A New Optical Technique for Rapid Determination of Creep and Fatigue Thresholds at High Temperature.
Final rept. Jan 81-Jan 84,
JOHNS HOPKINS UNIV BALTIMORE MD
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A laser-based interferometric displacement gage was used to measure crack opening displacements very near the tips of fatigue precracks. The test material was Inconel 718 and the temperature 650C. Creep and fatigue cracking thresholds were determined in times as short as one-half hour and found to be approximately 11 MPa-m to the 12 power in both cases. Details of the measurement technique as well as of the displacements measured near the tip are given. Author