Facet formation at the crack front under combined crack opening and anti-plane shear loading

This article addresses the topic of crack initiation and crack growth behaviour under combined cyclic mode I- and cyclic mode III-loading. Such loading combinations especially lead to a crack, which unscrews out of its initial orientation and segments into many single cracks respectively facets. This characteristic of facet formation depicts the crucial difference to crack propagation under pure mode I-loading, pure in-plane shearing (mode II) as well as 2D-mixed-mode-loadings. Since investigations about these stepped fractured surfaces are scarce till today, their characterisation remains to be researched deeper. Consequently, a facet quantification is performed by some characteristic dimensions, which will be presented and discussed within this paper. After the description of experiments for facet creation, a quantification of each facet will be analysed concerning characteristic dimensions by the crack profile near the initial position. Finally, the findings will be illustrated and discussed in this contribution. (C) 2016 Published by Elsevier Ltd.