Viscoelastic properties of polymeric materials are of fundamental importance to understand their mechanical behaviour, especially dealing with dynamic and vibration problems. In the present research, the generalized and modified yield theory of Goldberg constitutive model is used to predict the time dependent inelastic response of polymer materials. The approach that uses the complex-value amplitude relations is preferred rather than direct numerical integration of the complete set of constitutive equation for the material, in the other words, to simulate the response in terms of amplitudes, the relations between the amplitudes of main field variables are established with making use of complex moduli concept. It is usually done by making use of equivalent linearization technique. It is shown that this technique leads to overestimation of stress amplitude. To avoid this, the modified equivalent linearization technique is applied. Characterization of the complex moduli dependence on frequency and temperature as well as amplitude of stress intensity is performed. Results demonstrate a weak dependence of imaginary part of compliance moduli on the frequency of the loading within the wide interval of it, while variation of imaginary part of compliance moduli with increasing temperature is more pronounced.
Prof. Dr. Bilal BİLGİN