Harmonic Generation for Measurement of Microscopic Internal Stresses,
ROCKWELL INTERNATIONAL THOUSAND OAKS CA SCIENCE CENTER
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The role of microscopic internal stresses on mechanical properties in particular fatigue properties, on the other hand, seems to be not quite clear to the engineering world. The present task, therefore, has been addressed specifically to this subject. In particular, the internal stresses due to dislocations have been treated. These dislocations are the defects responsible for plasticity effects in metals and alloys. Experiments have been performed using acoustic harmonic generation and it is this technique that is being examined as a possible nondestructive tool to study the microscopic internal stress due to dislocations or, in other words plasticity effects. The work reported here by no means, is complete and many basic questions remain to be answered. It is hoped, however, that the results obtained will lead to a way to determine nondestructively the remaining life of a material in use.