| 摘要 |
PURPOSE:To predict the degradation of steel material in advance and establish a diagnosis method with high prediction accuracy and with superior evaluation of degradation of steel structures by casting ultrasonic wave on a steel material and measuring the longitudinal wave or reaching velocity of the longitudinal wave and transversal wove of the ultrasonic wave. CONSTITUTION:A steel material degrades with time due to weight load, repeated bend by the weight, vibration heat etc. Accompanied by the progress of degradation, carbide precipitates in grain boundary inside the steel material. If ultrasonic wave is cast on this degraded steel material, the transmission velocity of the ultrasonic wave becomes fast in the carbide layer precipitated in the grain boundary and the velocity of the incident wave and reflection wave becomes fast. Using this characteristics, the velocity characteristics of the reflection wave and incident wave at early stage, middle stage and final stage of the steel material are obtained for each kind of steel to form a standard characteristics. Then, by casting ultrasonic wave to a steel material in an arbitrary stage of time elapsing, the longitudinal wave of the incident wave and reflection wave or reaching velocity of the longitudinal wave and the transversal wave of the ultrasonic wave at this moment is measured, which is compared with a reference value to judge the degradation of the steel material. |
