Use of Acoustic Emission in Nondestructive Testing
Final technical rept. 1 Jul 1968 -31 Aug 1971
MICHIGAN UNIV ANN ARBOR DEPT OF ENGINEERING MECHANICS
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A model based on the activation of dislocation sources was developed for predicting the effect of microstructure on acoustic emission. The model predicts a minimum dislocation source length and slip distance below which no emission will be detected. Experimental results obtained on various metals and alloys having different microstructures substantiate the model. The effect of grain size on the acoustic emission from 99.99 aluminum and 99.9 copper suggests that macroscopic yielding in these metals occurs with the help of dislocation pile-ups that have been held up by grain boundaries and that the emission results from the activation of dislocation sources near the grain boundaries. Experimental results obtained under conditions of very low background noise level show that some metals produce acoustic emission when the applied load is removed. The amount of emission that is observed correlates with the magnitude of the Bauschinger effect in the metal. In those metals that show an unload acoustic emission effect there is the possibility of using it to investigate the magnitude of the residual stress in a specimen. Creep and fatigue phenomena can also be studied by the use of acoustic emission.
- Properties of Metals and Alloys
- Test Facilities, Equipment and Methods
- Solid State Physics