scholarly journals A dynamic discrete dislocation plasticity method for the simulation of plastic relaxation under shock loading

2013 ◽  
Vol 469 (2156) ◽  
pp. 20130141 ◽  
Author(s):  
Beñat Gurrutxaga-Lerma ◽  
Daniel S. Balint ◽  
Daniele Dini ◽  
Daniel E. Eakins ◽  
Adrian P. Sutton
Keyword(s):  
Shock Loading ◽  
Time Dependent ◽  
Plastic Relaxation ◽  
Uniform Motion ◽  
Infinite Plane ◽  
Two Dimensional ◽  
Elastic Fields ◽  
Discrete Dislocation ◽  
Dislocation Plasticity ◽  
Discrete Dislocations

In this article, it is demonstrated that current methods of modelling plasticity as the collective motion of discrete dislocations, such as two-dimensional discrete dislocation plasticity (DDP), are unsuitable for the simulation of very high strain rate processes (10 6  s −1 or more) such as plastic relaxation during shock loading. Current DDP models treat dislocations quasi-statically, ignoring the time-dependent nature of the elastic fields of dislocations. It is shown that this assumption introduces unphysical artefacts into the system when simulating plasticity resulting from shock loading. This deficiency can be overcome only by formulating a fully time-dependent elastodynamic description of the elastic fields of discrete dislocations. Building on the work of Markenscoff & Clifton, the fundamental time-dependent solutions for the injection and non-uniform motion of straight edge dislocations are presented. The numerical implementation of these solutions for a single moving dislocation and for two annihilating dislocations in an infinite plane are presented. The application of these solutions in a two-dimensional model of time-dependent plasticity during shock loading is outlined here and will be presented in detail elsewhere.

The Role of Homogeneous Nucleation in Planar Dynamic Discrete Dislocation Plasticity

2015 ◽  
Vol 82 (7) ◽  
Author(s):  
Benat Gurrutxaga-Lerma ◽  
Daniel S. Balint ◽  
Daniele Dini ◽  
Daniel E. Eakins ◽  
Adrian P. Sutton
Keyword(s):  
Homogeneous Nucleation ◽  
Dislocation Dynamics ◽  
Plastic Relaxation ◽  
Strain Rates ◽  
Dislocation Generation ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Dislocation Plasticity ◽  
Dislocation Densities

Homogeneous nucleation of dislocations is the dominant dislocation generation mechanism at strain rates above 108 s−1; at those rates, homogeneous nucleation dominates the plastic relaxation of shock waves in the same way that Frank–Read sources control the onset of plastic flow at low strain rates. This article describes the implementation of homogeneous nucleation in dynamic discrete dislocation plasticity (D3P), a planar method of discrete dislocation dynamics (DDD) that offers a complete elastodynamic treatment of plasticity. The implemented methodology is put to the test by studying four materials—Al, Fe, Ni, and Mo—that are shock loaded with the same intensity and a strain rate of 1010 s−1. It is found that, even for comparable dislocation densities, the lattice shear strength is fundamental in determining the amount of plastic relaxation a material displays when shock loaded.

Discrete Dislocation Plasticity Approach to Fast Moving Dislocations

1999 ◽  
Vol 578 ◽  
Author(s):  
A. Roos ◽  
E. Metselaar ◽  
J.Th.M. De Hosson ◽  
E. van der Giessen
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Strain Rates ◽  
Two Dimensional ◽  
Relativistic Case ◽  
Discrete Dislocation ◽  
Dislocation Plasticity ◽  
Isotropic Elasticity ◽  
Very High

AbstractThis paper concentrates on application of the so-called Discrete Dislocation Plasticity to high strain rate deformations. In particular the question is addressed if the DDP approach may capture the specific processes taking place at high strain rates. In particular the paper reports on tests of the validity of some approximations and provides some sample runs to show the applicability of the method. In assessing the results, one has to keep in mind two underpinning aspects: (1) the model is two-dimensional and (2) the results hold only in the regime where linear isotropic elasticity is valid. It was concluded that accelerations can not be neglected at very high strain rate deformations, both for the conventional and the relativistic case.

Comparison of Recovery and Recrystallization in Stainless Steel Following Plane-Wave Shock Loading and Explosive Forming

1970 ◽  
Vol 28 ◽  
pp. 428-429 ◽  
Author(s):  
J. A. Korbonski ◽  
L. E. Murr
Keyword(s):  
Stainless Steel ◽  
Shock Loading ◽  
Pressure Pulse ◽  
Shock Pressure ◽  
304 Stainless Steel ◽  
Strain Rates ◽  
Two Dimensional ◽  
Aisi 304 Stainless Steel ◽  
Aisi 304 ◽  
Explosive Forming

Comparison of recovery rates in materials deformed by a unidimensional and two dimensional strains at strain rates in excess of 104 sec.−1 was performed on AISI 304 Stainless Steel. A number of unidirectionally strained foil samples were deformed by shock waves at graduated pressure levels as described by Murr and Grace. The two dimensionally strained foil samples were obtained from radially expanded cylinders by a constant shock pressure pulse and graduated strain as described by Foitz, et al.

scholarly journals Integrable unsteady motion with an application to ocean eddies

1998 ◽  
Vol 5 (3) ◽  
pp. 145-151
Author(s):  
A. D. Kirwan, Jr. ◽  
B. L. Lipphardt, Jr.
Keyword(s):  
Potential Vorticity ◽  
Particle Motion ◽  
Gulf Stream ◽  
Incompressible Flows ◽  
Unsteady Motion ◽  
Ring System ◽  
Time Dependent ◽  
Two Dimensional ◽  
Ocean Eddies ◽  
Multilayered Systems

Abstract. Application of the Brown-Samelson theorem, which shows that particle motion is integrable in a class of vorticity-conserving, two-dimensional incompressible flows, is extended here to a class of explicit time dependent dynamically balanced flows in multilayered systems. Particle motion for nonsteady two-dimensional flows with discontinuities in the vorticity or potential vorticity fields (modon solutions) is shown to be integrable. An example of a two-layer modon solution constrained by observations of a Gulf Stream ring system is discussed.

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