Tula State University, Tula, Russia:
V. D. Kukhar, Dr. Eng., Professor, Head of the Dept. of Theoretical Mechanics
V. A. Korotkov, Cand. Eng., Associate Professor, Dept. of Mechanics of Plastic Forming
S. S. Yakovlev, Postgraduated Student, Dept. of Mechanics of Plastic Formings, e-mail: fiz-site@yandex.ru
A. A. Shishkina, Student, Dept. of Labour and Environment Protection

Obtaining shells with riffling inner surface is a complex and urgent task, therefore, a new riffling method has been developed, which is characterized by high efficiency and low metal consumption of the structure relative to existing ones. At the same time, there are practically no works devoted to the assessment and study of stresses, deformations, and material damage when knurling by local form change. The paper analyzes the intensity of deformations, average stresses and the risk of destruction when knurling the inner surface of the shell during local shaping using tools that have different-shaped lead-in parts of the wedge protrusions. A comparative analysis of the stress-strain state is performed for various methods of knurling in one direction – local shaping and reduction through a conical matrix. The study was carried out in order to determine the most appropriate method of knurling in terms of obtaining the favorable stress-strain state. The stress-strain state when knurling of the opposite direction in the zone of their intersection in the process of forming a mesh of riffles by local shaping is also considered. To solve the problem, computer simulation was carried out in the DEFORM program with subsequent interpretation of the results.
The work was carried out within the framework of the grant of the Government of the Tula region in the field of science and technology No. DS/167.

1. Gurel E. Modeling and simulation of shaped charges; to graduate work for the degree of master of science. Turkey: Middle East Technical University, 2009. 150 p.
2. Harikrishnan S., Murthy K. P. S. Inconsistent performance of a tandem-shaped charge warhead. Defence Science Journal. 2010. Vol. 60. No. 2. pp. 164–168.
3. Popov E. A. Method of knurling of lengthwise riffles. Patent RF. No. 2087239. Applied: 06.07.1995. Published: 20.08.1997.
4. Yakovlev S. S. Analysis of the intensity of stresses and deformations when knurling of the inner surface. Izvestiya Tulskogo gosudarstvennogo universiteta. Tekhnicheskie nauki. 2021. No. 5. pp. 88–93.
5. Kukhar V. D., Korotkov V. А., Yakovlev S. S., Shishkina А. А. Formation of a mesh of spiral wedge protrusions on the inner surface of a steel shell by local plastic deformation. Chernye Metally. 2021. No. 6. pp. 65–68. DOI: 10.17580/chm.2021.06.12
6. Mitin О. N. Formation of screw rifts on the inner surface of a cylindrical shell. Izvestiya Tulskogo gosudarstvennogo universiteta. Tekhnicheskie nauki. 2013. No. 3. pp. 548–552.
7. Mitin О. N., Ivanov Yu. А. Stress-strain state of the material when reducing a cylindrical shell by a punch with riffles. Izvestiya Tulskogo gosudarstvennogo universiteta. Tekhnicheskie nauki. 2013. No. 4. pp. 111–116.
8. Kukhar V. D., Kireeva А. Е. The study of the stress-strain state of the material at the manufacture of steel axisymmetric products with internal spiral corrugations by reduction method. Chernye Metally. 2020. No. 3. pp. 31–39.
9. Samudre S. S., Nair U. R., Gore G. M., Sinha R. K., Sikder A. K., Asthana S. N. Studies on an improved plastic bonded explosive (PBX) for shaped charges. Propellants Explosives Pyrotechnics. 2009. Vol. 34. pp. 145–150.
10. Moskvichev Е. N., Skripnyak V. А., Karakulov V. V., Lychagin D. V. Effect of microstructural changes at knurling by cyclic pressing on the mechanical behavior of Mg – Mn – Ce alloy. Vestnik Tomskogo gosudarstvennogo universiteta. Matematika i mekhanika. 2019. No. 58. pp. 109–118.
11. Moskvichev E. N., Skripnyak V. A., Skripnyak V. V., Kozulin A. A., Lychagin D. V. Influence of structure to plastic deformation resistance of aluminum alloy 1560 after groove pressing treatment. Letters on Materials. 2016. Vol. 6. No. 2. pp. 141–145.
12. Pack K., Mohr D. Combined necking and fracture model to predict ductile failure with shell finite elements. Engineering Fracture Mechanics. 2017. Vol. 182. pp. 32–51.
13. Roth C. C., Mohr D. Ductile fracture experiments with locally proportional loading histories. International Journal of Plasticity. 2016. Vol. 79. pp. 328–354.
14. Bakulin V. N. Block based finite element model for layer analysis of stress strain state of threelayered shells with irregular structure. Mechanics of Solids. 2018. Vol. 53. pp. 411–417.
15. Vlasov А. V. On the application of the Cockcroft-Latham criterion for predicting fracture during cold forging. Izvestiya Tulskogo gosudarstvennogo universiteta. Tekhnicheskie nauki. 2017. No. 11–1. pp. 46–58.