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Dislocation and Grain Derived Theory for Kinematic Metrics of Finite Deformation to Replace Existing Elastic-Plastic Phenomenological Metrics
Published online by Cambridge University Press: 15 February 2011
Abstract
Most existing continuum kinematic metrics used for correlating experimental data sets from finite deformation tests are traceable to a two reference state configuration analysis proposed primarily by Lee[1]; namely, a deformed elastic-plastic back to an idealized zero stress plastic state. These analyses admit that material discontinuities would exist in arriving at a virtual state of zero residual stress, however, the elastic-plastic deformation process is considered a mathematically continuous spatial function process. Hence, atomic length scale metrics are not analytically introduced because of the continuity requirements of the embedded deformation function space. This is not a valid physical description given that the microscopic dislocation mechanism for the non-recoverable kinematics of crystal material deformations creates discontinuities between atomic planes of grains in a material sample. In addition, the mathematical structure of current continuum kinematic metrics is deterministic. This is also not physically realistic in describing materials' responses that are dependent on intrinsic metallic grain characteristics. This follows since an ensemble of material specimens have a randomness for the physical numbers per unit material volume per unit species volume for both dislocation density and grain lattice structure density function characteristics. These random functions are best described as classical probability density functions in a spatial, time, and species variable domain. A stochastic description for dislocation density in solids has been developed, and explicitly introduced in a finite deformational functional[2]. This finite deformational functional will be extended to include an explicit dependence on a stochastic grain lattice structure density function. Finally, analyses of this dislocation-grain deformational functional provide stochastic kinematic metrics for void or microcrack-type opening deformations at grain boundaries that contain length scale measures based on the physical attributes of both dislocations and grains.
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- Copyright © Materials Research Society 2003