ABSTRACT
When the relationship between the external load and deection experienced by a deformable system cannot be represented by a straight line, the system is said to be nonlinear. The natural frequency of such a system or structure is most often amplitude dependent, unlike the case of the perfectly linear system, where frequency remains constant regardless of amplitude. The usefulness of this, or the natural period concept in shock and impact analyses lies mainly in the fact that the deection from the initial position to the nal one can be regarded as taking place in one-half or one quarter of the natural period. For the system acted upon by a prescribed impulse, the main objectives are to determine the magnitude of that deection (pseudo-amplitude) as well as duration of motion. This chapter is devoted to calculating these quantities.
