Ultrasonic velocity measurement for analysis of brick structure

In order to evaluate material properties of brick structures constructed for railroads more than one hundred years ago, ultrasonic velocity measurements were performed around Japanese island of Honshu, and relationships between ultrasonic velocity and material properties (compressive and tensile strength, and elastic modulus) of brick structure was analyzed. Ultrasonic velocity is related to mechanical properties of material; therefore strength of brick structures can be estimated from ultrasonic velocity measurements. It was found that there are significant relationships between ultrasonic velocity and material properties. Acoustic physical properties of brick structures were measured at the same time. A new cross-correlation velocity measurement method was developed. In this method, a 50-kHz Gaussian pulse was used with its spectrum is matched to the transducer bandwidth for effective enhancement of measurements in large attenuations, and received signal was cross-correlated with transmitted Gaussian pulse. This method was very much effective to noisy weak signals propagating through brick structures.