Strain distribution in the neck of a flat sample of titanium vt1-00 under uniaxial tension | Mekhanika | kompozitsionnykh | materialov i konstruktsii
> Volume 25 > №4 / 2020 / Pages: 522-530

Strain distribution in the neck of a flat sample of titanium vt1-00 under uniaxial tension



The components of linear and shear elastic-plastic deformations in the symmetric neck of a flat sample under uniaxial tension are determined by the digital image correlation method. The material of the specimen is the titanium grade VT1-00 with hexagonal tightly Packed crystal lattice ( phase). The specimens were extracted from sheet metal that had undergone recrystallization annealing in vacuum. The structure of the surface layer was determined by the standard method. For this material, the main feature of the mesostructure of the first level (polycrystal grain) is the presence of a large number of annealing twins. The proportion of grains with is approximately twenty to thirty percent for the entire grain array. Modern high-precision equipment, such as Instron 8801 testing machine and Strain Master digital optic system are used in experiments. The fields of displacement vectors of the sample surface areas in the neck region are determined. Irregularities of relief arising on the surface of the sample during the tension testing were taken as reference targets. In each moment of time, the linear local mesodeformations of the first kind and the value of distortion (at the level of the grain of polycrystalline specimen) was determined by using the field of the components of the displacement vectors. The deformations is calculated on virtual lines parallel to the specimen axis. The distance between the lines is taken to be half a millimeter. An approximate evaluation of the deformation value in the direction perpendicular to the specimen plane is performed by means of the incompressibility condition. The kinetics of longitudinal and transverse deformations is determined along with the tensile axis of the sample. The coefficients of mutual correlation between the parameters of the strain state are calculated. The distribution densities of linear strain and distortion tensor components are determined. The density distribution is used to determine the probability of occurrence of large values of deformations in the neck area. These probabilities are equal to the ratio of the number of grains of a polycrystal with a deformation greater than some fixed value to the total number of grains in the neck area. The work was carried out within the framework of the State Assignment of the Institute of Mechanical Engineering of the Ural branch of the Russian Academy of Sciences.