2134/36042 Jamal Umer Jamal Umer Nick Morris Nick Morris Michael Leighton Michael Leighton Ramin Rahmani Ramin Rahmani Sashi Balakrishnan Sashi Balakrishnan Homer Rahnejat Homer Rahnejat Nano and microscale contact characteristics of tribofilms derived from fully formulated engine oil Loughborough University 2018 AFM in lateral force mode (LFM) Tribo-film ZDDP Friction Mechanical Engineering not elsewhere classified Mechanical Engineering 2018-11-16 14:47:02 Journal contribution https://repository.lboro.ac.uk/articles/journal_contribution/Nano_and_microscale_contact_characteristics_of_tribofilms_derived_from_fully_formulated_engine_oil/9547418 A systematic approach is required in order to determine the frictional characteristics of a contacting pair in the presence of a tribofilm. Despite the clear benefits in functionality and in reducing wear, the generation of ZDDP-based tribofilms often lead to increased frictional losses. Such an increase is also observed in the tribometric tests reported here, as well as in open literature. This paper investigates the underlying mechanics for the rise in friction using an integrated methodology, based upon Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). The use of an analytical contact mechanics model demonstrates that the pressure coefficient of boundary shear strength, measured using lateral force microscopy, provides an explanation for the observed increase in measured friction at micro-scale.