The density of deformation distribution in a plane of VT1-00 sample under uniaxial strain

The inhomogeneity of the plastic deformation field is a common property of all polycrystalline materials. Numerical indicators of deformation inhomogeneity are defined using various experimental methods. The grade grid method with grid sizes commensurable with the average size of the material grain is meant to be the classical one. This method allows obtaining full characteristics of the field inhomogeneity for mesodeformations (at the grain level and inside the individual grains of the material). The grid method is considerably laborious and has limitations in accuracy. Statistically reliable data require performing a large number of measurements. The coordinates of grid points are measured by a visual observation of the magnified image in a microscope eyepiece. The development of modern means of computer technology and digital video cameras with high resolution allows using more advanced experimental methods. This article based on the method of digital image correlation provides the technique for defining statistical parameters of the deformation field inhomogeneity in the surface layer of the sample under loading. On the basis of digital images correlation method we propose a technique aimed at identification of statistical parameters of the deformation field inhomogeneity in a surface layer of the sample. The tests were performed using uniaxial strain of plane VT1-00 titanium samples. It is a single-phase material (α- phase) with the hexagonal crystal grid. The metallographic studies of material structure of the sample have been performed. The average grain size is determined using the random linear intercept method. The grains are equiaxial. The sample material has annealing twins. There are fields of vectors for irreversible displacements, components of the tensor for elastic-plastic deformations in orthogonal directions about the axis of the sample and shear deformations in a plane of the sample that have been determined. The third component of linear deformations has been defined according to the material’s incompressibility. The deformation relief on a surface of the sample during the strain was used as reference targets. The main logarithmic elastic-plastic deformations, its intensity and random Nadai-Lode parameters characterizing the stress-strain state of individual sections of the sample’s surface have been calculated. Distribution densities of the specified parameters have been built up and correlation functions of deformation intensity have been obtained. The results of the study have been compared with the experimental data obtained by the grain grid method under uniaxial strain of titanium grade VТ1-0 samples, similar in chemical composition to titanium VT1-00. There are more impurities in titanium VТ1-0.