scholarly journals A Micropitting Study Considering Rough Sliding and Mild Wear

Coatings ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 639 ◽  
Author(s):  
Zhou ◽  
Zhu ◽  
Liu
Keyword(s):  
Surface Topography ◽  
Contact Fatigue ◽  
Elastohydrodynamic Lubrication ◽  
Surface Damage ◽  
Sliding Contact ◽  
Maximum Pressure ◽  
Surface Evolution ◽  
Mild Wear ◽  
As Stress ◽  
Wear Law

Micropitting is a typical surface contact fatigue in rolling–sliding contact. The kinematic sliding is of great significance in the initiation and progression of micropitting. A numerical surface fatigue model considering rolling–sliding contact and surface evolution is developed based on mixed-EHL (elastohydrodynamic lubrication) theory, rainflow cycle counting method and Archard’s law. Surface evolution is evaluated using Archard’s wear law based on measured teeth surface topography. Surface damage is determined via the Palmgren–Miner line rule and Goodman diagrams. The effect of rolling speed and surface roughness are discussed in detail. Results show that stress micro-cycles are introduced by rough sliding in the rolling–sliding contact. The mild wear reduces the height of asperities, the maximum pressure and alleviates subsurface stress concentration. For rolling–sliding contact, the faster moving surface dominates the composite height of asperities, then decides the fluctuations of pressure, as well as stress ranges. The combination of surface topography should be considered in the surface design.

Experimental and Fracture Mechanics Study of the Pit Formation Mechanism Under Repeated Lubricated Rolling-Sliding Contact: Effects of Reversal of Rotation and Change of the Driving Roller

1997 ◽  
Vol 119 (4) ◽  
pp. 788-796 ◽  
Author(s):  
Y. Murakami ◽  
C. Sakae ◽  
K. Ichimaru ◽  
T. Morita
Keyword(s):  
Fatigue Crack ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Surface Damage ◽  
Fatigue Tests ◽  
Rolling Contact ◽  
Sliding Contact ◽  
Hydraulic Pressure ◽  
Pit Formation ◽  
Original Crack

Five rolling contact fatigue tests, Tests {1}–{5} have been conducted. In Tests {1}–{3}, when a fatigue crack was initiated on the surface of a follower, the test was halted. Then, in Test {1} the rotating direction was reversed. In Test {2} the follower and driver were interchanged, and in Test {3} the test was continued unchanged. In Test {3} the original crack grew to a pit. In Tests {1} and {2} the original crack immediately stopped propagating. In Tests {4} and {5}, mating with a harder roller, a softer roller was used as the follower in Test {4} and as the driver in Test {5}. A typical pit occurred in Test {4}. In Test {5}, surface damage substantially different from a typical pit was generated. Based on these experimental results, a 3-D crack analysis including the effect of frictional force on the contact surface and oil hydraulic pressure on crack surfaces, was conducted to elucidate the mechanisms of pit formation and surface damage in contact fatigue.

Assessment of Topography Parameters During Running-In and Subsequent Rolling Contact Fatigue Tests

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Deepak K. Prajapati ◽  
Mayank Tiwari
Keyword(s):  
Surface Topography ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Elastohydrodynamic Lubrication ◽  
High Energy ◽  
Sem Analysis ◽  
Fatigue Tests ◽  
Rolling Contact ◽  
Small Scale ◽  
Average Roughness

Rolling contact fatigue (RCF) is one of the major problems observed in gear mechanisms, which leads to high friction, ultimately resulting in high energy consumption. This paper demonstrates the evolution of surface topography during running-in and subsequent RCF tests under boundary or mixed-elastohydrodynamic lubrication regimes. The case-hardened disks of equal surface finish and hardness are used in the experiments, and the evolution of surface topography is investigated using a white light interferometer. Surface topography at different load stages is measured at three distinct points, on the disks and average roughness and topography parameters are reported. Semi-quantitative techniques are used to determine the asperity-level parameters at different load stages. From the running-in experiment, it is found that running-in is a fast process where substantial change in surface topography occurs due to plastic deformation of most prominent asperity. From the RCF test, it is concluded that within range of the fatigue cycles, the root-mean-square (RMS) roughness (Sq) is negatively correlated with the summit radius (R) and the autocorrelation length (Sal) and positively correlated with the summit density (Sds) and the RMS slope (Sdq). Scanning electron microscope (SEM) analysis reveals the disappearance of grinding ridges, the formation of micropits at a very small scale, and pit growth in the sliding direction.

scholarly journals Investigation on stress micro-cycles and mild wear mechanism in gear contact fatigue

2021 ◽  
Author(s):  
Ye Zhou ◽  
Caichao Zhu ◽  
Huaiju Liu ◽  
Houyi Bai ◽  
Xiaona Xu
Keyword(s):  
Fatigue Life ◽  
Fatigue Behavior ◽  
Contact Fatigue ◽  
Sliding Contact ◽  
Premature Failure ◽  
Mild Wear ◽  
Safety And Reliability ◽  
Contact Fatigue Life ◽  
Stress Cycles ◽  
Gear Contact

Gear contact fatigue is becoming a primary limitation for the growing demand of power density and service life in gear-driven equipment. The unchecked surface fatigue crack could further cause premature failure and put a serious risk to the safety and reliability of mechanical systems. In this work, an attempt is made to investigate the effects of rolling-sliding and mild wear on contact fatigue behavior. A comprehensive contact model is developed to capture the variation instantaneous pressure and stress field is calculated with the transient mixed EHL approach. Rolling-sliding contact is simulated with the time-varying roughness topography updated by Archard wear equation. The stress cycles are extracted and the relative contact fatigue life is obtained by using Zaretsky criterion. Results suggest that in rolling-sliding contact the contact fatigue life is obviously lower compared with pure rolling. The increases in the number and amplitude of stress micro-cycles is found to be the main contributors to the reduction of fatigue life. Mild wear tends to smooth the surface, subsequently mitigates the stress concentration and reduces stress cycles, then decrease the risk of surface contact fatigue.

Simulation of Sliding Wear in Mixed Lubrication

2007 ◽  
Vol 129 (3) ◽  
pp. 544-552 ◽  
Author(s):  
Dong Zhu ◽  
Ashlie Martini ◽  
Wenzhong Wang ◽  
Yuanzhong Hu ◽  
Bohdan Lisowsky ◽  
...  
Keyword(s):  
Surface Topography ◽  
Contact Pressure ◽  
Sliding Wear ◽  
Numerical Models ◽  
Elastohydrodynamic Lubrication ◽  
Numerical Approach ◽  
Engineering Practice ◽  
Wear Process ◽  
Local Contact ◽  
Wear Law

Sliding wear is a significant surface failure mode in many mechanical components. The magnitude of changes in surface topography due to wear may be comparable to or larger than the original surface roughness and elastic deformation. However, wear has rarely been incorporated into the numerical models used as predictive tools in engineering practice. This paper presents a numerical approach to simulate the wear process based on the deterministic mixed elastohydrodynamic lubrication (EHL) model developed and modified by Zhu and Hu (2001, Tribol. Trans., 44, pp. 383–398). It is assumed that wear takes place at locations where the surfaces are in direct contact, and the wear rate at those local contact spots is proportional to the relative sliding speed, the local contact pressure, and inversely proportional to the hardness of the surface. At each simulation cycle, the distributions of lubricant film thickness and contact pressure are calculated by using the mixed EHL model. The material removal at each contact location is evaluated and the surface topography modified correspondingly. The renewed surface topography is then used for the next cycle. The model is formulated such that any mathematically expressed wear law can be implemented, and therefore, the simulation can be applied to a wide variety of engineering applications.

Finite Element Analysis of a Polymer- Polymer Sliding Contact for Schallamach Wave and Wear

2007 ◽  
Vol 348-349 ◽  
pp. 633-636 ◽  
Author(s):  
Muhammad Azeem Ashraf ◽  
Bijan Sobhi-Najafabadi ◽  
Özdemir Göl ◽  
D. Sugumar
Keyword(s):  
Finite Element ◽  
Polymer Surface ◽  
Sliding Contact ◽  
Quasi Steady State ◽  
Nodal Solutions ◽  
Element Analysis ◽  
Steady State Analysis ◽  
Initiation And Propagation ◽  
Wear Law ◽  
Nodal Level

Sliding polymer-polymer surface contacts, due to their inherent elastic properties, exhibit detachment waves also termed as Schallamach waves. Such waves effect the initiation and propagation of wear along the sliding contacts. This paper presents quasi steady-state analysis of such a sliding contact using finite element. The contact is modeled and nodal solutions for pressure are obtained for small sliding steps. Analysis of orthogonal pressure components at the contact nodes reveals the formation of Schallamach wave phenomenon. Further, appropriate wear law is used for calculation of wear at nodal level.

Two Dimensional Modified Reynolds Equation Including Pressure Dependent Viscosity Effect

2012 ◽  
Author(s):  
Jung Gu Lee ◽  
Alan Palazzolo
Keyword(s):  
Reynolds Equation ◽  
Elastohydrodynamic Lubrication ◽  
Fluid Film ◽  
Maximum Pressure ◽  
Elastic Solids ◽  
Pressure Distributions ◽  
Pressure Dependent Viscosity ◽  
Modified Reynolds Equation ◽  
Dependent Viscosity ◽  
Modified Equation

The Reynolds equation plays an important role for predicting pressure distributions for fluid film bearing analysis, One of the assumptions on the Reynolds equation is that the viscosity is independent of pressure. This assumption is still valid for most fluid film bearing applications, in which the maximum pressure is less than 1 GPa. However, in elastohydrodynamic lubrication (EHL) where the lubricant is subjected to extremely high pressure, this assumption should be reconsidered. The 2D modified Reynolds equation is derived in this study including pressure-dependent viscosity, The solutions of 2D modified Reynolds equation is compared with that of the classical Reynolds equation for the ball bearing case (elastic solids). The pressure distribution obtained from modified equation is slightly higher pressures than the classical Reynolds equations.

scholarly journals On the Two-Scale Modelling of Elastohydrodynamic Lubrication in Tilted-Pad Bearings

Lubricants ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 78 ◽  
Author(s):  
Gregory de Boer ◽  
Andreas Almqvist
Keyword(s):  
Surface Topography ◽  
Load Capacity ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Multiscale Methods ◽  
Operating Conditions ◽  
Real Surface ◽  
Micro Scale ◽  
Macro Scale ◽  
Heterogeneous Multiscale

A two-scale method for modelling the Elastohydrodynamic Lubrication (EHL) of tilted-pad bearings is derived and a range of solutions are presented. The method is developed from previous publications and is based on the Heterogeneous Multiscale Methods (HMM). It facilitates, by means of homogenization, incorporating the effects of surface topography in the analysis of tilted-pad bearings. New to this article is the investigation of three-dimensional bearings, including the effects of both ideal and real surface topographies, micro-cavitation, and the metamodeling procedure used in coupling the problem scales. Solutions for smooth bearing surfaces, and under pure hydrodynamic operating conditions, obtained with the present two-scale EHL model, demonstrate equivalence to those obtained from well-established homogenization methods. Solutions obtained for elastohydrodynamic operating conditions, show a dependency of the solution to the pad thickness and load capacity of the bearing. More precisely, the response for the real surface topography was found to be stiffer in comparison to the ideal. Micro-scale results demonstrate periodicity of the flow and surface topography and this is consistent with the requirements of the HMM. The means of selecting micro-scale simulations based on intermediate macro-scale solutions, in the metamodeling approach, was developed for larger dimensionality and subsequent calibration. An analysis of the present metamodeling approach indicates improved performance in comparison to previous studies.

A Theoretical Tribological Comparison Between Soft and Hard Coatings of Spur Gear Pairs

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Huaiju Liu ◽  
Caichao Zhu ◽  
Zhanjiang Wang ◽  
Ye Zhou ◽  
Yuanyuan Zhang
Keyword(s):  
Surface Deformation ◽  
Tribological Behavior ◽  
Elastohydrodynamic Lubrication ◽  
Spur Gear ◽  
Hard Coatings ◽  
Radius Of Curvature ◽  
Maximum Pressure ◽  
Gear Pair ◽  
The Coefficient Of Friction ◽  
Squeeze Effect

A thermal elastohydrodynamic lubrication (TEHL) model is developed for a coated spur gear pair to investigate the effect of soft coatings and hard coatings on the tribological behavior of such a gear pair during meshing. The coating properties, i.e., the ratio of the Young's modulus between the coating and the substrate, and the coating thickness, are represented in the calculation of the elastic deformation. Discrete convolution, fast Fourier transform (DC-FFT) is utilized for the fast calculation of the surface deformation. The variation of the radius of curvature, the rolling speed, the slide-to-roll ratio, and the tooth load along the line of action (LOA) during meshing is taken into account and the transient squeeze effect is considered in the Reynolds equation. Energy equations of the solids and the oil film are derived. The temperature field and the pressure field are solved iteratively. The tribological behavior is evaluated in terms of the minimum film thickness, the maximum pressure, the temperature rise, the coefficient of friction, and the frictional power loss of the tooth contact during meshing. The results show discrepancies between the soft coating results and hard coating results.

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