Nonlinear Thermo-Visco-Elastic Behaviour

Abstract

Many materials have viscoelastic properties that are both nonlinear and time-dependent. Any complete theory of thermo-visco-elasticity should be able to describe the local deformation gradient in terms of the properties of the material and the forces acting on the material. The main difficulty in characterising thermo-visco-elastic behaviour, from an experimental point of view, is the accurate simultaneous measurement of all the variables needed to describe the process. A guide to the choice of observables in an experiment is that the governing equation used should be in a closed form, for example, the conservation laws in a control volume should contain terms for all of the physical processes which significantly contribute to the process. The characterisation obtained from the data can then be related to the theory underpinning the process. Generally speaking, the ability of current data analysis methods to accurately and consistently quantify all of these interactions under general dynamic boundary conditions is severely limited. Thus, there is a need to develop and refine data analysis techniques that can separate and quantify the thermo-visco-elastic processes and their interactions and relate them to an appropriate theoretical description of the process.