What is Stribeck number?
Stribeck curve is basically a curve between coefficient of friction and bearing number. Bearing number can be defined as sliding velocity, what we are talking about the relative sliding velocity lubricant with viscosity per unit load.
How do you make a Stribeck curve?
The simplest method to obtain a Stribeck curve and the method most commonly used, provided one has the appropriate converging gap geometry, is to keep two variables fixed (e.g., load and viscosity) and vary the third (e.g., velocity) over a suitable range so that the contact interface goes through the region of …
What is Stribeck velocity?
The Stribeck friction, FS, is the negatively sloped characteristics taking place at low velocities [1]. The Coulomb friction, FC, results in a constant force at any velocity. The viscous friction, FV, opposes motion with the force directly proportional to the relative velocity.
What is Stribeck effect?
The stribeck effect and the breaking force in the description of friction in friction pairs in the HOPI–SOPG system. One of the tribological phenomena widely described in the literature is the Stribeck effect, which manifests as a nonlinear dependence of friction on sliding speed [406, 407][406][407].
What is Stribeck equation?
For straight roller bearings, Co = Kd LZ / 5 where L and d are diameter and length of rollers. Stribeck’s equation to determine basic static capacity of ball bearings is based on assumptions specified below: 1) After loading races retain their circular shape and are rigid.
What are the 3 regimes of lubrication?
Lubrication regimes describe the type of lubrication film that is created under specific operating conditions and is dependent on the degree of contact between surfaces. There are three primary lubrication regimes: Boundary, Mixed, and Hydrodynamic Lubrication.
What is Elastohydrodynamic lubrication?
Elastohydrodynamic Lubrication (EHL) is the type of fluid film lubrication that occurs where very high contact pressure causes elastic deformations of the contacting surfaces of at least the same order of magnitude as the film thickness separating them.
What are the assumptions made in Stribeck equation?
STRIBECK’S EQUATIONStribeck’s equation gives the static load capacity ofbearing. It is based on the followingassumptions:(i) The races are rigid and retain their circular shape. (ii) The balls are equally spaced. (iii) The balls in the upper half do not support any load.
How do you find the bearing life?
Bearing Rating Life Calculation C = Dynamic Capacity (dN or Lbs) P = Equivalent Bearing Load (N or Lbs) N = Rotating speed in RPM. e = 3.0 for ball bearings, 10/3 for roller bearings.
What is the formula of viscosity index?
Viscosity Index Calculator Y = kinematic viscosity at 100 °C of the petroleum product whose viscosity index needs to be calculated, mm2 /s. H = kinematic viscosity of an oil at 40 °C of 100 viscosity index having the same kinematic viscosity at 100 °C as the oil whose viscosity index needs to be calculated, mm2 /s.
What is full film lubrication?
Hydrodynamic or full film lubrication is the condition when the load carrying surfaces are separated by a relatively thick film of lubricant. This is a stable regime of lubrication and metal- to-metal contact does not occur during the steady state operation of the bearing.
What is a good viscosity index?
The viscosity index (VI) is an arbitrary, unit-less measure of a fluid’s change in viscosity relative to temperature change….Classification.
| Viscosity index | Classification |
|---|---|
| Under 35 | Low |
| 35 to 80 | Medium |
| 80 to 110 | High |
| Above 110 | Very high |
What viscosity index is better?
A higher VI is more desirable because it enables the lubricant to provide a more stable lubricating film over a wider temperature range. Some oils may have the right viscosity at certain temperatures but do not quite meet the needs of both ends of the temperature range.