About this Abstract |
Meeting |
2022 TMS Annual Meeting & Exhibition
|
Symposium
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30 Years of Nanoindentation with the Oliver-Pharr Method and Beyond
|
Presentation Title |
NOW ON-DEMAND ONLY – Work-based Definition of the Strain Rate in indentation |
Author(s) |
Donald S. Stone, Z. Humberto Melgarejo, Abdelmageed A. Elmustafa |
On-Site Speaker (Planned) |
Donald S. Stone |
Abstract Scope |
Plastic deformation is often path dependent. This means that in an indentation test, the hardness at given depth and rate of penetration also depends on how fast the indenter was loaded, prior to measurement. A constant load creep test and a load relaxation experiment should therefore produce different strain rate sensitivity, useful for exploring thermal activation of hardening and softening during deformation. To measure the strain rate sensitivity using indentation, experimenters often rely on (1/h)(dh/dt) to specify the strain rate, where h is the depth of penetration of the indenter. This formula does not work for high hardness/modulus (H/E*) materials because it fails to give consistent results depending on how the experiment is performed even for materials where plastic deformation is not intrinsically path dependent. Here, we employ a work-based argument to derive an expression for the strain rate that works for both high and low H/E* materials. |
Proceedings Inclusion? |
Planned: |
Keywords |
Mechanical Properties, Modeling and Simulation, Other |