Determining the Fatigue Characteristics of Material on the Basis of Stress-Wave Emission

Abstract

Assessment of the fatigue of test samples on the basis of stress-wave emission is considered. Experiments are conducted on the basis of previously published material regarding the use of synergetically organized acoustic emission. Experimental data for various materials demonstrate that the acoustic-emission signal permits ongoing determination of mechanical characteristics and, in particular, the fatigue. The samples for fatigue tests are prepared from five grades of steel and also from BrAZh9-34 bronze. Five experiments are conducted for each metal. The experimental samples are subjected to loads in small increments. In each step, the emission signal is recorded, and the next series of dislocations is prepared for subsequent loading of the crystal surface and the emission of a stress wave. Thus, energetically prepared dislocations ensuring sufficient power for stable signal recorded are emitted. The experimental data obtained on the basis of the synergetically organized acoustic emission are compared with the fatigue limit of the material determined from empirical formulas in terms of the strength. According to the Fisher test, the experimental results are adequate at the 5% significance level. Assessment of the experimental data for the fatigue limit obtained from the acoustic-emission signal by means of the Cochran test indicates that the dispersion of the experimental measurements is uniform for all the materials considered. The conclusion is that determination of the fatigue limit of a material on the basis of synergetically organized acoustic emission yields real-time experimental data on the fatigue limit, with sufficient precision.