Detection of rational frequency of the sample incremental loading during its tests for endurance on the basis of a synergetically organized acoustic emission

The article considers results of the evaluation of rational frequency effecting the sample when implementing the method of determining the fatigue characteristics of materials based on synergistically organized emission of stress waves. The essence of this process lies in the fact that a flow of the emission signal is formed with a small-scale loading of the tested sample at each step of loading. At the same time, another series of dislocations is being generated, capable of reaching the crystal surface at the next moment of loading and emitting a stress wave. The magnitude of this signal characterizes the processes occurring in the material at a particular load, and allows the power parameters corresponding to such value as endurance limit to be recorded. The purpose of this work is to determine the frequency of small-scale loading, providing the maximum wave signal when implementing the method for determining the fatigue characteristics of materials based on synergistically organized emission of stress waves. The analysis of the movement of material elements was made. Based on previously published materials on the use of synergistically organized acoustic emission, the process of behavior of the metal structural components was analyzed; the process of the behavior of its grain under the influence of dislocation movements is identified and described. The strength of each such impact was represented by the delta function. The behavior of metal grains was described by the second order differential equation. The probability of a grain moving from impulse action from the side of lying crystals and from its own impulses is described by the density of movement probability of this grain. Considering jointly the dynamic and probabilistic description of the grain behavior, the Kolmogorov – Focker – Planck equation was obtained. Due to the fact that in the present work, the oscillatory nature of the metal grain movement was of interest, the above-mentioned equation was transformed into a wave-mechanical function of the process of grain behavior. The solution of wave-mechanical function is wave equation. As a result of consideration of the wave equation, natural frequency of material grain oscillations was revealed. This frequency falls in the range of frequencies that can be reproduced under stepwise loading of the test sample. This makes it possible to realize a resonance effect as applied to behavior of the metal crystal structure. Thus, frequency at which fluctuations in the material structure at the grain level will resonate with an external effect on the sample is determined. Resonant interaction of the material structure and external incremental loading of the sample will ensure a more powerful value of the emission signal at the same value of the steps under small-scale loading.

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