FATIGUE DESIGN-MODEL BASED ON DAMAGE MECHANISMS REVEALED BY ACOUSTIC-EMISSION MEASUREMENTS

Integration of the microcomputer into acoustic emission instrumentatio n has brought AE monitoring of fatigue rests into the realm of practic ality. On-line processing makes available a selection of software tool s, enhancing classical techniques for eliminating the background noise which usually blanked out the desired data. Fatigue tests monitored f or acoustic emission were carried out at room tp,temperature on Incolo y 901 material specimens, over a stress-ratio range of -1 less than or equal to R less than or equal to .2. Valid AE data were obtained even when the load cycle passed through zero. The AE data permitted specif ic identification of the various phenomena occurring on the way to fin al failure. These included initial plasticity, crack nucleation and pr opagation phases. The AE findings were supported by microscopic examin ation. Based on the experimental data, a preliminary damage-prediction model was formulated.