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.