Surface Evaluation Using Acoustic Emission
Artificially induced surface flaws in dense silicon nitride may be activated by applying a thermal stress with a CO2 laser to the near surface of the material. The extension of these flaws may then be recorded by acoustic emission (AE) instrumentation and this response then serves as an indication of surface integrity. Surface degradation of test specimens was achieved by thermal shocking with the laser to produce surface cracks. The laser was then used to thermally stress the near surface and activate the small cracks. Flexural tests were used to determine the extent of damage by noting the reduction in strength associated with various levels of AE recorded during laser thermal shocking. Utilizing these parameters on an unknown surface should result in obtaining meaningful data in terms of the presence of surface defects and their influence on material strength.
KeywordsAcoustic Emission Flexural Strength Surface Crack Crack Extension Acoustic Emission Event
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