Multiscale modeling and simulation of rolling contact fatigue

Abstract

iii ABSTRACT In this thesis, a hierarchical multiscale method was developed to predict rolling contact fatigue lives of mechanical systems. In the proposed multiscale method, the molecular modeling and simulation of lubricant was conducted to investigate the friction between rolling contact surfaces. The calculated friction coefficient was passed to the continuum model of rolling contact components to predict fatigue lives.Molecular dynamics modeling and simulation of thin film lubrication and lubricated contact surfaces were carried out to investigate mechanisms of hydrodynamic lubrication at nano-scale first. Although various lubricant alkane chains were considered in the molecular model, the chain length of eight united molecules were mainly employed in this thesis. In addition, the effects of temperature and nano-particles (debris) on the friction forces were discussed. It was found that the existing of nano-particles (debris) could increase the friction force between contact surfaces with hydrodynamic lubrication.In the continuum model of the developed multiscale method, finite element analysis was employed to predict rolling contact fatigue life of rolling contact components, including bearing and gear-tooth. Specifically, the fatigue crack initiation of bearing was studied, and then the fatigue crack initiation and propagation in gear-tooth. In addition, the enhancement of gear-tooth fatigue life by using composite patches was discussed as well. It should be noted that the friction coefficient used in the continuum model was calculated in the molecular model. It is one-way message passing in iv the developed multiscale method.Another continuum method was studied and developed in this thesis to provide alternate methods for the continuum model in the proposed multiscale framework.Peridynamics method has advantages in modeling and simulation of discontinuities, including cracks, over the conventional finite element methods. The applications of Peridynamics in predicting fatigue crack initiation and propagation lives were discussed in this thesis. v PUBLIC ABSTRACTThis research aims to develop a hierarchical multiscale method to predict rolling contact fatigue lives of mechanical systems. In the proposed multiscale method, the molecular modeling and simulation of lubricant was conducted to investigate the friction between rolling contact surfaces. The calculated friction coefficient was passed to the continuum model of rolling contact components to predict fatigue lives.Molecular dynamics modeling and simulation of thin film lubrication and lubricated contact surfaces were carried out to investigate mechanisms of hydrodynamic lubrication at nano-scale first. In addition, the effects of temperature and nano-particles (debris) on the friction forces were discussed. It was found that the existing of nanoparticles (debris) could increase the friction force between contact surfaces with hydrodynamic lubrication.In the continuum model of the developed multiscale method, finite element analysis was employed to pred...

Peridynamics with Corrected Boundary Conditions and Its Implementation in Multiscale Modeling of Rolling Contact Fatigue

“…We proposed a hierarchical multiscale method 79 to study RCF, as shown in Fig. 15, with the consideration of lubricant e®ects.…”

“…To conduct fatigue crack initiation simulation in FEM, 79 we employ the ANSYS parametric design language for stress analysis. Then, we use a shear-based damage model 90 with the material strain-life data to predict fatigue crack initiation life, which is 5500 cycles.…”

“…[70][71][72][73][74][75][76][77] However, when using those models to study RCF, the mechanical components were assumed to be well-lubricated, and the friction force was prescribed on the contact surface to calculate the RCF lives. Gha®ari and co-workers 78 employed MD to study the lubricant between sliding solids and proposed a hierarchical multiscale method 79 to study RCF. In their method, the coe±cient friction on the contact surface was calculated by MD, and then it was passed to the¯nite element (FE) model to predict RCF life.…”

“…The recommendations will be concluded about applying¯ctitious walls in peridynamic methods. Then, peridynamics with corrected boundary conditions is implemented in the hierarchical multiscale method 79 to study RCF.…”

A fatigue life prediction method from magnetic pole material to simulation part

“…Besides, some fatigue assessment guidances can be used to design S–N curves (Haibach, 2003; Sims, 2012). And nowadays there are many fatigue studies based on finite element method (FEM) (Ghaffari et al., 2018; Zhang et al., 2018). Computer simulations can not only obviously reduce cost and time, but also simply determine the optimal set of parameters to perform the experiment for a specific application.…”