Nonlinear Acoustic Measurements Ahead of a Notch During Fatigue (Postprint)
Interim rept. 25 Jun 2009-31 Jan 2013
AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH STRUCTURAL MATERIALS DIV
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This paper presents measurements of relative nonlinear acoustic parameter rel, ahead of a notch in Al 7075-T651 dog bone samples, subjected to fatigue. It is compared with crack growth measurements on the same samples. Measurements performed on two samples subjected to identical fatigue conditions that failed at vastly different number of fatigue cycles are described. The rel measurement for both samples as a function of fatigue cycles was fit a Boltzmann curve. The role of changing rel ahead of a notch is explored as a possible approach for remain life evaluation.