Volume 14, Issue 1 (January 1986)
Determination of Fracture Toughness by CTOD Resistance Curve Method
Fracture toughness δi of AISI 4340 steel in the hardened and tempered condition has been determined by the multiple-specimen CTOD (crack tip opening displacement) resistance curve method. This fracture toughness δi value has been compared with the JIc fracture toughness also obtained by the multiple-specimen JR curve technique. The investigation also examines the effect of specimen size, thickness, and width on δi and δR curve behavior. The effect of these parameters on the constraint factor m in the J-δ relationship has also been examined. Compact tension specimens with TL orientation were used. All specimens satisfied ASTM E 813 standard size requirements.
This investigation demonstrates that Jδi values obtained by the CTOD resistance curve method are similar to JIc values obtained from the J-integral resistance curve method. The specimen thickness has no significant influence on δi or δR curve behavior. On the other hand, specimen width has a distinct influence on constraint factor m and δR curve behavior.