A Portable Fixed Base Support for Modal Survey Tests

Fixed base (FB) correction methods (FBCMs) have been increasingly used to transform flexible or dynamically active boundary conditions into fixed boundaries in modal tests. This chapter documents the development of a portable test setup to conduct an FB modal survey test that can be integrated into other environmental testing configurations to accelerate testing schedules. The test article is attached to a T-slot table via an adapter plate that is bolted at multiple locations via T-slot bolts. During testing, inflatable airbags are used to raise the T-slot table off the supports, thus creating a soft boundary condition. Using 11 electrodynamic modal shakers, nine constraint shapes were measured and used to remove the dynamics of the T-slot table via the FBCM. Overall, there was excellent agreement between the FB target modes and the extracted FB modes. With this deployable setup, FB modal tests can easily be integrated into existing testing schedules, providing the ability to correlate FB models of flight hardware.