| 摘要 |
PROBLEM TO BE SOLVED: To provide a method, capable of reducing measurement variations than in a visual method without depending on a visual check, and capable of determining the moment when the crack penetrates a plate thickness in a hole expanding test of a metal material.SOLUTION: The method includes the steps of: abutting and pressing a conical punch 2 into a punched hole 11 in a metal plate 10; imaging a profile of the punched hole 11 by an imaging device 4 according to time and inputting image data to a data processor 5; processing images for clarifying an inner circumferential end 13 of a punched hole plate thickness cross-section 12 in a picked-up image 7 at each time; acquiring position data of the inner circumferential end 13 in a circumferential direction over an entire circumference of the punched hole as a measuring point 15; defining a true circle approximate to the position data of the measuring point 15 as a pseudo circle 16; and determining a hole expanding limit when a distance between the measuring point 15 and the pseudo circle 16 exceeds a determination threshold at consecutive measuring points equal to or greater than predetermined determination points. |
