Pham D. Failure criterion of structural materials with taking into account damage

The dissertation is devoted to the development of the failure criterion of structural materials, working under complex stress conditions in the case of static load, taking into account damage. Various energy approaches were used to determine the value of the damage parameter, which are based on changes in the physical and mechanical characteristics of materials at simple loads (tensile and torsional). Based on the experimental results obtained on various structural materials, the model of description the kinetics of damage accumulation proposed by Bonora has been improved, depending on the level of plastic deformation. The dependence of the model parameters and the damage failure criterion on the elastic-plastic characteristics of the material were obtained. The obtained theoretical values ​​are compared with experimental ones. A method for determining the kinetics of damage accumulation in the case of torsion of cylindrical specimens has been developed, taking into account the heterogeneity of the deformation distribution in the cross section of the specimen. On the basis of the Davidenko-Friedman approach, the criterion of the limit state of structural materials was developed, taking into account the type of stress state and damage. The comparison of the results of the limit state obtained by the developed criterion, experimental data and other methods is presented.