Crystal plasticity is a long-standing problem in computational materials. Understandingdeep mechanism of plasticity, such as dislocation, multiplication, interaction, has been a
great challenge of major scientific significance since there exist many physical and technical
difficulties.
It is believed that plasticity in a crystal is strongly influenced by the aggregated dislocations.
The aggregated dislocations usually form definite dislocation networks or substrates when
plastic loading happens and the networks or substrates are usually called as dislocation
patterns. It is commonly known that dislocation patterns and their interactions determine
plasticity of crystalline material. Based on lots of experimental observations, it is found
that under the same loading and boundary conditions, the specific type of atomic crystal
structures usually generates very similar dislocation patterns. Therefore, it is believed that
the dislocation patterns emerged in crystalline materials are strongly related to the atomic
crystal structures of crystalline materials at the beginning stage of plastic deformation.
On the other hand, for metallic materials, especially Body-centered Cubic (BCC) crystal
materials, the thermally-activated dislocation glide has a tight link to crystal plasticity, such
as constitutive relation (stress-strain curve), screw dislocation glide and temperature-induced
Peierls-stress. Because the thermally-activated screw dislocation glide results to thermallyinduced
Peierls-stress and yield stress decreasing.
In this dissertation, it is developed that a temperature-dependent higher-order Cauchy-
Born (THCB) rule for Multiscale Crystal Defects Dynamics (MCDD) of crystalline solids
based on harmonic approximation. The THCB rule is employed to develop an atomistic-informed
constitutive model and the corresponding higher order stress are used to model
crystal plasticity of single crystals. It is shown in the dissertation that the developed finite
temperature atomistic-informed crystal plasticity finite element method is able to capture the
temperature-dependent dislocation substructure and hence crystal plastic deformation. The
main contributions and novelties of the present work are highlighted by following findings: (1)
A temperature-dependent higher-order Cauchy-Born rule and an atomistic-informed strain gradient theory have been developed, and the corresponding temperature-related higherorder
stress and elastic tensor formulations are derived; (2) The finite temperature MCDD
provides an atomistic-informed crystal plasticity finite element method that can simulate
anisotropic crystal plasticity in any orientation within the stereographic triangle at micron
scale and above; (3) The developed multiscale crystal defect dynamics (MCDD) is able
to capture the non-Schmid effects of BCC single crystals; (4) The developed multiscale
crystal defects dynamics (MCDD) is able to capture the size effect of single crystal plasticity,
and (5) The finite temperature MCDD can simulate the temperature dependent dislocation
substructure, and it captures cross-slip in single crystal at low temperature (~ 20K) and
captures dislocation cell structures at high temperature (~ 500K).