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1

The influence of strain amplitude, temperature and frequency on complex shear moduli of polymer materials under kinematic harmonic loading

Hashemi M., Zhuk Y.

Mechanics and Mechanical Engineering

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2017

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Vol. 21, nr 1

157--170

EN

Modeling of the cyclic deformation of viscoelastic materials as the key aspects of analysis of the structural behavior is performed. 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. Time dependent transient inelastic response of polymer materials to monoharmonic kinematic loading is simulated by the Goldberg constitutive model. To predict the steady-state 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 performed 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 strain intensity is performed. Results demonstrate a weak dependence of loss moduli on the frequency of the loading within the wide interval of it, while variation of storage moduli with increasing temperature is more pronounced.

2

Experimental and theoretical investigations of glass-fibre reinforced composite subjected to uniaxial compression for a wide spectrum of strain rates

Pieczyska E. A., Pęcherski R. B., Gadaj S. P., Nowacki W. K., Nowak Z., Matyjewski M. M.

Archives of Mechanics

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2006

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Vol. 58, nr 3

273-291

EN

Results of static and dynamic compression} tests for two types of glass fibre-reinforced polypropylene composites are presented. Stress-strain curves showing the influence of the strain rate on the composite mechanical properties have been obtained. A three-dimensional description of the material behavior during the deformation has been developed. The material constitutive parameters have been calculated. Specification of the parameters and description of the methods used for their identification have been worked out. The results are discussed in terms of the deformation processes and the material non-homogeneity.

3

A new integration procedure for thermo-elasto-viscoplasticity

Dornowski W.

Archives of Mechanics

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2002

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Vol. 54, nr 5-6

389-410

EN

A numerical integration algorithm for thermo-elasto-viscoplastic constitutive equations is presented. This algorithm satisfies the principle of material objectivity with respect to the total motion (translation, rotation and strain) of a material element. For this purpose, the properties of convective description are used. The explicit-implicit integration scheme for the plastic flow rule plays the crucial role in the proposed algorithm. The method of determining the stress state for inelastic deformations is based on the iterative solution of the dynamic yield condition with respect to the norm of the viscoplastic deformation rate tensor. The constitutive model being the subject of numerical analyses is described. Results of numerical calculations, which show an excellent performance of the proposed procedure, are presented.