Effect of temperature on measurement of stress by ultrasonic critical refractive longitudinal wave

Key words:  critical refractive longitudinal wave  stress  temperature  flight time  ultrasonic transducer

Abstract:

The ultrasonic critical refraction longitudinal wave (LCR wave) method is an effective method for nondestructive testing of structural stress. The ultrasonic LCR wave method is a sensitive measurement method, i.e. the temperature directly affects the propagation speed of the ultrasonic wave, and it also causes the size change of the ultrasonic transducer. According to the basic theory of ultrasonic stress measurement, i.e. the theory of acoustoelasticity, the quantitative relationship between the acoustoelastic coefficient, flight time and temperature under zero stress was analyzed, and the temperature compensation formula for ultrasonic stress measurement was obtained. The flight time of ultrasonic LCR wave at different temperatures was measured by experiments. The result shows that the effect of temperature on the stress measurement of ultrasonic LCR wave is attributed to the influence of temperature on the sound range of ultrasonic LCR wave propagation. The higher the temperature is, the longer the effective sound range of ultrasonic LCR wave propagation is. The designed ultrasonic transducer with one transmitter and two receivers can effectively eliminate the influence of acoustic wedge and coupling agent, reduce the influence of temperature to 10%, and significantly improve the measurement accuracy and stability. The relationships between flight time and temperature obtained by experimental measurement and theoretical calculation are in good agreement, and this fact fully verifies the accuracy of the compensation formula.