KRYLOV, V.V., LANDA, P.S. and ROBSMAN, V.A., 1993. Model of the evolution of acoustic emission as the randomization of transient processes in coupled nonlinear oscillators. Acoustical Physics, 39 (1), pp. 55-61.
The behavior of a crack as a resonator radiating acoustic emission (AE) pulses at instants of sudden growth
is investigated theoretically and experimentally. This resonance behavior of a growing crack is determined to
a large extent by surface waves propagating along its edges. The crack can therefore be regarded as an acoustic
resonator excited at the instant of growth of its tip. Transformations in the form of high-frequency harmonic
and combination-frequency subharmonic generation are observed in the spectra of the AE signals. The final
stage in the evolution of AE is characterized by the transition to a wideband noise spectrum. These facts lead
to the hypothesis that bifurcations analogous to those encountered in the onset of dynamic chaos take place
in the AE process. This hypothesis forms the basis of a mathematical model of the AE process as a system of
coupled nonlinear oscillators, each corresponding to an individual crack. The initial displacement in one of the
interacting cracks is adopted as the bifurcation parameter. Spectra calculated by computer simulation exhibit
qualitative agreement with the evolution of the spectra obtained in the processing of data from physical experiments.