R-curve evaluation and bridging stress determination in alumina by compliance analysis

A procedure is proposed which allows for bridging stress determination and R-curve evaluation from compliance data. R-curves were obtained on the single edge notched beam (SENB) and double torsion (DT) specimens by in situ and direct measurements of crack lengths. The compliance of DT specimens with different successive re-notching and without re-notching was compared. An approach for determining crack bridging stresses of the crack wake from the results of compliance measurements was extended for different grain sizes of alumina ceramics. By this compliance analysis, the KR- curve of alumina ceramics can be predicted from the compliance function, φ(Δa), versus the crack extension, Δa. The results show that compliance analysis can be a powerful tool for crack bridging stresses evaluation and even for R-curve prediction.