A. G. Makarov

A version of modeling of nonlinear-hereditary viscoelasticity of polymer materials

We propose a version of the mathematical model of nonlinear-hereditary viscoelasticity of polymer materials, which is used to predict strain processes of various complexity, from simple relaxation and simple creep processes to complicated strain recovery processes and reverse relaxation processes with alternating loading and unloading.

Creep and fracture kinetics of polymers

The creep kinetics and the fracture kinetics of oriented linear polymer (polypropylene) are compared. The distributions (scatter) of the specimen lives and the steady-state creep rate are studied on series of identical specimens loaded under the same conditions (load, temperature). It is found that the scatter of the specimen lives is significantly larger than the scatter of the creep rates at the same activation energy of fracture (the measure of which is the life) and creep. This finding reflects a localized character of fracture (break) of specimens and a delocalized character (involvement of the entire specimen volume) of creep. It is concluded that the equality of the activation energies of both processes is caused by the elementary acts of fracture of an oriented polymer (breaking of chain molecules), and they open up possibilities for creep acts, i.e., conformation transitions, in a polymer.

Prediction of Reverse Relaxation and Deformation—Recovery Processes in Synthetic Fibres

Use of “force” and “geometric” “deformation” variants of the nonlinear-hereditary viscoelasticity equation for prediction of complex processes by calculation is examined on the example of deformation-recovery and reverse relaxation processes in Lavsan synthetic fibres. A comparison of the calculated and measured values allows recommending the method of calculated prediction in which an elementary function — the normalized arctangent of the logarithm of the reduced time serves as the normalized relaxation or creep function.

Correction to: Development of Criteria for Reliability of the Prediction of the Deformation and Relaxation Processes of Polymeric Materials

The acknowledgement on page 139 should readThe work was financed within the framework of the base part of the state task of the Ministry of Education and Science of the Russian Federation, Project No. 11.4696.2017/8.9.

Modeling of Deformation-Relaxation Processes of Aramid Textile Materials – the Foundation for Analyzing Their Operational Properties

Methods for mathematical modeling of deformation-relaxation processes of aramid textile materials are described. It is shown that the increase in the competitiveness of these materials is closely tied to qualitative analysis methods of their operational-consumer and functional properties.

Development of Criteria for Reliability of the Prediction of the Deformation and Relaxation Processes of Polymeric Materials

The problems of the reliability of the prediction of the relaxation and deformation properties of polymer materials in the region of action of nondestructive loads close to the conditions of their operation are considered on the basis of mathematical modeling of the relaxation and creep processes. For practical evaluation of the reliability of this prediction, integral criteria are obtained on the basis of the determining equations of deformation and relaxation processes of these materials.

Variants of Mathematical Simulation and Systems Analysis of Mechanical Relaxation and Creep of Polymer Materials

Questions related to mathematical simulation and systems analysis of mechanical relaxation and creep of polymer materials are considered. Based on this discussion a prediction of relaxation and deformation processes of differing degrees of complexity, from simple relaxation with constant deformation and simple creep with constant load to compound processes of reverse relaxation and deformation-reduction processes with multi-stage deformation and loading, is presented.

Development of Methods of Mathematical Modeling of Processes of Relaxation and Creep of Polymer Filaments Based on a Spectral Interpretation

Methods of mathematical modeling of processes of relaxation and creep of polymer filaments on the basis of a spectral interpretation of the processes are described. It is shown that the analytic forms of the relaxation and delay (creep) spectra are completely determined by the mean-statistical values of the relaxation and delay times as well as by the structural coefficients of these processes, which basically characterize the intensity of relaxation and creep processes.

Initial stage of stress relaxation in oriented polymers

The initial stage of stress relaxation, i.e., a decrease of the stress with time in an extended solid at a fixed length of the specimen, has been studied in oriented fibers of a linear polymer, polypropylene, chosen as the object of investigation. Experimental data have been obtained, and the stress in the object from the beginning of tensile loading of the specimen has been analyzed. It has been found that the stress relaxation caused by thermal fluctuation conformational transitions in stretched chain polymer molecules occurs from the beginning of the stretching of the polymer fiber. The time dependence of the stress relaxation of polypropylene fibers in all initial stages of deformation of the fibers has been elucidated.

Comparative Analysis of the Deformational Properties of Aramid Fibers and Textiles Made from Them

The deformational properties of Aramid fibers are subjected to a comparative analysis. It is shown that dividing processes involving the deformation of Aramid textiles into an elastic component and a viscoelastic-plastic component allows the proper choices to be made among materials which have certain elastic-mechanical properties. Comparative analysis of the viscoelastic characteristics of Aramid fibers is the foundation for solving the engineering problems encountered in the design and selection of materials having specified elastic and viscoelastic-plastic properties.