Selection of Dynamic Testing Measurement Locations for Integrally Bladed Disks

The selection of sensor locations during dynamic testing of integrally bladed disks (Blisks) is discussed for measuring experimental mode shapes. As-manufactured geometries of the experimental Blisk are obtained in point-cloud form via a structured light optical measurement system. The nominal finite element mesh of the Blisk is then “morphed” to the average sector of as-measured, point-cloud geometry through a mesh metamorphosis algorithm. A ray-tracing algorithm is developed for selecting observable degrees of freedom (DOFs) of the morphed mesh to an overhead laser scanning vibrometer. This set of DOFs is then down-selected since measuring tens-of-thousands of points is in-feasible during experimental testing. This selection is carried out using a Cyclic Effective Independence Method that exploits a Blisk’s cyclic symmetry to greatly reduce computational expenses. Furthermore, the approach allows for selecting points belonging to specific engine order excitations typical in engine operating environments that can be excited during bench top traveling wave testing. Measurement point locations are compared for three cyclic symmetry finite element models: a nominal coarse mesh density, a nominal fine mesh density, and a fine mesh density morphed to average sector geometries.