A study of the void size effect based on the Taylor dislocation model

Void growth to coalescence in a non-local material

“…When voids become smaller and comparable to the internal material length parameter, void growth is significantly suppressed consistent with findings of Hutchinson (1997, 2001), Huang et al (2000), and Liu et al (2003Liu et al ( , 2005. This has the effect of increasing the attainable stress level and the strain at the onset of void coalescence.…”

“…This is reported in a number of investigations for hydrostatic loading by Fleck and Hutchinson (1997), Huang et al (2000) and Fleck and Hutchinson (2001), and for axisymmetric loading conditions by Liu et al (2003Liu et al ( , 2005, Wen et al (2005), Tvergaard and Niordson (2004) and Niordson andTvergaard (2006, 2007). Similar size effects are observed in metal matrix composites (Lloyd, 1994) which are well captured by gradient theories of plasticity (Bittencourt et al, 2003;Niordson, 2003).…”

“…Several researchers have investigated size-dependent void growth of single voids under hydrostatic loading (Fleck and Hutchinson, 1997;Huang et al, 2000;Fleck and Hutchinson, 2001). Liu et al, 2003 have extended the Rice-Tracey model of spherical symmetric void growth to account size-effects, while Liu et al, 2005 have extended this model to account for changes in the void shape during growth. A modified Gurson model accounting for the void size effect was proposed by Wen et al (2005).…”

Strain gradient plasticity analysis of elasto-plastic contact between rough surfaces

“…The plasticity size effects mentioned above have been attributed to geometrically necessary dislocations (GNDs) associated with non-uniform plastic deformation in small volumes (Nye, 1953;Ashby, 1970;Gao and Huang, 2003). Strain gradient plasticity theories (e.g., Poole et al, 1996;Fleck and Hutchinson, 1993;Gao et al, 1999;Huang et al, 2000;Gurtin, 2002) have been developed to describe size dependent behavior for problems with an externally imposed strain gradient, such as bending, torsion and indentation (Fleck et al, 1994;Gao et al, 2015;Xue et al, 2002) as well as in problems where plastic gradients develop as a consequence of constrained plasticity, such as in void growth and composite materials (Liu et al, 2005;Huang et al, 2000;Bittencourt et al, 2003). As a few of these cited works already suggest, another approach to analyzing plasticity at these size scales is Discrete Dislocation Plasticity (DDP) in which plastic deformation emerges from the nucleation and motion of discrete dislocations in an elastic background.…”

Strain Gradient Plasticity-Based Modeling of Damage and Fracture

“…The extent ahead of the crack tip where strain gradients play an important role suggests that gradient enhanced simulations may be relevant for continuum modeling of cleavage fracture [98], ductileto-brittle assessment [93], fatigue crack closure [99] and ductile damage [94,95,100]. Furthermore, accounting for the influence of GNDs in the vicinity of the crack may be particularly relevant in the modelization of hydrogen assisted cracking, due to the essential role that the hydrostatic stress has on both interface decohesion and hydrogen diffusion in relation to the fracture process zone (see [36]).…”