OBRABOTKAMETALLOV Vol. 27 No. 1 2025 technology Surface topography after electrical discharge machining was obtained using a laser scanning microscope (LSM) Lext OLS4000 (Olympus Corporation, Tokyo, Japan) based on a three-dimensional image model. The surface model was generated using the 3DRoughnessReconstruction software module (Olympus Corporation, Tokyo, Japan). The three-dimensional surface was constructed from optical slices acquired through X-Y-Z scanning of specific surface areas. Scanning was performed at ×200 and × 1,000 magnifications, with a scanning step of 2 μm along the Z-axis. A semiconductor laser with a wavelength of 405 nm served as the light source for scanning. For visual evaluation of the processing results, a Hitachi S-3400N scanning electron microscope was used in backscattered electron mode at a voltage of 25 kV. Cyclic tests were performed on a Biss-00-100 universal testing machine (Fig. 2, a) at a test frequency of 20 Hz in a symmetrical cycle (R = −1). Fatigue testing was controlled using a soft loading method, which involves a smooth and controlled increase in applied stresses. Three key factors, carefully monitored by specialized measuring equipment, served as criteria for test termination. The test was terminated when the specimen failed completely ‑ the most obvious indication that the material’s endurance limit had been reached. The test was also terminated upon reaching a predetermined number of loading cycles, a multiple of 100,000. This parameter reflects the accumulation of plastic strain in the material. A test termination occurred when the strain range increased by more than 20 % from the initial value. Exceeding the acceptable 20 % threshold signals a significant reduction in the specimen’s load-carrying capacity and indicates impending failure. It is important to note that this threshold may vary depending on the material type and test conditions. To investigate the influence of the surface WEDM process on fatigue characteristics, specimens were removed from tests after 100,000 cycles. Optical surface scanning was performed using a NewView 5010 optical profilometer (Fig. 2, b). This device enables the creation of a digital model of the surface relief and Fig. 1. Specimen geometry Ta b l e 1 WEDM modes Mode No. Ton, μs h, μs Toff, μs 1 21 10 60 2 30 3 21 15 4 30
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