| 摘要 |
PURPOSE:To automatically detect the proportional limit of a material, by a method wherein detection data related to the load and the elongation of a test piece are stored by sampling and the gradient of a stress-strain curve is calculated to calculate the relation of the newest gradient and the just-before gradient. CONSTITUTION:The load applied to a test piece W and the elongation of said test piece W are detected by a load cell 2 and an elongation gauge 4 and the detected values are taken in a control part 8 at every 50ms through amplifiers 3, 5 and A/D converters 6, 6 to be stored by RAM. The gradient of a stress- strain curve is calculated from the n-sets of data thereof by a method of least squares. The newest gradient dn and the gradient dn-1 just prior thereto are compared while the value of the formula alpha=(dn-1/dn-1)n is compared to a set value alpha' and, if the formula alpha>=alpha' is formed three times continuously, the load value at the initial forming point thereof is detected as proportional limit. By this method, the proportional limit is automatically detected. |
