Investigation on the rotational deformation of SEB specimens with various crack length to width ratio

AbstractA new CTOD calculation formula was proposed by using a correction factor for the blunted crack tip in the authors’ previous report[Kawabata et al(2016)], and the calculated CTOD by the formula significantly corresponded to the actual CTOD obtained by FE analysis in the wide range of specimen thicknesses. However, the use of the CTOD formula is limited to the frequently used crack depth-to-width ratio, a0/W, between 0.45 and 0.55, and this does not satisfy a strong demand for wider a0/W range. Meanwhile, ISO15653 covers a wider range of a0/W between 0.10 and 0.70, where J-based CTOD calculation formula has been specified in the annex-E of ISO15653. In this context, the plastic hinge model was investigated for a0/W between 0.05 and 0.70 by using FE analysis, and the analytical deformation of SEB specimens revealed that the plastic hinge model was applicable to the specimens even though their a0/W were out of the frequently used a0/W range from 0.45 and 0.55. Their rotational center points were almost steady when changing the applied load and the work hardening coefficient

OMAE2011-49594 DEVELOPMENT OF 6% NICKEL STEEL FOR LNG STORAGE TANKS

ABSTRACT 9% Ni steel has been used for LNG storage tanks for more than four decades although 5.5% Ni steel (N-TUF CR196) was developed in the 1970's using a special heat treatment method named L-treatment. The reason why the actual application of 5.5% Ni steel has not been attained to LNG storage tanks is mainly because the requirement of fracture properties is not confirmed for the tanks. Under the circumstances of expanding demand for natural gas and double-integrity in LNG storage tanks, we restarted developing low Ni steel for LNG storage tanks by using both conventional and advanced techniques. For the application of low Ni steel to the present LNG storage tanks, both fracture initiation and propagation properties of base metal plates and welded joints should be concerned. The fracture initiation and propagation properties of base metal were compensated with the intercritical reheating process (L-treatment), and the propagation property was additionally enhanced by combining TMCP with L-treatment. In addition, the chemical composition adjustment and the homogenization treatment of solute elements were conducted for improving the fracture initiation and propagation properties of welded joints. 6% Ni steel plates were manufactured by the process of continuous casting, reheating, hot rolling, direct quenching (TMCP), L-treatment, and tempering, and their chemical composition was 0.05C-0.06Si-1.0Mn-6.3Ni-Cr-Mo. As the results of fracture property evaluation including large-scale fracture tests such as the duplex ESSO test and the wide plate tensile test, it was demonstrated that 6% Ni steel has good characteristics regarding brittle fracture initiation and propagation in base metal plates and welded joints