Modeling and dynamic characteristics of engine casings based on hyperparametric shell and 20-node solid element

• Comparing hyperparameter shell (HPS) and 20-node solid (Solid20) elements. • Static and modal analysis of a connecting casing with variable cross-section. • Considering the effects of spoke plates in the modeling of supporting-frame casing. • Dynamic analysis of multi-frequency harmonic and impulse excitations on casings. • Studying vibration transmission characteristics of integrated assembling casing. To study the static and dynamic characteristics of connecting casing and supporting-frame casing applied in aeroengines, the dynamic models were established by the hyperparametric shell element (HPS) and the 20-node solid element (Solid20), respectively. The stiffness and mass matrices of both types of elements are derived theoretically, and then the static deformation of supporting-frame casing and connecting casings were solved, and the modal analysis for static characteristics was conducted. Moreover, the dynamic responses of supporting-frame casing and connecting casings modeled by 20-node solid elements induced by periodic- or impulse- exciting force were analyzed through the Newmark method and illustrated by time-domain waveforms and frequency-domain spectra. The vibration transmission characteristics of an assembling casing composed of the supporting-frame and connecting casings are also studied. The results indicated that both types of elements can be used for dynamic modeling of cylindrical shells and variable cross-section casings, and the computation time using hyperparametric shell is less than that of solid elements. Once the radial spoke plates of supporting-frame casing are considered, the results of 20-node solid elements are more realistic and accurate than those of hyperparametric shells. Furthermore, using the 20-node solid elements can accurately predict the maximum displacement amplitudes of the casing when subjected to an impulse exciting force, which is consistent with the results of the finite element software. The vibration transmission from the bearing housing to the supporting-frame casing, and then to the connecting casing, the amplitude decreases first and then increases on the horizontal path; the amplitude decreases in turn on the vertical path.