13.2 RESPONSE IN FREQUENCY DOMAIN

As speed increases in a cam-follower system, a rapid exchange of energy occurs within the system and the noise of operation also increases. This sudden energy shift takes place between the elastic members and the masses during operation. The energy shift is also visible as high follower vibration. This action is termed mechanical shock and its related system response a shock response.

A shock is defined as the physical manifestation of the transfer of mechanical energy from one body to another during an extremely short interval of time (see Chapter 9).

The shock response spectrum or the response spectrum is one of the two most commonly used methods of analyzing mechanical shock. The other method is the Fourier spectrum analysis. In both cases, the time history of the transient is converted into an amplitude versus frequency picture, or spectrum. Neklutin (1954) was the first to employ this technique in the study of cam-driven systems.

Thus, a valuable method of expressing the dynamic response of a cam-follower system is to obtain the dynamic response spectra (DRS) of the cam s excitations. A DRS is defined as a plot of individual peak-acceleration responses of a multitude of single-degree-of-freedom, mass-spring systems subject to a particular input transient. The ordinate is usually acceleration, or some normalized expression relating to acceleration, while the abscissa is in terms of the system natural frequency, or the ratio of pulse duration to the system natural period. Damping is a parameter, and if...