A lubricant is a substance introduced between contacting surfaces to reduce resistance to relative motion, wear or both. In fluid-film operation, the surfaces are separated by a layer whose viscous stress transmits the load and motion. A converging gap can generate lubrication pressure that supports a normal load while the solids remain apart.
When the film is too thin to prevent microscopic contact, surface interactions also matter; a low-viscosity fluid alone does not guarantee low friction. A simple comparison is to slide a loaded block over the same surface before and after applying a controlled film and measure the required tangential force. Changing load, speed and temperature can change the operating regime. The lubricant still dissipates mechanical energy through shearing and other losses, so reduced dry contact does not imply zero resistance.
Articles by others on the same topic
A lubricant is a substance that reduces friction between surfaces that are in contact, thereby facilitating easier movement and reducing wear and tear. Lubricants can be classified into several categories based on their composition and use: 1. **Types of Lubricants**: - **Liquid**: Common lubricants include oils (mineral oils, synthetic oils, and biodegradable oils) and greases (which are oil-based thickened with a soap).