The Application of Reverberation in Method of Mechanoelectrical Transformations for Estimation of Stress-Strain State in Solid Dielectrical Matter

The paper assesses the possibility of using the reverberation phenomenon to control the imperfections and the stress-strain state of solid dielectric materials by the method of mechanoelectrical transformations. The main advantage of reverberation is the repeated intersections of the excitation zones of inhomogeneities by acoustic waves, that is displayed in response parameters. The reverberation makes it possible to accumulate distortions of wave fronts. A comparative analysis of the responses from the sample under condition of uniaxial compression under different loads was performed. Differential analysis for the deterministic time component of the response in the interval (0–0.3) ms, and a statistical analysis of the differences for the pseudo-random component in the interval (0.8–1.8) ms were performed. For the statistical analysis, the distribution of the pulse flow is selected. The response was calculated according to the mathematical model under the conditions of a change in the speed of sound, which simulates a change in the sample inhomogeneity under load. The calculation showed a qualitative similarity with changes in responses in a real experiment. According to the obtained results, it was concluded that it is possible to use the deterministic and pseudo-random components of the responses in the reverberation condition to control the change in defectiveness and the degree of heterogeneity under the action of the mechanical load on the sample.

Possibility of Evaluating a Depth of Defects as a Hole in a Composite Dielectric Sample by the Parameters of Electric Response to Pulse Mechanical Excitation

The applicability of the method mechanoelectrical transformations (MET) to determine the depth of the macrodefects location in the sample on parameters of the electromagnetic response is evaluated. As the response parameter it was used the phase characteristic of the signal analytical representation.On the one-dimensional mathematical model it was shown the possibility to detect phase response changes when reflected from defect acoustic wave is mixed with the signal spurious component generated by a distributed MET sources. Experimental verification of mathematical model on a sample of concrete was conducted. It has been shown that the sensitivity of the method MET to evaluation of the macrodefect locate depth depends on the wavelength of the excitation pulse and the area of the macrodefect border closest to the emitter-receiver system.