Solidified lubes stay solid
Squeaks from lubricated surfaces are not caused by changes in the lubricant formation according to new research.
The study, published in the American Physical Journal by two researchers from George Washington University in the US, has revealed that stick-slip friction, which often causes squeaking, between lubricated surfaces is not caused by the lubricant changing from solid to liquid form.
Apparently, physicists generally believed that stick-slip friction was associated with changes in the physical properties of the lubricant during the the two phases of the process. So, for example, during the 'stick' phase the lubricant is solid, returning to liquid form to create the 'slip'.
However, Professor Yongsheng Leng and assistant Yajie Lei's latest research disproves the theory and demonstrates that once solidified, the lubricants do not change back into liquid form. The slip is, in fact, caused by the lubricant molecules slipping inside the lubricant film.
The research team used computerised molecular dynamics simulations to replicate the slip-stick process. As well as their solid/liquid results, they also discovered how friction energy is lost at different stages of the stick and slip cycle. The findings could have significant implications for the design of engine lubricants in enhancing fuel economy and reducing wear.
