Load rating

The load rating is a measure of the force or load that a machine element absorbs before it suffers permanent damage under continuous load .

use

The load rating is an important parameter when calculating the service life of machine elements using a standardized approximation formula . It is usually, such as B. in rolling bearings , specified by the manufacturer as a parameter of the machine element. The calculation based on a given load rating allows a statement to be made about the probable service life of the machine element used.

Conversely, when designing new assemblies, the necessary load rating is determined for suitable machine elements from a specified service life in accordance with the specifications and a corresponding component is sought or a design draft is checked for its feasibility.

Load ratings and units

A basic distinction is made between the static load rating and the dynamic load rating . The unit of these load ratings is Newton for bearings and the same for most guides . An exception is made for telescopic rail guides, whose load ratings are given in kilograms . ${\ displaystyle C_ {0}}$ ${\ displaystyle C}$

Static load rating

The static load rating is a parameter for the design of roller bearings or roller guides , e.g. B. in mechanical engineering . It relates to the machine element at rest, i.e. H. a dormant camp or a dormant leadership. ${\ displaystyle C_ {0}}$

For roller bearings, roller guides, ball screws and roller screws

In the case of roller bearings, this is the load limit of a material which causes permanent deformation - as the sum of the deformation of both bodies in contact - of 0.0001 times (0.01%) the roller diameter. If the load exceeds the static load rating, the function, the noise level and the accuracy of a bearing are adversely affected.

With other machine elements

Some manufacturers also specify a load rating for other machine elements such as lock nuts or sliding screw spindles. This is usually the maximum load that the component can take.

Dynamic load rating

The dynamic load rating is also a parameter for the design of roller bearings or roller guides, but it relates to the rotating bearing or the linearly moving guide, i.e. to a moving machine element. ${\ displaystyle C}$

With rolling bearings

The equivalent bearing load at which the probability of survival of a bearing after one million revolutions is 90%.

For ball screws and roller screws

The axial force at which the probability of survival of a ball or roller screw after one million revolutions is 90%.

With roller guides

The equivalent load at which the survival probability of a roller guide after 100,000 m of travel is 90%.