Volume 37, Issue 2 (March 2009)
Evaluating the Onset of Tearing in Elastic-Plastic Fracture Toughness Testing Using In Situ Optical Microscopy
Fracture toughness, in the sense of material resistance to ductile tearing from an initial sharp defect, is a common metric for structural integrity assessments of engineering components. While standardized test methods are well-suited for repeatable estimation of this metric, physical observation of crack-tip opening displacement (CTOD) and tearing may provide a supplemental means of evaluating the onset of tearing with greater accuracy in ductile materials. In contrast to previously documented methods of physical CTOD measurement, in situ optical microscopy on standard sidegrooved fracture toughness specimens presents an easily implemented, cost-effective tool for observing tearing onset. As an additional benefit, quantitative measurements of CTOD from in situ optical microscopy also provide a means of cross-checking standard J-integral results as determined from load-displacement test data.