Issue 37

A. Eberlein et alii, Frattura ed Integrità Strutturale, 37 (2016) 1-7; DOI: 10.3221/IGF-ESIS.37.01 1 Focussed on Multiaxial Fatigue and Fracture Crack front segmentation under combined mode I- and mode III- loading A. Eberlein University of Paderborn, Institute of Applied Mechanics, Pohlweg 47-49, 33098 Paderborn, Germany eberlein@fam.upb.de , http://mb.uni-paderborn.de/fam/ H. A. Richard University of Paderborn, Institute of Applied Mechanics, Pohlweg 47-49, 33098 Paderborn, Germany richard@fam.upb.de , http://mb.uni-paderborn.de/fam/ A BSTRACT . This article approaches the topic of crack initiation and crack growth behaviour under combined mode I- and mode III-loading conditions. Such loading combinations especially lead to a crack, which unscrew out of its initial orientation and segments into many single cracks respectively facets. This characteristic depicts the crucial difference to a crack growth under pure mode I-loading, pure in-plane shearing (mode II) as well as 2D-mixed-mode-loadings. Since this stepped fractured surfaces thus far are proved little and therefore their characterisation remains to be done, a facets quantification using some characteristic dimensions will be performed within this article. After the description of experiments for facet creation the facet’s quantification using the crack profile near the initial position each facet will be analysed concerning characteristic dimensions. Finally the findings will be illustrated and discussed in this contribution. K EYWORDS . 3D-mixed-mode; Facets; Fatigue; Fracture; CTSR-specimen. I NTRODUCTION by today unsolved and long existing research matter in fracture mechanics is the characterisation of crack initiation and growth behaviour under combined mode I- and mode III-loading. This loading combination specially leads the initial crack to twist out of its previous direction and separate at once into multiple daughter cracks, afterwards called facets. Building on the researches and findings from Sommer [1], Knauss [2] as well as Pons and Karma [3] within this article a quantification of facets will be presented and discussed. The purpose is to get new insights and facts about facets creation and initiation. E XPERIMENTS FOR F ACET C REATION reating facets experiments under mixed-mode I + III-loading were performed using the CTSR-specimen and corresponding loading device [4, 5]. A detailed explanation of the experimental procedure and CTSR-specimen’s geometry follows below. A C