ABSTRACT
The control of vibration is becoming more and more important for many industries as their products have to be sold in an increasingly competitive world. This generally has to be achieved without additional cost, and thus detailed knowledge of structural dynamics is required together with familiarity of standard vibration control techniques. There are many textbooks on mechanical vibrations, but there are only a few on vibration control (for example, Nashif et al. 1985; Mead 1998), and there are some book-chapters that deal with various control aspects (for example, Mead 1982; Ungar 1992a,b; Crede and Ruzicka 1995; Everett Reed 1995; Newton 1995). Although vibration control is predominantly carried out using passive means, more recently active vibration control has been applied, and there are several textbooks describing this approach (for example, Fuller et al. 1997; Preumont 1997). Because of the restrictions of space, this chapter will be confined to passive vibration control. A generic vibration control problem can be separated into three compon-
ents: the source, the transmission path and the receiver, as shown in Figure 12.1. The boundaries of the three components are defined by the person solving the problem, and it is probable that different people will define different boundaries. For example, if a gearbox is the vibration source the gears could be considered to be the vibration source, and the shaft and casing, etc. could be the transmission path. Alternatively, the whole gearbox could be considered to be the vibration source. Where the boundaries are drawn is largely unimportant; what is important is that the person who is solving the problem clearly defines the source, the transmission path and the receiver. Once this has been done the vibration control problem reduces to one of changing the size and distribution of mass, stiffness and damping to minimise the vibration at the receiver. Whilst this is very easy to write down, it can be very difficult to do in reality because of the difficulty in determining which
parameter to change. In general, vibration control solutions can be classified as follows:
• source modification; • vibration isolation; • vibration damping; • the addition of vibration absorbers/neutralisers; • structural modification; • material selection.
