The primary function of a joint in an engineering structure is to connect, usually stiffly, two separate substructures. This function is well accomplished; however, in doing so a secondary function of a joint is introduced in which it augments the dynamics of an assembled system. Joints thus introduce two features to a structure: amplitude dependent stiffness and amplitude dependent damping. With the state of the art techniques, the amplitude dependent stiffness can be predicted reasonably well (to within 10%); however, the amplitude dependent damping is still beyond predictive capabilities.
Written by: Matthew R. W. Brake – Sandia National Laboratories, Albuquerque, NM., USA