SKM 2023 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 4: Topical Session: Fundamentals of Fracture – Micromechanical Fracture Experiments
MM 4.5: Vortrag
Montag, 27. März 2023, 12:15–12:30, SCH A 216
Size effect in fracture mechanics: a detailed investigation regarding crack initiation and growth on the micro- and mesoscale — •Jutta Luksch1, Aloshious Lambai2, Gaurav Mohanty2, Florian Schaefer1, and Christian Motz1 — 1Materials Science and Methods, Saarland University, 66123 Saarbruecken, Germany — 2Materials Science and Environmental Engineering, Tampere University, 33014 Tampere, Finland
Fracture mechanics are strictly regulated by standards. This includes limitations of specimen size as a function of the plastic zone size that mainly depends on the material itself. Hence, established test procedures are not easily downscalsble to nanomechanic testing. With progress in specimen preparation by FIB and test design e.g. in-situ testing in SEM, there are now ways to investigate a size effect systematically according crack initiation and growth. In the present study nanocrystalline nickel with a grain size of 40-50 nm is used as material to ensure a polycrystalline, quasi-homogeneous microstructure even for small samples. Micro bending beams of different dimensions are made using a FIB in order to study the fatigue size effect. Special attention was layed to introduce a fatigue pre-crack into the sample by cyclic loading with R<0 in a SEM with a nanoindenter. A study of crack initiation stress and number of needed cycles was made. The focus was given on microstructural changes. This pre-crack is then subjected to fatigue (R>0) and crack growth is quantified by the compliance method. In addition, the stress intensity factor is evaluated and related to the crack growth.