TABLE OF CONTENTS This chapter discusses a particular phenomenon in the general field of shock and vibration usually referred to as impact. [1] An impact occurs when two or more bodies collide. An important characteristic of an impact is the generation of relatively large forces at points of contact for relatively short periods of time. Such forces sometimes are referred to as impulse-type forces.
Three general classes of impact are considered in this chapter: (1) impact between spheres or other rigid bodies, where a body is considered to be rigid if its dimensions are large relative to the wavelengths of the elastic stress waves in the body; (2) impact of a rigid body against a beam or plate that remains substantially elastic during the impact; and (3) impact involving yielding of structures.
The elementary analysis of the central impact of two bodies is based upon an experimental observation of Newton. [2] According to that observation, the relative velocity of two bodies after impact is in constant ratio to their relative velocity before impact and is in the opposite direction. This constant ratio is the coefficient of restitution; usually it is designated by e. [3]
Let 
and 
be the components of velocity along a common line of motion of the two bodies before impact, and 
and 
the component velocities of the bodies in the same direction after impact. Then, by the observation of...
