HOW IS A ROLLING BEARING LOADED?

Rolling bearings are machine elements of mechanical assemblies and usually separate stationary housings from rotating shafts. In doing so, they transmit the forces acting on the rotating shaft to the housing. Forces act on the shafts in the radial and axial direction with respect to the rotating shaft axis. Depending on the design of the bearings, these load collectives can be combined or absorbed and transmitted individually. In rolling bearings, the outer ring located in the housing and the inner ring located on the shaft are separated by rolling elements that are designed as balls, cylinders or cones. The relative movement of the inner and outer ring causes a rolling movement of the rolling elements, where the aim is to avoid sliding movements as far as possible.

PWFT develops and builds test benches with which you can apply individual or combined load collectives. The test data obtained gives you an insight into the loads on the bearings with varying external control variables and their influence on the bearings service life.

Rolling bearings are exposed to load collectives. The forces acting on the bearing are a significant load variable. As a rule, a distinction is made between axial and radial forces. The axial forces act in the direction of the shaft axis while radial forces are perpendicular to the shaft axis. The bearing forces result from the forces and moments acting in the mechanical system. In addition to the mechanical loads, the bearings are subjected to thermal loads. The thermal load collectives consist of an external heat input from the surrounding machine components and a temperature development due to the bearings friction. Rolling friction and unwanted sliding friction components between rolling elements and bearing rings generate heat. The temperature development of the bearing depends on the tribological conditions within the bearing, the speed of movement (rotational speed) and the bearing forces and has an influence on the wear and the service life of the bearing.

PWFT develops and builds test benches with which you can generate specific load conditions in your bearings.

The developments are made according to customer requirements. Combined load collectives of axial and radial forces can be varied, as can lubrication and contamination. The forces temperatures and vibrations are available as monitoring variables.

Rolling bearing manufacturers specify nominal service lives for their products. Since the applications, sizes and loads of the bearings are very different, these specifications are linked to load collectives and installation requirements. With regard to the stated or predicted service lives, rolling bearings are among the more safe machine elements. Nevertheless, it happens that bearings do not reach the calculated basic service life. The reasons for this are manifold. On the manufacturer's side, failures can be due to faulty design, material defects or deviations in the manufacturing process, such as overheating during grinding. On the user side, improper installation, incorrect operating conditions or errors in lubrication and maintenance can be the cause. Different causes of damage lead to different damage patterns. In the event of a failure, however, a clear cause of damage is not always given. The rolling bearing manufacturers try to test the bearings under operating conditions in the development process and before the start of series production.

PWFT builds rolling bearing test benches according to customer specifications and enables them to carry out service life testing in realistic load situations.

In the development of rolling bearings, binding statements must be made on bearing loads and bearing service life. In many cases, rolling bearing manufacturers develop bearings for specific applications and customer requirements and, especially in the case of series production, want to test the bearings under operating conditions during the development process, when no field experience is available yet. In the design and construction of the bearings, simulation systems are increasingly being used that reproduce specific load simulations with numerical calculation algorithms. Simulation systems usually help to better estimate the loads on a bearing design. They make prototype testing in the development process more efficient and contribute to the development of accurately fitting prototypes with a good simulation prediction. This saves iteration loops and the associated time and costs. However, the prediction quality of simulation systems is limited and must be verified. In the pre-series phase, this verification must take place with tests in the rolling bearing test bench. This applies even more if the load collectives and mechanical mechanisms of specific application situations can only be described accurately to a limited extent by simulation. In these cases in particular, testing on a test bench is indispensable. Rolling bearing test benches and simulation systems should therefore be seen as complementary.

PWFT develops and builds rolling bearing test benches according to customer requirements. As a competent development partner and test bench builder, we support our customers, especially in load and application situations that deviate from the standard. We adapt to your specific requirements.

Contamination of bearings is a very common cause of premature bearing failure. Both bearing manufacturers and their customers go to great lengths to prevent contamination of bearings. Sealing systems for fluids and solids are developed for dirt particles of different sizes and consistencies. Depending on the application, however, it is difficult to reliably prevent contamination. This results in the desire to test the seals for suitability under realistic operating conditions in advance of a series application.

PWFT has developed a test benches that can be used to introduce dosed quantities of dirt into an enclosure. The system allows the defined feeding of fluids and solids and records the dirt entry into the bearings as well as the effects on the bearing service life.