Article
Engineering, Mechanical
Haibin Wu, Constantine Khripin, Anand Jagota, Chung-Yuen Hui
Summary: It has been discovered that lubricated friction can be enhanced by the periodic variation of near-surface stiffness. In this study, we simulated the lubricated sliding of a rigid cylinder on a substrate with a periodic variation in mechanical stiffness. The results show that increasing the variation of near-surface stiffness can significantly increase the friction force. This research provides insight into the mechanism of friction enhancement and can guide the design of surfaces to control friction during lubricated sliding.
EXTREME MECHANICS LETTERS
(2022)
Article
Materials Science, Multidisciplinary
Haibin Wu, Chung -Yuen Hui, Anand Jagota
Summary: This paper investigates the problems in elasto-hydrodynamic lubrication when one of the contacting bodies is elastically soft. A numerical method is developed to solve both normal indentation and transient sliding lubrication problems, avoiding the difficulties of converging iterative methods.
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
(2023)
Article
Engineering, Mechanical
G. Boidi, P. G. Gruetzmacher, A. Kadiric, F. J. Profito, I. F. Machado, C. Gachot, D. Dini
Summary: This study demonstrated the potential of fast laser texturing techniques in improving the tribological performance of bearings and mechanical components. Dimples were found to reduce friction effectively compared to smooth surfaces, while grooves had less beneficial effects. Additionally, dimples promoted the formation of full film lubrication conditions at lower speeds.
Article
Engineering, Mechanical
Kazuyuki Yagi, Wataru Matsunaka, Joichi Sugimura
Summary: This study investigates the effect of textured patterns on lubrication performance in starved hydrodynamic lubrication. Longitudinal or transverse grooves on discs are found to improve lubricant supply into the lubricated area at high sliding conditions, compared to a flat disc.
TRIBOLOGY INTERNATIONAL
(2021)
Article
Engineering, Mechanical
Suhaib Ardah, Francisco J. Profito, Daniele Dini
Summary: This paper proposes an integrated finite-volume framework for solving thermal elasto-hydrodynamic lubrication problems and predicts the lubrication performance of non-conformal contacts. By considering fluid flow effects and thermal behavior, the framework is able to handle strong nonlinearity and improve convergence of the results.
TRIBOLOGY INTERNATIONAL
(2023)
Article
Engineering, Mechanical
James Layton, Benjamin C. Rothwell, Stephen Ambrose, Carol Eastwick, Humberto Medina, Neville Rebelo
Summary: Designing effective thermal management systems within transmission systems requires simulations to consider the contributions from phenomena such as hydrodynamic lubrication regions. Computational fluid dynamics (CFD) remains computationally expensive for practical cases of hydrodynamic lubrication while the thermo elasto-hydrodynamic lubrication (TEHL) theory has demonstrated good accuracy at a lower computational cost. This study takes an initial step by developing a TEHL solver within OpenFOAM such that the program is prepared to be interfaced with a CFD module in future versions. The OpenFOAM solver includes the Elrod-Adams cavitation model, thermal effects, and elastic deformation of the surfaces, and considers mixing between the recirculating flow and oil feed by applying energy and mass continuity. A sensitivity study of the film mesh is presented to show the solution variation with refinement along the circumferential, axial and radial directions. A validation case is presented of an experimental single axial groove journal bearing which shows good agreement in the pressure and temperature results. The peak pressure in the film is predicted within 12% and the peak temperature in the bush is predicted within 5% when comparing the centerline profiles.
Article
Chemistry, Multidisciplinary
Hao Dong, Nichole Moyle, Haibin Wu, Constantine Yuri Khripin, Chung-Yuen Hui, Anand Jagota
Summary: Lubricated contacts in soft materials are common in various applications. The transition between elasto-hydrodynamic lubrication (EHL) and mixed lubrication (ML) regimes governs the minimum sliding friction achievable. Previous belief held that the transition occurs when the thickness of the lubricant layer is comparable with the amplitude of surface roughness, but this study found that the transition can occur when the thickness of the liquid layer is much larger than the height of the asperities. Direct visualization showed the formation of wave-like surface wrinkles triggering the transition to the mixed regime.
ADVANCED MATERIALS
(2023)
Article
Engineering, Mechanical
He Li, Junkai Niu
Summary: This paper investigates the impact of texture on the tribological performance of journal bearings operating under starvation lubrication conditions. The P-theta model with mass conservation boundary conditions accurately predicts the oil film distribution in the full oil film/starvation region of the textured bearing. The study discusses the effects of different levels of starvation lubrication on parameters such as eccentricity, attitude angle, full film area, and friction coefficient in textured bearings. The results show that the severity of the texture's effect on bearing performance varies with starvation levels and that texturing can improve the bearing's operating performance, increase load carrying capacity, reduce friction coefficient, and enhance safety.
SURFACE TOPOGRAPHY-METROLOGY AND PROPERTIES
(2023)
Article
Engineering, Mechanical
Liming Wang, Chunlong Deng, Jin Xu, Lei Yin, Wennian Yu, Xiaoxi Ding, Yimin Shao, Wenbin Huang, Xiaoqing Yang
Summary: Spalling fault is a common issue in gear systems, causing performance degradation and increased downtime risk. Previous studies focused on the mechanism and effects of spalling fault on dynamic characteristics, neglecting the influence on lubrication characteristics. In this paper, a new dynamic modelling method considering 3D line contact elasto-hydrodynamic lubrication is proposed to study the contact characteristics and dynamic responses affected by spalling fault.
ENGINEERING FAILURE ANALYSIS
(2022)
Article
Chemistry, Multidisciplinary
Bongjun Kim, Junho Suh, Bora Lee, Yondo Chun, Geuntae Hong, Jungjoon Park, Yonghun Yu
Summary: This study investigates the impact of operating conditions, such as ambient temperature and sealing pressure, on the sealing performance of a typical U-cup seal. A developed analysis method, combining inverse fluid lubrication (IHL) theory and the Greenwood-Williamson contact model (G-W model), considers the effect of surface temperature increase due to frictional heat. Commercial FE software (ABAQUS) is used to simulate the interference fit analysis and pressurized process of rubber seals. The simulation results reveal the influence of fluid viscosity, surface temperature increase, and surface roughness at very small film thickness on film distribution, fluid leakage, and friction force in the sealing area.
APPLIED SCIENCES-BASEL
(2023)
Article
Engineering, Chemical
Mostafa Faraji, Alexander Seitz, Christoph Meier, Wolfgang A. Wall
Summary: This work presents a new model and numerical formulation for lubricated contact problems involving deformable 3D solid bodies and a fluid film. The model considers frictional contact tractions and hydrodynamic fluid tractions at each local point on the contact surface, and covers the entire range of lubrication. The finite element method is used for spatial discretization and several benchmark tests demonstrate the accuracy of the model.
Article
Engineering, Chemical
Ke Zhang, Kazuyuki Yagi
Summary: This study introduces a refined hydrodynamic lubrication model that incorporates a high-accuracy numerical algorithm for starved lubrication with free surfaces. The proposed method is compared against conventional models and numerical schemes, showing that it can accurately predict lubrication pressure and maintain accuracy under severe conditions.
Article
Engineering, Mechanical
Maximillian Zimmer, Sorin-Cristian Vladescu, Lars Mattsson, Mark Fowell, Tom Reddyhoff
Summary: Based on experiments with reciprocating rig, it was found that macro-scale surface texture can reduce friction by up to 35% in the hydrodynamic regime. The Shear-Area Variation mechanism suggests that macro-texture can reduce contact area and increase shear-rate, leading to reduced friction and potential efficiency improvements in machines.
TRIBOLOGY INTERNATIONAL
(2021)
Article
Engineering, Mechanical
G. H. G. van der Meer, F. Quinci, W. Litwin, M. Wodtke, R. A. J. van Ostayen
Summary: The study investigates the application of a modified MR fluid in lubrication performance using a journal bearing test bench. It is found that applying a local magnetic field can significantly reduce the transition speed of the bearing when lubricated with MR fluid, with only a minimal increase in friction. The lubricating performance of the MR fluid is compared to a reference oil.
TRIBOLOGY INTERNATIONAL
(2023)
Article
Engineering, Mechanical
Xuefeng Chang, Duoji Renqing, Longxing Liao, Peiyuan Zhu, Bingjing Lin, Yubin Huang, Shanming Luo
Summary: This paper investigates the impact of groove-type tooth surface texture on wear and adhesion in spur gear transmission. The core size parameters of the groove texture are optimized through experiments and simulations, showing that the groove texture can significantly reduce friction wear and adhesion, thereby improving the gear transmission life.
TRIBOLOGY INTERNATIONAL
(2023)
Article
Engineering, Mechanical
G. E. Morales-Espejel, P. M. Lugt, H. R. Pasaribu, H. Cen
TRIBOLOGY INTERNATIONAL
(2014)
Article
Engineering, Chemical
Lars G. Westerberg, Jinxia Li, Erik Hoglund, Piet M. Lugt, Pieter Baart
Article
Engineering, Mechanical
J. X. Li, Lars G. Westerberg, E. Hoglund, P. M. Lugt, P. Baart
TRIBOLOGY TRANSACTIONS
(2014)
Article
Engineering, Mechanical
Pieter Baart, Piet M. Lugt, Braham Prakash
TRIBOLOGY TRANSACTIONS
(2014)
Article
Engineering, Mechanical
Hui Cen, Piet M. Lugt, Guillermo Morales-Espejel
TRIBOLOGY TRANSACTIONS
(2014)
Article
Engineering, Mechanical
Hui Cen, Piet M. Lugt, Guillermo Morales-Espejel
TRIBOLOGY TRANSACTIONS
(2014)
Article
Engineering, Mechanical
Piet M. Lugt, Marco T. van Zoelen, Charlotte Vieillard, Frank Berens, Robert Gruell, Gerwin Preisinger, Paul Meaney
Summary: The research shows that in hybrid bearings, grease life is longer than in all-steel bearings. Additionally, for cylindrical roller bearings, hybrid bearings provide longer grease life at relatively lower speeds compared to all-steel bearings.
TRIBOLOGY TRANSACTIONS
(2021)
Article
Engineering, Mechanical
Qierui Zhang, Frieder Mugele, Dirk van den Ende, Piet M. Lugt
Summary: The study found that the Washburn-like model based on the affinity of the oil for the grease matrix is applicable for greases made of various thickeners and base oils. This model can potentially be used for modeling the bleeding of stationary grease and monitoring the change in bleeding properties of greases in a bearing.
TRIBOLOGY TRANSACTIONS
(2021)
Article
Engineering, Mechanical
Pramod Shetty, Robert Jan Meijer, Piet M. Lugt
Summary: This article introduces a model for base oil evaporation in grease-lubricated bearings, where volatiles leave the bearing through breathing. The model is applied to a typical drive cycle with varied temperatures, allowing for quantification of the impact of base oil volatility and sealing quality on evaporation losses.
TRIBOLOGY TRANSACTIONS
(2021)
Editorial Material
Engineering, Mechanical
Piet M. Lugt
PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY
(2021)
Article
Engineering, Mechanical
Robert Jan Meijer, Piet M. Lugt
Summary: Mechanical degradation by shear is a limiting mechanism in the lifetime of lubricating grease in rolling bearings, which can be quantified using a grease worker. This article presents a novel approach of measuring rheological properties of grease in situ while aging it, by calculating mechanical energy and pressure losses with a pipe flow model and power law rheology model. The model validity is verified using computational fluid dynamics simulations and rheometer measurements.
TRIBOLOGY TRANSACTIONS
(2021)
Article
Engineering, Mechanical
Jude A. Osara, Piet M. Lugt, Michael D. Bryant, Michael M. Khonsari
Summary: This study investigates the oxidation-thermal stability of lubricating greases using the ASTM 5483 standard and thermodynamic laws. A new model based on degradation-entropy generation (DEG) theorem is developed to predict the oxidation induction time. The results show that the high-pressure entropy transfer by oxygen mass flow is the primary contributor to oxidation induction time, and the DEG model accurately predicts induction times at different temperatures.
TRIBOLOGY TRANSACTIONS
(2022)
Article
Engineering, Mechanical
Pramod Shetty, Robert Jan Meijer, Jude A. Osara, Piet M. Lugt
Summary: This article presents a new method for measuring the film thickness in a rolling bearing and investigates the impact of speed on the film thickness.
TRIBOLOGY TRANSACTIONS
(2022)
Article
Engineering, Mechanical
Piet M. Lugt
Summary: The most commonly used equation to describe the temperature dependency of chemical reaction rates is the Arrhenius equation. However, the impact of temperature on grease life is usually described using a different equation. This note compares the two equations and shows that they are almost identical, despite the apparent engineering nature of the latter equation. This should eliminate any doubts about using this equation.
TRIBOLOGY INTERNATIONAL
(2023)
Article
Chemistry, Physical
Qierui Zhang, Frieder Mugele, Piet M. Lugt, Dirk van den Ende
