RU2002100682A - Method for detecting cracks in a solid body and device for its implementation - Google Patents

Claims (2)

1. A method for detecting cracks in a solid, which consists in the fact that primary acoustic waves of various frequencies are excited in a solid, which, interacting on a crack, generate secondary acoustic waves at combination frequencies, measure the amplitudes of the primary and secondary waves, based on which the presence coefficient is determined cracks, characterized in that the primary acoustic waves are produced by sequentially exciting ultrasonic waves at a number of frequencies simultaneously with each of the ultrasonic frequencies in excitation of elastic vibrations at natural frequencies by means of shock on a solid, the natural frequencies are measured, and the combination frequencies are defined as the sum and difference of each frequency of ultrasonic waves from each of the natural frequencies of elastic vibrations, and the crack presence coefficient is calculated by the formula

where K _nt - the coefficient of the presence of a crack; i = 1 ... N - numbers of natural frequencies of elastic vibrations; j = 1 ... M - numbers of frequencies of ultrasonic waves; N is the number of used natural frequencies of elastic vibrations, N≥2; M is the number of frequencies of ultrasonic waves, M≥2; A _ij is the amplitude of the elastic oscillation at the natural frequency with number i when an ultrasonic wave is excited at a frequency with number j; A _j is the amplitude of the ultrasonic wave at a frequency with number j; A $\genfrac{}{}{0ex}{}{\text{(-)}}{\text{ij}}$ - the amplitude of the wave at the combination frequency, formed as the difference in the frequency of the ultrasonic wave with number j and the natural frequency of elastic vibrations with number i; A $\genfrac{}{}{0ex}{}{\text{(+)}}{\text{ij}}$ - the wave amplitude at the combination frequency, formed as the sum of the frequency of the ultrasonic wave with number j and the natural frequency of elastic vibrations with number i. 2. A device for detecting cracks in a solid body, comprising a unit for generating elastic vibrations connected to a solid body and a unit for receiving transducers connected to an output processing unit, characterized in that a unit for impact excitation of elastic vibrations connected to a solid body is introduced at natural frequencies.