Thermo-Viscoelasticity. Viscoelastic Properties of Polymeric and Composite Materials
RESEARCH DIRECTIONS
MAIN RESULTS
Mathematical model of viscoelastic behavior
Determination of model parameters on the experimental data
Experimental data and computer algorithms
Computation of polymeric constructive elements
Composite polymeric materials
REFERENCES
RESEARCH DIRECTIONS
Development of thermodynamical theory for constitutive equations with internal variables of state in viscoelastoplastical materials.
Development of mathematical models for viscoelastical behavior of polymeric materials taking into account of thermorheological complex dependence of material properties on the temperature. ;
Development of experimental and numerical methods for identification of constitutive equations which describe viscoelastical properties of polymeric materials into wide limits of loading velocities (frequencies) and temperatures.
Development of computation methods for stress-strain states and strength of construction elements from polymeric and composite materials under thermomechanical loading.
Estimation of processing influence on the effective viscoelastical properties of polymeric composite materials.
MAIN RESULTS
Methods of research, mathematical modelling and prediction for thermomechanical properties of polymeric materials and constructions in the wide limits of temperatures and loading velocities (frequencies) have been developed.
Mathematical model of viscoelastic behavior
One is consequence of irreversible processes thermodynamics in the media with internal variables of state. For small strains this is described by the relations of hereditary type between sresses and strains with continuous spectrum of relaxation times. In this case the thermorheological complex dependence ones from temperature do not allow to applicate reduction method in the process of foundation of the model parameters on the experimental data.
Determination of model parameters on the experimental data
This is the nonlinear incorrect inverse problem for restoration of integral operator. The relaxation spectrum (i.e., distribution density of the relaxation times) and spectrum of activation energies of viscous flow are unknown functions of this problem.
Experimental data and computer algorithms
The methods for solution of above identification problem have been developed using experimental data for polymers in the regime of forced steady oscilations under different constant temperatures. The satisfactory results of the modelling and prognosis of viscoelastic properties for some amorphous polymers (e.g. PMMA and etc.), partially-crystalline ones (e.g. polyetilen and etc.) and some two-component mixtures of amorphous polymers in wide limits of oscilation frequencies and temperatures including transition from glassy state to high-elastical one have been obtained for this type of tests. Numerical algorithms for solution of this problem have rigorous mathematical basis. The methods and equipment for these experiments have been constructed.
Computation of polymeric constructive elements
Temperature stresses with dependence of material properties from temperature.
Polymeric elements of bearings, introduction of shaft in thin polymeric internal hoop of the sliding bearing with account of friction temperature.
Effects of heating during deformation.
Polymeric springs.
Composite polymeric materials
Dependences between effective viscoelastical moduli of one-directional fiber composite and technological residual stresses have been constructed. These give a possibility for influence on the composite processing with aim to obtain necessary rheological properties.
REFERENCES
Orlov V.S. Calculation of one-dimensional thermal stresses in heterogeneous sphere and cylinder // Problems of Mechanics and Applied Mathematics.-Rostov-on-Don University,1976, P. 41-53 (in Russsian).
Orlov V.S. On the solution for mixed problem of nonlinear thermo-visco-elasticity // Mixed Problems of Solids Mechanics.-Abstr. of Soviet Scientif. Conf.-Rostov-on-Don.-1977, V.1.-P. 137-138 (in Russian).
Orlov V.S. Approximate analysis of thermo-visco-elasticity equations // Izv. of North-Caucasses Sci. Centre of High School. Natural Sciences.-1978,No.3, P.25-30 (in Russian).
Gromov V.G. and Miroshnikov V.P. Effects of thermomechanical coherency in thermoviscoelasticity theory // Proc. of Science Academy of the USSR.-1978.-V. 240, No. 4.-P. 809-812.
Miroshnikov V.P. Effects of thermomechanical coherency during deformation of polymeric materials // PhD Thesis. Abstr., Rostov-on-Don University, 1979, 20 p. (in Russion).
Azarov A.D.,Orlov V.S. and Stepanenko Yu.P. Calculation of stress state for intermediate polymeric hoop enveloping external ball race hoop // Application of Polymeric Materials in Agricultural Engineering Industry.-Abstr. Soviet Sci.-Techn.Meet.(Rostov-on-Don, 1980).-Moscow, 1980, P. 242-244 (in Russian).
Orlov V.S. Influence effects of temperature and hydrostatical pressure on the properties of polymeric material in physical nonlinear axes-symmetrical problem for thermo-visco-elasticity // Mechanics of Continuous Media.-Rostov-on-Don University,1982, P.70-82 (in Russsian).
Orlov V.S. Constitutive equations for thermo-visco-elasticity theory of thermo-rheological complex materials // PhD Thesis, Rostov-on-Don University,1985, 151 P. (in Russsian).
Miroshnikov V.P. and Zanimonets Yu.M. On the influence of residual stresses in composite material on the effective rheological properties // Mechanics of Composite Materials (Riga).-1985.-No. 1.- P.59-66.
Orlov V.S. On the one problem for identification of constitutive equations for linear theory of thermoviscoelasticity // Applied Mechanics.-Kiev, 1987, V.23, No. 5.-P.77-82 .
Orlov V.S. On the thermorheological complication of viscoelastic properties of amorphous polymers in transition field from high-elastical state to glassy one // Mechanics of Composite Materials.-Riga, 1987, No. 5, P.945 (in Russian).
Orlov V.S. Mathematical modelling of viscoelastic properties of polymeric materials in wide limits of temperatures and vibration frequencies // Mechanics of Composite Materials.- Abstr.9th Int. Conf., Riga, 1995, P.77.
Orlov V.S. On the thermodynamics of inelastic media with distributions of internal variables of state // Modern Problems of Mechanics of Continuous Media.-Abstr Int.Conf., Rostov-on-Don University,1995, P.38 (in Russsian).
Orlov V.S. On the equations for thermo-visco-elasticity and thermo-visco-plasticity theories // Modern Problems of Mechanics of Continuous Media.-Kniga: Rostov-on-Don,1996, V.3, P.109-113 (in Russsian).
Orlov V.S. Computer simulation of viscoelastic properties of polymeric materials in wide limits of temperature alteration // Modern Problems of Mechanics of Continuous Media. - North-Caucases Scientific Centre of High School: Rostov-on-Don, 1999, V. 2, P.101-105 (in Russian).
Orlov V.S. On the mathematical modeling of thermomechanical properties of polymeric material mixes // Modern Problems of Mechanics of Continuous Media. - North-Caucases Scientific Centre of High School: Rostov-on-Don (in press).
Valentin S. Orlov, PhD, Senior Scientist led some scientific projects.
Vladimir P. Miroshnikov, PhD, Senior Scientist.