Abstract
Nix and Gao established an important relation between microindentation hardness and indentation depth. Such a relation has been verified by many microindentation experiments (indentation depths in the micrometer range , but it does not always hold in nanoindentation experiments (indentation depths approaching the nanometer range). We have developed a unified computational model for both micro- and nanoindentation in an effort to understand the breakdown of the Nix-Gao relation at indentation depths approaching the nanometer scale. The unified computational model for indentation accounts for various indenter shapes, including a sharp, conical indenter, a spherical indenter, and a conical indenter with a spherical tip. It is based on the conventional theory of mechanism-based strain gradient plasticity established from the Taylor dislocation model to account for the effect of geometrically necessary dislocations. The unified computational model for indentation indeed shows that the Nix-Gao relation holds in microindentation with a sharp indenter, bur it does not hold in nanoindentation due to the indenter tip radius effect.
Original language | English (US) |
---|---|
Pages (from-to) | 3423-3434 |
Number of pages | 12 |
Journal | Journal of Materials Research |
Volume | 19 |
Issue number | 11 |
DOIs | |
State | Published - Nov 2004 |
Funding
Y.H. acknowledges support from NSF (Grant No. CMS-0084980) and ONR (Grant No. N00014-01-1-0205, program officer Dr. Y.D.S. Rajapakse). Support from NSFC is also acknowledged. Y.H and W.D.N. gratefully acknowledge support from an NSF-NIRT project “Mechanism Based Modeling and Simulation in Nanomechanics,” through Grant No. NSF CMS-0103257, under the direction of Dr. Ken Chong.
ASJC Scopus subject areas
- General Materials Science
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering