ABSTRACT
Blade stresses are determined from blade tip timing (BTT) data by relating the measured tip deflection to the stresses via Finite Element (FE) models. This process includes some uncertainties due to the following: 1) the shift in the equilibrium position of the blade tip due to steady deflection and/or movements, 2) the change in effective stiffness due to rotation-induced inertia, which affects the BTT-stress calibration factors, 3) the assumption of constant speed over a single revolution that is made in most of BTT algorithms, which is not appropriate for rapid speed rates. This study shows the effect of such uncertainties on the vibration measurement and blade stress estimations.
