Experimental J estimation equations for single-edge-cracked bars in four-point bend: homogeneous and bi-material specimens

The present paper provides the plastic η factor solutions for J testing of single-edge-cracked specimens in four-point bend (SE(PB)), based on limit (slip line field) and detailed finite element limit analyses. Both homogeneous specimens and bi-material specimens with interface cracks are considered. Moreover, two different η factor solutions are developed, one for J (or C* in creep crack growth testing) estimation based on the load–load line displacement (LLD) records, ηpVLL, and the other J estimation based on the load-crack mouth opening displacement (CMOD) records, ηpCMOD. found that the use of load–LLD records can be recommended only for testing deeply cracked SE(PB) specimens. Moreover, depending on how the LLD is measured, a different value of ηpVLL should be used. On the other hand, the use of load–CMOD records is recommended for all possible crack lengths. Moreover, the proposed ηpCMOD solution can be used not only for a homogeneous specimen but also for any bi-material specimen with an interface crack.