Crack-Length Determination for the Compact Tension Specimen Using a Crack-Opening-Displacement Calibration-Comparison of COD Measured Graphically and from the Gage Output.

摘要

To implement the increasing trend toward automated testing procedures, crack-length measurement during fatigue crack-growth-rate testing was determined using a COD gage technique. Data were analyzed both graphically and using the gage output measured in millivolts. To compensate for nonlinearity in the load-vs-COD traces, it was found necessary to sample differences in the load millivolt readings to produce smooth da/dN-vs-deltaK curves agreeing with those determined from graphical analysis of crack length. (Author)