R-curve behaviour of metallic glass ribbons

Abstract

In this paper we show that metallic glass ribbons obey the laws of plane stress fracture very well. The centre crack tensile specimen was used to investigate the subcritical crack extension prior to catastrophic failure on two alloys. The resulting R-curves are used to reconstruct the experimentally observed variation of the critical stress intensity factor,K _c, with initial crack length. Taking into account only the measured subcritical crack extension (up to 50μm) a good qualitative correlation is obtained. Starting from that experimental observation and using very simple assumptions about the variation of the shape of the R-curve as the material embrittles, we propose a schematic description of howK _c may vary when the ribbons are annealed and if short or large initial crack lengths are used. An experimental verification is made on one of the alloys.