Influence of contact geometry on hardness behavior in nano-indentation

Min Li, Weimin Chen, Yang Tse Cheng, Che Min Cheng

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


In this paper the influence of contact geometry, including the round tip of the indenter and the roughness of the specimen, on hardness behavior for elastic-plastic materials is studied by means of finite element simulation. We idealize the actual indenter by an equivalent rigid conic indenter fitted smoothly with a spherical tip and examine the interaction of this indenter with both a flat surface and a rough surface. In the latter case the rough surface is represented by either a single spherical asperity or a dent (cavity). Indented solids include elastic perfectly plastic materials and strain hardening elastic-plastic materials, and the effects of the yield stress and strain hardening index are explored. Our results show that due to the finite curvature of the indenter tip the hardness versus indentation depth curve rises or drops (depending on the material properties of the indented solids) as the indentation depth decreases, in qualitative agreement with experimental results. Surface asperities and dents of curvature comparable to that of the indenter tip can appreciably modify the hardness value at small indentation depth. Their effects would appear as random variation in hardness.

Original languageEnglish
Pages (from-to)315-320
Number of pages6
Issue number2
StatePublished - Sep 18 2009

Bibliographical note

Funding Information:
The authors would like to acknowledge support from the National Science Foundation of China, project nos. 10772183 and 10532070.


  • Hardness
  • Indenter tip roundness
  • Nano-indentation
  • Surface roughness

ASJC Scopus subject areas

  • Instrumentation
  • Condensed Matter Physics
  • Surfaces, Coatings and Films


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