On December 9, 2020, the City scientific seminar " Mathematical problems of natural science. Inverse and ill-posed problems»

Session № 70 (101)

Seminar leaders:

• M.A. Bektemessov - d.ph.-ms., professor, Senior Vice-rector of Abai KazNPU;
• B. Rysbaiuly - d.ph.-m.s., professor, Head of the Department of IITU;
• Zhakebaev D.D. - PhD, Dean Faculty of Mechanics and Mathematics.

Theme of thesis: «Modeling and investigation of the influence of the loading mode on creep and  

damage of rheonomic materials»

           Abstract. When assessing the strength and durability of materials, the influence of the loading mode on creep and damage of rheonomic materials was modeling and investigated.

This work proposes an effective algorithm for description of nonlinear deformation of rheonomic materials based on Rabotnov’s method of isochronous creep curves. Relevant equations have been determined from the nonlinear integral equation of Yu.N. Rabotnov for the application cases of Rabotnov’s fractional exponential kernel and Abel’s kernel for nonlinear deformation of hereditary materials at creep. The improved methods have been given for determination of creep parameters a, e₀, d, b and l. New efficient method has been proposed for determining of parameters (a, d) for Abel’s kernel. Algorithm and relevant software have been developed for calculating of parameters α and δ. The notions have been introduced for experimental and model rheological parameters and similarity coefficients of isochronous curves. It has been shown how using them, one can find instantaneous strains at various stress levels for description of nonlinear deformation of rheonomic materials at creep.

By processing and using test results for materials nylon 6, glass-reinforced plastic TC 8/3-250 (Ѳ=0°, 45°, 90°), SVM aramid fibers, EDT-10 epoxy resin, epoxyphenolic glass-reinforced plastic at temperatures Т=20, 30, 40, 50, 60° С, polycrystalline graphite and polyester polymer-concrete, the process has been shown for sequential implementation of the developed methods for description of linear and nonlinear deformation of these materials at creep. Nonlinear deformation of asphalt concrete at creep is adequately described by the proposed methods. Efficient methods and relevant software have been developed for calculation of values of instantaneous strain and creep strain for rheonomic materials.

In the work results of experimental investigation of an asphalt concrete deformation under cyclic loading, at different loading rates, step loading on the scheme of direct tension are presented. Test temperature was 22-24° С. The influence of the loading mode on creep and damage of asphalt concrete samples was investigated.

Speaker:

Yensebayeva Gulzat Muratbekovna – PhD student, specialty 6D060300 – «Mechanics»

Local scientific supervisors: Iskakbayev Alybai – d.ph.-m.s., professor;

                                               Teltayev Bagdat Burkhanbayuly –d.tech.s., professor;

Foreign scientific supervisor: Cesare Oliviero Rossi – PhD, professor, University of Calabria, Italy.

Link to connect: https://us02web.zoom.us/j/86756875462?pwd=QVM4SVJsODk5MmhUZlpuUHdPSzFydz09

Conference ID: 867 5687 5462

Access code: 044492