Investigation of Experimental Response of Bladed Disk with Under-Platform Dampers Using Tip Timing and Strain Gauge Responses

Abstract

There has been an extensive amount of research done developing reduced order models (ROMs) for bladed disks using single sector models and a cyclic analysis. Several ROM methods currently exist to accurately model a bladed disk with under-platform dampers. To better predict the complex nonlinear response of a system with under-platform dampers, this work demonstrates how two linear models can help determine bounds for the nonlinear system response. The two cases explored are where the under-platform damper is completely stuck to the blade and also where the damper is allowed to slide along the blade surface without friction. This work utilizes the component mode mistuning method to model small mistuning and a parametric reduced order model method to account for changes in system properties due to rotational speed effects. Previously, these ROM methodologies have been used to model freestanding bladed disk systems. To evaluate the ROM in predicting the response bounds, blade tip amplitudes from the computational simulations are compared with high-speed rotating experiments conducted in a large, evacuated vacuum tank. The experimental data was collected during testing using strain gauges and laser blade tip timing probes. The strain gauge data is compared to the blade tip deflection data using strain gauge elements added to the finite element model of the blade. The strain gauge elements were used to correlate the tip deflection amplitudes to strains at specific locations to match the experimental strain gauge locations. The blade amplitudes of the tip timing data, strain gauge data, and computational simulations are compared to determine the effectiveness of the simplified linear analysis in bounding the nonlinear response of the physical system.