A review of some tribo-dynamics phenomena from micro to nano-scale conjunctions

The paper provides some highlights in the developments of theories of lubrication and contact mechanics from early pioneering works of Reynolds and Hertz to the establishment of elastohydrodynamic phenomenon by Ertel and Grubin. Some historical discourse is made on the development of elastohydrodynamic theory in the past 5-6 decades, with particular attention paid to the contact of rolling element bearings. The steady miniturisation of devices has led to progressively smaller contacts of individual features with lighter load share and diminishing gaps. The ultra-thin films are supported by interaction potentials that significantly deviate from bulk continuum behaviour of lubricating films, with insignificant contributions due to viscous-elastic nature of contacts. Using the same theme of rolling element contacts, the paper highlights the action of some of these dominant forces at close range.