Measurement of Hysteresis Energy Using Digital Image Correlation With Application to Energy Based Fatigue Life Prediction

Abstract

A modified experimental method using digital image correlation (DIC), a non-contact optical method for measuring full-field displacements and strains, is used to interrogate accumulated fatigue damage for low and high cycle fatigue (LCF/HCF) at continuum scales. Previous energy based fatigue life prediction methods have shown that cyclic strain energy dissipated during fatigue acts as a key damage parameter for accurate determination of total and remaining fatigue life. DIC enables the collection of accurate strain energy measurements or damaging energy of complex geometries that would otherwise be exceedingly difficult and time consuming using traditional strain measurement techniques. Thus, the use of DIC to obtain strain energy measurements of gas turbine engine components is highly advantageous for energy-based fatigue life prediction methods. Presented in this study is the experimental characterization of the cyclic strain energy dissipation as a means of predicting fatigue performance and assessment of damage progression of Aluminum 6061 subjected to fully reversed axial fatigue loading utilizing DIC. Validation of total and cyclic strain energy dissipation DIC measurements are accomplished with the simultaneous use of axial extensometery for direct comparison and implementation to strain energy based life prediction methods.