Understanding Acoustic Emission Testing- Reading 1 Part B-A

The signal that is detected by a sensor is a combination of many parts of the
waveform initially emitted. Acoustic emission source motion is completed in a
few millionths of a second. As the AE leaves the source, the waveform travels
in a spherically spreading pattern and is reflected off the boundaries of the
object. Signals that are in phase with each other as they reach the sensor
produce constructive interference which usually results in the highest peak of
the waveform being detected. The typical time interval from when an AE wave
reflects around the test piece (repeatedly exciting the sensor) until it decays,
ranges from the order of 100 microseconds in a highly damped, nonmetallic
material to tens of milliseconds in a lightly damped metallic material.
Decay Time:
highly damped (intrinsic) , nonmetallic material → order of 100 microseconds
(10 -6 s)
lightly damped metallic material → tens of milliseconds (10 -3 s)
Charlie Chong/ Fion Zhang