Strain rate dependency of dislocation plasticity

Area of Science:

• Materials Science
• Condensed Matter Physics
• Mechanical Engineering

Background:

• Dislocation glide is a fundamental deformation mechanism controlling the mechanical strength of metals.
• Understanding the interplay between strain rate, dislocation density, and material strength is crucial for predicting metal behavior under stress.

Purpose of the Study:

• To investigate the strain rate and dislocation density dependence of the strength in bulk copper and aluminum single crystals.
• To establish an analytical relationship linking material strength, dislocation density, strain rate, and dislocation mobility.
• To develop a unified framework for understanding plastic deformation and hardening phenomena.

Main Methods:

• Utilizing discrete dislocation dynamics (DDD) simulations.
• Employing molecular dynamics (MD) simulations.
• Comparing simulation results with published experimental data.

Main Results:

• Material strength exhibits a transition from strain rate hardening to classical forest hardening as dislocation density increases.
• Observed a strain rate-independent regime followed by a strain rate hardening regime with increasing strain rate.
• Developed a single scaling function relating scaled strength to a coupling parameter (dislocation density and strain rate).

Conclusions:

• The proposed analytical relationship accurately predicts simulation and experimental results.
• The coupling parameter effectively governs plasticity localization, dislocation flow fluctuations, and velocity distributions.
• A unified understanding of metal strength dependence on microstructural and dynamic parameters is achieved.