Analysis of acoustic emission waveforms from fatigue cracks on a steel bridge hanger

Fatigue cracks on a steel bridge hanger were monitored for acoustic emission in conjunction with strain gage monitoring. Waveforms of emissions were collected and classified using source location, strain magnitude, position on strain cycle and uniqueness of waveforms as the primary criteria. A vast majority of AE from the cracks were found to be due to crack face rubbing and the crushing of corrosion products between the crack faces while limited crack growth emissions were detected. AE was monitored from A588 compact tension specimens under variable amplitude tension-tension fatigue loading, results of which were used to aid in the interpretation of AE data from the hanger. Crack growth AE were detected only on overload cycles mostly above 92% of maximum load while AE due to crack face rubbing occurred throughout the strain cycle.