Name: RUBSON MAÇÃO CAMPOREZ
Publication date: 30/01/2024
Examining board:
Name |
Role |
|---|---|
| CHERLIO SCANDIAN | Presidente |
| NATHAN FANTECELLE STREY | Examinador Interno |
| ROBERTO MARTINS DE SOUZA | Examinador Externo |
| VALDICLEIDE SILVA E MELLO | Examinador Interno |
Summary: The increase in contact temperature resulting from friction during sliding between bodies influences tribological behavior, leading to changes in the microstructure and properties of materials. This thermal increase can induce softening and melting of the bodies, phenomena particularly impactful in polymers due to their low glass transition and melting temperatures. Therefore, studying and predicting the contact temperature for polymeric materials is of paramount importance to maximize their tribological application. The calculation of the contact temperature can be performed by numerical methods or through
mathematical models developed for problems of lesser geometric complexity and boundary conditions. Despite the relevance and presence of methodologies for determining the contact temperature, this challenge persists in contexts involving polymeric pairs. The obstacle arises from simplifications and from not considering changes in material properties as a function of temperature. A case that occurs with polymers is the alteration of thermal conductivity, which is sensitive to the molecular ordering of polymer chains, as well as to temperature and contact pressure. The literature has gaps to be filled regarding the contact temperature of polymers, especially polymer-polymer pairs. In this context, an investigation of the contact temperature of spheres and cylindrical pins (geometry) of two different diameters (dimension) of polyetheretherketone (PEEK), an ultra-high-performance polymer, sliding against brass, PEEK, and alumina discs was conducted, varying the normal load (13 different loads) and sliding velocity (0.5 and 1 m/s). Additionally, the surface temperature of the disc was measured during the test using an infrared thermal camera. Overall, it was observed that sliding velocity, geometry, dimension, and nature of the discs influenced the parameters used in calculating the contact temperature, such as heat partition and the Peclet number. In contrast, regarding the
increase in flash temperature, nominal temperature, and maximum contact temperature, sliding velocity did not influence, while the geometry, dimension, and nature of the discs did. Errors between the temperature measured with the thermal camera and one of the components of the contact temperature were observed, and to improve the accuracy of the mathematical model, the use of correction factors called 1 and 2 was proposed, which multiply the thermal conductivities of the pin/sphere and disc, respectively. With their use, errors were reduced to zero under some conditions, increasing the applicability of the mathematical model of contact temperature.
