| 摘要 |
PURPOSE:To discriminate the condition of an internal crack and judge whether a metallic test piece having a crack at the top end of a notch is non-defective or defective by pulling both side parts of the notch thereof to the outside and measuring the change in the width in the aperture of the notch. CONSTITUTION:The test piece is manufactured by forming the notch 3 to a test piece 1 and pulling repeatedly both side parts 4 to generate the crack 2 at the top end of the notch 3. The crack 2 is not always generated in a straight line shape and is generated sometimes as shown by a dotted line (b) in this stage. The width D in the aperture increases when tension F is exerted to the parts 4 to outer side. The ratio D/F changes with the actual length of the crack entering the inside of the test piece, for example, the tension point 5 and the length d2 of the internal crack. The width D in the aperture is then measured and the crack d2 is estimated therefrom. The crack d2 and the crack d1 on the surface are compared. Whether the compared value is within a prescribed reference or not is determined and the length of the internal crack is discriminated. Since the internal crack is discriminated, whether the test piece has the ideal crack or not is adequately judged. |
