yield condition, plastic potential, associated flow rule, mathematical theory of plasticity, equivalent stress, equivalent strain.

We consider alternative forms of Tresca’s yield condition. It is noted that features of the representation of Tresca’s condition by the principal invariants of the stress tensor are common for piece-wise linear conditions of plasticity. The approach to determining equivalent stresses and plastic deformations is discussed. Different invariant definitions of equivalent stresses and deformations are proposed.

Artemov Mikhail Anatolievich e-mail: artemov_m_a@mail.ru, Head of the Chair, Dr. Sci. Phys. & Math., Professor, Voronezh State University, Voronezh, Russia Baranovskii Evgenii Sergeevich e-mail: esbaranovskii@gmail.com, Associate Professor, Cand. Sci. Phys. & Math., Voronezh State University, Voronezh, Russia Semka Eleonora Viktorovna e-mail: semka_elya@mail.ru, Lecturer, Military Educational and Scientific Center of the Air Force “N. E. Zhukovsky and Y. A. Gagarin Air Force Academy”, Voronezh, Russia Tretyakova Yuliya Nikolaevna e-mail: ulia_tretyakova1993@mail.ru, Postgraduate student, Voronezh State University, Voronezh, Russia