Validity requirements for fracture toughness measurements obtained from small circumferentially notched cylindrical specimens

The authors have earlier proposed a small cylindrical circumferentially notched and fatigue cracked specimen for estimating K_Ic Finite element studies carried out are discussed with specific attention to the comparison between K_Ic thus obtained to that obtained experimentally. The size of the plastic zone is of particular interest in respect of the validity of the results; the F.E. result is compared to that obtained using Von Mises and Irwin approximations. Validity requirements are proposed for this specimen considering general yield of the final ligament, final ligament size, plastic zone size and depth of fatigue crack.