Acoustic Emission Analysis for Determining Crack Initiation During Instrumented Notched Bar Impact Testing.

Good agreement has been obtained between enhanced acoustic emission intensity and the onset of crack initiation in the case of static loading, but the experience gained with acoustic emission testing is only partly applicable to dynamic testing. This is due mainly to the generation of rebound signals from the hammer impact which must be separated from the acoustic emission signals. The possibility of separating these interference signals from the useful signals through the use of filters or by shifting the time of onset of crack propagation by using lower impact velocities is considered. A test arrangement for microcomputer-controlled instrumented notched bar impact testing is described.