On the Determination of a Viscoelastic Model for Stress Analysis of Plastics

A method of assessing whether or not the measured variation of complex compliance with frequency for a viscoelastic material is consistent with a four-element model is presented. The four-element model was chosen since it is relatively simple to analyze, and exhibits the three main types of viscoelastic response; namely, instantaneous elasticity, viscous flow, and delayed elasticity. If the compliance measurements are found to conform with the behavior of a four-element model over the whole or part of the frequency range studied, a graphical method of determining the model constants is presented. The significance of the application of such a model to stress analysis under transient loading is discussed.