Вестник МГТУ. 2019, Т. 22, № 4.

Introduction The tensile tests were conducted with the intentions of generating stress - strain diagrams and thermographic images of the DIN 50125 standard steel specimens1. These tests were performed at room temperature conditions (25°). The tensile tests were repeated multiple times to ensure that repeatability of the results. Methods GUNT® Hamburg Universal Material Tester The GUNT® Hamburg universal material tester2, displayed in Fig. 1, was used to carry out all the experimental tensile tests in this study. The tensile specimens are clamped between the upper cross member and the crosshead. The test force is generated by means of a hand-operated hydraulic system and displayed on a large force gauge with the pressure indicator. A dial gauge measures the elongation of the specimens. Fig. 1. The GUNT® Hamburg universal material tester Рис. 1. Универсальный тестер GUNT® Hamburg DIN 50125 Standard Steel Test Specimens The test specimens used were DIN 50125 standard steel3. The steel specimen has a circular cross-section, with two center punch marks on the shafts to mark the test length, as shown in Fig. 2. Fig. 2. The steel specimen with a circular cross-section Рис. 2. Стальной образец с круглым поперечным сечением Data Acquisition The universal material tester used was equipped with an electronic measuring system. By using this system, measured values for force and displacement can be transferred to a computer and analyzed with the system software (Fig. 3). Measured values are evaluated in the user-friendly software, so stress - strain diagrams can be recorded. The raw data were exported and stored for all tensile tests performed. 1Ju Feng Special Steel Co., Ltd. URL: https://www.jfs-steel.com/en/steelDetail/DIN-9SMn28/DIN-9SMn28.html. 2 GUNT® Hamburg Universal material tester. [Online]. URL: https://www.gunt.de/en/products/engineering- mechanics-and-engineering-design/testing-of materials/tensile-compression-bending-and-hardness-testing/materials-testing 20kn/020.30000/wp300/glct-1:pa-148:ca-34:pr-1540. 3 Ju Feng Special Steel Co., Ltd. URL: https://www.jfs-steel.com/en/steelDetail/DIN-9SMn28/DIN-9SMn28.html.