ABSTRACT
This chapter introduces the spectra, to derive approximate interrelations between the viscoelastic functions, and to assemble all the viscoelastic functions with their interrelations, with the aim of developing physical insight regarding the structure of viscoelasticity theory. Viscoelastic response is a single physical reality which can be manifest in many ways, some of which are conceptualized in terms of viscoelastic functions. Each viscoelastic function, if known over the full range of time or frequency, contains complete information regarding the material's linear behavior. The transient functions were introduced first as fundamental, primarily because most engineers or scientists interested in viscoelasticity initially prefer the time domain to the frequency domain. Viscoelastic response is a single physical reality which can be manifest in many ways, some of which are conceptualized in terms of the viscoelastic functions. The relation between the dynamic modulus and the dynamic compliance is also the most easily grasped mathematically: it is simply an inverse as in the case of elasticity.
