| 摘要 |
PROBLEM TO BE SOLVED: To provide a thickness measuring method which can accurately measure a thickness.SOLUTION: A method for measuring a thickness d by propagating an ultrasonic wave 12 to a cast iron member 1 to be measured detects a surface reflection wave S which bounces on a surface 1a of the member 1 to be measured, a first reflection wave B1 which bounces one time on a rear surface 1b of the member 1 to be measured, and a second reflection wave B2 which bounces two times on the rear surface 1b of the member 1 to be measured. A time difference ratio of a first time difference from a time point at which the surface reflection wave S is detected up to a time point at which the first reflection wave B1 is detected, and a second time difference from a time point at which the first reflection wave B1 is detected up to a time point at which the second reflection wave B2 is detected is acquired, the second time difference when the time difference ratio is within a 1±error value is set as an effective second time difference, the second time difference when the time difference ratio is out of the 1±error value is set as an invalid second time difference, and the thickness d of the member 1 to be measured is calculated by using the effective second time difference without using the invalid second time difference. |
