A NEW METHOD FOR MEASUREMENT OF FRACTURE-TOUGHNESS K(1C) BY 3 POINT BEND SPECIMEN

The relationship between the three point bend (TPB) specimen size and the measured fracture toughness K(IC) value is analyzed by the theory of crack opening displacement (COD). According to the concept of plane strain fracture toughness K(IC), a new formula for K(IC) is presented. For small-scale or large-scale TPB specimens, the K(IC) values of material can all be obtained from the new formula and the corresponding curve of load versus crack mouth opening displacement (CMOD). For large-scale specimens, the new formula is compatible with the ASTM standard.