Professor and Associate Chair for Academics, University of Washington, Seattle, WA
NASA Glenn Research Center, Cleveland, OH
Research Scientist, National Institute for Standards and Technology, Gaithersburg, MD
Professor, Worcester Polytechnic Institute, Worcester, MA
Pages: 27 Published: Jan 2002
The dawn of a new age in understanding fracture of brittle material occurred in 1999 (eight years after an ASTM task group on fracture toughness of advanced ceramics was formed) when a national full consensus fracture toughness test method standard was approved as ASTM Test Methods for the Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperature (C 1421 ). C 1421 uses common flexure test specimen geometries (typically 3 × 4 × 50 mm) in conjunction with three and fourpoint flexure test configurations. Three different types of notch/crack geometries are employed: single edge precracked beam (SEPB); surface crack in flexure (SCF); and chevron-notched beam (CNB). Extensive experimental, analytical, and numerical evaluations were conducted prior to and during the approval of the standard. Several round robins (e.g., VAMAS) verified and validated the choice of dimensions and test parameters. Two concurrent post-approval implementations of the standard are cited: i) fracture tests of a single composition of an advanced ceramic led to the introduction of a standard reference material (SRM) for fracture toughness and ii) fracture tests on two different compositions of a ceramic system showed the statistically significantly greater fracture toughness of one material for a wear application.
advanced ceramic, fracture toughness, chevron notched beam (CNB), single edge precracked beam (SEPB), surface crack in flexure (SCF)
Paper ID: STP10471S