PSI - Issue 42

Toru Yagi et al. / Procedia Structural Integrity 42 (2022) 702–713 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

704

3

1500m/s based on the experiment, but the crack decelerates during the crack propagation, so the crack speed is set to be 100m/s in this study. Based on this theory, the maximum crack length of un-affectedly arrested brittle crack in the standard bending specimen is 4% of ligament and it corresponds to 5% of load drop ratio of pop-in which is shown is Fig. 1.4.

Fig. 1.3 Schematic illustration of pop-in and stress wave propagation in a three-point bending test specimen.

Fig. 1.4 Relationship ∆ / 0 and 0 /W

1.3. Objective

The mechanism of a pop-in crack formation is not clarified. The reasons are the followings. • Difficulty to produce a test specimen that can stably generate pop-ins. • Difficulty to analyse the behaviour of a pop-in crack since a pop-in crack is a microscopic high-speed brittle crack which originates, propagates, and arrests within the plate. • Difference in the loading mode between bending test and the real structures. The objective of this study is to investigate of mechanism of formation of pop-in and improve the pop-in acceptance criteria. In this study, two approaches are used to breakthrough. • Utilizing the stress intensity factor. • Applying the FEM analysis with the idea of energy dissipation..

Nomenclature B

thickness of test specimens [mm] width of test specimens [mm]

W