Verification of stress-intensity factors for various middle-crack tension test specimens

Recently, the stress-intensity factor equation used in the ASTM Standard Test Method for Measurement of Fatigue Crack Growth Rates (E-647) for the middle-crack tension M(T) specimens (friction-gripped or pin-loaded) has been questioned due to the influence of the specimen “height” specified in the standard. A boundary-element code has been used to calculate the stress-intensity factors for a wide range of crack-length-to-width ratios and various height-to-width ratios for M(T) specimens under remote uniform stress, remote uniform displacement, or pin-loaded holes. Comparisons are made with some of the well-known stress-intensity factor solutions and equations in the literature. Recommended specimen heights and stress-intensity factor equations have been made.