ABSTRACT

When a wing is in steady flight, it is subjected to wind loads that cause bending and twisting deformations in the wing. The moment resulting from the lift force on the wing generally tends to twist the wing. As the wing undergoes twisting deformation, the resulting wind pressure distribution causes additional lift force and twisting moment, which in turn increase the twisting deformation. There exists a critical speed at which the elastic stiffness is barely sufficient to hold the wing in a deformed position causing static failure of the wing, and this speed is called divergence speed. If a torque is applied at the tip of a cantilever airplane wing, there is a corresponding resisting torque set up in the wing that limits the wing twist, measured at the tip. As the external torque is increased, there is a corresponding increase in the resisting torque as well as in the torsional deformation of the wing.