The effects of in-plane and out-of-plane constraints on J-R curves for X80 steel: A study using clamped SENT specimens

Abstract

In the present paper, an experimental program was carried out to develop J-R curves using clamped single edge notched tension (SENT) specimens. A wide range of geometrical parameter variations is considered including different crack depth to plate width ratios (a/W) and plate thickness to width ratios (B/W). The material studied is the oil and gas pipeline steel API X80. Power law curve fitting parameters and tearing modulus are obtained for the J-R curves using the unloading compliance (UC) method for the clamped SENT specimens. Moreover, in-plane and out-of-plane constraint effects on J-R curves using clamped SENT specimens are studied, the second terms in the Williams’ series expansion are used to quantify the constraint effects. Specifically, it is demonstrated that the normalized T11 and the independent portion of T33, which equals T33-νT11, can be used to quantify the in-plane and out-of-plane constraint effects, respectively. Comparisons show that the constraint dependent J-R curves can reproduce well with all experimental data for clamped SENT specimens. Finally, the present approach is applied to predict the J-R curves of ductile crack extension for other specimens or real engineering structures with varying in-plane and out-of-plane low constraint conditions.