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Microstructural effects on spall fracture in 1008 steel

Description: The brittle fracture behavior of 1008 carbon steel was characterized under dynamic spall loading conditions. The role of grain size, carbide morphology, and high strain rate plastic deformation on the spall induced cleavage fracture were quantitatively estimated following the analysis of Lin, Evans, and Ritchie. 7 refs., 2 figs., 14 tabs.
Date: January 1, 1989
Creator: Zurek, A.K. & Follansbee, P.S.
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Partner: UNT Libraries Government Documents Department
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Microstructural aspects of spallation in copper

Description: Compressive shock waves result in a specific kind of fracture called a spall. The metallurgical aspects of copper spalling and crack or void initiation sites, the effects of grain size and substructure, and the micromechanical aspects of growth and coalescence have not received the detailed attention that other deformation phenomena have received. The present work was stimulated by the observation that under identical shock loading conditions the spall strength of copper can vary between 0.4 to… more
Date: January 1, 1987
Creator: Zurek, A. K. & Frantz, C. E.
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Partner: UNT Libraries Government Documents Department
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DYNAMIC DUCTILE EVOLUTION AND TENSILE FRACTURE: NEW EXPERIMENTAL INSIGHTS FOR MODELS EVALUATION

Description: Under dynamic loading conditions, the rapid nature of the fracture process may simultaneously activate a considerable number of nucleation sites for void formation at the region of the tensile stress field. The growth and coalescence of these voids forms the deformation plane and eventually the fracture surface. Attempts to quantify damage evolution during fracture using microstructural observations, specifically for spallation, were pioneered by Seaman and his coworkers. They performed incipie… more
Date: August 2000
Creator: Zurek, A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Characterization of dynamic fracture in copper under uniaxial stress and uniaxial strain

Description: We have characterized fracture modes in copper under conditions of dynamic uniaxial tension (expanding ring tests) and dynamic uniaxial strain (spall tests). The spall strength in copper was measured as a function of grain size, purity and initial porosity. A unified model for ductile fracture is developed, and a qualitative prediction of the relative magnitudes of porosity and plastic deformational strain for spall and uniaxial tension tests is presented. 17 refs., 6 figs.
Date: January 1, 1988
Creator: Zurek, A. K.; Johnson, J. N. & Frantz, C. E.
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Partner: UNT Libraries Government Documents Department
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Modeling of Final Structure Obtained Under High Strain-Rate Deformation

Description: This paper discusses results of experimental research and a model implementation of the hot deformation process in the two-phase region under high strain rate. Hot compression tests were employed to determine the behavior of deformed microalloyed steel over a range of strain rates (1 x 10{sup -3} s{sup -1} - 2.5 x 10{sup 3} s{sup -1}) and temperatures (650 C - 850 C). The thermomechanical history of the material is consequently integrated in the simulation and compared with the experimental res… more
Date: January 1, 1999
Creator: Majta, J. & Zurek, A.K.
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Partner: UNT Libraries Government Documents Department
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Dynamic mechanical deformation of a SiC[sub p]/Al-Li (8090) composite

Description: The deformation behavior in compression of a silicon carbide particle-reinforced aluminum-lithium (8090) matrix composite, at strain rates in the range of 10[sup [minus]3] to 6500 s[sup [minus]1], was investigated, and compared with that of unreinforced alloy samples. Dynamics strengthening in these composites was found to change depending on the direction of testing. These differences were attributed to differences in the orientation of the reinforcing particles. 4 refs, 5 figs.
Date: January 1, 1993
Creator: Vaidya, R. U. & Zurek, A. K.
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Partner: UNT Libraries Government Documents Department
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Dynamic testing and characterization of pre-fractured ceramic

Description: Nearly all of the mechanical behavior studies of armor ceramics, to date, havc involved the characterization and testing of pristine ceramic material. However, balhstic impact causes a strong shock front to propagate rapidly through the ceramic before much penetration can occur. A strong shock wave can result in localized compressive failure and fragmentation of the ceramic before its amplitude is amnuated below the compressive strength of the ceramic. Goals of this effort were to creatc shock-… more
Date: January 1, 1993
Creator: Zurek, A.K. & Hunter, D.A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Dynamic mechanical deformation of a SiC{sub p}/Al-Li (8090) composite

Description: The deformation behavior in compression of a silicon carbide particle-reinforced aluminum-lithium (8090) matrix composite, at strain rates in the range of 10{sup {minus}3} to 6500 s{sup {minus}1}, was investigated, and compared with that of unreinforced alloy samples. Dynamics strengthening in these composites was found to change depending on the direction of testing. These differences were attributed to differences in the orientation of the reinforcing particles. 4 refs, 5 figs.
Date: June 1, 1993
Creator: Vaidya, R. U. & Zurek, A. K.
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Partner: UNT Libraries Government Documents Department
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Modeling of Developing Inhomogeneities in the Ferrite Microstructure and Resulting Mechanical Properties Induced by Deformation in the Two-Phase Region

Description: The differences in microstructure development of hot deformed steels in the austenite and two-phase region have been effectively described using an integrated computer modeling process. In general, the complete model presented here takes into account kinetics of recrystallization, precipitation, phase transformation, recrystallized austenite grain size, ferrite grain size, and the resulting mechanical properties. The transformation submodel of niobium-microalloyed steels is based on the nucleat… more
Date: July 13, 1999
Creator: Majta, J; Zurek, A.K. & Pietrzyk, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Dynamic strength and strain rate effects on fracture behavior of tungsten and tungsten alloys

Description: An investigation of the stress-strain response as a function of strain rate, spall strength, and dynamic fracture behavior of pure W, W-26Re, W-Ni-Fe and W-Ni-Fe-Co has been performed. Spall strength measurements, obtained in symmetric-impact tests, showed an increase in spall strength from 0.4 GPa for pure tungsten to 3.8 GPa for 90W- 7Ni-3Fe. Concurrent with increase in spall strength was a change in fracture mode from cleavage (for pure W) to a mixture of transgranular and intergranular frac… more
Date: January 1, 1991
Creator: Zurek, A. K. & Gray, G. T., III
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Partner: UNT Libraries Government Documents Department
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Accurate estimation of the elastic properties of porous fibers

Description: A procedure is described to calculate polycrystalline anisotropic fiber elastic properties with cylindrical symmetry and porosity. It uses a preferred orientation model (Tome ellipsoidal self-consistent model) for the determination of anisotropic elastic properties for the case of highly oriented carbon fibers. The model predictions, corrected for porosity, are compared to back-calculated fiber elastic properties of an IM6/3501-6 unidirectional composite whose elastic properties have been deter… more
Date: May 1997
Creator: Thissell, W. R.; Zurek, A. K. & Addessio, F.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Mechanical properties and failure mechanisms of carbon fiber reinforced epoxy laminated composites

Description: The mechanical behavior of quasi-isotropic and unidirectional epoxy-matrix carbon-fiber laminated composites subjected compressive loading at strain rates of 10{sup {minus}3} and 2000 s{sup {minus}1} are described. Failure in the studied composites was dominated by delamination which proceeded by brittle fracture of the epoxy-matrix. The matrix-fiber bonding in these composites is very strong and prevented the occurrence of significant fiber-pullout. The mode I delamination strain energy releas… more
Date: September 1, 1995
Creator: Thissell, W.R.; Zurek, A.K. & Addessio, F.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Ductile damage modeling based on void coalescence and percolation theories

Description: A general model for ductile damage in metals is presented. It includes damage induced by shear stress as well as damage caused by volumetric tension. Spallation is included as a special case. Strain induced damage is also treated. Void nucleation and growth are included, and give rise to strain rate effects. Strain rate effects also arise in the model through elastic release wave propagation between damage centers. The underlying physics of the model is the nucleation, growth, and coalescence o… more
Date: September 1, 1995
Creator: Tonks, D.L.; Zurek, A.K. & Thissell, W.R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Spall behavior and damage evolution in tantalum

Description: The authors conducted a number of plate impact experiments using an 80-mm launcher to study dynamic void initiation, linkup, and spall in tantalum. The tests ranged in shock pressure so that the transition from void initiation, incipient spall, and full spall could be studied. Wave profiles were measured using a velocity interferometry system (VISAR), and targets were recovered using soft recovery techniques. The authors utilized scanning electron microscopy, metallographic cross-sections, and … more
Date: September 1, 1995
Creator: Zurek, A.K.; Thissell, W.R. & Tonks, D.L.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Rate-dependent spallation properties of tantalum

Description: Spallation experiments are conducted on high-purity tantalum using VISAR instrumentation for impact stresses of 9.5 GPa and 6.0 GPa. The high-amplitude experiment exhibits very rapid initial spall separation, while the low-amplitude shot is only slightly above the threshold for void growth and thus exhibits distinct rate-dependent spallation behavior. These experiments are analyzed in terms of simple tensile fracture criteria, a standard rate-dependent void-growth model, and a rate-dependent vo… more
Date: September 1, 1995
Creator: Johnson, J.N.; Hixson, R.S.; Tonks, D.L. & Zurek, A.K.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Mechanical properties, microscopy, and failure mechanisms of carbon fiber reinforced epoxy laminated composites

Description: The mechanical behavior of quasi-isotropic and unidirectional epoxy- matrix carbon-fiber laminated composites subjected to compressive loading at strain rates of 10{sup {minus}3} and 2000 s{sup {minus}1} are described. Failure in the studied composites was dominated by delamination which proceeded by brittle fracture of the epoxy matrix. The matrix-fiber bonding in these composites is very strong and prevented the occurrence of significant fiber-pullout. The mode I delamination strain energy re… more
Date: December 1995
Creator: Thissell, W. R.; Zurek, A. K. & Addessio, F.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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The effect of structural defects in SiC particles on the static & dynamic mechanical response of a 15 volume percent SiC/6061-Al matrix composite

Description: Static and Dynamic mechanical tests, and microstructural examinations performed on a SiC particle reinforced 6061-Al matrix composite indicated that particle cracking significantly affected the strength, strain hardening, and failure mechanism of the composite. Cracks were observed to nucleate and propagate on stacking faults and interfaces between the various phases within the reinforcing SiC particles. Planar defects were the predominant artifacts seen in the SiC particles. Partial dislocatio… more
Date: September 1, 1995
Creator: Vaidya, R. U.; Song, S. G.; Zurek, A. K. & Gray, G. T., III
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Surface modification of Ti{sub 3}Al for improved oxidation resistance

Description: Ti{sub 3}Al has very attractive properties such as low density and high temperature mechanical strength for elevated temperature structural applications. Its major drawback however, is poor oxidation resistance at temperatures above 600{degrees}C. Potential use of Ti{sub 3}Al in high temperature applications depends on its protection from excessive oxidation. To this effect, Al{sub 2}O{sub 3} and Al{sub 3}Ti were selected as coating materials chemically compatible with Ti{sub 3}Al. Al{sub 2}O{s… more
Date: August 1, 1993
Creator: Vaidya, R. U.; Zurek, A. K.; Castro, R.; Sin, Y. W. & Subramanian, K. N.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Micromechanics of spall and damage in tantalum

Description: The authors conducted a series of plate impact experiments using an 80-mm launcher to study dynamic void initiation, linkup, and spall in tantalum. The tests ranged in peak shock pressures so that the effect of peak pressure on the transition from void initiation, incipient spall, and full spall could be studied. Wave profiles were measured using a velocity interferometry system (VISAR), and targets were recovered using {open_quotes}soft{close_quotes} recovery techniques. The authors utilized s… more
Date: May 1, 1996
Creator: Zurek, A.K.; Thissell, W.R.; Johnson, J.N.; Tonks, D.L. & Hixson, R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Spallation modeling in tantalum

Description: A gas gun plate impact spallation experiment has been performed on commercial purity rolled tantalum. The shock pressure achieved was about 7 Gpa and was sufficient to induce incipient spallation. The particle velocity was measured at the free surface of the spalled plate, and the spalled sample was recovered and examined metallographically using image analysis. The quantitative image analysis results are being used to develop a damage model. The model is micromechanically based and involves no… more
Date: September 1, 1997
Creator: Tonks, D.L.; Hixson, R.; Zurek, A.K. & Thissell, W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Quantitative analysis of damage clustering and void linking for spallation modeling in tantalum

Description: In a companion paper in this volume by Zurek et al, micrographs of incipient spallation damage in rolled tantalum were numerically analyzed using image analysis techniques. Void sizes, locations, and overall porosity were measured and tabulated. In this paper, we extend this analysis to include void clusters and examine the correlation between cluster size and the ranges of local instabilities between voids visible in the micrographs. The implications for spallation modeling will be given.
Date: May 1997
Creator: Tonks, D. L.; Zurek, A. K.; Thissell, W. R. & Hixson, R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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