Elastoplastic Deformation of L63 Brass Along a Complex Smooth Curvilinear Trajectory

The article presents results of a complex loading experiment on thin-walled brass L63 tubular specimens, demonstrating a highly non-trivial relationship between stresses and strains during elastoplastic deformation. The experimental program, as well as the interpretation and discussion of the obtained data, are based on the terminology and theoretical provisions of A.A. Ilyushin’s theory of elastoplastic processes. The experimental study was carried out in the deviatoric strain space on the automated testing machine SN-EVM under combined axial tension-compression and torsion loading of thin-walled tubular specimens. A distinctive feature of this study was the complex curvilinear strain trajectory consisting of five circles internally tangent at the coordinate origin. Each trajectory segment featured varying curvature values and circle center positions along the axis. According to A.A. Ilyushin’s definition, this trajectory qualifies as smooth since it contains no break points. During the experiment, the scalar and vector properties of the L63 brass material were studied. It was experimentally established that a change in the trajectory curvature causes a “dive” of stresses on the stress-strain diagram, which is similar to the dive that appears when there is a break angle in the trajectory, for example, in two-link broken trajectories. It was also established that the obtained experimental diagrams reflecting the vector properties of the material have a pronounced oscillatory behavior. The experimental results will be useful for verification of existing mathematical models of plasticity theory.