The real contact area is crucial in tribology, as it plays a significant role in the behavior of contacts between surfaces. During their design, we must carefully analyze the real contact area and interactions on it, as they influence various contact characteristics such as temperature, pressure, wear, as well as electrical and thermal conductivity. All these characteristics are essential for contact performance and affect its lifespan. In this study, the surfaces of specimens made of two different steels with three different roughness levels were loaded up to the yield strength of the material against sapphire glass, while capturing images of the contact in real-time to observe changes on the contact surface. The images were converted into binary format and analyzed using a custom software code. Additionally, the surface before and after loading was examined using an interferometer. The real contact area increases almost uniformly during loading, while the number of asperities initially rises in the first half of the loading process but then starts to decline. The hardness of the steel did not affect the contact area, whereas increasing roughness reduced the ratio between the real and nominal contact area. For a roughness of Ra = 0.1 µm the ratio is up to 24 %, for Ra = 0.3 µm up to 19 % and for Ra = 1 µm up to 9 %.
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