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1 Introduction

Figure 1.22: Important measures for the strength of a material.

stress/strain curve, and toughness is the area under the curve of both the ideal and the

real region of the curve.

In engineering, it is always important to predict what a material is going to do under

ideal and real conditions, and the prediction should be quantitative. So how can one

calculate what is going to happen to a material under certain forces in the future? For

that, mathematical models are needed. Here, only the most basic ones will be presented.

As viscoelasticity is described as the combination of elasticity and flow viscosity,

the models for each will be combined to mathematically express viscoelasticity (Fig-

ure 1.23). A spring following Hooke’s law represents elasticity, and a dashpot (a liquid-

Figure 1.23: Basic models of viscoelasticity to predict stress and strain in materials.