Journal ArticleDOI
The effect of grain size on the high-strain, high-strain-rate behavior of copper
TLDR
In this paper, it was shown that the grain-size dependence of shock response can significantly affect the performance of shaped charges, leading to a prediction of the shock threshold stress for twinning as a function of grain size.Abstract:
Copper with four widely differing grain sizes was subjected to high-strain-rate plastic deformation in a special experimental arrangement in which high shear strains of approximately 2 to 7 were generated. The adiabatic plastic deformation produced temperature rises in excess of 300 K, creating conditions favorable for dynamic recrystallization, with an attendant change in the mechanical response. Preshocking of the specimens to an amplitude of 50 GPa generated a high dislocation density; twinning was highly dependent on grain size, being profuse for the 117- and 315-μm grain-size specimens and virtually absent for the 9.5-μm grain-size specimens. This has a profound effect on the subsequent mechanical response of the specimens, with the smaller grain-size material undergoing considerably more hardening than the larger grain-size material. A rationale is proposed which leads to a prediction of the shock threshold stress for twinning as a function of grain size. The strain required for localization of plastic deformation was dependent on the combined grain size/shockinduced microstructure, with the large grain-size specimens localizing more readily. The experimental results obtained are rationalized in terms of dynamic recrystallization, and a constitutive equation is applied to the experimental results; it correctly predicts the earlier onset of localization for the large grain-size specimens. It is suggested that the grain-size dependence of shock response can significantly affect the performance of shaped charges.read more
Citations
More filters
Journal ArticleDOI
Mechanical properties of nanocrystalline materials
TL;DR: The mechanical properties of nanocrystalline materials are reviewed in this paper, with emphasis on their constitutive response and on the fundamental physical mechanisms, including the deviation from the Hall-Petch slope and possible negative slope, the effect of porosity, the difference between tensile and compressive strength, the limited ductility, the tendency for shear localization, fatigue and creep responses.
Journal ArticleDOI
Overview of constitutive laws, kinematics, homogenization and multiscale methods in crystal plasticity finite-element modeling: Theory, experiments, applications
TL;DR: In this paper, a review of continuum-based variational formulations for describing the elastic-plastic deformation of anisotropic heterogeneous crystalline matter is presented and compared with experiments.
Journal ArticleDOI
The onset of twinning in metals: a constitutive description
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.
Journal ArticleDOI
Deformation twinning in nanocrystalline materials
TL;DR: In this paper, a review of deformation twinning in nanocrystalline materials is presented, including deformation twins observed by molecular dynamics simulations and experiments, twinning mechanisms, factors affecting the twinning, analytical models on the nucleation and growth of deformations, interactions between twins and dislocations, and the effects of twins on mechanical and other properties.
Journal ArticleDOI
Microstructural evolution in adiabatic shear localization in stainless steel
TL;DR: In this paper, electron backscattered diffraction (EBSD) was used to reveal gradual lattice rotations of the grains approaching the core of the shear band, leading to the formation of a unique microstructure formed by rotational dynamic recrystallization.
References
More filters
Journal ArticleDOI
An Investigation of the Mechanical Properties of Materials at very High Rates of Loading
TL;DR: In this article, a method of determining the stress-strain relation of materials when stresses are applied for times of the order of 20 microseconds is described, using a modification of the Hopkinson pressure bar and detonators were used to produce large transient stresses.
Book
Physical Metallurgy Principles
TL;DR: Physical Metallurgy Principles as mentioned in this paper is intended for use in an introductory course in physical metallurgy and is designed for all engineering students at the junior or senior level and is largely theoretical, but covers all aspects of physical metelurgy and behavior of metals and alloys.
Journal ArticleDOI
Dislocation-mechanics-based constitutive relations for material dynamics calculations
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.
Journal ArticleDOI
A constitutive description of the deformation of copper based on the use of the mechanical threshold stress as an internal state variable
P.S. Follansbee,U.F. Kocks +1 more
TL;DR: In this article, the axisymmetric deformation behavior of 0.9999 Cu is investigated at strain rates from 10−4 to 104 s−1, and it is shown that the athermal dislocation accumulation rate, or Stage II hardening rate, becomes a strong function of strain rate.
Journal ArticleDOI
On the validity of the hall-petch relationship in nanocrystalline materials
TL;DR: In this paper, a study experimentale de la variation de la durete en fonction de la grosseur de grain for des materiaux nanocristallins is presented.