Improved core model of the indentation for the experimental determination of mechanical properties of elastic-plastic materials and its application

摘要

The improvement of Johnson's model (Johnson (1970), (1985)) takes into account the additional pressure and shear stresses jump at the boundary with the hydrostatic core where it is formed from the material of the elastic-plastic zone. This causes additional volumetric deformations and additional pressure in the core that increases the magnitude of the constant in the Tabor ratio. The effects of the proposed improvement of the Johnson model: additional volumetric deformations and pressure in the core, changes in the Tabor constant and related values of yield strength as well as characteristic size of the elastic-plastic region, were determined on a wide class of materials with different elastic-plastic properties. An analysis of the concept of characteristic (representative) strain is given for these materials.