In-situ profilometry for transient testing of automotive materials

Start-stop technology is now widely available on mass-produced automotive vehicles. The engine is able to automatically stop when power is not required (at traffic lights, for example) and quickly start up again when the driver needs to move again. This is a useful technology that saves fuel and reduces exhaust emissions. However there are potential problems with the technology as vehicles get older. The engine needs to be running to generate the oil films that protect surfaces from wearing out. When the engine is stopped and then started again, the amount of friction and wear increases compared to when it is continuously running. This could be a problem as vehicles get older as they may wear out earlier than anticipated, causing environmental emissions and being expensive to replace. There is currently no test standard to compare how the surfaces of automotive materials behave when they are repeatedly stopped and started as little scientific work has been done in this area.

In this project we will build a sensor that will measure the extent to which surfaces are being damaged when they are stopped and started many times and compare it to how they behave when they run continuously. This is challenging as the surfaces are often covered in oil and difficult to measure, meaning people usually have to wait until the end of the test to measure them. They then have to perform many tests to try and find out the overall behaviour. This proves expensive and impractical, such that a continuous test is usually preferable.

We propose to develop a sensor that automatically measures how much wear was being generated in a single test, which will make it easier to compare how different materials in the engine behave under transient (start-stop) conditions.

To do this, we will build a profilometer based on a Hall effect sensor. This sensor uses a magnet to detect changes in height. We will use 3D printing to construct a flexure that integrates a very sharp diamond tip and the Hall effect probe into one assembly and then attach it to a 3-axis motor controller. This will allow us to scan surfaces quickly when they have stopped and measure how fast start-stop operation is wearing them out. It is challenging to measure oily surfaces, so we would develop new technology that will clean the surface using compressed air. If successful, this will allow us to measure the durability of existing materials that are subject to environmentally friendly start-stop operation. The test could then be used to look for new materials and coatings to ensure they would last the life-cycle of the vehicle and not become prematurely degraded, causing more emissions or engine repair costs. Ultimately, the project could be key to the way that future materials are chosen for our vehicles because the methodology simulates real engine driving conditions and would form part of automotive material testing standards.

Through this project we seek to create a novel in-situ profilometer for measuring the response of automotive cylinder liner surfaces to transient start-stop engine cycles.

This will be of benefit to the automotive sector to assess resilience of cylinder liner surfaces in vehicles that experience significant start-stop engine duty cycles in traffic heavy inner city routes. The project would enable the development of design criteria in this sector that would improve the quality of manufactured engines surfaces such that they don't degrade after many years of start-stop operation, benefiting consumers by retaining fuel efficiency and avoiding costly repair. The research has the potential to lead to a new category in engine test standards influencing policy in this area and would be achieved through existing collaborative research links with the Southwest Research Institute, Texas, USA.

The environmental benefits of understanding start-stop engine degradation will ensure current vehicles meet the existing Euro6 emissions standards later in the life-cycle and that future engines are prepared for likely even stricter future emissions targets. The work will enable progress in meeting future emissions targets, support achieving air quality goals and thus impacting health and the wider environment. The project will also give the UK a leading advantage in a globally competitive niche market of tribological test equipment by exploitation of the technology through project partners Phoenix Tribology, transforming the way dynamic in-situ measurement of wear are made across a range of sectors and applications. This will facilitate future research collaborations with surface engineers and lubricant chemists to design the next generation of powertrain surfaces for the vehicles of the future.