A. Odeshi - Academia.edu (original) (raw)

Papers by A. Odeshi

International Journal of Modern Physics B, 2008

There are at present several applications where high strength ceramics have replaced metals that ... more There are at present several applications where high strength ceramics have replaced metals that are subjected to high speed impact from projectiles. This requires an evaluation of behavior of ceramics under impact at high strain rates. This current study provides information on high strain-rate behavior of alumina tested in shear using torsional Hopkinson bar. Dynamic stress-strain curves were generated to

DYMAT 2009 - 9th International Conferences on the Mechanical and Physical Behaviour of Materials under Dynamic Loading, 2009

A high hardness armor (HHA) steel plate was subjected to a standard V50 ballistic impact test. Mi... more A high hardness armor (HHA) steel plate was subjected to a standard V50 ballistic impact test. Microstructural evolution leading to deformation and perforation of the plates during projectile penetration is investigated. Penetration of the steel plate by the projectile is promoted by shear strain localization and occurrence of adiabatic shear bands which were observed around the perforations. Cracking of the shear bands triggered the failure and perforation of the steel plate during the ballistic impact. The primary transformed bands enveloping the projectile has an average thickness of about 55 mm, while narrower secondary shear bands of about 12 mm wide branched out of the primary band leading to secondary cracking which propagated from the wall of perforation into the armor plate.

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing - MATER SCI ENG A-STRUCT MATER, 2009

The deformation and fracture of quench-hardened and tempered AISI 4340 steel samples at high stra... more The deformation and fracture of quench-hardened and tempered AISI 4340 steel samples at high strain-rates were investigated. The steel samples were quench-hardened and tempered at 205, 315 or 425°C for 1h before they were subjected to high velocity impact testing. Irrespective of the tempered condition of the martensitic steel samples, failure occurred predominantly by ductile shear fracture along the path of heat waves generated in the material during impact. Adiabatic heating and the associated thermal softening were found to play a more dominant role in the deformation and fragmentation of the samples than the dislocation multiplication effect of plastic deformation. Rather than the anticipated cleavage fracture or shattering of the quench-hardened steel samples into several fragments, the test specimens showed clear evidence of ductile shear and knobby fracture modes for all tempering temperatures. The elongated dimples observed on the fracture surface of the samples tempered at...

Journal of Materials Processing Technology, 2005

Some results of an experimental study on high strain rate deformation of a low alloy steel are di... more Some results of an experimental study on high strain rate deformation of a low alloy steel are discussed in this paper. Cylindrical specimens of the steel in quench-hardened and tempered condition were subjected to high strain rate deformation by direct impact using a modified Split Hopkinson Pressure Bar (SHPB). The deformation process is dominated by stress collapse due to thermal softening effect of adiabatic heating in some narrow bands within the material under deformation. The time for the onset of the stress collapse leading to strain localization was found to increase with strain rate. The critical strain at which adiabatic shearing occurs depends on the strain rate and microstructure. Steel samples that were tempered at 425 • C exhibits greater tendency to adiabatic shearing than those tempered at 315 • C. The time and critical strain for the onset of stress collapse and adiabatic shearing are lower. Whereas single white adiabatic shear bands were observed to initiate and propagate during the high strain rate deformation in samples tempered at 315 • C, multiple shear bands were found to initiate and dynamically propagate in the samples tempered at 425 • C. Of these multiple shear bands, the one closest to the centre of the cylindrical test pieces were white etching bands while the rest appeared as deformed bands. The higher tendency of the samples tempered at 425 • C to formation of adiabatic shear bands has been attributed to increased perturbation in the steel samples as a result of the heat treatment procedure. The type of shear bands formed in the steel at high strain-rates can be explained as due to the accompanying fragmentation of martensite laths and dissolution of carbides during adiabatic heating and shearing, which eventually determines the size of the micro-constituents of the adiabatic shear band and the resolvability by optical microscopy.

Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2007

Alumina particle-reinforced aluminum 6061-T6 composites are subjected to deformation at high stra... more Alumina particle-reinforced aluminum 6061-T6 composites are subjected to deformation at high strain rates in torsion and in compression using Hopkinson bars. The volume content of alumina particles in the aluminum alloy are 10 and 20 pct. While occurrence of adiabatic shear bands is evident under compression, the specimens fractured rapidly in torsion at high strain rates. Fracture occurs in both testing

Journal de Physique IV (Proceedings), 2006

High strength materials such as used as armor plate have been investigated in torsion using Split... more High strength materials such as used as armor plate have been investigated in torsion using Split Hopkinson Bars for the purpose of obtaining stress-strain curves and for examining the mechanism of plastic deformation in terms of mechanical instability due to thermal softening at high strain rates. A comparative study of the plastic deformation behavior of RHA steel, Aluminum 5083 H131 alloy and Tungsten A90S alloy under the loading condition at high strain rates is carried out and the effect of strain rate on shear flow stress and stress-strain profiles is presented. Strain rate sensitivities of the materials are evaluated and discussed with respect to mechanical instability and adiabatic shear strain localization.

Canadian Metallurgical Quarterly, 2012

Materials Science and Engineering: A, 2015

Mechanical and microstructural responses of AA 2017-T451 and AA 2624-T351 aluminum alloys to dyna... more Mechanical and microstructural responses of AA 2017-T451 and AA 2624-T351 aluminum alloys to dynamic impact loading were investigated using the split Hopkinson pressure bar (SHPB) and electron backscattered diffraction (EBSD) analysis. Although both alloys were subjected to the same impact loads, the strain rate developed in the AA 2017 alloy was higher and the peak stress in the dynamic stressstrain curve is observed to be higher for the AA 2624 alloy. The higher deformation resistance observed in the AA 2624 alloy under dynamic impact loading is a consequence of its higher capacity for strain hardening that effectively overcomes the effects of thermal softening and dynamic recovery during impact loading. Strain hardening is quickly dominated by thermal softening in AA 2017-T451 alloy leading to a lower resistance to deformation and a higher tendency to form transformed adiabatic shear bands consisting of dynamic recrystallized (DRX) grains as observed in the EBSD measurements. Although shear bands were also observed in the AA 2624 alloy, EBSD analyses suggest that the shear band region consist of deformed grains with high intensity of localized strains and dislocation accumulation. Whereas both alloys exhibited nearly the same high angle grain boundary fractions before dynamic impact loading, a higher in-grain (kernel) misorientation were observed in the AA 2624 alloy after impact. Larger fraction of high angle grain boundaries (HAGBs) was observed in the impacted AA 2017 alloy. The results of the EBSD measurements on both the as-received alloys and the impacted specimens such as grain boundary fractions, area fractions of selected fibers as well as Schmid factor and the corresponding Schmid factor distribution are discussed. The study provides a consolidated understanding of the microstructure developments during deformation and its relation to the mechanical response of the alloys to dynamic impact loading.

International Journal of Modern Physics B, 2008

There are at present several applications where high strength ceramics have replaced metals that ... more There are at present several applications where high strength ceramics have replaced metals that are subjected to high speed impact from projectiles. This requires an evaluation of behavior of ceramics under impact at high strain rates. This current study provides information on high strain-rate behavior of alumina tested in shear using torsional Hopkinson bar. Dynamic stress-strain curves were generated to

DYMAT 2009 - 9th International Conferences on the Mechanical and Physical Behaviour of Materials under Dynamic Loading, 2009

A high hardness armor (HHA) steel plate was subjected to a standard V50 ballistic impact test. Mi... more A high hardness armor (HHA) steel plate was subjected to a standard V50 ballistic impact test. Microstructural evolution leading to deformation and perforation of the plates during projectile penetration is investigated. Penetration of the steel plate by the projectile is promoted by shear strain localization and occurrence of adiabatic shear bands which were observed around the perforations. Cracking of the shear bands triggered the failure and perforation of the steel plate during the ballistic impact. The primary transformed bands enveloping the projectile has an average thickness of about 55 mm, while narrower secondary shear bands of about 12 mm wide branched out of the primary band leading to secondary cracking which propagated from the wall of perforation into the armor plate.

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing - MATER SCI ENG A-STRUCT MATER, 2009

The deformation and fracture of quench-hardened and tempered AISI 4340 steel samples at high stra... more The deformation and fracture of quench-hardened and tempered AISI 4340 steel samples at high strain-rates were investigated. The steel samples were quench-hardened and tempered at 205, 315 or 425°C for 1h before they were subjected to high velocity impact testing. Irrespective of the tempered condition of the martensitic steel samples, failure occurred predominantly by ductile shear fracture along the path of heat waves generated in the material during impact. Adiabatic heating and the associated thermal softening were found to play a more dominant role in the deformation and fragmentation of the samples than the dislocation multiplication effect of plastic deformation. Rather than the anticipated cleavage fracture or shattering of the quench-hardened steel samples into several fragments, the test specimens showed clear evidence of ductile shear and knobby fracture modes for all tempering temperatures. The elongated dimples observed on the fracture surface of the samples tempered at...

Journal of Materials Processing Technology, 2005

Some results of an experimental study on high strain rate deformation of a low alloy steel are di... more Some results of an experimental study on high strain rate deformation of a low alloy steel are discussed in this paper. Cylindrical specimens of the steel in quench-hardened and tempered condition were subjected to high strain rate deformation by direct impact using a modified Split Hopkinson Pressure Bar (SHPB). The deformation process is dominated by stress collapse due to thermal softening effect of adiabatic heating in some narrow bands within the material under deformation. The time for the onset of the stress collapse leading to strain localization was found to increase with strain rate. The critical strain at which adiabatic shearing occurs depends on the strain rate and microstructure. Steel samples that were tempered at 425 • C exhibits greater tendency to adiabatic shearing than those tempered at 315 • C. The time and critical strain for the onset of stress collapse and adiabatic shearing are lower. Whereas single white adiabatic shear bands were observed to initiate and propagate during the high strain rate deformation in samples tempered at 315 • C, multiple shear bands were found to initiate and dynamically propagate in the samples tempered at 425 • C. Of these multiple shear bands, the one closest to the centre of the cylindrical test pieces were white etching bands while the rest appeared as deformed bands. The higher tendency of the samples tempered at 425 • C to formation of adiabatic shear bands has been attributed to increased perturbation in the steel samples as a result of the heat treatment procedure. The type of shear bands formed in the steel at high strain-rates can be explained as due to the accompanying fragmentation of martensite laths and dissolution of carbides during adiabatic heating and shearing, which eventually determines the size of the micro-constituents of the adiabatic shear band and the resolvability by optical microscopy.

Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2007

Alumina particle-reinforced aluminum 6061-T6 composites are subjected to deformation at high stra... more Alumina particle-reinforced aluminum 6061-T6 composites are subjected to deformation at high strain rates in torsion and in compression using Hopkinson bars. The volume content of alumina particles in the aluminum alloy are 10 and 20 pct. While occurrence of adiabatic shear bands is evident under compression, the specimens fractured rapidly in torsion at high strain rates. Fracture occurs in both testing

Journal de Physique IV (Proceedings), 2006

High strength materials such as used as armor plate have been investigated in torsion using Split... more High strength materials such as used as armor plate have been investigated in torsion using Split Hopkinson Bars for the purpose of obtaining stress-strain curves and for examining the mechanism of plastic deformation in terms of mechanical instability due to thermal softening at high strain rates. A comparative study of the plastic deformation behavior of RHA steel, Aluminum 5083 H131 alloy and Tungsten A90S alloy under the loading condition at high strain rates is carried out and the effect of strain rate on shear flow stress and stress-strain profiles is presented. Strain rate sensitivities of the materials are evaluated and discussed with respect to mechanical instability and adiabatic shear strain localization.

Canadian Metallurgical Quarterly, 2012

Materials Science and Engineering: A, 2015

Mechanical and microstructural responses of AA 2017-T451 and AA 2624-T351 aluminum alloys to dyna... more Mechanical and microstructural responses of AA 2017-T451 and AA 2624-T351 aluminum alloys to dynamic impact loading were investigated using the split Hopkinson pressure bar (SHPB) and electron backscattered diffraction (EBSD) analysis. Although both alloys were subjected to the same impact loads, the strain rate developed in the AA 2017 alloy was higher and the peak stress in the dynamic stressstrain curve is observed to be higher for the AA 2624 alloy. The higher deformation resistance observed in the AA 2624 alloy under dynamic impact loading is a consequence of its higher capacity for strain hardening that effectively overcomes the effects of thermal softening and dynamic recovery during impact loading. Strain hardening is quickly dominated by thermal softening in AA 2017-T451 alloy leading to a lower resistance to deformation and a higher tendency to form transformed adiabatic shear bands consisting of dynamic recrystallized (DRX) grains as observed in the EBSD measurements. Although shear bands were also observed in the AA 2624 alloy, EBSD analyses suggest that the shear band region consist of deformed grains with high intensity of localized strains and dislocation accumulation. Whereas both alloys exhibited nearly the same high angle grain boundary fractions before dynamic impact loading, a higher in-grain (kernel) misorientation were observed in the AA 2624 alloy after impact. Larger fraction of high angle grain boundaries (HAGBs) was observed in the impacted AA 2017 alloy. The results of the EBSD measurements on both the as-received alloys and the impacted specimens such as grain boundary fractions, area fractions of selected fibers as well as Schmid factor and the corresponding Schmid factor distribution are discussed. The study provides a consolidated understanding of the microstructure developments during deformation and its relation to the mechanical response of the alloys to dynamic impact loading.