Investigating phase transitions and strength in single-crystal sapphire using shock–reshock loading techniques

Reinhart, William D.; Chhabildas, L.C.; Vogler, Tracy

doi:10.1016/j.ijimpeng.2006.09.083

Cited by 39 publications

(36 citation statements)

References 15 publications

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“…This initial QE release observed in nearly all tests is consistent with previous studies on aluminum [2,3] and is typical of other metals such as beryllium [26], copper [27], tungsten [28,29], and even within ceramics [4,7,30]. In analyzing the unloading and reloading profiles to estimate strength properties, it is usually assumed that the initial release from the shocked state is also isentropic, which is a good assumption for both QE and plastic unloading and reloading waves because the stress deviators make a relatively low contribution to entropy or temperature increase [31].…”

Section: Resultssupporting

confidence: 90%

Flow Strength of 6061-T6 Aluminum in the Solid, Mixed Phase, Liquid Regions

Reinhart

Alexander

Chhabildas

et al. 2015

J. dynamic behavior mater.

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Shock waves have been used to determine material properties under high shock stresses and very-high loading rates. The objectives of the present experiments were to obtain information on the mechanical response of aluminum at shock stresses approaching and in the solidliquid mixed phase regions, which is not routinely available with other methods. The accurate determination of compressive strength under shock compression has proven to be difficult due to the need for accurate reshock experiments from the initial shock state, with the consequence that estimates of shear strength have been limited to relatively low stresses. In this investigation, we have significantly improved the shock/reloading technique to obtain high quality data on reloading from the shocked states for initial shock stresses up to about 80 GPa. This has allowed the first self-consistent determination of the shear strength and the initial shear stress state of aluminum in the shocked state in this stress region. In addition, unloading experiments have been extended to over 140 GPa to understand how the strength of the material behaves when shocked beyond the solid-liquid mixed phase boundary. The combined wave velocity and strength data provide estimates of the onset and completion of shock-induced melting.

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Section: Resultssupporting

confidence: 90%

Flow Strength of 6061-T6 Aluminum in the Solid, Mixed Phase, Liquid Regions

Reinhart

Alexander

Chhabildas

et al. 2015

J. dynamic behavior mater.

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“…Driving forces for slip, twinning and fracture can be computed and compared with (4.1)-(4.3) and observations from shock physics experiments (Barker & Hollenbach 1970;Graham & Brooks 1971;Chen & Howitt 1998;Reinhart et al 2006) to provide more suitable estimates for yield and failure criteria. This analysis also provides insight into which inelastic deformation mechanisms are most likely responsible for macroscopic yielding in shock physics experiments.…”

Section: Application: Sapphire Single Crystalsmentioning

confidence: 99%

“…Stress-induced phase transformations are thought to occur only at very high pressures (approx. 79 GPa; Reinhart et al 2006) and are not considered.…”

Section: Application: Sapphire Single Crystalsmentioning

confidence: 99%

A continuum description of nonlinear elasticity, slip and twinning, with application to sapphire

Clayton

2008

Proc. R. Soc. A.

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A model is developed for elasticity, plasticity and twinning in anisotropic single crystals subjected to large deformations. Dislocation glide and deformation twinning are dissipative, while energy storage mechanisms associated with dislocation lines and twin boundaries are described via scalar internal state variables. Concepts from continuum crystal plasticity are invoked, with shearing rates on discrete glide and twinning systems modelled explicitly. The model describes aspects of thermomechanical behaviour of single crystals of alumina over a range of loading conditions. Resolved shear stresses necessary for glide or twin nucleation at low to moderate temperatures are estimated from nonlinear elastic calculations, theoretical considerations of Peierls barriers and stacking fault energies and observations from shock physics experiments. These estimates are combined with the existing data from high-temperature experiments to provide initial yield conditions spanning a wide range of temperatures. The model reflects hardening of glide and twin systems from dislocations accumulated during basal slip. Residual elastic volume changes, predicted from nonlinear elastic considerations and approximated dislocation line energies, are positive and proportional to the dislocation line density. While the model suggests that generation of very large dislocation densities could influence the pressure-volume response, volume increases from defects are predicted to be small in crystals deformed via basal glide on a single system.

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“…The single crystal elastic constants for sapphire, c ij , are Thus, in a polycrystalline alumina, basal slip will always be initiated first, unless the slip planes are oriented so that the resolved shear stress on the basal plane is small, and this will lead to stress concentrations which will result in intergranular cracking. 31,32 The most complete of these is that by Graham and Brooks. 28 Further, material parameters are temperature dependent even in polycrystalline materials.…”

Section: Methodsmentioning

confidence: 99%

On the Hugoniot elastic limit in polycrystalline alumina

Bourne

Millett

Chen

et al. 2007

Journal of Applied Physics

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The use of polycrystalline ceramics in engineering applications requires a better knowledge of microstructural response than exists at present. The continuum response of the alumina AD995 to shock loading has been extensively investigated. This work aims to connect microstructural response with continuum observations. Over recent years, workers have reported failure in various polycrystalline ceramics occurring behind a propagating front running behind the shock. These phenomena have been investigated using embedded stress sensors and a recovery technique that has allowed the observation of the microstructure above and below the Hugoniot elastic limit ͑HEL͒. These results are brought together here to explain the observed behavior. The failure front velocity is found to change with the applied stress, in particular, it slows markedly as the HEL is exceeded. Further, the curvature of histories recorded by sensors may be related to the observed response. The evidence in the microstructure shows that the response below HEL is dominated by the intergranular failure, while above it by plasticity in grains ͑including twinning͒, which alters the deformation and failure characteristics. These microstructural features are combined with the continuum observations to review the response of the alumina.

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Investigating phase transitions and strength in single-crystal sapphire using shock–reshock loading techniques

Cited by 39 publications

References 15 publications

Flow Strength of 6061-T6 Aluminum in the Solid, Mixed Phase, Liquid Regions

Flow Strength of 6061-T6 Aluminum in the Solid, Mixed Phase, Liquid Regions

A continuum description of nonlinear elasticity, slip and twinning, with application to sapphire

On the Hugoniot elastic limit in polycrystalline alumina

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