The grid division of thin section angular contact bearings

  In carries on the grid division of thin section angular contact ball crossed roller bearings , the possible contact parts need unit size control slewing gear , using 5 units of the adjacent node distance of different mesh. Finite element model graph after mesh partitioning as follows.

Simplified model of thin section angular contact bearings

The simplified model adopt for 2 ball contact model, the smaller ball diameter size is 3.175mm, and the actual cross roller bearings steel ball size consistent in size.

  Larger ball thin section bearings diameter  size is 10mm. load is simplified as concentrated load, effect of point in the ball at the top of the center, the size of the load is 100N, so it can calculate 0 ~ 100N contact size and contact stress of bearing beyond load effect .

  The ball material is 9Cr18 stainless steel. In order to reduce the analysis time and improve the efficiency of analysis, the ANSYS analysis method was used to analyze the axial symmetry.

Grid density of bearing model

From the static analysis, accuracy of  thin section angular contact  bearing's analysis resultsand  has a direct relationship with grid density.

  If the grid is too sparse,the error analysis results will be greater. Too close greatly increases the computational analysis of time.

  Before build the finite element model of miniature linear bearings ,we should adopt a simplified model for determining the density of grid ,then carry on the grid division of the bearing model by the determined grid density.

Finite element analysis of thin section angular contact bearings

For multi body contact deformation in coordination of thin section angular contact bearings's stiffness analysis , the axial stiffness characteristics research  take 71718 bearing as an example of the thin section angular contact bearings.

  According to the impact of unit size on the analysis results to determine the reasonable size of unit.

  Use the determined cell size to establish three-dimensional finite element model of 71718 bearings , and analyse the axial stiffness.

  Build the bearing axial stiffness testing platform,  using for the test of the 71718 axial stiffness.

  The comparison of the experimental results and the  analytical results shows  , using Hertz analytical solution calculation with larger error , the solution obtained by the finite element method with the actual test results within an error of 10%.

The bearing stiffness and bearing preload force

Under axial load, radial displacement of the bearing ring of thin section angular contact bearing is not negligible, but based on the contact analysis of Hertz theory does not consider these factors.

  With the development of CAE technology, finite element analysis technique is widely used in the bearing, and has a relatively high accuracy.

  As everyone knows,the pretightening force of reasonable bearing design can not only to improve the turning precision bearings and reduce vibration and noise, but also can prolong the working life of bearing. the bearing rigidity is an important basis for bearing preload selection.

Hypothesises on the basic theory of Hertz contact theory

In recent years, with the development of the equipment manufacturing industry, light thin wall bearing plays a more and more important role, especially in the application of aerospace field.

  Hertz  contact theory is a classical solution, what can solve most problems of the rolling bearing stress, the strain.

  Using Hertz theory for bearing contact analysis ,we need to make the following a few basic assumptions.

• the contact body material shall be homogeneous and isotropic.

• load vertical perpendicular to  the contact surface, that is to say the     contact surface is a smooth surface, where only the normal force exist, tangential friction does not.

• contact body is linear elastic body, obey the generalized Hooke law.

• compared to the radius of curvature of the contact surface of the object,the contact surface size is small.

  Therefore, Hertz theory usually used to solve the contact problems of the more regular contact body shape and the relatively simple boundary conditions.

Waffle radial sliding bearing

Radial sliding bearing has three kinds of typical structure, respectively is the waffle radial sliding bearing, the radial sliding bearing and  self-aligning radial sliding bearing.

  Waffle sliding bearing is composed of a bearing seat,  bearing cover, split bearing and stud etc.. Subdivision surface often artist stepped, in order to prevent lateral dislocation of neutralization. The bearing cover is arranged at the upper part of the threaded hole, for the installation of the oil cup. Bush is split, usually loaded by the lower bearing shell bearing .

  In order to save precious metals or other needs, often cast a layer of bearing liner  on the inner surface of  the bush . In the bearing inner wall of non load bearing area open oil tank.Oil through the oil hole and an oil slot into the bearing clearance.

  Bearing section  and the load direction had better approximately vertical,though most bearing subdivision surface is horizontal (also made into inclined).

 

Waffle radial sliding bearing assembly and disassembly is convenient, and the bearing wear can adjust bearing clearance with the gasket thickness of reducing the split surface .

Lubricated bearings

Commonly used lubricants have oil, water, air and other fluids and graphite, MoS2 Solid, according to the applications and requirements of bearing . Using liquid as radial bearing lubricant lubrication film thickness according to the divided into thin film lubrication bearing and thick film lubrication bearing.

  In the thick film lubrication bearing according to the formation mechanism of thick film is divided into liquid dynamic pressure radial bearing and the liquid static pressure radial bearing.

What manufacture bearing bush?

Bearing bush  reduced with manufacturing of friction good sliding bearing materials, including metal material,such as copper alloy, aluminum alloy and Babbitt.And non metal materials ,such as plastics, graphite, rubber and wood.

  Some antifriction metal material strength is low ,such as Babbitt. Cast a layer only in the bearing surface of materials with higher strength,which called bearing lining. Support bearing lining part called bearing backing, used to be made by mild steel, cast iron or bronze.

  In order to further improve the bearing lining surface properties, plate a thin layer of metal  on the surface of reducing friction of the better ,such as indium.

  It is composed of different  multilayer metal material  called multi-layer metal bush. Bearing inner hole shape is basically not affected by the shape of the bearing seat hole called thick walled bearing.

  Inner hole shape depends mainly on the bearing seat hole shape called a thin wall bearing bush. Thin wall bearing is widely used in the machine of internal combustion engine, air compressor with mass production.