The role of macroscopic hardening and individual length-scales on crack tip stress elevation from phenomenological strain gradient plasticity

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• 作者：Uday Komaragiri ; Sean R. Agnew ; Richard P. Gangloff ; Matthew R. Begley
• 关键词：Strain gradient plasticity ; Scaling ; Cracking
• 刊名：Journal of the Mechanics and Physics of Solids
• 出版年：2008
• 出版时间：December 2008
• 年：2008
• 卷：56
• 期：12
• 页码：3527-3540
• 全文大小：722 K

文摘

This paper quantifies the effect of strain gradient plasticity (SGP) on crack tip stress elevation for a broad range of applied loading conditions and constitutive model parameters, including both macroscopic hardening parameters and individual material length-scales controlling gradient effects. Finite element simulations incorporating the Fleck–Hutchinson SGP theory are presented for an asymptotically sharp stationary crack. Results identify fundamental scaling relationships describing (i) the physical length-scales over which strain gradients are prominent, and (ii) the degree of stress elevation over conventional Hutchinson–Rice–Rosengren (HRR) fields. Results illustrate that the three length-scale theory predicts much larger SGP effects than the single length-scale theory. Critically, the first length-scale parameter dominates SGP stress elevation: this suggests that SGP effects in fracture can be predicted using the length-scales extracted from nanoindentation, which exhibits similar behavior. Transitional loading/material parameters are identified that establish regimes of SGP relevance: this provides the foundation for the rational application of SGP when developing new micromechanical models of crack tip damage mechanisms and associated subcritical crack propagation behavior in structural alloys.