Intricacies involving the evaluation of fracture toughness obtained by the surface-crack-in-flexure method

Lubauer J, Lohbauer U, Henrich M, Munz M, Lube T, Belli R (2022)

Publication Type: Journal article

Publication year: 2022

Journal

Journal of the American Ceramic Society Wiley-Blackwell

DOI: 10.1111/jace.18667

Abstract

Among the several methods available for the measurement of the fracture toughness (KIc), the surface-crack-in-flexure (SCF) has the advantages of being based on an easy-to-produce short (application relevant) crack size of defined geometry with a naturally sharp crack tip. The production of ready-to-test cracked specimens is fast and uncomplicated, rendering accurate results with low scatter. However efficient and reliable, the procedural steps for the obtainment of a valid crack need revisions, especially on aspects concerning the polishing depth, the removal of lateral cracks, the obtainment of an appropriate crack geometry, and the use of adequate solutions for the geometry factor. In this study we attend to these issues by systematically polishing a large number of specimens of two ceramic materials having very distinct subsurface Knoop crack systems to assess the effect of remnants of lateral cracks. By evaluating the geometry factor of the median precrack along the entire crack front, we provide valid ranges for the crack geometry regarding the crack-surface intersection angle as resulting from the polishing depth, extending the applicability of the Strobl et al. solution to shallow cracks in detriment of the Newman and Raju formula that is poised to overestimations of KIc of up to 10%. Our results debunk the belief that lateral cracks affect the obtained KIc, but demonstrate the necessity of a minimum polishing depth for the attainment of valid crack geometries.

Authors with CRIS profile

Julia Lubauer Department of Operative Dentistry and Periodontology Ulrich Lohbauer Medizinische Fakultät Martina Henrich Department of Operative Dentistry and Periodontology Renan Belli Department of Operative Dentistry and Periodontology

Involved external institutions

Montanuniversität Leoben AT Austria (AT)

How to cite

APA:

Lubauer, J., Lohbauer, U., Henrich, M., Munz, M., Lube, T., & Belli, R. (2022). Intricacies involving the evaluation of fracture toughness obtained by the surface-crack-in-flexure method. Journal of the American Ceramic Society. https://doi.org/10.1111/jace.18667

MLA:

Lubauer, Julia, et al. "Intricacies involving the evaluation of fracture toughness obtained by the surface-crack-in-flexure method." Journal of the American Ceramic Society (2022).

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