In this article nonlinearity is taken as a basic property of continua
or any other wave-bearing system. The analysis includes the convention
al wave propagation problems and also the wave phenomena that are not
described by traditional hyperbolic mathematical models. The basic con
cepts of continuum mechanics and the possible sources of nonlinearitie
s are briefly discussed. It is shown that the technique of evaluation
equations leads to physically well-explained results provided the basi
c models are hyperbolic. Complicated constitutive behavior and complic
ated geometry lead to mathematical models of different character and,
as shown by numerous examples, other methods are then used for the ana
lysis. It is also shown that propagating instabilities possess wave pr
operties and in this case the modeling of energy redistribution has a
great importance. Finally, some new directions in the theory and appli
cations are indicated. (C) 1995 John Wiley & Sons, Inc.