Understanding Acoustic Emission Testing- Reading 1 Part B-A

16.6 Parameters Affecting Acoustic Emissions from Concrete
16.6.1 The Kaiser Effect
The earliest acoustic emission studies of concrete, such as the work of Rüsch,
indicated that a true Kaiser effect (see above) exists for concrete; that is,
acoustic emissions were found not to occur in concrete that had been unloaded
until the previously applied maximum stress had been exceeded on
reloading. This was true, however, only for stress levels below about 75 to 85%
of the ultimate strength of the material; for higher stresses, acoustic emissions
began again at stresses somewhat lower than the previous maximum stress.
Subsequently, a number of other investigators have also concluded that
concrete exhibits a Kaiser effect, at least for stresses below the peak stress of
the material. (felicity effect)
Keypoints:
For concrete This was true, however, only for stress levels below about 75 to
85% of the ultimate strength of the material
Charlie Chong/ Fion Zhang