What Is a Journal Bearing?

The journal bearing is a simple yet effective way to eliminate friction from moving parts.

It works by allowing the shaft to rotate inside a curved shell containing washers.

The washers rotate independently to match the curvature of the shaft, reducing friction and increasing shaft stability.

Journal bearings can be lubricated or dry to reduce friction.

Journal-bearing oils are used when cooling is required or if contamination needs to be flushed out.

Journal bearings

Journal bearings are simple bearings that slide over a surface.

They are also referred to as sliding contact or slide bearings.

Their basic function is to allow the rotating shaft to fit into a hole and slide across the bearing surface.

They are the most common type of bearings used in machinery and are a very popular choice for many applications.

Surface texturing improves the frictional performance of journal bearings by providing a reservoir for oil or debris, which can generate hydrodynamic pressure.

Texturing of different tribological elements has been demonstrated by many researchers to reduce friction force and improve lubrication performance.

However, despite these findings, the validity of numerical models has not been established.

Journal bearings consist of a rotating shaft fitted into a larger circular bearing.

The rotating shaft exerts a load on the journal bearing.

As the shaft climbs up the side of the bearing, the friction force causes the shaft to climb up the other side of the bearing.

To avoid such a situation, lubricants are added to the two surfaces.

Journal bearings are manufactured with a variety of materials.

For instance, two-piece journal bearings are generally bronze or copper alloy.

Common backing bronze materials include CC493K, SAE 660, and LG4 (BS 1400).

Their composition can vary, depending on the type of application.

For example, CC493K has a higher zinc content than SAE 660 and LG4, making it a good choice for marine applications.

Journal bearings are usually lubricated with oil. This type of grease disperses the oil evenly over the journal’s surface.

Typically, the grease has a viscosity of 150 to 220 cSt at 40 degC.

High-temperature and high-load greases may use different thickeners and special additive formulations.

Full-contact bearings

Full-contact journal bearings are a common choice for many industrial applications.

They have many benefits and are a very cost-effective alternative to conventional ball bearings.

In this article, we’ll look at some of the characteristics of these bearings and how they affect performance.

Our findings are based on numerical analysis of these bearings using ANSYS 13.0 software.

Grease is used to lubricate these bearings. Typically, this grease has a base oil viscosity of between 150 and 220 CST at 40 degC.

In some applications, this viscosity is higher. Different greases contain different thickeners and may contain EP or other special additives.

Texturing the contact surface can reduce friction. The effect of different textures depends on the size of the textured region.

For example, a partially textured journal bearing has a more positive effect on load-bearing capacity compared to a smooth journal bearing.

Further, a partially textured sleeve can improve carry capacity.

Oil-lubrication is another important feature to consider.

The oil-film inside a bearing can become cavitated because of the friction caused by metal-to-metal contact.

However, this condition is avoidable by changing the viscosity of the oil or the temperature of the bearing.

Full-contact journal bearings are not suitable for large-scale machines.

In this case, they should be lubricated before starting the engine and during operation.

In addition to this, the oil pump may be used to lubricate the bearing.

If the journal is not properly aligned with the shaft, it can cause the bearing to lose lubrication and be unstable.

There are several types of journal bearings. The full-contact bearings have 360-degree contact with the journal while partial-contact journal bearings have 180-degree contact with the shaft.

Full-contact journal bearings are usually used for applications where the load is varying in multiple directions, such as engine crankshafts.

Partial-contact journal bearings are usually used in single-direction applications where the load is constant.

Partial contact bearings

Partial contact journal bearings have the advantage of supporting steady loads with minimal relative motion.

They achieve this by forcing a lubricant between the two journal members.

Because of this, they are used for a wide range of applications.

This paper discusses some important factors about the design of partial journal bearings.

First, you should choose the right material. The material used should have adequate fatigue strength to withstand repeated loads.

In addition, it must be conformable. It should also be able to accommodate deflections of the shaft and accommodate small particles without scoring the journal.

This is especially important when using high-capacity bearings, which are often made by bonding a thin layer of bearing material to a high-strength steel shell.

Another consideration is oil viscosity. In general, journal bearings should have an oil viscosity of at least 13 cSt.

However, high-viscosity oils can generate high temperatures and increase the likelihood of cavitation.

When oil is heated, it will create high and low-pressure zones in the bearing, which can lead to cavitation.

The pressure distribution in a partial journal bearing is determined by the force per unit area.

The load area is the diameter times the length of the bearing.

The force per unit area varies from six hundred and seventy kPa to several hundred psi.

The load zone of a partial journal bearing is usually between sixty and two hundred percent of its diameter.

As mentioned, this is a hybrid type of bearing that provides a minimum hydrodynamic degradation. It is therefore suitable for marine applications.

Integral bearings

Integral journal bearings are a type of bearing that has a hole in the center that acts as a bearing surface.

The most common type of integral journal bearing is the pillow block bearing, which has a cast iron housing and a chromium steel alloy bearing surface with grease nipples.

These bearings are installed into shafts by an interference fit.

The size of the bushing is dependent on the size of the shaft and housing.

The hydrodynamic lubrication of radial journal bearings is often considered by applying the Reynolds equation.

The Generalized Integral Transform Technique is then used to obtain a hybrid numerical-analytical solution.

The parametric analysis used in this method allowed a comparison of the various solutions to be conducted. These comparisons demonstrated the accuracy and consistency of the results.

Journal bearings are popularly used in many engineering systems due to their simplicity and low cost.

The journal is a boundary-lubricated bearing, which means that the oil between the bearing surface and the journal rotates at a faster rate than the bearing itself.

The hydrodynamic lubrication method requires an oil wedge that forces oil between the journal and bearing surfaces.

The effective flow rate of oil in an Integral journal bearing is defined as the difference between the supplied oil flow rate and side leakage.

This effective flow rate is determined by introducing a Q integration factor, which varies between 0.2 and 0.4.

This factor is heavily dependent on the type of bearing, pad shape, and orifice configuration, as well as eccentricity ratios.

Unlike bushings, which can be replaced if necessary, integral journal bearings cannot be replaced.

This means that they are not as common as bushings, which are generally cheaper and replaceable.

But they are still widely used in some machinery from the 19th century, though their use declined as interchangeable manufacturing methods took hold.

Sleeves

Sleeves for journal bearings are a simple way to improve the reliability of these products.

Because sleeve bearings are self-lubricating, they eliminate the need for external lubricants.

However, the space between the inner bearing and the sleeve can become worn.

This wear can adversely affect the movement of the mechanism.

In addition, lubrication may not be sufficient or may become viscous due to temperature changes.

When lubrication is absent, the bearing will stop working altogether.

Sleeves for journal bearings are an excellent choice in many applications.

Many of these products are designed to reduce the maintenance operations associated with bearings.

By reducing the number of moving parts, sleeves are less expensive and more effective.

They also last longer than other types of bearings.

Another major advantage of sleeve bearings is that they don’t require lubrication, making them an excellent choice for applications that require high uptime.

Sleeves for journal bearings are essentially cylindrical in design, with only two moving parts, a shaft and a supporting component (sleeve).

While sleeve bearings can be divided into two halves, most spherical ball bearings are symmetrical.

In addition, they contain a ring of small balls within their interior cavity.

Journal bearings can be made of many materials, including steel, cast iron, and babbitt.

The shaft of a journal bearing is often hardened, which increases its wear resistance.

The bearing pad is usually made of a softer material.

The rotation of the shaft tends to climb up the wall, creating a region of high pressure between the bearing surface and the bearing pad.

This high-pressure region is capable of supporting radial and shock loads.

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