On the proportionality between area and load in line contacts

On the proportionality between area and load in line contacts

van Dokkum, J.S. (TU Delft (OLD) MSE-7)
Khajeh Salehani, M. (TU Delft (OLD) MSE-7)
Irani, N. (TU Delft (OLD) MSE-7)
Nicola, L. (TU Delft (OLD) MSE-7; Università degli Studi di Padova)

2018

The relative contact area of rough surface contacts is known to increase linearly with reduced pressure, with proportionality factor κ. In its common definition, the reduced pressure contains the root-mean-square gradient (RMSG) of the surface. Although easy to measure, the RMSG of the entire surface does not coincide, at small loads, with the RMSG over the actual contact area g¯ _r, which gives a better description of the contact between rough surfaces. It was recently shown that, for Hertzian contacts, linearity between area and load is indeed obtained only if the RMSG is determined over the actual contact area. Similar to surface contacts, in line contacts, numerical data are often studied using theories that predict linearity by design. In this work, we revisit line contact problems and examine whether or not the assumption of linearity for line contacts holds true. We demonstrate, using Green’s function molecular dynamics simulations, that κ for line contacts is not a constant: It depends on both the reduced pressure and the Hurst exponent. However, linearity holds when the RMSG is measured over the actual contact area. In that case, we could compare κ for line and surface contacts and found that their ratio is approximately 0.9. Finally, by analytically deriving the proportionality factor using g¯ _r in the original model of Greenwood and Williamson, a value is obtained that is surprisingly in good agreement with our numerical results for rough surface contacts.

Contact area
Greenwood and Williamson
Random rough surface
Reduced pressure
Root-mean-square gradient

http://resolver.tudelft.nl/uuid:8b895c16-a386-4109-872c-5574a1f4af11

https://doi.org/10.1007/s11249-018-1061-7

1023-8883

Tribology Letters, 66 (3)

Institutional Repository

journal article

© 2018 J.S. van Dokkum, M. Khajeh Salehani, N. Irani, L. Nicola