Further analysis of indentation loading curves: Effects of tip rounding on mechanical property measurements

Cheng, Yang‐Tse; Cheng, Chin‐Hsiang

doi:10.1557/jmr.1998.0147

Cited by 113 publications

(76 citation statements)

References 19 publications

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“…where h * is the transition depth and θ is the semi-angle of the conical part (Cheng & Cheng, 1998;VanLandingham et al, 2005;Constantinides et al, 2007). For an axisymmetric approximation of a Berkovich probe, θ = 70.3° and h * = 0.0585 R. Thus, the sharp indenter with R = 125 nm has a predicted transition at h * = 7.3 nm, which is smaller than any of the measured pop-in depths and explains the pronounced 3-fold symmetry of the surface-stress contours in Fig.…”

Section: Comparison Of Fea Results To Experimentsmentioning

confidence: 99%

Effect of the Spherical Indenter Tip Assumption on the Initial Plastic Yield Stress

Ma¹,

Levine²,

Dixson³

et al. 2012

Nanoindentation in Materials Science

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Section: Comparison Of Fea Results To Experimentsmentioning

confidence: 99%

Effect of the Spherical Indenter Tip Assumption on the Initial Plastic Yield Stress

Ma¹,

Levine²,

Dixson³

et al. 2012

Nanoindentation in Materials Science

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“…The polynomial fitting (F N = c 0 h 2 + c 1 h + c 2 ) for the total loading curve [15] has been widely applauded. But it provides no information about initial effects, gradients, or phase transformations at all, and polynomial fittings are unreliable in view of linear regressions.…”

Section: Resultsmentioning

confidence: 99%

“…But it provides no information about initial effects, gradients, or phase transformations at all, and polynomial fittings are unreliable in view of linear regressions. Furthermore, iterated parameters c 0 and c 1 are often used to calculate exceedingly large "effective tip radii" up to 3.3 µm (for example for a Vickers with 68° semi-angle Θ that is close to the one of Berkovich at 65.3°), depending on the yield-strength/modulus ratio [15]. However, blunt Berkovich tip radii range from 150 to 300 nm.…”

Section: Resultsmentioning

confidence: 99%

Important Consequences of the Exponent 3/2 for Pyramidal/Conical Indentations-New Definitions of Physical Hardness and Modulus

Kaupp¹

2016

J Material Sci Eng

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The now physically founded exponent 3/2 that governs the relation of normal force to depth 3/2 in conical/pyramidal indentation is a physically founded (F N = k h 3/2 ). Strictly linear plots obtain non-iterated penetration resistance k (mN/ µm 3/2 ) as slope, initial effects (including tip rounding), adhesion energy, and phase transitions with their transformation energy and activation energy. The reason for the failing of the Sneddon theory, claiming wrong exponent 2 (as do ABAQUS or ANSYS finite element simulations) is their neglect of long-range effects by shearing. Previous undue trials to rationalize the non-occurrence of exponent 2 are polynomial fittings and "best or variable exponent" iterations for curve fittings that lose all unique information from the loading curve. Also ISO 14577 unloading hardness H ISO and reduced elastic modulus E r-ISO lack physical reality. They are redefined to physical dimensions as new indentation parameters H phys and E r-phys . For the first time physically sound indentation hardness H phys is obtained without iterations solely from loading curves. Also all mechanical indentation parameters relying on Sneddon's exponent 2 are unphysical. They require redefinition with new dimensions. This applies also to visco-elastic-plastic parameters in a recent NIST tutorial. The present ISO-standards create dilemma with physics. But the risk from using wrong mechanical parameters against physics is dangerous, subject to change.

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“…4(a) also shows the experimental load-displacement result for conventional aluminum. 19,21 Through comparison, one finds that the nanocrystallized Al-alloy material has the much higher hardness value than that of the conventional aluminum. From Fig.…”

Section: B Surface-nanocrystallized Al-alloy Materialsmentioning

confidence: 99%

Size effect measurement and characterization in nanoindentation test

2004

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Nanoindentation test at scale of hundreds of nanometers has shown that measured hardness increases strongly with decreasing indent depth, which is frequently referred to as the size effect. Usually, the size effect is displayed in the hardness-depth curves. In this study, the size effect is characterized in both the load-displacement curves and the hardness-depth curves. The experimental measurements were performed for single-crystal copper specimen and for surface-nanocrystallized Al-alloy specimen. Moreover, the size effect was characterized using the dislocation density theory. To investigate effects of some environmental factors, such as the effect of surface roughness and the effect of indenter tip curvature, the specimen surface profile and the indentation imprint profile for single-crystal copper specimen were scanned and measured using the atomic force microscopy technique. Furthermore, the size effect was characterized and analyzed when the effect of the specimen surface roughness was considered.

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Further analysis of indentation loading curves: Effects of tip rounding on mechanical property measurements

Cited by 113 publications

References 19 publications

Effect of the Spherical Indenter Tip Assumption on the Initial Plastic Yield Stress

Effect of the Spherical Indenter Tip Assumption on the Initial Plastic Yield Stress

Important Consequences of the Exponent 3/2 for Pyramidal/Conical Indentations-New Definitions of Physical Hardness and Modulus

Size effect measurement and characterization in nanoindentation test

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