Design of journal bearing pdf

Esaki, S. Saito, Y. Kanemitsu, T. Iwatsubo, M. Tanaka et al. Back Matter Pages About this book Introduction Journal bearings, which are used in all kinds of rotating machinery, do not only support static loads, such as the weight of rotors and load caused by transmitted torque of reduction gears, but are, in addition almost the only machine element that is able to suppress various exciting forces acting on the rotating shaft.

The flow is one dimensional, i. Sliding Contact Bearing Materials bearing material should have high compressive strength to withstand this maximum pressure so as to prevent extrusion or other permanent deformation of the bearing.

Fatigue strength. The bearing material should have sufficient fatigue strength so that it can withstand repeated loads without developing surface fatigue cracks. It is of major importance in aircraft and automotive engines.

It is the ability of the bearing material to accommodate shaft deflections and bearing inaccuracies by plastic deformation or creep without excessive wear and heating.

It is the ability of bearing material to accommodate or embed small particles of dust, grit etc. Many high capacity bearings are made by bonding one or more thin layers of a bearing material to a high strength steel shell. Thus, the strength of the bond i. Corrosion resistance. The bearing material should not corrode away under the action of lubricating oil.

This property is of particular importance in internal combustion engines where the same oil is used to lubricate the cylinder walls and bearings. In the cylinder, Thermal conductivity. The bearing material should be of high thermal conductivity so as to permit the rapid removal of the heat generated by friction.

Thermal expansion. The bearing material should be of low coefficient of thermal expansion, so that when the bearing operates over a wide range of temperature, there is no undue change in the clearance.

Materials used for Sliding Contact Bearings 1. Babbit metal. The tin base and lead base babbits are widely used as a bearing material, because they satisfy most requirements for general applications. Cast iron. The cast iron bearings are usually used with steel journals. Such type of bearings are fairly successful where lubrication is adequate and the pressure is limited to 3. The silver and silver lead bearings are mostly used in aircraft engines where the fatigue strength is the most important consideration.

Non-metallic bearings. The various non-metallic bearings are made of carbon-graphite, rubber, wood and plastics. Such type of bearings are used in food processing and other equipment where contamination by oil or grease must be prohibited. These bearings are also used in applications where the shaft speed is too low to maintain a hydrodynamic oil film.

The soft rubber bearings are used with water or other low viscosity lubricants, particularly where sand or other large particles are present. The rubber bearings are used mainly on marine propeller shafts, hydraulic turbines and pumps. The wood bearings are used in many applications where 1.

The Nylon is stronger, harder and more resistant to abrasive wear. It is used for applications in which these properties are important e. The Teflon is rapidly replacing Nylon because of the following properties: 1. It has lower coefficient of friction, about 0.

It is dimensionally stable because it does not absorb moisture, and 4. It is practically chemically inert. Semi-liquid, and 3. The liquid lubricants usually used in bearings are 1. The mineral oils are most commonly used because of their cheapness and stability.

A grease is a semi-liquid lubricant having higher viscosity than oils. The greases are employed where slow speed and heavy pressure exist and where oil drip from the bearing is undesirable. The solid lubricants are useful in reducing friction where oil films cannot be maintained because of pressures or temperatures. They should be softer than materials being lubricated. A graphite is the most common of the solid lubricants either alone or mixed with oil or grease. Properties of Lubricants 1.

Viscosity index. The term viscosity index is used to denote the degree of variation of viscosity with temperature. Flash point. It is the lowest temperature at which an oil gives off sufficient vapour to support 6. Fire point. It is the temperature at which an oil gives of 7. Pour point or freezing point. Pressure Dam Brito et al. A relief pocket is milled under combinations of high eccentricity and low feeding into the bearing surface, as seen in figure 6.

The relief pressure. Papadopoulos et al. This increased pressure, bearings by response measurement at any arbitrarily usually located on the top of the bearing, applies an point. The stability of a rotating system with worn artificial downward force on the shaft to greatly reduce clearances is also examined, indicating the future stable instabilities. A relief is sometimes included over the or unstable operation of the system. Sharma et al. The of minimum fluid film thickness and a reduction in the artificial forces result in significant power losses, and the value of coefficient of friction as compared to a precise machining involved to fabricate this bearing is corresponding similar slot-entry hybrid journal bearing also significant.

Prasad et al. Also there is significant change in pressure and temperature while non-Newtonian fluid is considered. Montazeri [11] showed that compared with Newtonian fluids, that micro polar fluids exhibit the increase in load capacity and temperature, but the decrease in coefficient of friction and side leakage flow. Typical Pressure Dam Journal Bearing distortion field due to pressure plays an important role in predicting the behaviour of the bearing, particularly on II.

Panday et al. The maximum pressure is noted at On the basis of numerically simulated results presented in minimum oil film thickness. Turbulent viscosity of the this paper. Lin et al. Boubendir et al. Gertzos et al. The load carrying capacity, the in the load capacity and attitude angle is a consequence film pressure, and the frictional force of a Bingham solid of the increasing permeability.

Nicodemus et al. Deligant et al. The distribution in the lubricating film of a lemon- bore influence of micropolar effect of lubricant on bearing journal bearing. The model has been used to study the performance is predominantly affected by the geometric influence of different design parameters on the maximum shape of recess and restrictor design parameter. Wang et al. Rahmatabadi et al. The lubricant with couple stress does improve the circular and noncircular lobed journal bearings.

Garg et performance of journal bearings. A thermo hydrodynamic THD model for bearing Variation of viscosity due to temperature rise and non- analysis can be developed which treats the viscosity as a Newtonian behavior of lubricant affects the bearing function of both the temperature and pressure.

Moreover, performance quite significantly. Bhaskar et al. The thermo hydrodynamic model can to find the pressure distribution over the bearing surface. Mongkolwongrojn et al. An attempt would be made to compare the stability of the bearing system deteriorates with performance of two bearing configurations of same decreasing both the power law exponent and the elastic geometrical size by using common commercial grade oils modulus of bearing liner material.

The rough surface under similar operating conditions. Nair et al. Nassab et al. Gertzos, P. Nikolakopoulos, C. Deligant, P. Podevin, G. Mishra et al. Bompos, Pantelis G. Chasalevris, D. Kuznetsov et al. Brito, A. Miranda, J.