On the Relation between Pop-Ins in Nanoindentation Tests and the Ideal Shear Strength

abstract

English

The nanoindentation test in the dislocation free volume of the grain in a metallic polycrystal was simulated by utilizing a multiscale analysis. The onset of microplasticity, associated with the pop-in effect identified in experimental nanoindentation tests (generation of first dislocation loops), is assumed to be related to the moment of reaching the value of the ideal shear strength for that crystal. In particular, the influence of the compressive normal load on the shear plane on the ideal shear strength value, the three dimensionality of the nanoindentation test, the nonlinearity of the stress-strain relation, the orientation of relevant crystallographic planes and the anisotropy of elastic response of the crystal were considered in the model. The orientation of grains towards the directions of the applied load was determined by means of the EBSD technique. The mechanical characteristics of the perfect metallic crystal (grain) were calculated by using the ab initio approach. The three-dimensional isotropic FEM analysis, based on the ANSYS code, was used to simulate the development of the stress-strain field in the substrate. The computed displacement value was compared with experimentally measured pop-in effect in the nickel crystal and a good agreement was obtained. The results reveal that the nanoindentation test can serve as a sufficiently precise tool for experimental determination of the ideal shear strength.

Nanoindentation; Ideal Shear Strength

HORNÍKOVÁ, J.; BURŠÍKOVÁ, V.; ČERNÝ, M.; ŠANDERA, P.; POKLUDA, J.

10. 12. 2007

University of Dar es Salaam

Dar es Salaam

o-88

o-88

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