Moscow Polytechnic University, Moscow, Russia

S. A. Tipalin, Cand. Eng., Associate Prof., Dept. of Mechanical Design and Automation, e-mail: tsa_mami@mail.ru
Yu. K. Filippov, Cand. Eng., Prof., Dept. of Mechanical Design and Automation, e-mail: yulianf@mail.ru
Doan Xuan Quang, Postgraduate Student, Dept. of Mechanical Design and Automation, e-mail: doanquang1809@gmail.com
A. A. Gnevashev, Postgraduate Student, Dept. of Mechanical Design and Automation
N. I. Kuminova, Head of the CAD Laboratory
V. N. Timofeev, Cand. Eng., Associate Prof., Dept. of Mechanical Design and Automation

Accurately constructing a material’s hardening curve is a key factor influencing the reliability of numerical simulations of technological processes. This is particularly true in cold die forging, where the material is subjected to large plastic deformations. However, standard compression tests on cylindrical specimens reduce the reliability of the results due to friction on the contact surfaces. Contact friction with the tool surface causes a “barreling” effect, leading to uneven strain distribution and an overestimation of the calculated stress value. As a result, the hardening curve loses reliability for logarithmic strain values greater than 0.6. This article proposes an improved method for compressing cylindrical specimens using soft inserts, aimed at actively controlling material flow. The method is based on a basic cylindrical specimen (grade 10 steel) with inserts inside the ends made of a softer, highly deformable material (A5M aluminum), placed in recesses on the end surfaces. The mechanism of action is as follows: significant transverse expansion of the soft inserts under a compressive load creates localized tensile forces acting radially along the end face of the main specimen, effectively compensating for frictional resistance. This ensures high radial deformation uniformity, eliminates the “barreling” effect, and achieves conditions of near-uniaxial compression. Using computer modeling, this study conducted a numerical selection process to determine the optimal geometric parameters of the inserts, ensuring the required equilibrium of compensating forces. Analysis revealed that the use of A5M aluminum inserts with a diameter of 12 mm and a thickness of 2.9 mm is the optimal configuration for true strain near unity. This configuration demonstrated the ability to provide a virtually uniform distribution of logarithmic strain intensity across the entire specimen cross-section, significantly reducing strain fluctuations compared to traditional methods.

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