Abstract
The free vibration analysis of one-layered and two-layered metallic cylindrical shell panels is evaluated in this work. The free frequency values are investigated for both thermo-mechanical and pure mechanical problems. Thermo-mechanical frequencies are calculated by means of a fully coupled thermo-mechanical model where both the displacement and temperature are primary variables in the considered governing equations. Pure mechanical frequencies are obtained from a mechanical model where the effect of the temperature field is not included in the stiffness matrix and the displacement is the only primary variable of the problem. The inclusion of the thermal part in the stiffness matrix gives larger frequencies. Both thermo-mechanical and pure mechanical models are developed in the framework of Carrera's Unified Formulation (CUF) in order to obtain several variable kinematic models. Both equivalent single layer and layer wise approaches are considered for multilayered shells. The use of refined two-dimensional theories for shells permits the evaluation of the effects of the thermo-mechanical coupling for lower and higher order modes, higher frequency values, multilayered configurations, thick and thin shells and several values of the radius of curvature of the shell geometry. It has mainly been concluded that the thermo-mechanical coupling is not influenced by the curvature of the shells, therefore, the main conclusions already given for the plate geometry are here confirmed: – the thermo-mechanical coupling is correctly determined if both the thermal and mechanical parts are correctly approximated; – it is small for each investigated case; – it influences the various vibration modes in different ways; – it has a limited dependence on the considered case, but this dependence vanishes if a global coupling is considered.
Highlights
A fully coupled thermoelastic analysis permits to evaluate the effect of the temperature field on the deformation field and the changes in the temperature field due to the deformation of a body [1]: the thermo-mechanical coupling is not a one-way phenomenon
The employed refined two-dimensional theories are obtained as in Section 2; the displacement can be modelled in both Equivalent Single Layer (ESL) and Layer Wise (LW) form, but the temperature is always approximated in LW form
A large variety of shell theories are obtained, in a unified manner, by means of Carrera’s Unified Formulation (CUF) [26,27]: the governing equations are written in terms of a few fundamental nuclei which do not formally depend on the order of expansion N in the thickness direction and on the description of variables (equivalent single layer (ESL) or layer wise (LW))
Summary
A fully coupled thermoelastic analysis permits to evaluate the effect of the temperature field on the deformation field and the changes in the temperature field due to the deformation of a body [1]: the thermo-mechanical coupling is not a one-way phenomenon. A fully coupled thermoelastic analysis considers both temperature and displacement fields as primary variables in the governing equations, as proposed in [2,3] for plate and shell geometries, respectively. The effect of thermo-mechanical coupling is investigated in the free vibration analysis of onelayered and two-layered metallic shells, in terms of frequency values, by using a fully coupled thermo-mechanical model. The use of refined two-dimensional theories for the free vibration analysis is mandatory for multilayered structures, moderately thick plates and shells, composite layers, higher order modes and higher frequency values (for details about the pure mechanical vibration analysis see [12], a preliminary discussion about the thermo-mechanical effects has been proposed in [13]). A global energetic parameter is introduced in order to investigate the global thermo-mechanical effect
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