In-plane vibration of thin circular structures submitted to pulsed microwave

Abstract

The absorption of microwaves by material induces a temperature rise that generates a mechanical deformation in the irradiated structure by thermoelastic effect. As a continuous development of this recent generation technique, the present study investigates the in-plane mechanical vibration of disks and rings submitted to pulsed microwaves in order to develop a contactless evaluation method. The vibration of a disk submitted to microwave irradiations depends on the distribution of the electromagnetic field in the sample. If the irradiation is axisymmetric, the purely radial eigenmode is generated. On the contrary, if the irradiation field is not axisymmetric, the vibration is angular dependent. Consequently, one can choose to use various eigenfrequencies for determining the geometrical properties of a circular plate and the mechanical properties of the material. A semi-analytic model is presented to predict the in-plane vibration eigenfrequencies of thin rings and disks. Wave equations are solved by taking into account the angular dependence in order to estimate the maximum number of disk or ring eigenfrequencies. The model is validated by comparison between the theoretical and the experimental results and applied for the evaluation of rings and disks geometries and their constitutive material properties using the microwave excitation technique.