Understanding Acoustic Emission Testing- Reading 1 Part B-A

16.2 Historical Background
The initial published studies of acoustic emission phenomena, in the early
1940s, dealt with the problem of predicting rockbursts in mines; this technique
is still very widely used in the field of rock mechanics, in both field and
laboratory studies.
The first significant investigation of acoustic emission from metals (steel, zinc,
aluminum, copper, and lead) was carried out by Kaiser. Among many other
things, he observed what has since become known as the Kaiser effect: “the
absence of detectable acoustic emission at a fixed sensitivity level, until
previously applied stress levels are exceeded.”
While this effect is not present in all materials, it is a very important
observation, and it will be referred to again later in this review. The first study
of acoustic emission from concrete specimens under stress appears to have
been carried out by Rüsch, who noted that during cycles of loading and
unloading below about 70 to 85% of the ultimate failure load, acoustic
emissions were produced only when the previous maximum load was
reached (the Kaiser effect).
Charlie Chong/ Fion Zhang