ANALYSIS OF ACOUSTIC EMISSIONS FROM A STEEL BRIDGE HANGER

A steel bridge hanger with three fatigue cracks was monitored for acou stic emission (AE) using combined source location, strain gauge monito ring, and waveform analysis. AE activities from all three cracks were clearly identified and classified as crack growth or noise signals usi ng location, strain magnitude, position on strain cycle, and uniquenes s of waveforms as the primary criteria. A vast majority of AE from the cracks was 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. Results from laboratory tests on A588 compact tension specimens under variable-amplitude tension-tension fatigue lo ading were used to aid in interpreting AE data from the hanger. Crack growth AEs from these tests were detected only on overload cycles most ly above 92% of the maximum load while AE due to crack face rubbing oc curred throughout the load cycle.