Damping from Thermoelasticity in Structures Under Torsional Loading

The study of damping is a fundamental area in mechanical vibrations. Damping is the cause of the loss of energy in vibrating structures. However, the process in which the energy is dissipated depends on the material properties, structure, and other parameters. One of the base sources of damping in solid materials is the conversion of energy into heat, which can be modeled using the thermoelastic model. This model couples the standard mechanical wave equation with the heat equation and predicts that the dissipated energy is converted into Entropy. While thermoelastic damping is more prominent in smaller structures (e.g., microresonators), it is present in all structures under any deformation that generates a change in volume, albeit at the lower end of the frequency spectrum. The main goal of this paper is to determine the damping profile with the frequency generated by the torsional load in non-circular cross-section structures using a Finite Element Analysis with 3D solid elements. The simulation results show that, while the thermoelastic damping generated by torsion is smaller than the one generated by bending, it cannot be ignored for some noncircular cross-sectioned geometries.