Optimization of raceway profile of cylindrical roller

bearings to compensate for misalignments.

Accurate life prediction by ROMAX

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Introduccion

Optimization of raceway profile of cylindrical roller bearings to compensate for misalignments. Accurate life prediction by ROMAX

Modern grinding and superfinishing equipment with modern numeric control allows the manufacturing of

complex profiles in the raceways of cylindrical roller bearings with a grate degree of accuracy.

But the design optimization of these profiles for a specific application requires:

• first to be able to calculate accurately the expected misalignment in every bearing position

• and second to calculate the internal load distribution in the bearing of the loads applied on it depending

on the raceway profile and therefore, the fatigue life according to ISO/TS16281.

The calculations required for this optimization process, as explained, are so complex that, usually, the

results offered by most of the calculation tools are not accurate enough and require too much physical

testing, not being practical for medium or small batch sizes.

Results offered by Romax are much more accurate and the physical testing is reduced allowing the

optimization of the raceway profiles for a bigger range of applications where quantities involved are not big

enough for the former designing way.

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Theoretical basis

Axially and or moment loaded cylindrical roller bearings

Cylindrical roller bearings which support thrust and/or moment loading in addition to predominant radial

loading have flanges on both the inner and outer rings to accommodate the thrust loading carried by the

rollers. The roller thrust loading causes roller tilting and friction moments about the rotating axis

perpendicular to both the bearing and roller axis. The friction moments in turn give rise to roller skewing

which increases roller-raceway loading, affecting bearing friction heat generation and fatigue endurance.

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Theoretical basis

Roller misalignment and skew

Misalignment in cylindrical roller bearings is one of the most important parameters which influence the life

and performance of the bearing. In a perfectly aligned bearing the roller simply rotates about its polar axis

and the contact with the two races is fairly uniform and symmetric about the roller center. When the races

are misaligned relative to each other, however, the polar axis of the roller also misaligns relative to the

bearing axis. This causes certain rotation of the roller about its transverse axis. The rotation about an axis

normal to the plane containing the bearings axis and the radial vector locating the roller center relative to

the bearing center is referred to as misalignment, while the rotation about the transverse axis along the

radial vector is known as roller skew. Both misalignment and skew appear simultaneously.

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Practical example

Gearbox

In this example, we will isolate a shaft assembly from a complete gearbox and will analize how to modify

the bearing raceways profiles to minimize the stress concentrations consequence of the misalignment of the

bearing.

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Practical example

Shaft assembly case of study

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Practical example

Calculation of each bearing position

Using Romax, NBI engineers can have accurate calculation of forces, moments and misalignment in each

bearing position. This data is reliable and is the basis for further stress and life calculations.

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Practical example

Advance bearing calculationn

Romax calculates the performance of the bearings offering:

• Static analysis (loads, displacements, misalignments)

• Lives (ISO281 and ISO/TS16281 for this example)

• Load distribution (roller load sharing, reactions on raceways and stresses)

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Practical example

Shaft assembly case of study

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Practical example

Calculation of each bearing position

Using Romax, NBI engineers can have accurate calculation of forces, moments and misalignment in each

bearing position. This data is reliable and is the basis for further stress and life calculations.

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A First Class Brand

Practical example

Advance bearing calculation

Romax calculates the performance of the bearings offering:

• Static analysis (loads, displacements, misalignments)

• Lives (ISO281 and ISO/TS16281 for this example)

• Load distribution (roller load sharing, reactions on raceways and stresses)

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Practical example

Cylindrical roller bearing NJ2328-E-M1

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Practical example

Cylindrical roller bearing NJ2328-E-M1

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Practical example

Cylindrical roller bearing NJ2328-E-M1

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Practical example

Optimization of raceway profile of NJ2328-E-M1

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Practical example

Cylindrical roller bearing NJ2328-E-M1 after optimization

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Practical example

Cylindrical roller bearing NJ2328-E-M1 after optimization

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Practical example

Cylindrical roller bearing NJ2328-E-M1 after optimization

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Practical example

Conclusion

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Optimization of raceways profiles of bearing NJ2328-E-M1 has increased

life according ISO/TS 16281 in 13%