In order to investigate the validity on a size requirement for K_Ic testing in the proposed revision of ISO12135, W-a≥1. 1 (K_Q⁄σ_ys)² , and on that in the present standard of ISO12135, W-a, a, B≥2. 5 (K_Q⁄σ_ys)², we analytically investigated the effect of plasticity at the crack tip on a provisional fracture toughness K_Q calculated from the force, at which a force-displacement curve (F-V curve) intersects a secant line given in accordance with the above standard. The nonlinear component of the F-V curve is the sum of two parts, one due to the plasticity at the crack tip and the other to actual crack extension. 3-dimensional elastic-plastic finite element analyses of CT specimens with varying sizes have been performed to calculate K_Qpl, which means K_Q obtained as a result of the plasticity at the crack tip without the crack extension. In the case of standard specimen (W⁄B=2, a⁄W=0. 5) , the correlation between K_Qpl and ligament size (W-a) was approximately given by W-a=1. 5 K_Q⁄σ_ys)² . It was found that the present standard leads to a plane strain fracture toughness K_Ic with a crack extension more than about 1%of the initial crack length, provided that W-a≥2. 5 (K_Q⁄σ_ys)² . Meanwhile, in the case of the proposed revision of ISO12135, it was shown to recognize K_Qpl as K_Ic, although the size requirement of W-a≥1. 1 (K_Q⁄σ_ys)² was met.

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Effect of overloading types on the fatigue crack growth threshold of SUS316 was studied. Three types of overloading: tensile (type I) , tensile+compression (type II) , and tensile+compression+tensile (type III) were applied to compact tension specimens, then the fatigue tests were carried out to determine the apparent threshold stress intensity factor range Δ^NK_th. The results showed that the Δ^NK_th values increased with increasing the single tensile overload stress intensity factor K_ov above the K_ov > ΔK_th. Additional compressive loading (type II) led to decrease in Δ^NK_th to the ΔK_th=6MPa×m^1⁄2within the all tested K_ov values ranging from -45MPa×m^1⁄2 ≤K_ov<0MPa•m^1⁄2. This is due to the fact that the compressive residual stress field at crack tip changed to the tensile stress field by the compressive loading. Furthermore, the Δ^NK_th values increased again by additional tensile overloading (type III) from ΔK_th to the almost same Δ^NK_th values as that by Type I loading. This means that the almost same compressive residual stress field formed by type III overloading as the type I overloading. The experimental Δ^NK_th increasing behaviors were discussed by Finite Element Method (FEM) .

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The influences of the coating covered over the butt-welded bottom plate joint of oil tanks on the ultrasonic transmission factor and detectability of surface flaws are summarized in this paper, which were performed as one of the parts of projects for development of rational maintenance management of national oil-stockpiling tanks from 2009 by Japan Oil, Gas and Metals National Corporation.
As the rational examination method to substitute the magnetic particle examination that requires the removal of the present coating, the ultrasonic examinations by the creeping wave technique and the phased array technique using sector scans were discussed in this research.
Existence of coating is rather suitable for the ultrasonic transmission and reception of the creeping wave, and there was no necessity in particular for compensation of transmission loss. However, when the thickness of the coating had irregularity and the incidence angle to a specimen changed from the condition to emit creeping wave, amplitude of transmitted creeping wave was made rapidly small.
In the angle beam method, when the coating became thick, the transfer loss became larger, but it was able to evaluate flaws without underestimating to 1500 micrometers in coating thickness, by performing sensitivity compensation of 10 dB beforehand by using the polystyrene resin for the wedge material.
When flaw detectability was discussed using the butt-welded joints induced EDM notches and simulated natural flaws on the surface of welds and covered with the coating, especially in creeping wave technique, the result inferior to the detection of flaws induced on the reinforcement part was obtained. It was considered as a factor that bringing a result in which the creeping wave should spread the lower part of a notch due to height of the reinforcement of welds, and the propagation distance of a creeping wave became long, and attenuation became large.
On the other hand, according to phased array technique using the sector scans and the focusing ultrasonic beams, all flaws including simulated natural flaw could be detected, and it was evident that the phased array technique examined on the coated surface had sufficient ability of flaw detection for substitution of magnetic particle examination conducted after removal of the coating.

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In the former report, phased array testing which carried out the sector scan using focus beam had discussed and reported to have sufficient ability to detect the surface flaws on the butt-welded joint of the bottom plates in state-oil-stockpiling tank covered with tight coating painted to prevent corrosion of bottom plates. In this report, ultrasonic test system and scanning machine were discussed in order to apply to actual tanks. And confirmation test results for flaw detectability which performed using the test plates with EDM notches on the weld surfaces simulated the actual joint configuration of the bottom plates in state-oil-stockpiling tank and field verification test results which performed using weld line of about 1. 5km in 3 actual tanks were reported.
Simultaneous test system for flaws along the weld direction and flaws vertical to the weld direction were discussed. Two phased array probes were located at both sides of weld line in order to detect flaws along the weld direction from both sides of weld line with sector scans and to use by pitch-and-catch method for coupling check. Two angle probes of refraction angle of 70 degree were located emitting and receiving the ultrasonic beam in the direction of 45 degree to the weld line and crossing two beams at weld center line with 1 skip for vertical flaw detection to weld line. Scanning machine with laser tracking equipment was prototyped and proved to trace the laser beam emitted from over 50m distance through weld centerline by commercial low output laser transmitter with high accuracy.
In the confirmation tests using the test plates simulated the actual tank welds and in the actual 3oil tanks, it was confirmed that scanning system mounted ultrasonic test system was sufficiently functioning under 75mm⁄sec. of traveling speed, and had sufficient flaw detectability.

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The author has reported the incidents of the storage facilities for energy products in EST-1 Committee of High Pressure Institute of Japan. The information was obtained from the Internet at the time of the occurrence of incidents. In this paper, the outlines of 74 incidents of the storage facilities for energy products ocuured in 2012 are introduced.

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