Experimental study of mechanical properties of steel 40Cr in the necking area of specimen during the postcritical deformation

Abstract The work is devoted to the experimental study of the evolution of mechanical properties of the structural steel 40Cr during postcritical deformation of solid cylindrical specimens in conditions of strain localization formation in the form of neckat tension. The methodical issues of providing tests by ‘specimen from specimen’ scheme are observed. Different levels of preliminary postcritical deformation of initial samples are realized, and the results of testing specimens cut from the initial samples with a neckare obtained. To measure the displacement and strain fields in the gauge length of specimens with the neckthe noncontact 3D video system Vic 3D, based on the digital images correlationtechnique, was used. On the base of test results, the stiffness and strength of steel 40Cr were evaluated in a neckedspecimen at various stages of postcritical deformation. The hardness distribution on the specimen after neckingwas analyzed too. It is shown that the material in the peripheral areas of the gauge length of the sample is in a strengthened state, which does not depend on the degree of previously achieved postcritical deformation, and the strength of the material in the neck-forming zone on the initial specimens is thereby increased.