Stress-wave propagation in axiallysymmetric test specimens
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When a body is stressed, dislocations tend to pile up against an obstacle. If they suddenly break through the obstacle, then a small stress wave, known as an acoustic emission, is generated. Acoustic-emission research is attempting to correlate this phenomenon to the onset of yielding of a tensile-test specimen. The reliable detection of the acoustic emissions depend on the proper design of the system consisting of the test specimen, the instrumentation and the experimental techniques. In turn, the design must be based on a fundamental knowledge of the stress-wave propagation through the specimen.
In this paper, a theoretical and experimental investigation of the stress-wave propagation through a test specimen due to a stress-wave source, similar to an acoustic emission, is presented. This stress-wave propagation is shown to be typical for more general types of excitation of any similar type of axiallysymmetric body.
The method of producing the stress-wave source is described. The instrumentation system for detection of the stress wave must contain a variable electronic filter to clean up the signal and eliminate noise. Several different size and differently proportioned test specimens are used to determine scale effects and to optimize the specimen design.
Stress waves are also mechanically introduced into separate components of the test specimen to confirm the theoretical predictions for the modes of stress-wave propagation through these components.
The theoretical predictions of the stress-wave propagation through the entire test specimen are verified by the experimental investigations.
An optimum design of the entire system is presented.
KeywordsFluid Dynamics Experimental Investigation Acoustic Emission Theoretical Prediction Test Specimen
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