Fatigue life test of reinforced grinding bearings

There are 4 groups of car wheel bearings, in which the inner ring of the 2 groups of bearings were reinforced by grinding process while the other 2 groups of bearings were not. After finishing grinding, then following by superfinishing to make them fit with steel and cage. When it was completed, 4 groups of bearings on the bearing fatigue testing machine were able to test the change of surface quality, operation temperature, vibration and clearance. The result shows that the surface quality, operating temperature, vibration and clearance changes of bearings are better than those untreated after reinforced grinding.


1.Introduction
Bearing is an important and basic component, which is widely used in military and civilian areas.With the implementation of 2015 China's manufacturing, intelligent, automation of mechanized equipment improve continuously, a new challenge about the strength, reliability and fatigue life of the bearing is emerging.In terms of fatigue life of bearings, many scholars have done a lot of researches.P.C. Bastias, S.T.
Hadfield [1,2] et al believe that the fatigue failure of the bearing is divided into two stages.The first stage is the plastic deformation of the material, and cracks are formed in the plastic deformation zone.This stage is relatively short, accounting for about 10% of the damage process, but it creates the condition for the formation, expansion and spalling of crack in the second stage.
Therefore, the plastic deformation of metal is the precondition of crack generation.G.R. Miller [3] et al studies and suggests that rolling contact fatigue is mainly in two forms: initial rolling contact fatigue of the subsurface and of the near-surface.Li Xunjiao [4] et al thinks that the rolling bearing contact fatigue is under the action of alternating cyclic contact stress, local permanent cumulative damage is occurred on the contact surface and experienced the process of crack generation , expansion, and resulted in small pieces or small pieces of metal peeling .Wanchang Sen and G.. John [5,6] at al introduce that under the condition of normal use, the materials of bearing surface are subjected to repeated action of high contact stress, crack initiation on the surface or subsurface, and ultimately lead to fatigue failure of rolling bearings.This paper will make a fatigue life test on reinforced grinding bears and untreated bearings.The reliability and feasibility of reinforced grinding process are revealed by comparing different aspects.It is beneficial to improve the fatigue life of bearings.

The principle of reinforced grinding
Reinforced grinding is a processing method based on composite fatigue resistance, corrosion resistance and wear precision machining technology of metal materials.This kind of processing technology can help obtain bearing ring with residual stress.The principle is shown in Figure 1 and 2. We fused strengthened abrasive material with high pressured gas and used injection system to produce mixed high-pressure gas liquid solid three-phase jet flow.As the collision of ring surface happened randomly [1] , thereby grinding on the workpiece surface was strengthened.

Process parameters of Reinforced grinding
The process parameters are set up and then processed, process parameters are shown in table2 and table3.Processing time(min) 3 Workpiece speed(r/min) 100 Jet pressure(Mpa) 0.6

3.Rolling contact fatigue life test
After grinding, the raceway surface of 4 groups of bearings is machined to superfinish.The processing capacity is 10μm after superfinish.The No.

Figure 9 .
Figure 9.Bearing clearance variation5 Conclusion(1) The bearing will be yellow and purple after running

Table 1 .
Main dimensions of DAC34640037B Figure 3.Inner and outer rings