| 摘要 |
PURPOSE:To simplify the operation of a crack length, in a test for obtaining a fatigue crack developing curve according to a charge removing compliance method, by calculating the origin of plastic aperture displacement in a region where the variation width of stress magnifying coefficient is a threshold value or less. CONSTITUTION:A compact test piece 7 is set to a tester and an actuator 1 is operated by the order from a computer 4 to introduce a fatigue crack with a predetermined length into said test piece 7. Subsequently, the actuator 1 allows repeating load to act on the test piece 7 while the variation width of stress magnifying coefficient is made constant under the control of a servo controller 5 and the computer 4 calculates a crack developing speed. This operation is repeated until the aforementioned variation width reaches a threshold value while gradually reduces. At this time, the computer 4 calculates the origin, that is, plastic aperture displacement at the time of the min. load according to the method of least squares and is subsequently changed over to plastic aperture displacement constant control and uses the origin according to a charge removing compliance method to operate a crack length.
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