Indentation size effect: a study via the Mechanism-based Strain-Gradient plasticity theory

A study of particle size effect and interface fracture in aluminum alloy composite via an extended conventional theory of mechanism-based strain-gradient plasticity

The indentation size effect in the spherical indentation of iridium: A study via the conventional theory of mechanism-based strain gradient plasticity

The effective threshold for fatigue crack propagation: a plastic size effect?

Small scale, grain size and substrate effects in nano-indentation experiment of film–substrate systems

In a remarkable series of experiments, Elssner et al. (1994) and Korn et al. (2002) observed cleavage cracking along a bimaterial interface between Nb and sapphire. The stress required for cleavage cracking is around the theoretical strength of the material. Classical plasticity models fall short to reach such a high stress level. We use the conventional theory of mechanism-based strain gradient plasticity (Huang et al., 2004) to investigate the stress field around the tip of an interface crack between Nb and sapphire. The tensile stress at a distance of 0.1 µm to the interface crack tip reaches 13.3σY ,w hereσY is the yield stress of Nb. This stress is nearly 4 times of that predicted by classical plasticity theory (3.6σY ) at the same distance to the crack tip, and is high enough to trigger cleavage cracking in materials and interfaces. This is consistent with Elssner et al.'s (1994) and Korn et al.'s (2002) experimental observations.

Mode I and mode II stress intensity factors and dislocation density behaviour in strain gradient plasticity

Modeling damage and fracture within strain-gradient plasticity

Indentation size effects in face centered cubic single crystal thin films

Establishment of damage estimation rules for brittle fracture after cyclic plastic prestrain in steel

RETRACTED: Prediction Charpy impact energy of bcc and fcc functionally graded steels in crack divider configuration by strain gradient plasticity theory

Micromechanical modeling of damage evolution and fracture behavior in particle reinforced metal matrix composites based on the conventional theory of mechanism-based strain gradient plasticity

Taylor-based nonlocal theory of plasticity: numerical studies of the micro-indentation experiments and crack tip fields

Bauschinger and size effects in thin-film plasticity

In this paper, the continuous stiffness measurement (CSM) indentation is employed to investigate fatigue mechanical properties of structural steel under cyclic loading. For this purpose, several representative analytical approaches were introduced to estimate the basic mechanical properties including Young’s modulus and indentation hardness from the characteristics of the loading/unloading curves. Several experiments including CSM nanoindentation, low-cycle fatigue experiment for four strain amplitude levels, optical microscope (OM), and transmission electron microscopy (TEM) examinations were conducted to observe the variation characteristics of mechanical properties at the microscale and their micro-mechanisms. The microstructural evolution of the specimens deformed by the low-cycle fatigue was observed using the OM and TEM examinations. The standard nanoindentation experiments were then performed at different strain rate levels to characterize the influences of strain rate indentation on hardness of the material. The micro-mechanisms established based on the microstructural evolution and strain gradient plasticity theory were introduced to be responsible for the variation of indentation hardness under cyclic loading. Finally, the indentation size effect (ISE) phenomenon in SS400 structural steel was investigated and explained through the strain gradient plasticity theory regarding geometrically necessary dislocations underneath the indenter tip. The experimental results can be used for practical designs as well as for understanding the fatigue behavior of SS400 structural steel.
 Keywords:
 cyclic loading; fatigue; nanoindentation; indentation size effect; strain rate sensitivity; structural steel.

A two-step simulation procedure and corresponding computational approach are developed for modeling the particle-reinforced composites comprising several inclusions embedded within the metal matrix to account for the residual stresses and particle interaction. A temperature-dependent strain-gradient plasticity constitutive relation is used to handle the particle size-effect in the model of the particle-reinforced composites. The corresponding computational approach is successfully performed in the two-step simulation procedure based on the mechanism-based strain gradient plasticity theory combining with parametric quadratic programming technique. Numerical results demonstrate the validity of the proposed computational approach using the temperature-dependent strain-gradient plasticity constitutive relation.