High temperature modal analysis of a non-uniformly heated rectangular plate: Experiments and simulations

Structures in demanding environments where high-temperatures and high-frequency vibratory loads are combined often experience fatigue which shortens their lifecycle. A limited amount of experimental data is available on the mechanical behaviour of plates under such thermo-acoustic loading. In this work, on Hastelloy-X plates, non-contact techniques were used to simultaneously acquire full-field temperature and out-of-plane displacement data for a thin plate. The plate was heated using halogen quartz lamps arranged in two different configurations and mechanically loaded using a commercially-available shaker. The centre of the plate was mounted to the shaker through a stinger with a bolted connection. The structure's resonant frequencies were determined using experimental modal analysis when mechanically loading the plate using a randomly varying signal from 0 to 800 Hz. Modal shapes were studied by exciting the plate to its first eleven resonant frequencies and acquiring displacement data using a PL-DIC (Pulse Laser Digital Image Correlation) method. Infra-red imaging was used to acquire temperature maps across the specimen. A finite element model was developed to include temperature-dependent material properties in the prediction of the plate's resonant frequencies and mode shapes. For the first time, experimental results showed the resonant response of the plate to strongly depend on the temperature distribution across the structure, correlating well with past predictive work in the literature. This was supported by the results from the finite element model, which were validated against experimental data and found to yield reliable predictions.