Diagnostics of closing cracks in rodlike elements at nonlinear resonances by the method of variation of the asymmetry of driving forces

The vibrations of elastic bodies with closing cracks are essentially nonlinear. As a specific feature of these vibrations, we can mention the manifestation of so-called nonlinear effects, in particular, sub- and superharmonic resonances and the nonlinearity of vibrations at these resonances. We propose a method for the diagnostics of cracks based on the variation of the asymmetry of driving forces. The static component of the concentrated harmonic driving force changes the state of a crack: it becomes partially or completely open or closed. Moreover, the degree of nonlinearity of vibrations for any nonlinear resonance varies from the maximum level (in the absence of static component) to its almost complete absence in the case where the crack becomes open or closed in the course of vibrations under the action of the static component. The proposed method enables one to detect the presence of cracks without any preliminary data on the analyzed object in the intact state.