepared by thermal decomposition of high purity ammonium metavanadate in air at 400 °C for 2 hours. Previous studies of the microstructure of this compound, by HREM, SEM and gas adsorption, showed it to be non— porous with a very low surface area of 6m2/g3. The metal loading of the catalyst used was lwt%Rh on V2Q5. It was prepared by wet impregnating the support with an aqueous solution of RhCI3.3H2O.

Observations of dislocation interactions with recrystallized grain boundaries

1988 ◽  
Vol 46 ◽  
pp. 628-629
Author(s):  
C. W. Price
Keyword(s):  
Dislocation Density ◽  
Grain Boundary ◽  
Strain Rate ◽  
Grain Boundaries ◽  
Dislocation Structure ◽  
Hot Deformation ◽  
Static Recrystallization ◽  
High Dislocation Density ◽  
High Angle ◽  
Dislocation Interactions

Little evidence exists on the interaction of individual dislocations with recrystallized grain boundaries, primarily because of the severely overlapping contrast of the high dislocation density usually present during recrystallization. Interesting evidence of such interaction, Fig. 1, was discovered during examination of some old work on the hot deformation of Al-4.64 Cu. The specimen was deformed in a programmable thermomechanical instrument at 527 C and a strain rate of 25 cm/cm/s to a strain of 0.7. Static recrystallization occurred during a post anneal of 23 s also at 527 C. The figure shows evidence of dissociation of a subboundary at an intersection with a recrystallized high-angle grain boundary. At least one set of dislocations appears to be out of contrast in Fig. 1, and a grainboundary precipitate also is visible. Unfortunately, only subgrain sizes were of interest at the time the micrograph was recorded, and no attempt was made to analyze the dislocation structure.

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