A Class of Rate-Independent Lower-Order Gradient Plasticity Theories: Implementation and Application to Disc Torsion...

Area of Science:

• Materials Science
• Mechanical Engineering
• Continuum Mechanics

Background:

• Plasticity phenomena diverge at micro/nanoscales compared to macroscales.
• Understanding these deviations is crucial for advanced material design and manufacturing.
• Existing models may not fully capture scale-dependent plasticity effects.

Purpose of the Study:

• To investigate the gap in understanding plasticity at decreasing scales.
• To compare phenomenological and crystal plasticity models using a gradient-enhanced approach.
• To analyze the influence of different dislocation types and gradient origins on material behavior.

Main Methods:

• Employed a lower-order gradient enhanced approach.
• Utilized phenomenological continuum and crystal plasticity models.
• Incorporated statistically stored dislocations (SSDs) and geometrically necessary dislocations (GNDs) into hardening models.
• Used a rate-independent formulation to avoid artificial hardening.

Main Results:

• Both models successfully incorporated GNDs into hardening mechanisms.
• Simulations revealed distinct behaviors based on structurally imposed vs. inherent gradients.
• The study quantified the impact of gradient types on plasticity at smaller scales.

Conclusions:

• Gradient-enhanced models provide valuable insights into scale-dependent plasticity.
• The distinction between imposed and inherent gradients is critical for accurate micro/nanoscale plasticity prediction.
• Further research can refine these models for predicting the behavior of materials at reduced characteristic scales.