Considerations on the method of determining mortar-received heat using aerial ultrasonic waves with finite amplitude

We examine a non-contact method of examining mortar samples, which were exposed to heat about 500° C to 1,000° C. This method makes use of high-intensity aerial converging ultrasonic waves (20 kHz) with finite amplitude. Mortar samples were vibrated at frequencies corresponding to the fundamental frequency (20 kHz) and plural harmonic components (40 kHz to 100 kHz) of the ultrasonic wave. It was found that the mortar samples influenced by the heat had clearly different vibration velocity ratios respectively produced by the ultrasonic emission at each frequency. This allows us to determine the influence of any previous heating of a sample by analyzing its vibrational characteristics.