A capability of conducting linear elastic (KIC) and elasticplastic (JIC) fracture toughness tests on three point bend specimens is demonstrated. Machine-to-specimen interface grips and fixtures are designed and fabricated. Provisions are made for easy modification to testing of compact tension (CT) or four point bend specimens.
ASTM E399-72 standard test for plane strain fracture toughness determination; ASTM task group E24.01.09 multiple identical specimens (R-curve) test and energy rate test for elastic-plastic fracture toughness determination are conducted. A ductile, CSA G.40.8/A-3, steel and a brittle, 4340-800F, steel are employed in the experimental investigation.
Fatigue crack growth rate data is obtained for both steels during fatigue precracking of specimens.
Estimation formulations of Rolfe and Novak and Hahn and Rosenfield are used to obtain KIC estimates. Analytical estimation procedures of Bucci et al and Rice et al are utilized in obtaining JIC estimates.
Fracture toughness values obtained via various testing and estimation methods are compared and success of each method is discussed.