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Angular contact ball bearings are common basic components in rotating machinery. During the operation of the bearing, the rolling slips, resulting in contact sliding friction between it and the raceway, which in turn causes wear in the rolling element and increase in the radial clearance of the bearing. The increase in clearance also affects the stiffness of the bearing, which in turn affects the natural frequency and fatigue life of the bearing. At present, there are few studies on the influence of bearing wear (variation of clearance) on life. In this paper, the finite element model based on the theory of contact mechanics is established for the angular contact ball bearing with medium- and high-speed rotation, and the mechanical properties and fatigue life influenced by the internal action of the bearing are analyzed. The effects of radial load and deflection angle on the mechanical properties and fatigue life of the bearing are also studied. Based on the analysis results of bearing contact mechanical properties and clearance changes, the calculation method of bearing life under rolling element wear is established. The influence of the variation of clearance and preload clearance on bearing life is analyzed, and the optimal preload is obtained. The research results of this paper can provide a theoretical basis for optimizing the installation of angular contact ball bearings, reasonably determining the service conditions, and prolonging the service life of bearings, which is necessary for engineering practice. [ABSTRACT FROM AUTHOR]

To improve the understanding of wheel/rail contact behaviour and damage mechanisms in turnouts, the 3D explicit finite element model of a wheelset rolling over a switch is introduced. This takes into account the arbitrary geometrical profile of the wheel-rail system, the relative motion between switch/stock rail, the nonlinear materials and actual moving postures of the wheelset. Precise frictional rolling contact solutions and dynamic response, including contact stress, surface shear stress, microslip, roll angle and lateral displacement, are all studied to obtain a better understanding of the wheel-rail frictional rolling contact behaviour in the switch panel. The simulated results are then verified through field tests on the Qingdao-Jinan line. The results indicate that the proposed explicit finite element method can be an efficient tool for solving the problems of frictional rolling contact behaviour and damage mechanism in switch panels. [ABSTRACT FROM AUTHOR]

Positive Displacement Motor (PDM) is one of the most commonly used deep hole power drills. The thrust ball bearing unit is one of the vulnerable parts of the PDM. Failure of the thrust bearing greatly affects the PDM and can drastically reduce its drilling efficiency. In order to improve its service life, we have designed a new deep cavity tapered roller thrust bearing. In this analysis, we will evaluate the new product. In the past, results have shown that there is a serious stress concentration at both ends of the roller. The new deep cavity design will result in the improvement of the stress factor of tapered rollers. If the cavity depth and diameter are too small, the stress concentration at both ends of the roller becomes serious. If they are too large, the stress on the middle part of the roller is also too high. Deformation of the roller increases with an increase in the deep cavity's length and depth. Consequently, the deep cavity design can improve the PDM. [ABSTRACT FROM AUTHOR]

Small reciprocal movements in bearings can cause wear damage at the contact between the rolling elements and the raceway due to fretting phenomena. This damage is also called false brinelling or fretting corrosion, attending to lubrication conditions and causes vibrations and noisy operation, finally resulting in the need for the replacement of the component. Previous works from the literature have focused on experimental analyses of the damage and methodologies to simulate the occurrence of this phenomenon. These previous methodologies are centred on the effects of isolated fretting modes, such as radial fretting, rotational fretting and tangential fretting. However, the effects of external loads in angular bearings lead to high complex scenarios in which multiple fretting modes act simultaneously. In response to this demand, a novel methodology has been developed to analyse fretting damage as a consequence of the variable load and rolling motion. In addition, an analysis of the effects of each fretting mode is accomplished to determine the need to simulate both. The validation of the method is accomplished in two stages. First, a numerical validation through the finite element method (FEM) shows good agreement in the calculation of the contact reaction, the contact angle and tangential stresses, with relative differences under 5% and a considerable time reduction. Second, an experimental validation, which show a 16.1% mean relative difference between the damage areas and a 76% mean overlap of the damage areas. [Display omitted] • A complete methodology for the analysis of fretting damage at angular contact bearing raceways. • An experimental and numerical validation of the proposed methodology. • An analysis on the contribution of the present fretting modes: radial and rotational fretting to the final damage. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to develop a numerical approach to solve the transient rolling contact problem with the consideration of velocity dependent friction. Design/methodology/approach – A three dimensional (3D) transient FE model is developed in elasticity by the explicit finite element method. Contact solutions with a velocity dependent friction law are compared in detail to those with the Coulomb’s friction law (i.e. a constant coefficient of friction). Findings – The FE solutions confirm the negligible influence of the dependence on the normal contact. Hence, analysis is focussed on the tangential solutions under different friction exploitation levels. In the trailing part of the contact patch where micro-slip occurs, very high-frequency oscillations are excited in the tangential plane by the velocity dependent friction. This is similar to the non-uniform sliding or tangential oscillations observed in sliding contact. Consequently, the micro-slip distribution varies greatly with time. However, the surface shear stress distribution is quite stable at different instants, even though it significantly changes with the employed friction model. Originality/value – This paper proposes an approach to solve the transient rolling contact problem with the consideration of velocity dependent friction. Such a problem was usually solved in the literature by the simplified contact algorithms, with which detailed contact solutions could not be obtained, or with the assumption of steady rolling. [ABSTRACT FROM AUTHOR]

Abstract: In this paper mixed finite element methods of higher-order for time-dependent contact problems are discussed. The mixed methods are based on resolving the contact conditions by the introduction of Lagrange multipliers. Dynamic Signorini problems with and without friction are considered involving thermomechanical and rolling contact. Rothe’s method is used to provide a suitable time and space discretization. To discretize in time, a stabilized Newmark method is applied as an adequate time stepping scheme. The space discretization relies on finite elements of higher-order. In each time step the resulting problems are solved by Uzawa‘s method or, alternatively, by methods of quadratic programming via a suitable formulation in terms of the Lagrange multipliers. Numerical results are presented towards an application in production engineering. The results illustrate the performance of the presented techniques for a variety of problem formulations. [Copyright &y& Elsevier]

To simulate the contact and separation of wheels and rails accurately, the stiffness between them should be correct. This paper developed a nonlinear moving wheel element based on a simple point contact scheme to simulate moving train problems, where the element stiffness is set to a power function directly fitted from the finite-element result of the wheel and rail contact analysis. The finite-element result of the wheel/rail contact analysis indicates that the changes in vertical stiffness with changing contact forces can be accurately fitted by using the proposed power function, and the horizontal stiffness can be simply regressed using a constant. The validated example in this paper shows that the nonlinear moving wheel element can simulate the complicated contact and separation problem correctly, both in the displacement and contact force fields, and the major advantage is that a fine mesh is not necessary in the moving train contact analysis. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a new method to directly and explicitly calculate all of the components of the sub-surface stress field in plane contacts once the surface contact stress distributions are known. The method is applicable when the contacting bodies have isotropic elastic behaviour, identical mechanical properties and can be modelled as elastic half-planes. Although the method presented here has direct application in the case of plane contacts, it is also applicable in other mechanical problems that lead to a stress distribution at the surface. The procedure described here is applied to find the interior stress field generated by the well-known Carter''s solution for a rolling contact. [Copyright &y& Elsevier]

Abstract: Current theoretical bearing models differ in their stiffness estimates because of different model assumptions. In this study, a finite element/contact mechanics model is developed for rolling element bearings with the focus of obtaining accurate bearing stiffness for a wide range of bearing types and parameters. A combined surface integral and finite element method is used to solve for the contact mechanics between the rolling elements and races. This model captures the time-dependent characteristics of the bearing contact due to the orbital motion of the rolling elements. A numerical method is developed to determine the full bearing stiffness matrix corresponding to two radial, one axial, and two angular coordinates; the rotation about the shaft axis is free by design. This proposed stiffness determination method is validated against experiments in the literature and compared to existing analytical models and widely used advanced computational methods. The fully-populated stiffness matrix demonstrates the coupling between bearing radial, axial, and tilting bearing deflections. [Copyright &y& Elsevier]

Abstract: We revisit the classical creep theory for a belt drive system as a rolling contact problem between a rubber ring and rigid cylinders to evaluate the effects of linear viscoelasticity and large strain of the belt on the system in a steady state. We first construct the general theory of belt mechanics for a multi-pulley system by dimensional reduction from 3D extensible, unshearable rod. We then develop the belt mechanics for a linear viscoelastic belt and show that the effect of retardation time can be involved in the effective friction coefficient: the classical Euler''s belt formula can be recovered. Next, we assume that the belt is a neo-Hookean material and examine the effect of large strain of the belt on the contact pressure distribution. We compare the theory with the results by finite element analysis and show that the theory provides good quality. [Copyright &y& Elsevier]

Abstract: Wheel–rail frictional rolling contact has been solved for linear elasticity and statics and with the half-space assumption in three dimensions. In recent years, the normal contact problem has also been treated in elasticity and elasto-plasticity with the finite element (FE) method; the half-space assumption is dropped. In this paper, a 3D transient FE model is presented to solve both the normal and the tangential contact problems simultaneously for arbitrary geometry. The explicit time integration scheme employed renders it intrinsically suitable for transient analysis of high frequency dynamic processes. The model is first validated with Hertz theory and Kalker''s computer program CONTACT for the normal solution and with CONTACT for the tangential solution, for the case of wheel tread–rail top contact. Subsequently, the influence of element size on solution accuracy is examined by comparing the results of different element sizes. The analyses show that the presented model is valid for the solution of frictional rolling. [Copyright &y& Elsevier]

Abstract: The development of a quadratic programming formulation for the solution of layered elastic contact problems in the presence of friction is presented in this paper. Conveyor belts, tyred wheels, composite cylinders, and conrod bearings, are classical examples of systems which can be studied using the efficient numerical methodology proposed here. In this type of mechanical assembly, micro-slip between the mating surfaces often occurs and may eventually lead to system failure. Accurately capturing the evolution of slip and stick areas using a computationally inexpensive procedure (as an alternative to full finite element analysis) is therefore key to preventing these failures and to improving the design of various engineering components. The proposed approach is first tested and validated against classical marching-in-time solutions for two-dimensional layered systems in the presence of both static and moving loads. Results are then extended to demonstrate the feasibility of the technique to study systems with multiple slip regions and to solve rolling contact problems of practical interest. Finally, the numerical methodology is successfully applied to the prediction of frictional creep of tyred cylinders. Experimental corroboration has been obtained by testing tyred discs. [Copyright &y& Elsevier]

Two-dimensional elastic contact problems, including normal, tangential, and rolling contacts are treated with the finite element method in this study. Stress boundary conditions and kinematic conditions are transformed into multiple point constraints for nodal displacements in the finite element method. Upon imposing these constraints into the finite element system equations, the calculated nodal stresses and nodal displacements satisfy stress and displacement contact conditions exactly. Frictional and frictionless contacts between elastically identical as well as elastically dissimilar materials are treated in this study. The contact lengths, sizes of slip and stick regions, the normal and the shear stresses can be found. [ABSTRACT FROM AUTHOR]

In this work a three-dimensional planar crack on the surface of elastic half-space was analyzed under rolling contact load. The stresses interior to an elastic half-space body under rolling contact load and those produced by an infinitesimal displacement jump loop for the elastic half-space body were used to reduce the planar crack problem to the solution of a system of two-dimensional hypersingular integral equations with unknown displacement jump. The ideas of finite element discretization were employed to construct numerical solution schemes for solving the integral equations. An appropriate treatment of the associated hypersingular integral in the numerical solution to the integral equations was proposed in Hadamard's finite-part integral sense. The numerical results showed that the present procedure yields solutions with high accuracies. The stress intensity factors near the crack front edge under rolling contact load were indicated in graphical form with varying the crack shape, the radius of rolling contact zone and the friction coefficients, respectively. In addition, the influence of the lubricant infiltrating the crack surfaces on the crack propagation was also discussed in the paper. [ABSTRACT FROM AUTHOR]

Ancorsteel1000C is commonly used for important components including bearing rollers, gears, connecting rods, wheels and rails; most failures of these components are caused by rolling contact fatigue (RCF). In this study the fatigue damage indicator based on Fatemi-Socie critical plane were determined in a local hot spot area in finite element (FE) model in case of Hertzian stress with zero slip condition. The simulation results compared with respect to experimental data, which is in good agreement. Therefore, this approach can be implemented as a useful tool for lifetime calculations in RCF in the process of structure fatigue design. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

An introduction to the journal is presented which discusses various papers published within the issue, inclidong "Finite Element Analysis of Tires in Rolling Contact," "Dual Mortar Methods for Computational Contact Mechanics--Overview and Recent Developments," and "Isogeometric Contact: A Review."