About the importance of introducing a correction factor in the Sneddon relationship for nanoindentation measurements

Troyon, M.; Lafaye, S.

doi:10.1080/14786430600606834

Cited by 20 publications

(15 citation statements)

References 12 publications

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“…␤ is a numerical factor, which is usually assumed to be 2/ 1/2 ‫ס‬ 1.128. Recent authors [22][23][24] have reported that the conventional value is too low and that the actual value, which varies a little depending on specimen properties and indenter shape, is closer to 1.2. At present, we find that ␤ ≅ 1.23 works best based on our analysis of indents placed in a fused silica standard.…”

Section: A Standard Oliver-pharr Analysismentioning

confidence: 93%

Experimental method to account for structural compliance in nanoindentation measurements

et al. 2008

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The standard Oliver-Pharr nanoindentation analysis tacitly assumes that the specimen is structurally rigid and that it is both semi-infinite and homogeneous. Many specimens violate these assumptions. We show that when the specimen flexes or possesses heterogeneities, such as free edges or interfaces between regions of different properties, artifacts arise in the standard analysis that affect the measurement of hardness and modulus. The origin of these artifacts is a structural compliance (C s ), which adds to the machine compliance (C m ), but unlike the latter, C s can vary as a function of position within the specimen. We have developed an experimental approach to isolate and remove C s . The utility of the method is demonstrated using specimens including (i) a silicon beam, which flexes because it is supported only at the ends, (ii) sites near the free edge of a fused silica calibration standard, (iii) the tracheid walls in unembedded loblolly pine (Pinus taeda), and (iv) the polypropylene matrix in a polypropylene-wood composite.

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Section: A Standard Oliver-pharr Analysismentioning

confidence: 93%

Experimental method to account for structural compliance in nanoindentation measurements

et al. 2008

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“…(7) should have a correction factor different from 1 and dependent on both indenter geometry and Poisson's coefficient. 22,23 Other works [8][9][10][11][12] found dependence of b in relation to the indentation size and, consequently, in relation to the indenter tip defects. …”

Section: Indentation Variablesmentioning

confidence: 99%

“…[4][5][6] In these cases, the changes in the shape of the loading curve can also be confused with those caused by the material work hardening, 7 which leads to errors in the calculation of the work-hardening coefficient. Furthermore, significant changes on the correction factor b, used to adjust Sneddon's equations, [8][9][10][11][12] have been recently observed due to indenter tip roundness.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the tip roundness effects on the micro- and macroindentation response of elastic–plastic materials

2009

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In this work, the effects of indenter tip roundness on the load-depth indentation curves were analyzed using finite element modeling. The tip roundness level was studied based on the ratio between tip radius and maximum penetration depth (R/h max ), which varied from 0.02 to 1. The proportional curvature constant (C), the exponent of depth during loading (a), the initial unloading slope (S), the correction factor (b), the level of piling-up or sinking-in (h c /h max ), and the ratio h max /h f are shown to be strongly influenced by the ratio R/h max . The hardness (H) was found to be independent of R/h max in the range studied. The Oliver and Pharr method was successful in following the variation of h c /h max with the ratio R/h max through the variation of S with the ratio R/h max . However, this work confirmed the differences between the hardness values calculated using the Oliver-Pharr method and those obtained directly from finite element calculations; differences which derive from the error in area calculation that occurs when given combinations of indented material properties are present. The ratio of plastic work to total work (W p /W t ) was found to be independent of the ratio R/h max , which demonstrates that the methods for the calculation of mechanical properties based on the indentation energy are potentially not susceptible to errors caused by tip roundness.

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“…In the literature, it has been suggested that the effect of the indentation size is caused by tip roundness effects 5,32,33 ; yet the effect caused by the ratio R/h max reported in Refs. 5, 32, and 33 was obtained by an increment of h max while maintaining a constant radius.…”

Section: F Correction Factor Of the Sneddon's Equationmentioning

confidence: 99%

“…(4), 23 where b is a correction factor, which is dependent on both indenter geometry and Poisson's coefficient. [27][28][29] Other works have shown dependence of b with the indentation size when the indenter tip presents some roundness 5,[30][31][32][33] and with the indenter elastic deformation.…”

Section: Indentation Variablesmentioning

confidence: 99%

Analysis of the effects of conical indentation variables on the indentation response of elastic–plastic materials through factorial design of experiment

2009

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In this work, the effects of conical indentation variables on the load-depth indentation curves were analyzed using finite element modeling and dimensional analysis. A factorial design 2 6 was used with the aim of quantifying the effects of the mechanical properties of the indented material and of the indenter geometry. Analysis was based on the input variables Y/E, R/h max , n, y, E, and h max . The dimensional variables E and h max were used such that each value of dimensionless Y/E was obtained with two different values of E and each value of dimensionless R/h max was obtained with two different h max values. A set of dimensionless functions was defined to analyze the effect of the input variables:, P 2 = h c /h, P 3 = H/Y, P 4 = S/Eh max , P 6 = h max /h f , and P 7 = W p /W T . These six functions were found to depend only on the dimensionless variables studied (Y/E, R/ h max , n, y). Another dimensionless function, P 5 = b, was not well defined for most of the dimensionless variables and the only variable that provided a significant effect on b was y. However, b showed a strong dependence on the fraction of the data selected to fit the unloading curve, which means that b is especially susceptible to the error in the calculation of the initial unloading slope.

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About the importance of introducing a correction factor in the Sneddon relationship for nanoindentation measurements

Cited by 20 publications

References 12 publications

Experimental method to account for structural compliance in nanoindentation measurements

Experimental method to account for structural compliance in nanoindentation measurements

Analysis of the tip roundness effects on the micro- and macroindentation response of elastic–plastic materials

Analysis of the effects of conical indentation variables on the indentation response of elastic–plastic materials through factorial design of experiment

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