Aeroelasticity In Aircraft Engineering

1.1 - Background

Aeroelasticity is[the field of study that considers the interaction between aerodynamic, elastic and inertia forces t as shown in schematic figure(1.1), Hodges and Pierce 2002. Also see Bisplinghoff et al 1996. Physical phenomena due to aeroelasticity can occur nature, such as the movement of the wings of birds and the vibration of tall trees under wind loads. However aeroelasticity applications that occur in mechanical and civil engineering such as aircraft wings, turbomachine blades, bridge vibrations and tall buildings under wind loads are more common in engineering practice. Aeroelasticity is of high interest for aeronautical engineering because airborne bodies are aften flexible structures that have significant deformations

The lifting surfaces such as wings and tail unit and control surfaces are the important part undergoing aeroelastic phenomena especially the interaction between wing and control surfaces.

The smaller aerodynamic surfaces for wings and tailplane were created to develop to improve aerodynamic performance by using a control system rather than by twisting flexible structures as the Wright brothers had done. The control surfaces such as aileron, spoiler, flaps, tabs, rudder and elevators are shown in figure (1.2) with hinged connectors and unscrewed gaps splitting them from the main wing and tailplane structure. The design and connecting processes of hinged surfaces especially at hinge point between two surfaces such as at present work between main wing-flap and flap-tab connectors have nonlinear behavior due to the free space distance between two connected points or gears which drive the hinge surface. This free space is called freeplay and its size is difficult to estimate because it depends on the design processes and manufacturing accuracy as well an many operational factors such as wear, plastic deformation and gear

The external load may be caused by the forced deflection of the elastic body, such as the deformation of an aircraft wing or control surface, or by gust load disturbance. In some cases the limit cycle oscillations can become unstable and the lead to large amplitudes. This is often called flutter which is a dynamic aeroelastic instability in which small excited in the flow stream around aeroelastic model may produce oscillations of large amplitude. It is an aeroelastic phenomenon concerning the oscillation of aircraft wings and control surfaces that has been detected since the early days of