Laser-induced shock compression of monocrystalline copper: characterization and analysis
TL;DR: In this paper, a method for estimating dislocation densities is proposed, based on nucleation of loops at the shock front and their extension due to residual shear stresses behind the front.
About: This article is published in Acta Materialia.The article was published on 2003-03-14. It has received 219 citations till now. The article focuses on the topics: Slip (materials science) & Crystal twinning.
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TL;DR: In this paper , the surface microstructure of AISI 420 martensitic stainless steel was modified using laser shock peening (LSP) technique, and the deformation mechanisms based on microstructural evolution was investigated.
47 citations
TL;DR: Bringa, Eduardo Marcial as mentioned in this paper, and Marcial, Federico, et al. as mentioned in this paper presented a study at the Lawrence Livermore National Laboratory (LLNL) in the US.
46 citations
TL;DR: A femtosecond Ti:sapphire laser was used to ablate samples of copper, strontium titanate (STO), a nickel alloy Rene 88DT (R88), single crystal silicon, and gallium nitride (GaN) in situ in a focused ion beam scanning electron microscope (FIB-SEM) as mentioned in this paper.
46 citations
TL;DR: In this article, a correspondence theorem which relates the solutions of displacement boundary value problems in classical and couple stress elasticity is formulated and applied to derive the solutions for edge and screw dislocations in an infinite medium.
45 citations
Cites background from "Laser-induced shock compression of ..."
...…with extremely high dislocation densities, as arise in localized or non-localized regions of severe plastic deformation (shear bands, wear, wire drawing, high-pressure torsion, equal channel angular pressing), or in the plastically deformed layer behind the shock front (Meyers et al., 2003)....
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...For example, in a metallic crystal with the dislocation density q ¼ 1010 cm� 2, the radius of influence of each dislocation (defined as the average distance between dislocations) is of the order of q� 1=2 ¼ 100 nm ( Meyers and Chawla, 1999 )....
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TL;DR: In this paper, a modified mechanical threshold stress (MTS) model is applied to the two orientations, incorporating both slip and twinning, and the threshold pressure for twinning is calculated, considering the effect of shock heating.
Abstract: Pure copper monocrystals with [001] and [\(\bar 1\)34] orientations were subjected to ultrashort shock pulses ranging in initial duration from 2.5 to 10 ns, induced by a laser at energies ranging from 10 to 70 MJ/m2. The deformation structure was significantly dependent on the crystallographic orientation and depth from the laser-impacted surface, as characterized by transmission electron microscopy (TEM). The threshold pressure for twinning in the [001] direction was observed to be in the range of 20 to 40 GPa compared with 40 to 60 GPa for the [\(\bar 1\)34] orientation. Dislocation densities were also different for the two orientations, under similar shock conditions. The [\(\bar 1\)34] dislocation density was systematically lower. This is attributed to the activation of fewer slip systems resulting in a lower rate of hardening. The different results found for [001] and [\(\bar 1\)34] copper single crystals are described and effects of pressure decay in [\(\bar 1\)34] specimens are discussed. Differences in the mechanical response between the two orientations are responsible for differences in the shear stress in the specimens at the imposed pressures and associated strains. The [\(\bar 1\)34] orientation is initially subjected to deformation by single slip, (111)[101], which has a Schmid factor of 0.4711 and a well-defined easy glide region followed by a cross-slip regime with secondary slip. The [001] orientation has eight slip systems {111}〈110〉 with identical Schmid factors of 0.4082, which lead to immediate work hardening. At an imposed and prescribed pressure (that establishes the strain), the [\(\bar 1\)34] orientation exhibits a lower shear stress. The orientation dependence of the twinning stress is much lower, as expressed by Schmidt factors. This higher stress for [001] predisposes the onset of twinning in this orientation. The results are interpreted in terms of a criterion in which slip and twinning are considered as competing mechanisms. A constitutive description using a modified mechanical threshold stress (MTS) model is applied to the two orientations, incorporating both slip and twinning. The threshold pressure for twinning is calculated, considering the effect of shock heating. The constitutive description provides a rationale for the experimental results: the calculated thresholds are 17 GPa for [001] and 25 GPa for [\(\bar 1\)34].
44 citations
References
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Book•
27 Sep 1994
TL;DR: In this paper, the authors present a method to produce dynamic deformation at high strain rates by using Shear Bands (Thermoplastic Shear Instabilities) and dynamic fracture.
Abstract: Dynamic Deformation and Waves. Elastic Waves. Plastic Waves. Shock Waves. Shock Waves: Equations of State. Differential Form of Conservation Equations and Numerical Solutions to More Complex Problems. Shock Wave Attenuation, Interaction, and Reflection. Shock Wave-Induced Phase Transformations and Chemical Changes. Explosive-Material Interactions. Detonation. Experimental Techniques: Diagnostic Tools. Experimental Techniques: Methods to Produce Dynamic Deformation. Plastic Deformation at High Strain Rates. Plastic Deformation in Shock Waves. Shear Bands (Thermoplastic Shear Instabilities). Dynamic Fracture. Applications. Indexes.
2,609 citations
"Laser-induced shock compression of ..." refers background or methods in this paper
...[22]....
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...The dislocation density can be expressed as a function of pressure, P, through one of the equations obtained directly from the Rankine–Hugoniot equations and the equation of state [22]:...
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...In a similar manner, the residual temperature, TR, can be obtained from [22]:...
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TL;DR: An improved description of copper and ironcylinder impact (Taylor) test results has been obtained through the use of dislocation-mechanics-based constitutive relations in the Lagrangian material dynamics computer program EPIC•2.
Abstract: An improved description of copper‐ and iron‐cylinder impact (Taylor) test results has been obtained through the use of dislocation‐mechanics‐based constitutive relations in the Lagrangian material dynamics computer program EPIC‐2. The effects of strain hardening, strain‐rate hardening, and thermal softening based on thermal activation analysis have been incorporated into a reasonably accurate constitutive relation for copper. The relation has a relatively simple expression and should be applicable to a wide range of fcc materials. The effect of grain size is included. A relation for iron is also presented. It also has a simple expression and is applicable to other bcc materials but is presently incomplete, since the important effect of deformation twinning in bcc materials is not included. A possible method of acounting for twinning is discussed and will be reported on more fully in future work. A main point made here is that each material structure type (fcc, bcc, hcp) will have its own constitutive beha...
1,718 citations
TL;DR: In this article, a constitutive expression for the twinning stress in BCC metals is developed using dislocation emission from a source and the formation of pile-ups, as rate-controlling mechanism.
1,366 citations
TL;DR: In this paper, a periodic relation between shear stress and atomic shear displacement is assumed to hold along the most highly stressed slip plane emanating from a crack tip, which allows some small slip displacement to occur near the tip in response to small applied loading and, with increase in loading, the incipient dislocation configuration becomes unstable and leads to a fully formed dislocation which is driven away from the crack.
Abstract: Dislocation nucleation from a stressed crack tip is analyzed based on the Peierls concept. A periodic relation between shear stress and atomic shear displacement is assumed to hold along the most highly stressed slip plane emanating from a crack tip. This allows some small slip displacement to occur near the tip in response to small applied loading and, with increase in loading, the incipient dislocation configuration becomes unstable and leads to a fully formed dislocation which is driven away from the crack. An exact solution for the loading at that nucleation instability is developed via the J -integral for the case when the crack and slip planes coincide, and an approximate solution is given when they do not. Solutions are also given for emission of dissociated dislocations, especially partial dislocation pairs in fcc crystals. The level of applied stress intensity factors required for dislocation nucleation is shown to be proportional to √γ us , where γ us , the unstable stacking energy, is a new solid state parameter identified by the analysis. It is the maximum energy encountered in the block-like sliding along a slip plane, in the Burgers vector direction, of one half of a crystal relative to the other. Approximate estimates of γ us are summarized and the results are used to evaluate brittle vs ductile response in fcc and bcc metals in terms of the competition between dislocation nucleation and Griffith cleavage at a crack tip. The predictions seem compatible with known behavior and also show that in many cases solids which are predicted to first cleave under pure mode I loading should instead first emit dislocations when that loading includes very small amounts of mode II and III shear. The analysis in this paper also reveals a feature of the near-tip slip distribution corresponding to the saddle point energy configuration for cracks that are loaded below the nucleation threshold, as is of interest for thermal activation.
1,320 citations
01 Jan 1940
TL;DR: In this paper, the size of a dislocation and critical shear stress for its motion were calculated for a single dislocation with respect to the size and motion of the dislocation.
Abstract: Calculations are made of the size of a dislocation and of the critical shear stress for its motion.
1,226 citations