A New Approach to Determine the Effect of Nonmetallic Inclusions on Material Behavior in Rolling Contact

Abstract

Nonmetallic inclusions have an important influence on rolling element bearing behavior. Though this has been well-known for a long time, consideration of nonmetallic inclusions is usually done on the base of empirical results. This paper shows a new approach to describe the influence of inclusions partly analytical on a mechanical base. The notch effect of inclusions due to their mechanical properties in difference to the steel matrix was calculated by finite element method (FEM). The results were used to discuss the material reaction on nonmetallic inclusions in stress fields related with Hertzian contacts. Additionally, residual stresses were considered, and the interaction of both inclusions and residual stresses in rolling contact fatigue is discussed.

Microstructure evolution and mechanical properties of X12CrMoWVNbN10-1-1 steel during quenching and tempering process

“…The presence of variety of inclusions and their high density indicated the inadequate cleanliness of the alloy. These inclusions adversely affected the fracture toughness and fatigue strength of the steel [30]. They acted as stress raisers and are potential sites for crack inclusion/matrix interface results in the formation and opening of void.…”

Some Basic Reflections About the Influence of Non-Metallic Inclusions on Rolling Contact Fatigue of Bearing Steels

“…Inclusions influence the stress distribution in their vicinity due to the differences between the properties of the inclusion and the matrix . This effect has been discussed by previous authors in detail [5][6][7][8][9][10][11][12][13][14]. Two separate effects have to be considered.…”

“…First, due to different thermal expansion coefficients residual stress fields develop around inclusions during cooling if the thermal expansion of the inclusion is lower than that of the matrix [5][6][7]. Second, the different deformation behaviour of the inclusion disturbes the stress flow due to external loads in the vicinity of inclusions [8][9][10][11][12][13][14]. This last effect was called the notch effect of inclusions.…”

“…In the special case of uniaxial external loading, maximum stressing occurs for stiff inclusions (E i /E m =2.0) a little bit before and behind the inclusion in the loading direction. For pliable inclusions (E i /E m =0.5) maximum stressing occurs at the equator, where the loading direction is tangential to the inclusion surface [11][12][13]. Fig.…”

“…Yet the amount of analytical research is low [5][6][7][8][9][10]. To give a basic overview of the behaviour of inclusions the author discussed the influence of inclusions on the stress distribution in the steel matrix [11][12][13]. Based on the first results achieved from this work, some general effects resulting from the disturbance of the stress state close to inclusions shall be deduced.…”