Article
Chemistry, Multidisciplinary
Marvelucia Almeida, Flavia Bastos, Sara Vecchio
Summary: This article presents a mathematical and computational model to analyze sliding friction in lubricated contact between bearing surfaces using a realistic 3D model on a microscopic scale. The fluid-structure interaction model evaluates the effects of lubricant film thickness on friction in hydrodynamic and mixed lubrication regimes. Higher contact pressures were observed at the peaks of asperities, particularly during mixed lubrication where the fluid volume is smaller. The calculated friction coefficients, obtained through a homogenization procedure of shear and normal forces in hydrodynamic and mixed lubrication, were accurate and fell within the range specified in the Stribeck curve. The results demonstrate the capability of the computational model to examine the effects of lubrication on rough surface contact.
APPLIED SCIENCES-BASEL
(2023)
Article
Computer Science, Interdisciplinary Applications
Alexandre Silva, Veniero Lenzi, Albano Cavaleiro, Sandra Carvalho, Luis Marques
Summary: In this work, we present FELINE, a C++ solver for hydrodynamic lubrication problems. The solver utilizes the inexact Newton iteration algorithm and a finite element method framework to accurately describe cavitation regions and solve linear complementarity problems. The performance and robustness of the solver are tested and validated against known cases in literature and industrially relevant cases of dimpled textures. A benchmark for a complex dimpled texture case is provided to evaluate the implementation's performance and robustness.
COMPUTER PHYSICS COMMUNICATIONS
(2022)
Article
Engineering, Mechanical
Fabricio Vieira Silva, Mauricio Araujo Zanardi, Teofilo Miguel de Souza
Summary: This study investigated the dynamics of different non-Newtonian fluids in short journal bearings using computational fluid dynamics, finding that Herschel-Bulkley and Bingham non-Newtonian fluids showed advantages in various performance parameters compared to Newtonian fluid.
JOURNAL OF THE BRAZILIAN SOCIETY OF MECHANICAL SCIENCES AND ENGINEERING
(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
Simon Pfeil, Hauke Gravenkamp, Fabian Duvigneau, Elmar Woschke
Summary: This study introduces a semi-analytical solution of the Reynolds equation based on the Scaled Boundary Finite Element Method to reduce the numerical effort in rotor system dynamics simulation. By discretizing the two-dimensional pressure field in one direction and using an analytical formulation in the other direction, a new approach is employed to solve the system of non-homogeneous ordinary differential equations.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2021)
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
S. Boedo, V. N. Santhanam
Summary: The optimal shape design of hydrodynamic axisymmetric spherical bearings under transient axisymmetric pure squeeze conditions has been investigated using genetic algorithms. The study found that the GA-based optimal designs yield significantly larger impulse values compared to random designs or optimal ellipsoidal geometries. A sample design application demonstrated that an optimal GA-inspired composite clearance specification can be constructed, providing better bearing performance and being less sensitive to deviations in clearance shape, load impulse, and viscosity variation compared to similar variations in the optimal ellipsoidal design.
TRIBOLOGY INTERNATIONAL
(2023)
Article
Engineering, Mechanical
Amaroju Kartheek, Kiran Vijayan, Xiaodong Sun, Steffen Marburg
Summary: Rotating shaft instability causing high amplitude vibration is a significant issue in various industrial applications. This study focuses on a conceptual model of a flexible shaft supported on hydrodynamic bearings (HDBs) to identify response statistics and propose design strategies to mitigate the vibration. The critical speeds that result in high responses are identified through a Campbell diagram analysis. The effects of whirling modes on the response are investigated considering the uncertainty introduced by manufacturing processes and operating conditions. Control strategies are designed to reduce the excitation of the first mode by altering the relative position of unbalance masses. Stochastic analysis is conducted to verify the effectiveness of the strategy.
MECHANICAL SYSTEMS AND SIGNAL PROCESSING
(2023)
Article
Mathematics, Applied
Hua Zheng, Xuping Zhang, Xiaoping Lu
Summary: This paper analyzes the efficiency of the MAOR method in solving horizontal linear complementarity problems arising from finite-difference discretizations of hydrodynamic lubrication. The convergence range of the relaxation parameters is given and numerical examples are provided to demonstrate the effectiveness of the proposed theoretical results.
APPLIED MATHEMATICS LETTERS
(2021)
Article
Engineering, Mechanical
Chao Zhao, Risheng Long, Yimin Zhang, Yibing Wang, Yueyong Wang
Summary: In this study, three types of vein-bionic textures were designed on the raceways of cylindrical roller thrust bearings using a fiber laser marking system. The effects of different veins and vein-structure characteristics on the tribological behavior of vein-bionic textured bearings were investigated. The results showed that the original vein-bionic pattern inspired by the Ash had the best friction-reducing performance, while the texture with the no-chief vein obtained by Clausena lansium had the best wear resistance.
TRIBOLOGY INTERNATIONAL
(2022)
Article
Mechanics
Weixuan Zhou, Xiaofeng Wei, Gaston Haidak, Dongyun Wang
Summary: In this paper, the dynamics of the textured piston/cylinder pairs are predicted using the Reynolds equation coupled with the Half-Sommerfeld boundary condition, and the optimal geometry parameters are predicted using the characteristic function. The combination of the shearing coefficient and the characteristic function can predict the cavitation region and the critical inclination angle. The results of this paper provide theoretical guidance for the surface texture design on piston/cylinder pairs.
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
Qinggang Guo, Long Zheng, Yinghui Zhong, Shukun Wang, Luquan Ren
Summary: Numerical models of continuous groove textures with X-shaped units were established in this study. The effects of geometric parameters and sliding speed on tribological properties were systematically investigated. The optimal geometric parameters for each texture shape were determined. It was found that the circular texture exhibited the best lubrication performance at lower area densities, while the square texture with a groove depth increase and an orientation of theta = 90 degrees showed better tribological performance when the area density exceeded 25%. The lubrication mechanism was explained as a trade-off between fluid flow and the generation of hydrodynamic pressure.
TRIBOLOGY INTERNATIONAL
(2022)
Article
Engineering, Mechanical
Mert Yusuf Cam, Matteo Giacopini, Daniele Dini, Luca Biancofiore
Summary: Hydrodynamic lubrication plays a fundamental role in mechanical systems by reducing energy losses and preventing mechanical breakdown. The classical linear Reynolds equation is insufficient for describing the lubricant characteristics on engineered surfaces, and non-linearities introduced by wall slip and cavitation need to be considered. Therefore, a modified two-dimensional Reynolds equation is proposed to capture both the cavitation presence and wall slippage, leading to improved accuracy and computational efficiency.
TRIBOLOGY INTERNATIONAL
(2023)
Article
Mathematics, Applied
Hua Zheng, Seakweng Vong
Summary: This paper investigates the convergence of the modulus-based successive overrelaxation iteration method for horizontal linear complementarity problems in hydrodynamic lubrication. The numerical examples demonstrate the significance of the proposed theorems.
APPLIED MATHEMATICS AND COMPUTATION
(2021)
Article
Engineering, Mechanical
Songtao Hu, Weifeng Huang, Jinbang Li, Tom Reddyhoff, Xiaobao Cao, Xi Shi, Zhike Peng, Andrew Demello, Daniele Dini
Summary: The study introduces a rigid-flexible hybrid surface design that enables fast droplet sliding and waterproof performance, and retains its water-repellent properties even after a certain number of wear cycles.
Article
Engineering, Mechanical
Yilun Xu, Daniel S. Balint, Christian Greiner, Daniele Dini
Summary: Discrete dislocation plasticity calculations are used to investigate the response of a single crystal under sliding loading conditions with a rigid sinusoidal asperity contact. The study identifies lattice rotations and stored energy as the key factors causing microstructure change in the dislocation structure. Maps of surface slip initiation and substrate permanent deformation obtained from the calculations suggest ways to optimize the interface and microstructural material properties for different frictional loads.
Review
Biophysics
Mohamed A. A. Abdelbar, James P. P. Ewen, Daniele Dini, Stefano Angioletti-Uberti
Summary: When polymer chains are densely grafted to solid surfaces, they form brushes that can alter surface properties and reduce friction in water-lubricated systems. Molecular simulations have been used to understand the mechanisms of friction reduction and improve the design of polymer brushes. This review focuses on the progress in molecular simulations of polymer brush friction, from simple models to more detailed ones that capture brush topology, chemistry, and electrostatic interactions. Matching experimental data and addressing remaining challenges are discussed to enhance the predictive capability of molecular simulations for optimizing brush structures and reducing friction.
Article
Engineering, Electrical & Electronic
Zilin Feng, Min Yu, Simos A. Evangelou, Imad M. Jaimoukha, Daniele Dini
Summary: This article presents a combined mu-synthesis PID control scheme, employing a frequency separation paradigm, for a recently proposed novel active suspension, the Parallel Active Link Suspension (PALS). The developed mu-synthesis control scheme is superior to the conventional H-infinity control, previously designed for the PALS, in terms of ride comfort and road holding (higher frequency dynamics), with important realistic uncertainties, such as in vehicle payload, taken into account. The developed PID control method is applied to guarantee good chassis attitude control capabilities and minimization of pitch and roll motions (low frequency dynamics).
IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY
(2023)
Article
Biochemistry & Molecular Biology
Tian Yuan, Yi Yang, Wenbo Zhan, Daniele Dini
Summary: Magnetic nanoparticles (MNPs) can be used as a drug delivery system in brain diseases. However, achieving desired drug distribution patterns in the complex microstructure of brain tissues, particularly the white matter, is still unclear. In this study, a mathematical model was used to investigate the effects of key parameters on MNP diffusion in the brain white matter. The results show that a uniform distribution of MNPs can be achieved by adjusting particle size and magnetic field, and particle size plays a key role in determining MNPs' diffusion behaviors. Axon tortuosity may affect MNP transport, but this can be mitigated by applying an external magnetic field perpendicular to the local axon track.
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
(2023)
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, Biomedical
Tian Yuan, Wenbo Zhan, Daniele Dini
Summary: This study reveals the impact of interactions between neurons and surrounding fluid on the macroscopic transport behavior of brain tissue, shedding light on unresolved issues related to brain functions and medical treatments. For the first time, a microstructure-informed permeability tensor was established to accurately model the transport properties of brain tissue. This study is important for improving the prediction accuracy of brain tissue transport properties and neural tissue engineering.
ACTA BIOMATERIALIA
(2023)
Article
Materials Science, Multidisciplinary
Fernando Patino-Ramirez, Catherine O'Sullivan, Daniele Dini
Summary: This paper proposes two algorithms to identify the network of percolating contacts that control the response of loaded granular media, and to decompose this network into the individual force chains. The results show that the contribution of force chains in the network is highly centralized, composed by a small set of strong and long-lived force chains, plus a large set of weak and short-lived force chains.
Article
Chemistry, Physical
Muhammad Rizwanur Rahman, Li Shen, James P. Ewen, Benjamin Collard, D. M. Heyes, Daniele Dini, E. R. Smith
Summary: Using non-equilibrium molecular dynamics simulations, we investigate the retraction of thin films and correct the Taylor-Culick (TC) theory for nanoscale films by deriving a new mathematical formulation for surface shape and considering locally varying surface tension.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
D. M. Heyes, D. Dini, S. Pieprzyk, A. C. Branka
Summary: This work provides new theoretical tools and criteria to determine the extent of deviation from perfect isomorphicity for pair potentials using the Lennard-Jones system as a test case. A simple prediction method using the freezing line as a reference is shown to accurately predict isomorphs in the fluid range for the LJ system. The physical significance of correlations found previously in the literature can be evaluated using this method.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Mechanics
Navraj S. Lalli, Li Shen, Daniele Dini, Andrea Giusti
Summary: Previous studies have shown that a magnetic field can alter the drainage in soap films containing magnetic particles. However, it is still unclear whether a magnetic field can control the rate of drainage and film stability, as well as its effect on key drainage mechanisms. This experimental study investigates the behavior of soap films containing magnetite nanoparticles, revealing that a magnetic field can have a stabilizing or destabilizing effect on magnetic soap films depending on their composition.
Article
Engineering, Mechanical
Mert Yusuf Cam, Matteo Giacopini, Daniele Dini, Luca Biancofiore
Summary: Hydrodynamic lubrication plays a fundamental role in mechanical systems by reducing energy losses and preventing mechanical breakdown. The classical linear Reynolds equation is insufficient for describing the lubricant characteristics on engineered surfaces, and non-linearities introduced by wall slip and cavitation need to be considered. Therefore, a modified two-dimensional Reynolds equation is proposed to capture both the cavitation presence and wall slippage, leading to improved accuracy and computational efficiency.
TRIBOLOGY INTERNATIONAL
(2023)
Article
Chemistry, Physical
Erik Weiand, Francisco Rodriguez-Ropero, Yuri Roiter, Peter H. H. Koenig, Stefano Angioletti-Uberti, Daniele Dini, James P. P. Ewen
Summary: The adsorption behavior of surfactants at solid-liquid interfaces is studied using molecular dynamics simulations. Cationic surfactants adsorb in two stages, forming monolayers and then bilayers at high concentrations. Anionic surfactants weakly adsorb via hydrophobic interactions, forming only monolayers. Applying cationic surfactant solutions to bleached hair restores low friction and increases hydrophobicity.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2023)
Proceedings Paper
Engineering, Mechanical
M. Lasen, L. Salles, D. Dini, C. W. Schwingshackl
Summary: This work presents the approach and results of the Dynamics Group at Imperial College in face of the Tribomechadynamics 2021 challenge. The Dynamics Group's approach consists of predicting the behavior caused by friction nonlinearities at the location of the highest energy dissipation. The results show a slight softening at the contact point, with an overall shift of the linear frequency by 2.6% and a 1.5% increase in damping compared to linear damping.
NONLINEAR STRUCTURES & SYSTEMS, VOL 1
(2023)
Proceedings Paper
Engineering, Mechanical
M. Lasen, D. Dini, C. W. Schwingshackl
Summary: This paper proposes a novel concept of active manipulation of contact shape and contact pressure distribution in frictional interfaces. The concept is initially tested through computational simulations and has shown promising results. A physical prototype of the proposed system has been manufactured for further experiments.
NONLINEAR STRUCTURES & SYSTEMS, VOL 1
(2023)
