Dresden 2017 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 70: Mechanical Properties II

MM 70.2: Talk

Thursday, March 23, 2017, 17:15–17:30, IFW D

Towards understanding fracture toughness experiments at the microscale — •Steffen Brinckmann and Gerhard Dehm — Max-Planck-Institut für Eisenforschung

Micrometer cantilever beams are frequently employed to determine the fracture toughness of (1) single phases in poly-phase materials as well as (2) particular grain boundaries. The determination of the mechanical properties mostly relies on the experimentally determined maximum force and analytical models which are build for brittle and isotropic materials. However, the vast majority of materials has a limited amount of plasticity and is anisotropic. Moreover, the cantilever width has an influence on the fracture toughness since the crack driving force is maximal in the beam center and plane-stress conditions apply at the beam surface. This contribution uses the results of more than a thousand 3D simulations and quantifies the influence of anisotropy, Poisson's ratio and beam geometry. At the end of the contribution, we discuss the influence of plasticity and its challenges. We give best-practice guidelines for microbeams and discuss the changes in fracture toughness, if guidelines cannot be fulfilled or if anisotropic materials are studied.