Dislocation evolution during plastic deformation: Equations vs. discrete dislocation dynamics study

Abstract

Explaining the work hardening behavior of metals has been a big challenge over the past eighty years. Although individual processes are well understood, the study of the overall effects of these processes was difficult before the emergence of computer modeling. In this paper, we employ discrete dislocation dynamics to establish a continuum-based model for the evolution of the dislocation structure in polycrystalline thin films. The Taylor equation is evaluated and expressions are developed for the density of active dislocation sources, as well as dislocation nucleation and annihilation rates. We demonstrate how the size effect naturally enters the evolution equation. Very good agreement between the simulation and the model results is obtained. The current approach is based on a two-dimensional discrete dislocation dynamics model, but can be extended to three-dimensional models.

Hardening and Strain Localisation in Helium-Ion-Implanted Tungsten

“…where the term 𝐶 ′ 𝐺 𝑏 √𝜌 𝐺𝑁𝐷 accounts for strain hardening using a Taylor hardening law 32,33 and 𝜏 𝐻 (with initial value 𝜏 𝐻 0 at t = 0) accounts for the increased resistance to dislocation glide by the helium-implantation-induced defects. 𝐺 is the shear modulus of tungsten, 𝜏 𝑐 0 the initial critically resolved shear stress (CRSS), 𝜌 𝐺𝑁𝐷 the sum of the GNDs produced on all slip-systems and 𝐶 ′ the proportion of GNDs considered contributing to hardening.…”

Modified deformation behaviour of self-ion irradiated tungsten: A combined nano-indentation, HR-EBSD and crystal plasticity study

“…The evolution of these GNDs increases the number of obstacles encountered by gliding dislocations. The second term accounts for this strain hardening using a Taylor hardening law (Davoudi and Vlassak, 2018;Taylor, 1934) where 𝐶 ′ is a hardening factor, 𝐺 the shear modulus of tungsten and 𝜌 𝐺𝑁𝐷 the sum of the GNDs produced across all slipsystems. Only two parameters were fitted to the experimental results (nano-indentation and AFM surface profile) of the unimplanted sample; 𝜏 𝑐 0 , and 𝐶 ′ .…”

Nonlinear ultrasonic evaluation of disorderedly clustered pitting damage using an in situ sensor network

“…Featuring a large quantity of clustered, localized, small-scale craters, and cracks with numerous dislocations and sub-grains, a pitted region introduces plastic deformation and consequently plastic strains to polycrystalline solids of the material. [35][36][37] The interaction of craters and cracks with a probing GUW embraces two alternating phases: (1) crack opening during the tensile stage of GUW propagation, which triggers wave scattering and mode conversion and (2) crack closing during the compressional stage, in which wave propagation remains unchanged without distortion. Together, both jointly drive the crack to manifest a ''breathing'' manner and give rise to the generation of CAN.…”