APPLICABILITY OF THE CONTOURED DOUBLE CANTILEVER BEAM SPECIMEN FOR CRACK GROWTH TESTS UNDER CONSTANT STRESS INTENSITY FACTOR

摘要

Contoured double cantilever beam (CDCB) specimens have been used for stress corrosion crack growth tests in high temperature water since they give constant stress intensity at constant load independent of the crack length. In addition, cracking behavior can be evaluated based on longer crack penetration lengths, and therefore precise growth rates and transition behavior attributable to temperature, water chemistry have been reported by several researchers. CDCB specimen size and geometry are designed according to the similarity rule considering the limitation of testing felicities and required crack penetration length for the tests. It is known that the constant trend of stress intensity along the crack length is dependent on the specimen size. In this current investigation, constancy of stress intensity factor and its valid range in the crack length is experimentally evaluated. According to the crack growth rates obtained along the crack length, stress intensity along crack length was confirmed to show constant trend within a limited variation for each specimen type. Some of the specimen types showed constant trends in which stress intensity variation within 5% was maintained in more than 10 mm of crack length range, even those specimen widths were only 60 mm. Recommendations regarding the range of acceptable behavior as a function of the specimen geometry are included.