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Analysis of the tip roundness effects on the micro- and macroindentation response of elastic–plastic materials

Published online by Cambridge University Press:  31 January 2011

Sara Aida Rodríguez Pulecio*
Affiliation:
Surface Phenomena Laboratory, Department of Mechanical Engineering, University of São Paulo, 05508-900 São Paulo - SP. Brazil
María Cristina Moré Farias
Affiliation:
Surface Phenomena Laboratory, Department of Mechanical Engineering, University of São Paulo, 05508-900 São Paulo - SP. Brazil
Roberto Martins Souza
Affiliation:
Surface Phenomena Laboratory, Department of Mechanical Engineering, University of São Paulo, 05508-900 São Paulo - SP. Brazil
*
a) Address all correspondence to this author. e-mail: [email protected]
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Abstract

In this work, the effects of indenter tip roundness on the load–depth indentation curves were analyzed using finite element modeling. The tip roundness level was studied based on the ratio between tip radius and maximum penetration depth (R/hmax), which varied from 0.02 to 1. The proportional curvature constant (C), the exponent of depth during loading (α), the initial unloading slope (S), the correction factor (β), the level of piling-up or sinking-in (hc/hmax), and the ratio hmax/hf are shown to be strongly influenced by the ratio R/hmax. The hardness (H) was found to be independent of R/hmax in the range studied. The Oliver and Pharr method was successful in following the variation of hc/hmax with the ratio R/hmax through the variation of S with the ratio R/hmax. However, this work confirmed the differences between the hardness values calculated using the Oliver–Pharr method and those obtained directly from finite element calculations; differences which derive from the error in area calculation that occurs when given combinations of indented material properties are present. The ratio of plastic work to total work (Wp/Wt) was found to be independent of the ratio R/hmax, which demonstrates that the methods for the calculation of mechanical properties based on the indentation energy are potentially not susceptible to errors caused by tip roundness.

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Articles
Copyright
Copyright © Materials Research Society 2009

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