Issue 78

M. Bronovets et alii, Frattura ed Integrità Strutturale, 78 (2026) 367-377; DOI: 10.3221/IGF-ESIS.78.21

s. Fig. 3 shows the diagrams of the laser beam displacement during the processing of each type of sample and photos of the samples after processing.

Figure 3: Diagram of the laser beam path during processing and a photo of the processed sample.

LSP treatment was carried out on the samples with the aim of forming compressive residual stresses in the surface layer to reduce wear of the samples during their tribological testing and to prolong their service life. A series of tribological studies were carried out using a high-precision multifunctional tribometer MFT-5000 (Rtec, USA), allowing the control and recording of friction parameters in real time. This tribometer is equipped with precision friction and displacement sensors, ensuring high accuracy and reproducibility of results. The tests were carried out at a constant angular velocity of 500 rpm, which is equivalent to a linear rotational speed of V = 1 m/s with a rolling radius of 19 mm and a constant normal load of F = 1000 N. The disk specimens had a thickness of 8 mm. The contact assembly consisted of 21 bearing balls (diameter 6 mm, steel 52100) interacting with the disk. Based on Hertzian contact theory, considering the ball radius (3 mm) and the disk rolling radius (19 mm), the maximum contact pressure for a single ball under the 1000 N total load was calculated to be 2.61 GPa. The tests reproduced the rolling conditions in real rolling bearings. Fig. 4 shows a photograph of the test sample arrangement.

Figure 4: Arrangement of the test samples.

A series of tribological tests were conducted under two distinct lubrication regimes, encompassing a broad spectrum of operating conditions. The first mode was friction of unlubricated surfaces, characterized by the absence of lubricant between the contacting surfaces. This mode simulates critical situations that arise when the lubrication system fails or is

371