Validating a facile approach to measuring fracture toughness by instrumented indentation without imaging crack-lengths

Hempel, Jacob; Meyer, Arthur E.; Hill, Ryan; Cheng, Yang‐Tse

doi:10.1557/s43579-022-00176-7

Cited by 3 publications

(1 citation statement)

References 13 publications

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“…There are new approaches to understand the energetics and meaning of indentation cracks. However, they are not developed enough yet to establish reliable data for our study [31][32][33]. We therefore apply the widely-used formulation of Niihara et al [34]…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Knapping force as a function of stone heat treatment

Nickel

Schmidt

2022

PLoS ONE

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We propose a quantitative framework for understanding the knapping force requirements imposed by different raw materials in their unheated and heat-treated states. Our model interprets stone tool knapping as being the result of cracks formed during the first impact with a hammer stone, followed by continued stressing of these cracks that eventually leads to flake detachment. We combine bending strength, indentation fracture resistance and “Griffith” crack lengths of flint and silcrete to obtain functions identifying critical forces for flaking without or after heat treatment. We argue that these forces are a key factor for understanding the “knappability” of different raw materials, because only forces with 100N or less can be used for very precise strike control. Our model explains for the first time why experimental knappers frequently observe that flint (a stronger material, which, in our case, has a strength above 100 MPa) is easier to knap than silcretes (which is relatively weaker with strength values at or below 60 MPa). Our findings allow for understanding the differences between heat-treated and untreated flint and silcrete in terms of knapping quality, and they allow to compare the qualities of different raw materials.

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Section: Theoretical Backgroundmentioning

confidence: 99%

Knapping force as a function of stone heat treatment

Nickel

Schmidt

2022

PLoS ONE

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A Correction Function to Improve the Accuracy of Measuring Elastic Modulus by Instrumented Spherical Indentation

Xu,

Dou,

Chen

et al. 2024

Journal of Testing and Evaluation

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Instrumented indentation combined with the classic Oliver–Pharr method has been widely utilized to measure elastic modulus of various materials. However, the elastic modulus measured by instrumented spherical indentation (ISI) is not as accurate as that measured by instrumented sharp indentation, especially at large indentation depth. In this work, the effect of the maximum indentation depth on measurement of elastic modulus by ISI was deeply investigated through finite element simulations and experiments. It was found that errors in measured elastic moduli increase significantly due to the inaccurate estimation of contact radius and excessive increase in initial unloading stiffness as maximum indentation depth increases. A correction function was then proposed to correct the measured elastic modulus. After correction, the errors were effectively reduced to within ±5 % for most cases. This work contributes to discovery of the error source in the measurement of elastic modulus by ISI, thereby improving the measurement accuracy.

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