Fatigue design model based on damage mechanisms revealed by acoustic emission measurements

Integration of the microcomputer into acoustic emission instrumentation has brought AE monitoring of fatigue tests into the realm of practicality. On-line processing makes available a selection of software tools, enhancing classical techniques for eliminating the background noise which usually blanked out the desired data. Fatigue tests monitored for acoustic emission were carried out at room temperature on Incoloy 901 material specimens, over a stress-ratio range of -1 ≤ R ≤.2. Valid AE data were obtained even when the load cycle passed through zero. The AE data permitted specific identification of the various phenomena occurring on the way to final failure. These included initial plasticity, crack nucleation and propagation phases. The AE findings were supported by microscopic examination. Based on the experimental data, a preliminary damage-prediction model was formulated.