APPLICATION OF STRESS WAVES EMISSION FOR DETERMINATION OF FATIGUE CHARACTERISTICS OF MATERIAL

Results of experimental evaluation of the fatigue characteristics of tested samples material are considered based on emission of stress waves. Using previously published data on synergistically organized acoustic emission, an experiment was prepared and performed. In experiments on different materials, possibility of using acoustic emission signal for operative determination of mechanical characteristics and, above all, the limit of endurance were demonstrated. Samples for strength testing of materials were made of five steel grades and one grade of Br AZh9-4 bronze. Five experiments were conducted on each of the materials. The samples in the experiment underwent a fine-step loading, at each step of it radiation of signal occurred simultaneously, and another series of dislocations was prepared, that could reach surface of crystal and emit a stress wave at the next moment of loading. Thus, the joint radiation of energy dislocations prepared for movement was already formed. A comparison of experimental data, obtained on the basis of acoustic emission, with calculated values of endurance limit, obtained by empirical formulas through the ultimate strength of this material, performed by the Fisher criterion, has shown their adequacy at a significance level of 5 %. Evaluation of the experimental results of endurance limit determination on basis of acoustic emission by the Cochran test indicates that variances of measurement results in experiment are uniform for all types of used materials. The results have shown that such method on the basis of synergistically organized acoustic emission allows us to quickly obtain experimental values of endurance limit of material with sufficiently high degree of accuracy.