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Use of models to predict deformation during the elastic-plastic nano-indentation of coatings.

Hunt, R A; McCartney, L N (2003) Use of models to predict deformation during the elastic-plastic nano-indentation of coatings. NPL Report. MATC(A)46

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The objective of this report is to describe progress that has been made with the development of a methodology to estimate, from nano-indentation tests involving elastic-plastic deformation, the elastic properties of coatings whose thicknesses are in the micron range. The report summarises the results of new work that has been carried out, and intercomparison results that formed part of the international INDICOAT project.
The performance of finite element analysis (FEA) predictions of indentation into coated systems is described. A key issue has been the selection of appropriate plastic properties for use in the FEA. It is shown that the use of yield and work hardening properties derived for macroscopic testing (tension and compression) does not lead to realistic load-penetration curves, including unloading. It is concluded that the use of conventional FEA will require plasticity values derived from indentation tests, thus introducing an undesirable circularity into the predictive methodology.
For elastic-plastic axisymmetric deformations, the load-penetration curves predicted in the INDICOAT project, by FEA modelling, are generally in agreement when steps are taken to ensure that identical problems are analysed by contributing partners, thus indicating that the FEA packages ABAQUS and ANSYS models are producing results that appear to be consistent with one another.
When analysing FEA results to estimate the indentation modulus of the system following the conventional Oliver and Pharr analysis, which involves extracting the effective modulus from the unloading part of experimental elastic-plastic load penetration curves, it is found that results depend significantly on the maximum load, and that predictions of the indentation modulus can lie outside the range defined by values for coating and substrate. Thus, for elastic-plastic FEA analyses, the Oliver and Pharr data reduction method does not lead to indentation modulus values that are a characteristic only of the coating/substrate properties and the coating thickness.

Item Type: Report/Guide (NPL Report)
NPL Report No.: MATC(A)46
Subjects: Advanced Materials
Advanced Materials > Materials Modelling
Nanoscience > Nano-Materials
Last Modified: 02 Feb 2018 13:16
URI: http://eprintspublications.npl.co.uk/id/eprint/2712

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