A New Approach for Fatigue Damage Modeling of Subsurface-Initiated Spalling in Large Rolling Contacts

Abstract

Large bearings employed in wind turbine applications have half-contact widths that are usually greater than 1 mm. Previous numerical models developed to investigate rolling contact fatigue (RCF) require significant computational effort to study large rolling contacts. This work presents a new computationally efficient approach to investigate RCF life scatter and spall formation in large bearings. The modeling approach incorporates damage mechanics constitutive relations in the finite element (FE) model to capture fatigue damage. It utilizes Voronoi tessellation to account for variability occurring due to the randomness in the material microstructure. However, to make the model computationally efficient, a Delaunay triangle mesh was used in the FE model to compute stresses during a rolling contact pass. The stresses were then mapped onto the Voronoi domain to evaluate the fatigue damage that leads to the formation of surface spall. The Delaunay triangle mesh was dynamically refined around the damaged elements to capture the stress concentration accurately. The new approach was validated against previous numerical model for small rolling contacts. The scatter in the RCF lives and the progression of fatigue spalling for large bearings obtained from the model show good agreement with experimental results available in the open literature. The ratio of L10 lives for different sized bearings computed from the model correlates well with the formula derived from the basic life rating for radial roller bearing as per ISO 281. The model was then extended to study the effect of initial internal voids on RCF life. It was found that for the same initial void density, the L10 life decreases with the increase in the bearing size.

A numerical study of the contact and vibration characteristics of a roller bearing with a surface crack

“…The height H r is equal to the real value of the thickness of the raceway. The contact width, deformation, and stress between the roller and the raceway without the surface crack from the FE model are compared with those from the empirical formulas in equations (1) to (4). The comparison results in Table 1 can verify the FE model.…”

“…Cracks are the main incipient failures in the bearings, which include subsurface and surface failures. 1 When the surface cracks occur on the bearing bodies, some abrupt changes in the contact characteristics will be generated. 2 If the incipient cracks cannot be detected, they can cause abnormal vibrations and lead to serious losses.…”

An overview of dynamic modeling of rolling-element bearings

“…Correspondingly, 3D FE dynamic models predicted the propagation of crack under a moving compressive load, subsurface strains and stresses in the crack zone, influences of the plastic strain accumulation and subsurface damage on the contact pressure, the refurbishing on the bearing life, and initial internal voids on rolling contact life. 96–108…”

New Damage Accumulation Model for Spall Propagation Mechanism in Bearing Raceways

“…Spall evolution in raceways can be divided into three stages: (i) spall initiation by a rolling contact fatigue (RCF) mechanism, (ii) steady spall propagation, and (iii) accelerated spall propagation until final failure. As the spall initiation process has been studied both empirically [ 1 , 2 , 3 ] and theoretically [ 4 , 5 , 6 , 7 , 8 , 9 ], the present research focused on the spall propagation process and factors that affect it. While several studies attempted to quantify the spall growth mechanism, such as those of Arakere et al [ 10 ] and Branch et al [ 11 , 12 ], none have addressed the progression of cracks and removal of material from the spall edge, which results in flake release and spall propagation.…”