Sliding bearings, according to their friction state, why bearings and what bearings?
2. boundary frictionThe boundary of oil film thickness is less than 1 microns to two metal surface is completely separated from each other, when the movement of two metal surfaces, metal surface asperities will still considerable rubbing cut, this friction is called boundary friction. The friction law of boundary friction, basically the same with the dry friction, but the friction coefficient decreases, f = 0.1 ~ 0.3. boundary friction though not completely avoid the metal surface wear, but can greatly reduce wear.
Sliding bearings, according to the friction between the surface of the friction, the friction state is divided into the following1. dry friction. Two relative motion surface direct contact friction, without any lubricant called dry friction (Figure 16.1, a). The dry friction will be accompanied by a lot of friction power loss and severe wear in sliding bearing will lead to severe temperature rise, and even burn the bush. So, not allowed to appear in the dry friction sliding bearing.
3. fluid frictionWhen the two friction surfaces have sufficient lubricating oil, the oil film thickness is large enough to form a two surface asperity completely separated, the friction between the molecules of the fluid inside only when relative motion is called fluid friction, the oil film is formed under certain high pressure oil film small load, prevent the direct contact between two friction surfaces, so the minimal friction coefficient (F = 0.001 ~ 0.01), significantly reduce friction and wear.In summary, the fluid friction is also called fluid lubrication, shaft neck is the ideal working environment. The long-term high speed rotating machines, should ensure that the bearing work in fluid lubrication conditions. In actual use, more friction in the mixed state of dry friction, boundary friction and fluid friction, called mixed friction (or incomplete fluid friction).
