パルスホログラフィ法を用いた高速進展き裂の表面特異性とき裂前線角に関する実験的研究

概要

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An optical system of pulsed holography is developed and applied to take instantaneous photographs of both the opening and the front edge of a crack which is propagating through a PMMA plate specimen at a speed of several hundred meters per second. Crack opening displacement (COD) on a specimen surface is measured along the crack in the vicinity of the tip where the 3-D (three-dimensional) stress field is developed. The COD is proportional to the square root of the distance r from the crack tip. It means that the stress field on a specimen surface has the singularity of 1/√<r>, even in the 3-D stress field. The singularity is unchangeable even though the crack speed changes. Crack front edge angles, which are angles between a crack front edge and specimen surfaces, are also measured, and they are obtuse. In the case of a lower crack speed, the measured angles agree with the numerical result of a slowly propagating crack given by Bazant and Estenssoro. As the crack speed increases, the angles decrease and seem to approach 90 degrees. Some mechanisms which make the crack front edge angle decrease are discussed.
一般社団法人日本機械学会の論文
1990-12-25