High speed holographic microscopy is applied to take three successive photographs of fast propagating.cracks at the moment of bifurcation. The cracks are propagated in PMMA plate specimens at a speed of about 660 m/s. From the photographs, crack opening displacement (COD) is measured along the cracks as a function of distance r from the crack tips. The measurement results show that the CODs are proportional to √r before bifurcation. After bifurcation, the COD, of mother cracks are proportional to √r, however, those of bifurcated cracks are not always proportional to √r. The energy release rate is obtained from the COD data, and is found to be continuous across the bifurcation point. The continuity of the energy release rate is explained through the fact that the bifurcated cracks appear as three dimensional cracks, not as through cracks.
|ジャーナル||Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A|
|出版ステータス||Published - 2001|
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