Mechanical Engineering Faculty Research


Evaluation of Crack Growth Models for Elevated-temperature Fatigue

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To date, only two models have been proposed for predicting crack growth rates in aircraft engine materials under typical operating conditions. Moreover, modeling to date has been performed on materials which exhibit limited amounts of time-dependent behavior. This investigation evaluates the predictive and interpolative capabilities of these models when applied to IN718, at 649 degrees C. At this temperature, this material exhibits significant time-dependent behavior. Experimental data were generated and used to assess the predictive and interpolative characteristics of each model. These data covered variations infrequency, stress ratio, and hold time. Values for the coefficients in the functional relationships between the constants and the test variables were obtained for the hyperbolic sine equation (SINH) model. Similar functional relationships were incorporated into the modified sigmoidal equation (MSE) model. Several important conclusions were drawn about the capabilities of these two models to predict crack-growth rates in turbine-engine materials at elevated temperature.

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Fracture Mechanics: Eighteenth Symposium

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