SKM 2023 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 4: Topical Session: Fundamentals of Fracture – Micromechanical Fracture Experiments
MM 4.6: Talk
Monday, March 27, 2023, 12:30–12:45, SCH A 216
Quantitative measurement of fracture toughness from the bridge notch failure in microcantilever — •Yinxia Zhang1, Matthias Bartosik2, Steffen Brinckmann3, Subin Lee1, and Christoph Kirchlechner1 — 1Institute for Applied Materials, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, 76344, Germany — 2Department of Materials Science, Montanuniversität Leoben, Leoben, 8700, Austria — 3Microstructure and Properties of Materials (IEK-2), Forschungszentrum Jülich, 52425, Jülich, Germany
Focused ion beam (FIB) milling has been widely used to prepare micron-sized specimens for micromechanical testing, but there are different types of artefacts originated from FIB. One is the imperfections in through-thickness notch geometries of microcantilevers. Bridge notches can overcome some of the problems by, upon loading, thin bridges fail first, creating atomically sharp natural cracks. Even though this bridge failure is widely assumed and predicted by FEM simulations, it has never been observed and quantified experimentally. This study presents the first experimental observation of cracking at the bridge notch and crack arrest before the entire through-thickness notch fails. This is possible by designing very thin bridges and using a very stiff loading rig with superior load resolution. Consequently, we obtained multiple fracture toughness values from one test. Using reported geometry correction factors calculated by FEM simulations, the fracture toughness estimated from the bridge failure was corrected and compared with the one from the failure of the through-thickness notch. The two approaches show consistent results.