Numerical simulation of the Mode-I fracture toughness measurement via cracked chevron notched semi-circular bend rock specimens

Feng Dai, Mingdong Wei, Nuwen Xu, Biao Li, Yuan Xu

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Abstract

Chevron notched samples achieve general acceptance for measuring the Mode-I (opening mode) fracture toughness of rocks. The cracked chevron notched semi-circular bending (CCNSCB) sample, which is developed from the International Society of Rock Mechanics suggested the cracked chevron notched Brazilian disc method, has recently received much attention. However, these chevron notched methods have not been fully mastered, some ideal assumptions based by their theories and formulas, such as the straight-through crack assumption (STCA), have not been verified detailedly. Fractures of CCNSCB specimens were numerically simulated considering different heterogeneities, geometrical and mechanical parameters. The results show that, the real fractures of CCNSCB specimens are never satisfied with the STCA. In fact, micro fractures not only occur in the notch tip but also the two chevron edges. Consequently, the crack front features prominently in a shape of parabolic curve, far from being straightthrough. Moreover, curvature of the crack front is only affected by shape of the chevron ligament. Cracks usually start from two sides of the notch tips rather than center of the notch width, and propagate deviating from the postulated fracture routes. These fracture mechanisms induce errors with the measurements, and thus more attentions should be paid to the real fractures of the chevron notched samples for measuring fracture toughness more accurately.
Original languageEnglish
Title of host publication13th ISRM International Congress of Rock Mechanics, 10-13 May, Montreal, Canada
Publication statusPublished - 2015
MoE publication typeA4 Article in a conference publication

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