Currently adopted modified-WOL specimen has difficulty in producing fatigue precrack. And Ktscc evaluation using the analytic compliance formula has many problems. Hence, Oh and Kim(1989) have designed such a specimen geometry as mixed modified-WOL with CT types. and proposed the experimental evaluation techruque for bolt-load(consequently KrscC>. With this specimen, stress corrosion cracking and subsequent Jic test has been performed in 20% HCI solution saturated with as gas.
Among the test methods to evaluate stress corrosion cracking on the basis of fracture mechanics, constant-displacement (bolt) loading method using modified-WOL specimen (Novak and Rolfe, 1969; Lisagor, 1984) is practically convenient test procedure because it needs no external stressing equipment. Besides, it facilitates exposure to operating service environments. As stress corrosion (or corrosion/corrosion fatigue) might show very different behaviors by the delicate change of the environment, the above facility can be considered as important merit for Industrial application. Fell this method meanwhile compliance formula is generally required to calculate bolt-load (consequently Kiscc) if Instrumented bolt (Gilbreath and Adamson 1976) is not used. By the way, the analytic compliance values have to be transformed according to the state-of-stress. And the exact values of material constants (E, v) are requisite to calculate the bolt-load. And also the possibility of stress relaxation and/or creep for long-term test cannot be considered. Furthermore, Oh and Kim(1989) have reported that the analytic compliance formula had difficulty in being, applied to the case of ductile materials. Therefore, it is necessary to develop new experimental evaluation method for bolt-load. In this study, we have adopted the altered configuration of modified- WOL specimen (that is, mixed modified-WOL With CT specimen geometries) in order to produce fatigue precrack easily and also to propose the experimental evaluation technique for boltload (or Krscc) instead of using the analytic compliance formula.
