A Voronoi Finite Element Study of Fatigue Life Scatter in Rolling Contacts

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Behrooz Jalalahmadi ◽  
Farshid Sadeghi
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Shear Stress ◽  
Elastic Modulus ◽  
Fatigue Life ◽  
Critical Stress ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Element Method

Microlevel material failure has been recognized as one of the main modes of failure for rolling contact fatigue (RCF) of bearing. Therefore, microlevel features of materials will be of significant importance to RCF investigation. At the microlevel, materials consist of randomly shaped and sized grains, which cannot be properly analyzed using the classical and commercially available finite element method. Hence, in this investigation, a Voronoi finite element method (VFEM) was developed to simulate the microstructure of bearing materials. The VFEM was then used to investigate the effects of microstructure randomness on rolling contact fatigue. Here two different types of randomness are considered: (i) randomness in the microstructure due to random shapes and sizes of the material grains, and (ii) the randomness in the material properties considering a normally (Gaussian) distributed elastic modulus. In this investigation, in order to determine the fatigue life, the model proposed by Raje et al. (“A Numerical Model for Life Scatter in Rolling Element Bearings,” ASME J. Tribol., 130, pp. 011011-1–011011-10), which is based on the Lundberg–Palmgren theory (“Dynamic Capacity of Rolling Bearings,” Acta Polytech. Scand., Mech. Eng. Ser., 1(3), pp. 7–53), is used. This model relates fatigue life to a critical stress quantity and its corresponding depth, but instead of explicitly assuming a Weibull distribution of fatigue lives, the life distribution is obtained as an outcome of numerical simulations. We consider the maximum range of orthogonal shear stress and the maximum shear stress as the critical stress quantities. Forty domains are considered to study the effects of microstructure on the fatigue life of bearings. It is observed that the Weibull slope calculated for the obtained fatigue lives is in good agreement with previous experimental studies and analytical results. Introduction of inhomogeneous elastic modulus and initial flaws within the material domain increases the average critical stresses and decreases the Weibull slope.

Investigating the Rolling Contact Fatigue in Rails Using Finite Element Method and Cohesive Zone Approach

2018 ◽  
Author(s):  
Mohamad Ghodrati ◽  
Mehdi Ahmadian ◽  
Reza Mirzaeifar
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Grain Boundaries ◽  
Fatigue Damage ◽  
Cohesive Zone ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Wheel Load ◽  
Element Method

A micromechanical-based 2D framework is presented to study the rolling contact fatigue (RCF) in rail steels using finite element method. In this framework, the contact patch of rail and wheel is studied by explicitly modeling the grains and grain boundaries, to investigate the potential origin of RCF at the microstructural level. The framework incorporates Voronoi tessellation algorithm to create the microstructure geometry of rail material, and uses cohesive zone approach to simulate the behavior of grain boundaries. To study the fatigue damage caused by cyclic moving of wheels on rail, Abaqus subroutines are employed to degrade the material by increasing the number of cycles, and Jiang-Sehitoglu fatigue damage law is employed as evolution law. By applying Hertzian moving cyclic load, instead of wheel load, the effect of traction ratio and temperature change on RCF initiation and growth are studied. By considering different traction ratios (0.0 to 0.5), it is shown that increasing traction ratio significantly increases the fatigue damage. Also by increasing traction ratio, crack initiation migrates from the rail subsurface to surface. The results also show that there are no significant changes in the growth of RCF at higher temperatures, but at lower temperatures there is a measurable increase in RCF growth. This finding correlates with anecdotal information available in the rail industry about the seasonality of RCF, in which some railroads report noticing more RCF damage during the colder months.

A Coupled Multibody Finite Element Model for Investigating Effects of Surface Defects on Rolling Contact Fatigue

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Zamzam Golmohammadi ◽  
Farshid Sadeghi
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Surface Defects ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Internal Stresses ◽  
Fe Model ◽  
Elastic Plastic ◽  
Pile Up

A coupled multibody elastic–plastic finite element (FE) model was developed to investigate the effects of surface defects, such as dents on rolling contact fatigue (RCF). The coupled Voronoi FE model was used to determine the contact pressure acting over the surface defect, internal stresses, damage, etc. In order to determine the shape of a dent and material pile up during the over rolling process, a rigid indenter was pressed against an elastic plastic semi-infinite domain. Continuum damage mechanics (CDM) was used to account for material degradation during RCF. Using CDM, spall initiation and propagation in a line contact was modeled and investigated. A parametric study using the model was performed to examine the effects of dent sharpness, pile up ratio, and applied load on the spall formation and fatigue life. The spall patterns were found to be consistent with experimental observations from the open literature. Moreover, the results demonstrated that the dent shape and sharpness had a significant effect on pressure and thus fatigue life. Higher dent sharpness ratios significantly reduced the fatigue life.

A 3D Finite Element Study of Fatigue Life Dispersion in Rolling Line Contacts

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Nick Weinzapfel ◽  
Farshid Sadeghi ◽  
Vasilios Bakolas ◽  
Alexander Liebel
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Material Properties ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Critical Shear Stress ◽  
Rolling Contact ◽  
Shear Stresses ◽  
Rolling Element Bearings ◽  
Rolling Element

Rolling contact fatigue of rolling element bearings is a statistical phenomenon that is strongly affected by the heterogeneous nature of the material microstructure. Heterogeneity in the microstructure is accompanied by randomly distributed weak points in the material that lead to scatter in the fatigue lives of an otherwise identical lot of rolling element bearings. Many life models for rolling contact fatigue are empirical and rely upon correlation with fatigue test data to characterize the dispersion of fatigue lives. Recently developed computational models of rolling contact fatigue bypass this requirement by explicitly considering the microstructure as a source of the variability. This work utilizes a similar approach but extends the analysis into a 3D framework. The bearing steel microstructure is modeled as randomly generated Voronoi tessellations wherein each cell represents a material grain and the boundaries between them constitute the weak planes in the material. Fatigue cracks initiate on the weak planes where oscillating shear stresses are the strongest. Finite element analysis is performed to determine the magnitude of the critical shear stress range and the depth where it occurs. These quantities exhibit random variation due to the microstructure topology which in turn results in scatter in the predicted fatigue lives. The model is used to assess the influence of (1) topological randomness in the microstructure, (2) heterogeneity in the distribution of material properties, and (3) the presence of inherent material flaws on relative fatigue lives. Neither topological randomness nor heterogeneous material properties alone account for the dispersion seen in actual bearing fatigue tests. However, a combination of both or the consideration of material flaws brings the model’s predictions within empirically observed bounds. Examination of the critical shear stress ranges with respect to the grain boundaries where they occur reveals the orientation of weak planes most prone to failure in a three-dimensional sense that was not possible with previous models.

The Modal Analysis of the Ceramic Ball’s Rolling Contact Fatigue Tester’s Drive Shaft

2012 ◽  
Vol 503-504 ◽  
pp. 1029-1032
Author(s):  
Jing Ling Zhou ◽  
Wei Ming Zuo ◽  
Yu Jing Li ◽  
Yu Song Ren ◽  
Wei Nan Zhu
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Modal Analysis ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Drive Shaft ◽  
Test Rig ◽  
Finite Element Software ◽  
Contact Fatigue Life

The Modal Analysis of the Ceramic Ball Rolling Contact Fatigue Life Test Rig Drive Shaft Abstract: With the increasing of the rolling contact fatigue life tester’s speed, the vibration problem is getting more and more serious. In order to optimize the dynamic performance test rig, the modal analysis of the drive shaft was carried. First the vibration mechanics model was got by simplifying the shaft and get the first order of horizontal natural frequency which is 787.4266Hz with the theoretic algorithm. Then the drive shaft’s modal analysis was made by using the finite element software and that is 779Hz. The relative error between the former and the latter is 1.1%. It has demonstrated the accuracy of the finite element result, and its modal analysis could be the basis of the dynamic optimization.

Finite Element Analysis to Ceramic Ball Pure Rolling Contact Stresses

2012 ◽  
Vol 503-504 ◽  
pp. 667-670
Author(s):  
Jing Ling Zhou ◽  
Wei Nan Zhu ◽  
Guo Qing Wu ◽  
Yu Song Ren
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Life ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Contact Stresses ◽  
Rolling Contact ◽  
Shear Stresses ◽  
Element Analysis ◽  
Contact Fatigue Life

The RCF (Rolling Contact Fatigue) life of bearing balls is a main method, to evaluate the performance of bearing materials and their production technology. In general, The RCF life of ceramic balls is a reliable technique to asses whether or not they are suitable to be used in rolling bearings. The RCF life of ceramic balls is depend on contact stresses chiefly. It applies the finite element analysis to calculate the surface stresses and subsurface stresses, including 1st principal tensile stresses and shear stresses. The theory results are compared with the finite element solutions. Very good agreement is observed. The finite element results in this paper have an important applied value. The results provided theoretical basis for rolling contact fatigue life prediction of the ceramic balls.

Effect of Grain Flow Orientation on Rolling Contact Fatigue Life of AISI M-50

1982 ◽  
Vol 104 (3) ◽  
pp. 330-334 ◽  
Author(s):  
A. H. Nahm
Keyword(s):  
Fatigue Life ◽  
Flow Line ◽  
Flow Direction ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Vacuum Arc ◽  
Type I ◽  
Grain Flow ◽  
Contact Fatigue Life

Accelerated rolling contact fatigue tests were conducted to study the effect of grain flow orientation on the rolling contact fatigue life of vacuum induction melted and vacuum arc remelted (VIM-VAR) AISI M-50. Cylindrical test bars were prepared from a billet with 0, 45, and 90 deg orientations relative to billet forging flow direction. Tests were run at a Hertzian stress of 4,826 MPa with a rolling speed of 12,500 rpm at room temperature, and lubricated with Type I (MIL-L-7808G) oil. It was observed that rolling contact fatigue life increased when grain flow line direction became more parallel to the rolling contact surface.

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