Development of Laboratory Test Methodology for the accurate simulation of Engine Tribochemistry (P10)
The aim of this research is to develop well-designed laboratory test methodologies that should quickly rank candidate materials, surface coatings, and lubricant chemistries with their relative performance in IC engines. This will involve the development of tribological/tribochemistry roadmaps by making tests harsher while maintaining the fundamental mechanisms corresponding to the components in actual operating conditions.
This research endeavour is necessitated by the current trend in lubricant technology which is geared at minimising exhaust emissions and improving wear/friction on interacting surfaces. Tribometers and Model test rigs such as the Single Cam Rig will be employed for the study to ascertain the operating parameters (e.g. temperature, contact stress, speed, and lubricant additives) which significantly affect the Engine tribochemistry. Surface analytical techniques such as RAMAN/FTIR spectroscopy, TEM, SEM/EDX, and XPS will be used for the characterisation and comparisms of the tribofilms formed on material surfaces. Similarities and/or differences between both experimental setups will be established to give a better understanding of the tribochemistry process.
1. BSc Mechanical Engineering at Obafemi Awolowo University, Ile-Ife, Nigeria (2008)
2. MSc Oilfield Corrosion Engineering, University of Leeds, UK (2012)
Institute of Engineering, Thermo fluids, Surface and Interfaces
Mechanical Engineering Department
University of Leeds
For more information contact MacDonald;
Supervisors: Prof Anne Neville and Dr. Ardian Morina.
Monthly reports are available here
Development of laboratory methodology for the simulation of valve train tribochemistry
My PhD thesis is in the field of tribology. It is principally an experimental study of lubrication friction and wear in the cam/follower system of an internal combustion engine. The study has involved the development of a new experimental facility which enables an accurate measurement of the frictional torque as a function of the cam angle. The study involves coupling the results from the experimental rig (in terms of frictional torque and wear) with advanced surface analysis measurements which are made post-test.
The single cam rig allows the investigation of torque, load and film composition across the camlobes/nose and correlating this to the wear of the systems. It looks at the effects of hard DLC coating on the follower and the consequencies these can have on the uncoated camlobes. A somewhat non-economical approach of coating both the cam and the follower was also investigate to observe if the unique coating features of low running-in, improved wear and friction will be achieved for valve train systems. Certain hard coating were not able to withstand the high pressure in the valve train system and hardness of the coating was not seen to be a prerequisite for better wear performance.
The newly developed facility also has the capability to evaluate the friction and wear performances between lubricants with close chemistries. Two commercially developed lubricants (from TOTAL) were investigated and their characteristics in preventing wear and friction were evaluated. This is achieved by an understanding of the composition, dispersion and mechanical properties of the tribofilms which were derived during the rubbing action of the surfaces. It was observed that the film dispersion has a significant role to play in the prevention of wear in a valve train system. This characteristic of film dispersion is strongly controlled by the detergent and dispersants which are used in the formulation of the lubricants.
The study also involves comparative test with reciprocating tribometers. Tests were performed on pin on plate reciprocating plate tribometer to compare the tribofilm between a purely sliding system and the films on the cam nose – which is also in a predominantly sliding regime. Insert samples from the rig were sectioned and used on the reciprocating tribometer to eliminate any material variability and give a basis for comparison.
As per tribochemistry investigation, the steel/Ferrous surfaces were observed to interact with the coating. Similar tribofilms were observed with ferrous surfaces on both systems but the pure sliding surface appeared more adherent, thick and well dispersed.
However, same cannot be said for the DLC coatings It is however ideal for the coatings to interact with the oil not just for friction and wear reduction but for coating survival as well. A threshold between hardness and coating interaction with the oil is envisaged for optimum performance of valve train systems.