| 摘要 |
PROBLEM TO BE SOLVED: To automatically switch from load speed control to retention control by capturing a time point when the aging change rate of a displacement-detection result exceeds a prescribed ratio as the transition time point of a test piece from an elastic region to a plastic region for controlling a load mechanism. SOLUTION: Both the ends of a test piece are gripped by gripping tools 14a and 14b provided between cross heads 11a and 12a of fixed and movable frames 11 and 12, and the movable frame 12 is moved up by the drive of a hydraulic ram cylinder 13 for applying pull to the test piece. The load, the displacement of the movable frame 13, and the extension of the test piece are detected by a pressure cell 41, a stroke detector 43, and an expansion meter 45, respectively, and are taken in by a control part 30. The control part 30 uses the load detection data for the load speed control of the hydraulic ram cylinder 13. Also, when a differenceΔL between the most recent and last displacement data of the movable frame 13 and displacement data differenceΔL' in the case of the previous data sampling do not satisfyΔL>=αΔL' (αis a prescribed coefficient), it is judged that the sample piece is still in an elastic region, and load speed control is continued. On the other hand, when they satisfy the expression, it is judged that the test piece has entered a plastic regions, thus switching to retention control.
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