METHOD AND APPARATUS FOR DETECTION OF CRACK IN BELTLIKE MATERIAL

摘要

PROBLEM TO BE SOLVED: To provide a method and an apparatus wherein a noise generated due to the shape defect of a steel plate is suppressed and only a crack is detected stably. SOLUTION: When the crack in a running beltlike material (12) is detected on the basis of the sampling value of an output from a sensor 22, it is judged to be a crack when the difference valueΔS(i) between a recent measured value S(i) and the mean value of the prescribed number of measured values in the past is large so as to exceed a prescribed threshold value and when the ratio of the difference valueΔS(i) to the value S(i) is within a prescribed range close to one.