Analysis of indentation creep

Finite element analysis is used to simulate cone indentation creep in materials across a wide range of hardness, strain rate sensitivity, and work-hardening exponent. Modeling reveals that the commonly held assumption of the hardness strain rate sensitivity (mH) equaling the flow stress strain rate...

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Bibliographic Details
Published in:Journal of materials research 2010-04, Vol.25 (4), p.611-621
Main Authors: Stone, Don S., Jakes, Joseph E., Puthoff, Jonathan, Elmustafa, Abdelmageed A.
Format: Article
Language:English
Subjects:
Applied and Technical Physics
Biomaterials
Hardness
Inorganic Chemistry
Materials Engineering
Materials Science
Nanoindentation
Nanotechnology
Outstanding Symposium Paper
Outstanding Symposium Papers
Stress/strain relationship
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Summary:Finite element analysis is used to simulate cone indentation creep in materials across a wide range of hardness, strain rate sensitivity, and work-hardening exponent. Modeling reveals that the commonly held assumption of the hardness strain rate sensitivity (mH) equaling the flow stress strain rate sensitivity (mσ) is violated except in low hardness/modulus materials. Another commonly held assumption is that for self-similar indenters the indent area increases in proportion to the (depth)2 during creep. This assumption is also violated. Both violations are readily explained by noting that the proportionality “constants” relating (i) hardness to flow stress and (ii) area to (depth)2 are, in reality, functions of hardness/modulus ratio, which changes during creep. Experiments on silicon, fused silica, bulk metallic glass, and poly methyl methacrylate verify the breakdown of the area-(depth)2 relation, consistent with the theory. A method is provided for estimating area from depth during creep.
ISSN:0884-2914
2044-5326
DOI:10.1557/JMR.2010.0092