High strength materials are prone to failure in presence of flaws/cracks and this is expressed through the fracture toughness of the material. In fracture base design, the structure should be designed such that for a detectable minimum/or design allowable flaw size the structure under given service condition, the stress intensity factor (K) at the crack tip should always be less than KIc, the plane strain fracture toughness. In view of the sensitiveness of the parameter to the material conditions in terms of heat treatment, grain size, etc. it has become generally necessary to confirm the achieved KIc with respect to what is required by the design. It has been found extremely difficult and impractical to follow standard tests for KIc determination especially at various stages of fabrication/quality control, in view of involved procedures, for testing and to meet the validity conditions of the test. In fracture toughness testing, the Compact Tension (CT) specimen is recommended as one of the standard specimens. Many times the test becomes invalid as per ASTM E 399 standard. Since fracture toughness testing is a costly affair, it is preferable to minimize the number of repeat tests. A simple J-integral method is adopted for assessing the fracture toughness from the invalid test data of standard CT specimens.
V.M.J. Sharma, V. Diwakar , K. Sree Kumar , B. Nageswara Rao and S.D. Pathak , 2006. A Simple J-integral Approach for Fracture Toughness Assessment on Invalid Test Data of Standard CT Specimens. Trends in Applied Sciences Research, 1: 132-143.