ULTRASONIC NONDESTRUCTIVE DETECTION METHOD FOR EXPANDED SIZE OF MICRO CRACK OF MATERIAL

摘要

An ultrasonic nondestructive detection method for the expanded size of a micro crack, comprising: constructing a measurement system; fabricating multiple reference samples, and performing repeated fatigue test on each reference sample respectively; performing metallographic observation after each fatigue test so as to obtain the length of micro cracks in each reference sample, and performing ultrasonic nonlinear Lamb wave measurement to obtain a nonlinear parameter β₀ of each reference sample; obtaining a nonlinear parameter-fatigue life curve, and marking micro crack sizes corresponding to various points on the curve; and performing nonlinear ultrasonic Lamb wave measurement on a sample to be tested, so as to obtain a nonlinear parameter β₀ thereof, finding a point corresponding to the nonlinear parameter β₀ in the curve, and finding the length of a micro crack corresponding to the point. Thus, the relationship between a micro crack size and a nonlinear parameter is used for determining the length of a micro crack and representing a fatigue damage, which will not damage in-service equipment, thereby quickly detecting the micro crack state of an active material at a low cost.