Abstract:

For acoustical low-frequency nondestructive testing, the free-oscillation method is used. However, in spite of wide practical application, the theoretical bases on this method are insufficiently investigated, which does not allow an analytical estimate of the basic acoustical testing data by using the free-oscillation method. For the first time, theoretical research of the free-oscillation method for NDT is given with account damping. A theoretical investigation is carried out to differentiate the spectral density data of free oscillations of materials in the presence and the absence of cracks, on the basis of which acoustical testing data are proposed. New analytical expressions between the estimates of spectral densities of acoustical signals and relative sizes of cracks, factors of damping, and the duration of nondestructive testing are received. Experimental test results of metal materials in the presence and the absence of fatigue cracks which match with analytical results are presented. [See NOISE-CON Proceedings for full paper.]