PURPOSE: To enable non-destructively evaluating the breaking characteristics of a brittle material by applying a tensile stress to subjects to be inspected, measuring the frequency of occurrence of acoustic emission generated from them, and calculating the damping characteristic of the frequency of occurrence.
CONSTITUTION: About 40 test pieces each of which is about 8cm by about 2cm by about 1.15cm are cut from a cordylite ceramics pipe which is about 14cm in bore, about 17cm in outside diameter and about 70cm in length, and the average bending strength is calculated from 10 of the test pieces. Next, two acoustic emission sensors are attached to each test piece, and the test piece is bent at three points for a destructive test, so that the number of acoustic emission (AE event number) per minute is measured. As tensile stress approaches the breaking stress of the test piece, the gradient of the damping curve of the AE event number gets gentler. Therefore, when a constant tensile stress is applied to a number of subjects to be inspected and the gradient of the damping curve of the AE event number generated is gentle, the breaking stress of the subjects to be inspected can be judged to be small.
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