title: Tribological Behavior of Aqueous Copolymer Lubricant in Mixed Lubrication Regime.
abstract: Although a number of experiments have been attempted to investigate the lubrication of aqueous copolymer lubricant, which is applied widely in metalworking operations, a comprehensive theoretical investigation at atomistic level is still lacking. This study addresses the influence of loading pressure and copolymer concentration on the structural properties and tribological performance of aqueous copolymer solution of poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEO-PPO) at mixed lubrication using a molecular dynamic (MD) simulation. An effective interfacial potential, which has been derived from density functional theory (DFT) calculations, was employed for the interactions between the fluid's molecules and iron surface. The simulation results have indicated that the triblock copolymer is physisorption on iron surface. Under confinement by iron surfaces, the copolymer molecules form lamellar structure in aqueous solution and behave differently from its bulk state. The lubrication performance of aqueous copolymer lubricant increases with concentration, but the friction reduction is insignificant at high loading pressure. Additionally, the plastic deformation of asperity is dependent on both copolymer concentration and loading pressure, and the wear behavior shows a linear dependence of friction force on the number of transferred atoms between contacting asperities.
authors.affiliation: School of Mechanical, Materials and Mechatronic Engineering, Faculty of Engineering and Information Sciences (EIS), University of Wollongong , Northfield Avenue, Wollongong, New South Wales 2522, Australia.
authors.forename: Thi D
authors.initials: TD
authors.lastname: Ta
authors.affiliation: School of Mechanical, Materials and Mechatronic Engineering, Faculty of Engineering and Information Sciences (EIS), University of Wollongong , Northfield Avenue, Wollongong, New South Wales 2522, Australia.
authors.forename: A Kiet
authors.initials: AK
authors.lastname: Tieu
authors.affiliation: School of Mechanical, Materials and Mechatronic Engineering, Faculty of Engineering and Information Sciences (EIS), University of Wollongong , Northfield Avenue, Wollongong, New South Wales 2522, Australia.
authors.forename: Hongtao
authors.initials: H
authors.lastname: Zhu
authors.affiliation: School of Mechanical, Materials and Mechatronic Engineering, Faculty of Engineering and Information Sciences (EIS), University of Wollongong , Northfield Avenue, Wollongong, New South Wales 2522, Australia.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhu
authors.affiliation: School of Mechanical, Materials and Mechatronic Engineering, Faculty of Engineering and Information Sciences (EIS), University of Wollongong , Northfield Avenue, Wollongong, New South Wales 2522, Australia.
authors.forename: Prabouno B
authors.initials: PB
authors.lastname: Kosasih
authors.affiliation: School of Mechanical, Materials and Mechatronic Engineering, Faculty of Engineering and Information Sciences (EIS), University of Wollongong , Northfield Avenue, Wollongong, New South Wales 2522, Australia.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.affiliation: School of Mechanical, Materials and Mechatronic Engineering, Faculty of Engineering and Information Sciences (EIS), University of Wollongong , Northfield Avenue, Wollongong, New South Wales 2522, Australia.
authors.forename: Guanyu
authors.initials: G
authors.lastname: Deng
keywords: aqueous lubricant; mixed lubrication; molecular dynamics; nanotribology; polymer