Study of the effect of pressurization on the vibration frequencies of fuselages

Resumo

In this research, an aerospace vehicle fuselage was modeled as a long-pressurized cylinder. The
investigation assessed the presence of high tensile stresses in the structure and their correlation with the values of
the undamped free vibration frequencies of the system, which vary according to its geometric stiffness. The
modeling was conducted utilizing the Finite Element Method, employing thin shell elements accounting for
geometric nonlinearity, as offered in commercial and academic software. Generally, such programs can address
the eigenvalue problem associated with this model, using a stiffness matrix considering application of the load,
i.e., pressurization. This can originate from the conditioning of the internal atmosphere of commercial aircraft or
the presence of large loads of fuel and oxidant in space vehicles (rockets). Another aspect to consider in this
analysis is the fact that these vehicles do not have supports, leading to the existence of so-called rigid body modes,
with zero vibration frequencies. Ultimately, a maximum variation of 45.29% in the natural frequency value of the
investigated structure was observed.