Evaluation of Fretting Streses Through Full-Field Temperature Measurements

摘要

The near-surface stress field in fretting has long escaped experimental characterization due in large part to the fact that the friction coefficient in the slip zones associated with the partial slip contacts cannot be evaluated from measured forces. Attempts at circumventing this through measurements of microslip or extent of the slip zones have been inconclusive. However, newly available infrared detector technology is capable of resolving finely, both spatially and temporally, subsurface temperatures near the fretting contact. These temperature changes are induced by both frictional heating at the surface due to microslip as well as the coupled thermoelastic effect arising from the strains in the material. A finite element model has been developed for fretting that includes the heat generation due to sliding and partial slip; and the coupled thermoelastic effect. The model also incorporates heat conduction, thermal deformation, and contact. The correlation between the temperature changes measured by the infrared camera and those predicted by the finite elements is remarkable. During gross sliding, a patch of heating throughout the contact length, attributed to frictional heating, is observed. As the friction coefficient rises and the contact transitions to a partial slip regime, the temperature changes are more clearly associated with strain through the coupled thermoelastic effect. The excellent agreement of the finite element results with the experiments demonstrates the ability of the model to provide validated values for fretting-induced stresses and microslip.