Title:
Experimental characterization of stress corrosion cracking sensitization in austenitic stainless steel using nonlinear ultrasonic Rayleigh waves
Experimental characterization of stress corrosion cracking sensitization in austenitic stainless steel using nonlinear ultrasonic Rayleigh waves
Author(s)
Lakocy, Alexander J.
Advisor(s)
Jacobs, Laurence J.
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Abstract
This thesis examines the use of nonlinear ultrasound to evaluate sensitization, a precursor to stress corrosion cracking in austenitic stainless steel. Ultrasonic Rayleigh surface waves are generated on a specimen; as these waves pass through sensitized material, second harmonic generation (SHG) increases. In austenitic stainless steel with oven-induced sensitization, this increase is due only to the formation of chromium carbide precipitates, key products of the sensitization process. Weld-induced sensitization specimens demonstrate additional increases in SHG, likely caused by increased residual stress and dislocation density as a result of uneven heating. Experimental data are used to calculate the acoustic nonlinearity parameter, which provides a single value directly related to the quantity of micro- and nano-scale damage present within any given sample. Using this procedure, the effects of weld- and oven-induced sensitization are compared. Results demonstrate the feasibility of using nonlinear Rayleigh waves to detect and monitor stress corrosion susceptibility of welded material.
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Date Issued
2015-12-08
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Thesis