In prior work techniques were developed for monitoring acoustic emission output during cyclic loading of notched metallic specimens. Crack propagation was monitored independently and concurrently with AE output. Attempts to correlate traditional AE parameters, such as amplitude, energy, cumulative counts or rate of counts, with initiation and propagation of fatigue damage were not totally successful. It was found, for example, that whereas crack length increases smoothly with fatigue cycles, acoustic emission counts occur irregularly showing occasional jumps. The phase of the loading cycle was identified as an important parameter in analysis of AE data and was successfully used in conjunction with AE parameters to identify the initiation and final stages of damage development. The propagation stage of fatigue crack development was correctly identified but correlation between AE parameters and crack growth measurement was poor due to the occurrence of highly concentrated AE signals in this stage. In order to have a better correlation of AE signals and fatigue damage development, further classification of the acquired AE signals is necessary. Examination of the waveforms has shown that they are distinct at different points along the AE count curve and are not related to rate or cumulative number of counts. An analysis of the acquired waveforms was undertaken in this study.
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