On the fracture toughness evaluation in weldments of a maraging steel rocket motor case

Fracture toughness of the weld joints of the maraging steel rocket motor case obtained from the limited Compact Tension (CT) specimens are found to be invalid due to the measured crack lengths through the thickness of the specimens exceeding 10% of the initial crack length. This paper proposes an indirect method to evaluate the pre-crack length of the CT specimen from the recorded load versus crack mouth opening displacement data. The Chauvenet’s criterion is applied. After confirming the initial crack size and other validity conditions, the evaluated fracture toughness is designated as the plane-strain fracture toughness (KIC).