| 摘要 |
PURPOSE:To make the stopping of the progression of a cracking during the course thereof possible in destructive testing by opening a through-hole of a circular shape in the central part of a rectangular test piece, providing a sharp notch on the extension of the diameter in the long side direction of said hole, and applying compressive load in the long side direction. CONSTITUTION:A rectangular test piece of which the length L in the y-axis direction is 2-5 times the width W in the x-axis direction is made and an opening 2 of a circular shape is penetrated in the central part. The diameter 2R of the opening 2 is set at 5-50mm., and the width W of the test piece at 2-15 times the 2R. In the end part of the diameter of the opening 2 in its y-axis direction, a sharp notch 3 of <=0.1mm. the radius of the leading end and the length about 0.2 times the 2R is worked on the y-axis. When compressive load sigma is loaded in the y-axis direction of this test piece, a cracking 5 is generated in the leading end part of the notch 3 and develops. At this time, the relations among the sigma, the cracking length (a), the coefft. K of stress expansion and the radius R are as shown in the figure, and if the a/R exceeds about 0.2, the K decreases with an increase in the (a). Hence, when constant load is applied, the progression speed of the cracking decreases gradually and stops on the way. |
