This study presents aero-thermo-elastic Instability of two-dimensional Non-linear Curved Panels. Aero-thermo-elasticity plays an important role in the design and optimization of supersonic aircrafts. Furthermore, the transient and nonlinear effects of the thermal and aerodynamic environment encompassing a curved surface cannot be ignored. Accordingly, a homogenous curved plate with a high length-to-width ratio and simply-supported boundary conditions is assumed. The effect of large deflection is included in the equations through von Kármán non-linear strain-displacement relations. The thermal load is assumed to be a steady-state temperature non-uniform distribution. Structural properties such as modulus of elasticity and thermal expansion coefficient are assumed to be temperature-dependent. The novelty is incorporating first-and third-order piston theory for the non-linear curved panel flutter analysis under the effects of inplane and thermal loads. Hamilton's principle is used and partial differential equations are derived. The semi-analytical weighted residual method for the nonlinear curved panel is utilized. The fourth-and fifth-order Runge-Kutta iterative method are deployed to obtain the non-linear aero-thermo-mechanical deflections. Non-linear frequency analysis of cambered panel with the combined effects of aerodynamics, thermal and in-plane loads is investigated for the first time. The increase in panel curvature leads to a complicated behavior in the non-linear structural frequency variations. With increasing in-plane compressive load, complicated oscillating behavior is observed. More critical instability boundary for cambered panel is detected through the use of third-order piston theory. In addition, with an increase in panel curvature from 0 to 3, the panel displacement increases and for higher camber ratio, it decreases. Keywords Panel flutter • In-plane load • Thermal effects • First-order piston theory • Third-order piston theory • 2D panel • Time domain
This paper presents dynamic and static instability characteristics of a free-free multi-stepped Timoshenko beam subjected to a follower force, where each step has a point mass with transverse and rotary inertia. A finite element code is developed to model two-dimensional multi-stepped Timoshenko beams using the extended Hamilton's principle. The effects of each section parameters on the type of instability and critical follower force have been studied for different models of multi-stepped beams. It is concluded that the assumption of a uniform beam to study most aerospace structures such as launch vehicles could lead to an unrealistic instability analysis, where any small change in the characteristics parameters for each step could change the instability behavior significantly. Furthermore, this paper introduces a new parametric approach concept for analyzing the characteristics effects of a multi-step aerospace structure.
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