Load-separation method, Spb, used to estimate crack extension for J-R curves, modified for geometric variations in blunt-notched remaining ligament

Abstract

The Spb method estimates stable crack growth in fracture mechanics precracked specimens test. It compares the load ratio between a precracked specimen that exhibits stable crack growth and a blunt-notched specimen with apparent constant crack length when tested at constant displacement. When it was applied to very tough material, it was found that bluntnotched remaining ligaments varied by as much as 11.83 %, affecting visibly the results. Therefore, to apply the Spb method to very tough material for which non-standard specimens could be used as coiled tubing, the methodology limits are investigated. In this work, particularly the effect of geometry changes through an incipient crack growth produced on the blunt-notched specimens for very tough materials is analyzed. Hence, a modified Spb method is presented that takes into account the change in geometry of the blunt-notched specimens. Results provided in this paper are quite encouraging.