Application of the Experimental-Calculation Approach for Identification of Deformation and Strength Characteristics of Elastic-Plastic Materials under Quasi- Static and Dynamic Loading

The paper presents numerical and experimental studies of deformation and fracture processes of 10G2FBU and St35 steels under various types of quasi-static and dynamic loadings: tension of a solid rod and M8 bolts with smooth and threaded working parts, as well as compression of compact cylindrical specimens. The developed experimental-calculation techniques are described in detail and shown schematically for quasi-static and dynamic true strain diagrams in tensile and compression experiments. Application of these techniques made it possible to determine quasi-static and dynamic true strain diagrams for steels 10G2FBU and St35. The obtained quasi-static deformation diagrams of 10G2FBU steel in tension and compression practically coincide. It was found that in the construction of true strain diagrams for 10G2FBU steel, the strain rate at values above 500 1/s has a significant influence. A coupled fracture model based on the kinetic equation of damage accumulation in combination with the strength criterion of the Pisarenko-Lebedev type is proposed and implemented to investigate and describe the deformation and fracture processes of elastoplastic materials. Based on the experimental-calculation approach, a new methodology for fitting material parameters for the proposed fracture model is developed. Accordingly, the material parameters of the coupled fracture model for St35 steel are determined. The results of numerical modeling of the fracture process of M8 bolts with smooth and threaded working part under quasi-static tension show a quantitative and qualitative correspondence of the type and character of fracture with the experiment. The joint application of the experimental-calculation approach and the proposed coupled fracture model allows a more accurate description of the deformation and fracture processes of elastic-plastic materials.