Abstract
Indentation hardness tests are widely used in engineering to test the hardness of a material, which can be performed on a macroscopic scale or microscopic scale. In the present work, copper specimens with different thicknesses were indented with a mechanically-instrumented Rockwell tester. The effects of spacing between indents, indent distance to the edge of the sample, and specimen thickness on the hardness measurement were systematically quantified. Non-linear finite-element modeling was performed, assuming elastic-plastic material response with strain hardening. The two-dimensional numerical modeling of stand-alone and multiple indentations helped to shed more light on the deformation field under indentation, especially the size of the plastic zones and any interaction between them. In addition to the geometric effects, the influence of strain hardening of the test material was also investigated using the finite element analysis. The combined experimental and numerical results provided a range of indent spacings and thicknesses, which yield small to no effect on hardness values. The simulations also quantified the size and shape of the plastic zone under an indent. Lastly, the modeling results showed a competition between the effect of intrinsic material hardening and indent spacing on the value of the measured hardness.
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Acknowledgments
The authors would like to thank the University of New Mexico’s (UNM) Mechanical Engineering Department for supporting this research work.
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Luo Li is a Ph.D. student in the Mechanical Engineering Department at the University of New Mexico. His research interests include materials science with emphasis on mechanical properties and characterization, mechanics of materials, composite materials, and advanced manufacturing.
Tariq Khraishi is currently a Professor of Mechanical Engineering at the University of New Mexico, U.S.A. He received his Ph.D. in Engineering from Washington State University. His research work is in the general areas of mechanics and materials science. In particular he has performed modelling, theoretical and/or experimental research in biomechanics, dislocation dynamics, eigenstrain theory/modelling, fracture mechanics, nano structures, irradiation damage, void growth/interaction in superplasticity, and stresses in thin films.
Yu-Lin Shen is currently a Professor and Chair of the Department of Mechanical Engineering at University of New Mexico, U.S.A. He received his Ph.D. in Engineering from Brown University. His research areas include mechanical behavior of materials and solid mechanics, with particular interests in applying modeling techniques to address micro-mechanical problems related to thin films, microelectronic devices and packages, and composite materials.
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Li, L., Khraishi, T. & Shen, YL. Investigation of the effect of indentation spacing, edge distance and specimen thickness on the measurement of hardness. J Mech Sci Technol 37, 687–696 (2023). https://doi.org/10.1007/s12206-023-0112-7
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DOI: https://doi.org/10.1007/s12206-023-0112-7