Entice

 Fellow Profile: Ali Ghanbarzadeh

Project Title:

Boundary Lubrication Multiscale Modelling by Interface Mechanics (P2)

Project summary

Most of the work done in the territory of boundary lubrication is experimental studies and there are few direct numerical models of boundary lubrication. Previous models cover contact mechanics part of boundary lubrication but they do not consider tribofilm properties or film formation and removal and their effects on mechanical properties. The main of this work is to implement tribochemistry into deterministic boundary lubrication models.

For this purpose, contact mechanics simulation of rough surfaces with taking in to account the tribofilm formation and removal and its mechanical properties will be developed. This contact model will consider tangential forces and elastic modulus and also hardness variations of tribofilm. The tribofilm is formed in each time step and is covered on the surface and only on the contact asperities. At the end, tribofilm fromed on the surfaces and also wear will be calculated.

In this work I am mainly dealing with contact mechanics and developing different codes for contact of rough surfaces. I also use different mathematical techniques to make the simulations faster. Thermodynamics of interfaces is used to develop tribochemical models.

Educational background:

1. BSc. Mechanical Engineering, Amirkabir University of Technology (Tehran Polytechnic), 2012.

  • BSc thesis: Investigating, modelling and predicting the gas consumption of a Gas industry.

Research Interests:

My research during my Bachelor studies was in the area of Fluid mechanics and heat transfer and I used CFD frequently. In addition I was performing as a member in Material Science Lab research group for investigation of Functionally Graded Steels and mathematically modelling the stress/strain relationships. Currently I am doing a PhD in tribochemitry and my main focus is on numerical modeling of boundary lubrication considering the tribochemitry phenomenon. For this purpose, variety of numerical procedures of contact mechanics and also chemical aspects of interfaces are taken in to account.

Conferences

1- STLE 69th Annual Meeting & Exhibition 2014
Ali Ghanbarzadeh, Mark Wilson, Ardian Morina, Anne Neville , Chemo-Mechanical Numerical Modelling of Boundary Lubrication

2-  41st LEEDS-LYON SYMPOSIUM ON TRIBOLOGY 2014
Ali Ghanbarzadeh, Mark Wilson, Ardian Morina, Duncan Dowson, Anne Neville, Mechano-Chemical Numerical Modelling of Boundary Lubrication

 

Publications

Ali Ghanbarzadeh, Mark Wilson, Ardian Morina, Duncan Dowson, Anne Neville, Development of a new mechano-chemical model in boundary lubrication. Tribology
International (2015), http://dx.doi.org/10.1016/j.triboint.2014.12.018i

  

Institute 

Institute of Engineering, Thermo fluids, Surface and Interfaces (iETSI)
Mechanical Engineering Department
University of Leeds

For more information contact Ali;    

E-mail:mnag@leeds.ac.uk

Supervisors: Dr. Mark Wilson, Dr. Ardian Morina and Prof. Anne Neville.

Monthly reports

Monthly reports are available here

 Extended Summary

Background and motivation

The effectiveness of boundary lubrication has been considered for a long time as a necessity for modern designs of machines with reliable operations. Because of the need for more energy efficiency, availability of new materials and machine part downsizing, the need for understanding true interactions in this regime is of great importance. The boundary lubrication regime has been the subject of many studies for more than 70 years and the majority of these studies are experimental investigations into the nature of what happens in this regime. Many of the studies cover the boundary film chemical, physical and mechanical properties and their effects on wear and friction reduction. The subject of many works has been to investigate different kinds of additives in oils and their effects on various aspects of tribological performance. As the boundary lubrication regime is mainly related to interactions of two surfaces and the additive-containing oils between them, the analytical studies of surfaces including topography measurements, chemical analyses, mechanical and physical studies are considerable. All these experiments give good insight into different chemical and physical characteristics covering various aspects of boundary lubrication systems.

It is clear from the wealth of experimental literature in this area that the phenomena happening in this regime are very complicated. Studying the entire problem needs a multiscale understanding ranging from component scale down to the micro-scale and also molecular interactions of films and lubricant additives. Experimentation across such scales is challenging and hence it is important to complement such studies with the ability to predict the friction and wear of a working system without running experiments. It is also important to analyse the system and optimise its performance in order to design cost-effective experiments. Many modelling attempts have been made in the past years but a comprehensive multiscale model of boundary lubrication considering tribochemistry phenomena in order to predict friction and wear of the system is still lacking.

Aims and objectives

Although there are some works in the literature which gave new insights into modelling of boundary lubrication, the consideration of some necessary parameters were still lacking. In this project, the main aim was to initiate a comprehensive modelling framework to consider tribofilm formation, removal and mechanical properties into the deterministic contact mechanics simulations in order to predict wear in the boundary lubrication regime. The main components of the developed modelling framework are listed as follows:

  • A flexible contact mechanics simulation to consider the elastic-perfectly plastic contact of rough surfaces in boundary lubrication 
  • A tribofilm growth model that considers both formation and removal concepts of the tribofilm
  • A new modification to Archard’s wear equation employing a spatially resolved coefficient of wear that considers the effect of antiwear additive in reducing the wear in the boundary lubrication. 

Methodology

In this project, a flexible contact mechanics model is developed which considers the elastic-perfectly plastic contact of rough surfaces. The contact mechanics model is based on the complementary potential energy approach and incorporates a Fast Fourier Transform (FFT) for numerical efficiency. A growth model for the tribofilm is developed which considers both formation and removal of the tribofilm based on the thermodynamics of non-equilibrium processes. The formation part of the tribofilm is based on the kinetics of the tribochemical reactions and the removal part is a phenomenological mathematical model to capture the behaviour. The local properties of the contact calculated by the contact mechanics model will be implemented into the tribochemical model to predict the growth of the tribofilm. A wear model is also proposed which can modify the local wear properties of the asperities. The wear model accounts for the effect of tribofilm in reducing wear and modifies the Archard wear equation.

Main contribution of Project 2 to the ENTICE project

-          Development of the numerical framework for contact of rough surfaces

-          Development of mathematical models for tribochemistry phenomena

-          Prediction of wear in boundary lubrication

-          Prediction of surface topography evolution

-          Linking experimental test rigs to the microscopic numerical simulations 

 

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Research Partners

University of Leeds Ecole Centrale LyonUniversity of Ljubljana Mercedes-Benz Act Research Total SKF 


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