On the Development of Experimental Methods for the Determination of Fracture Mechanical Parameters of Ceramics

Dänzer, Robert; Rasche, Stefan

doi:10.1007/978-3-319-21467-2_8

Cited by 4 publications

(2 citation statements)

References 54 publications

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“…Indentation K Ic values are therefore not accepted by many authors as an accurate test method (for an extended discussion see [30]). Indentation testing for K Ic , should better be named indentation fracture resistance [21], but will allow comparisons between materials and show trends that reflect real fracture toughness. There are new approaches to understand the energetics and meaning of indentation cracks.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…In this study, we therefore use indentation resistance measurements together with basic elastic properties to calculate a proxy for the true fracture toughness, because the direct experimental determination of it is very elaborate (e.g. [21]). We use these indentation resistance measurements to calculate the stresses necessary for fracturing and, by this, to explain how much force is needed for the knapping of different stones.…”

Section: Introductionmentioning

confidence: 99%

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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%

Section: Introductionmentioning

confidence: 99%

Knapping force as a function of stone heat treatment

Nickel

Schmidt

2022

PLoS ONE

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The mechanical properties of heat-treated rocks: a comparison between chert and silcrete

Schmidt

Buck

Berthold

et al. 2018

Archaeol Anthropol Sci

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The driving force behind tool-stone selection in the African Middle Stone Age

Schmidt,

Pappas,

Porraz

et al. 2024

Proc. Natl. Acad. Sci. U.S.A.

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In the Stone Age, the collection of specific rocks was the first step in tool making. Very little is known about the choices made during tool-stone acquisition. Were choices governed by the knowledge of, and need for, specific properties of stones? Or were the collected raw materials a mere by-product of the way people moved through the landscape? We investigate these questions in the Middle Stone Age (MSA) of southern Africa, analyzing the mechanical properties of tool-stones used at the site Diepkloof Rock Shelter. To understand knapping quality, we measure flaking predictability and introduce a physical model that allows calculating the relative force necessary to produce flakes from different rocks. To evaluate their quality as finished tools, we investigate their resistance during repeated use activities (scraping or cutting) and their strength during projectile impacts. Our findings explain tool-stone selection in two emblematic periods of the MSA, the Still Bay and Howiesons Poort, as being the result of a deep understanding of these mechanical properties. In both cases, people chose those rocks, among many others, that allowed the most advantageous trade-off between anticipated properties of finished tools and the ease of acquiring rocks and producing tools. The implications are an understanding of African MSA toolmakers as engineers who carefully weighed their choices taking into account workability and the quality of the tools they made.

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On the Development of Experimental Methods for the Determination of Fracture Mechanical Parameters of Ceramics

Cited by 4 publications

References 54 publications

Knapping force as a function of stone heat treatment

Knapping force as a function of stone heat treatment

The mechanical properties of heat-treated rocks: a comparison between chert and silcrete

The driving force behind tool-stone selection in the African Middle Stone Age

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