Abstract
Butterfly wings are closely related to the premature failure of rolling element bearings. In this study, butterfly formation is investigated using the developed semi-analytical three-dimensional (3D) contact model incorporating inclusion and material property degradation. The 3D elastic field introduced by inhomogeneous inclusion is solved by using numerical approaches, which include the equivalent inclusion method (EIM) and the conjugate gradient method (CGM). The accumulation of fatigue damage surrounding inclusions is described using continuum damage mechanics. The coupling between the development of the damaged zone and the stress field is considered. The effects of the inclusion properties on the contact status and butterfly formation are discussed in detail. The model provides a potential method for quantifying material defects and fatigue behavior in terms of the deterioration of material properties.
Highlights
The occurrence of premature failures due to white etching cracks (WECs) in rolling element bearings is a primary limitation to improving the service performance and reliability of advanced equipment, such as wind turbines, high-speed trains, and tunnel boring machines
WECs are closely related to butterflies, which are symbiotic microstructures that contain white etching areas (WEAs), cracks, and inclusions
The numerical model consists of four major components, as illustrated in Fig. 2. (i) The pressure and traction are determined using the compatibility conditions of the contact surfaces. (ii) The inhomogeneous inclusions are replaced by an imaginary equivalent homogeneous inclusion with eigenstrain. (iii) The elastic field incorporating the disturbance stress and displacement due to the eigenstrain is obtained. (iv) The damage accumulation and elastic modulus variation around the inclusions are updated to represent the microstructural alteration
Summary
The occurrence of premature failures due to white etching cracks (WECs) in rolling element bearings is a primary limitation to improving the service performance and reliability of advanced equipment, such as wind turbines, high-speed trains, and tunnel boring machines. WECs are closely related to butterflies, which are symbiotic microstructures that contain white etching areas (WEAs), cracks, and inclusions. The shape, size, rigidity, and distribution of inclusions may change the stress/strain behavior, affecting the initiation and evolution of butterflies [6, 7]
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