Variable amplitude fatigue testing apparatus and its dynamical characterization

A modified version of variable amplitude fatigue testing rig suitable for studying the effects of crack breathing phenomenon under variable R-ratios is presented. This system is intended to investigate the interaction between fatigue damage evolution and structural dynamics, and apply the acquired understanding to practical fatigue life prediction. Generalized frequency response function, sine-sweep, and restoring force surface methods were used to identify and characterize nonlinearities, and estimate the corresponding parameters. A simple, two-degrees-of-freedom model development and experimentally validation are also presented