Dislocation mechanics of copper and iron in high rate deformation tests

Armstrong, Ronald W.; Arnold, Werner; Zerilli, Frank J.

doi:10.1063/1.3067764

Cited by 99 publications

(75 citation statements)

References 21 publications

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“…(2.11) by 12) and to use a large enough value of the "diffusion constant" M that σ remains constant as a function of y. I have used both of these strategies for checking the accuracy of the numerical results shown in what follows. When using Eq.…”

Section: E Stressmentioning

confidence: 99%

“…Thanks to the pioneering work of Kocks, Mecking, Follansbee, Meyers and others [8][9][10], we have a first-principles picture of plastic deformation in copper. (Other papers that I have found useful for understanding the present state of this field include [11][12][13].) The trouble is that copper is not observed to undergo ASB, probably because its thermal conductivity is too high.…”

Section: Introductionmentioning

confidence: 99%

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Thermal effects in dislocation theory. II. Shear banding

Langer

2017

Phys. Rev. E

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The thermodynamic dislocation theory presented in preceding papers is used here to describe shear-banding instabilities. Central ingredients of the theory are a thermodynamically defined effective configurational temperature, and a formula for the plastic strain rate determined by thermally activated depinning of entangled dislocations. This plastic strain rate is extremely sensitive to variations of the stress and the ordinary temperature. As a result of this sensitivity, the system undergoes rapid shear banding instabilities when ordinary thermal relaxation is slow. It also undergoes rapid changes from elastic to plastic behaviors at yielding transitions.

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Section: E Stressmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermal effects in dislocation theory. II. Shear banding

Langer

2017

Phys. Rev. E

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“…Consequently, the elastic precursor decay was attributed to the density and initial velocity of pre-existing dislocations. Armstrong et al [10] studied the dislocation relaxation mechanisms during high strain rate shock loading, concluding that dislocation generation dominates plastic relaxation under shock loading. This is because the number of pre-existing dislocations is about two to three orders of magnitude less than that generated during the shock [1,4,7].…”

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confidence: 99%

Attenuation of the Dynamic Yield Point of Shocked Aluminum Using Elastodynamic Simulations of Dislocation Dynamics

et al. 2015

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When a metal is subjected to extremely rapid compression, a shock wave is launched that generates dislocations as it propagates. The shock wave evolves into a characteristic two-wave structure, with an elastic wave preceding a plastic front. It has been known for more than six decades that the amplitude of the elastic wave decays the further it travels into the metal: this is known as "the decay of the elastic precursor". The amplitude of the elastic precursor is a dynamic yield point because it marks the transition from elastic to plastic behaviour. In this letter we provide a full explanation of this attenuation using the first method of dislocation dynamics to treat the time dependence of the elastic fields of dislocations explicitly. We show that the decay of the elastic precursor is a result of the interference of the elastic shock wave with elastic waves emanating from dislocations nucleated in the shock front. Our simulations reproduce quantitatively recent experiments on the decay of the elastic precursor in aluminum, and its dependence on strain rate.The dynamic behaviour of crystalline solids subjected to shock compression plays a central role in diverse applications, including bird strikes in aerospace [1], crashworthiness in the automobile industry [2], and manufacturing processes such as laser shock peening [3], amongst many others. Upon being shocked within a range of strain rates and pressures of typically 10 6 − 10 10 s −1 and 5 − 50GPa [1], the shock front in crystalline materials often displays a characteristic two-wave structure near the loading surface: the plastic wave front leading to the Hugoniot shocked state is preceded by an elastic precursor wave [1]. The amplitude of the elastic precursor wave decays as the wave front advances[1, 4]-a phenomenon known as the 'decay of the elastic precursor'. The amplitude of the elastic wave marks the onset of plasticity, i.e. it is the dynamic yield point. The subsequent plastic wave is commonly ascribed to the generation and motion of dislocations, the agents of plasticity in crystalline solids [9].The cause of its attenuation remains unclear after six decades [4][5][6][7][8]. Clifton and Markenscoff [4] calculated analytically the amplitude attenuation of a planar elastic shock wave caused by the destructive interference of elastic wavelets emanating from pre-existing dislocations set into motion by the passage of a shock wave of infinite strain rate; dislocation generation by the shock was neglected. Consequently, the elastic precursor decay was attributed to the density and initial velocity of pre-existing dislocations. Armstrong et al.[10] studied the dislocation relaxation mechanisms during high strain rate shock loading, concluding that dislocation generation dominates plastic relaxation under shock loading. This is because the number of pre-existing dislocations is about two to three orders of magnitude less than that generated during the shock [1,4,7].In this letter we show that we can account for the experimentally observed residual disloca...

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“…It has been suggested that thermo-mechanical coupling is an important ingredient in this, especially in shock waves that are strong enough to engender stresses well in excess of the elastic moduli (Wallace 1981;Kalantar et al 2005;Kadau et al 2007;Hawreliak et al 2008;Murphy et al 2010). However, it is likely that dislocation nucleation and motion is the dominant microscale phenomenon (Davison & Graham 1979;Armstrong et al 2009). Unfortunately, many different kinds of dislocation configurations are possible, such as classical slip systems involving dislocations, geometrically necessary or otherwise, partial dislocations and stacking faults, and twinned dislocations (Hirth & Lothe 1982;Armstrong et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Mathematical modelling of elastoplasticity at high stress

Howell

Ockendon

2012

Proc. R. Soc. A.

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This study describes a simple mathematical model for one-dimensional elastoplastic wave propagation in a metal in the regime where the applied stress greatly exceeds the yield stress. Attention is focused on the increasing ductility that occurs in the overdriven limit when the plastic wave speed approaches the elastic wave speed. Our model predicts that a plastic compression wave is unable to travel faster than the elastic wave speed, and instead splits into a compressive elastoplastic shock followed by a plastic expansion wave.

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Dislocation mechanics of copper and iron in high rate deformation tests

Cited by 99 publications

References 21 publications

Thermal effects in dislocation theory. II. Shear banding

Thermal effects in dislocation theory. II. Shear banding

Attenuation of the Dynamic Yield Point of Shocked Aluminum Using Elastodynamic Simulations of Dislocation Dynamics

Mathematical modelling of elastoplasticity at high stress

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