PSI - Issue 21

Taiko Aikawa et al. / Procedia Structural Integrity 21 (2019) 173–184 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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1. DWTT test focusing on brittle crack propagation by container ship fracture scenario As shown in previous chapter, anti-crack-propagation property evaluated by three-sided slit Charpy test can support the arrest toughness difference by the fracture scenario evaluated by ultra-large test (Matsumoto, 2018). Although the three-sided slit Charpy test specimen is considered to contain much less initiation energy than the normal V-notch test specimen, it is true than some energies are dissipated due to crack initiation. Here, similar evaluations were carried out by the DWTT test which can focus on the propagation phenomenon of brittle crack. In this study the specially fabricated DWTT specimens were used in order to investigate the brittle crack propagation arresting property both in the thickness and in the width directions. As shown in Fig. 11 the central part of the specimen was replaced with TMCP material by electron beam welding, and the sampling position of the replacement part was changed so that the crack propagation direction was switched as shown in Fig. 12.

Fig. 12 Machining of the DWTT specimen and dimensions

Mark

TMCP part

#1

Crack propagation in thickness direction from plate surface

#2 Crack propagation in plate width direction Fig. 13 Test Specimen sampling method of the TMCP part

3.1. Test steel

The brittle running plate of the test piece was subjected to heat treatment (Quenching and Tempering) for toughness deterioration and elimination of the texture. The V-notch Charpy transition temperature, v T rs of the brittle running plate was estimated to be between -40 ° C and -50 ° C from the preliminary test. The brittle crack arrest performance was discussed by using the same material with the TMCP steel used in the three-sided slit Charpy test explained in the previous chapter.

3.2. Experiment and result