20 Minutes With Michael Burkinshaw
Rachel Fowler, Associate Editor | TLT 20 Minutes July 2015
This senior tribologist discusses surface engineering, turbochargers and the best ways to evaluate a tribosystem.
MICHAEL BURKINSHAW - The Quick File
Dr. Michael Burkinshaw is senior tribologist at Cummins Turbo Technologies where he is responsible for research and development conducted in the topic areas of tribology and surface engineering. Michael and his team’s current work is concentrated on developing innovative solutions to meet future engineering challenges within the turbomachinery industry, specifically materials and surface engineering to improve product durability, optimize frictional response and minimize product cost.
Michael holds a bachelor’s degree in mechanical engineering and a doctorate in tribology, both from The University of Leeds in the U.K. Michael has published a number of technical papers and delivers presentations at relevant technical events throughout the world.
Michael is a member of the IMechE Tribology Committee and responsible for Materials Engineering Functional Excellence for Tribology throughout Cummins.
Dr. Michael Burkinshaw
TLT: How did you become interested in tribology?
Burkinshaw: I first became interested in tribology when studying for my undergraduate degree in mechanical engineering at The University of Leeds in the U.K. After attending a tribology course at the university run by Prof. Ardian Morina, I became fascinated with the way surfaces interact at the submicron scale. Indeed, I began to appreciate the behavior of surfaces and how this influenced the frictional response and wear resistance of interacting substrates.
The more I learned about tribology, the more interested I became. I conducted my first tribology project as part of my undergraduate degree on the topic of how tribological mechanisms observed in the human knee joint could be applied to a polymer bearing/steel shaft tribosystem. This was my first experience with the various tribological experimental and analysis equipment.
TLT: What experiences have you had that have driven your career and passion toward tribology?
Burkinshaw: Toward the end of my undergraduate degree, I was approached by professor Anne Neville at the University of Leeds who asked if I would like to study for a Ph.D. in the field of tribology. The aim was to understand the methods by which a novel antiwear additive interacted within the aluminium-silicon cylinder liner/steel piston ring tribosystem. As a result of the fascinating experience I had during my undergraduate degree, I had no hesitation in accepting this opportunity to research further.
Throughout my Ph.D., I had many experiences that made me passionate about tribology, from the use of cutting-edge innovative methods to analyzing surfaces to the opportunities to present to world-renowned experts in the field. I realized early into my doctorate, however, that surface interactions were my main interest and still are to this day.
My Ph.D. afforded me the ability to learn a number of different technical processes, statistical analysis methodologies and project planning techniques, for which I will always be grateful. I also learned the art of perseverance as ring on liner experiments were particularly frustrating. As any engineer or scientist can affirm, the
eureka moment is the most rewarding part of any scientific study.
Upon graduation, I joined Cummins Turbo Technologies where I have continued to develop my knowledge of tribology and surface engineering. This has furthered my passion for tribology, since I have the opportunity on a daily basis to develop the tribological performance of real-world products and improve the technical proficiency of the organization.
TLT: Are there any technical advances you believe are particularly important within the field of tribology?
Burkinshaw: In order to further our understanding of the fundamental tribological performance of materials and surface treatments, I believe that there are two key areas that need to be focused upon.
First, there must be further development of
in situ high-resolution, high-magnification techniques for characterizing the surface interactions and tribochemistry within tribosystems. There have been numerous developments within this area, most notably using optical techniques to determine film thickness and AFM-based methodologies to study nanoscale tribological behavior. But further research is required to generate more comprehensive, multidisciplinary techniques. It would be particularly interesting to apply such technology to high-temperature tribology since there is little observed
in situ behavior of oxides and glazes when experiencing wear.
Second, the vast majority of tribological testing is conducted within laboratories using idealized test components. The benefits of this approach have been well-documented, but unless correlation to real-world tribological performance is generated, it is difficult to conclude upon the resultant impact on the tribosystem under evaluation. This is because tribology is a cross-functional subject and numerous external influences can affect the friction and wear behavior of a specific interface. From experience, I have learned that it is extremely important to correlate friction and wear performance across testing platforms, as lab-based testing cannot replicate the entirety of a specific tribosystem. Furthermore, depending on the skill of the replicator, the results can vary significantly. I therefore suggest that, where possible, researchers use lab-based, component-based and final product testing in tandem, in order to conclude upon the tribological performance of a specific tribosystem.
TLT: How important is tribology to a turbocharger?
Burkinshaw: The frictional response and wear performance of numerous tribosystems are critical to the correct function of a turbocharger. Some of these tribosystems are lubricated and have operating temperatures less than 150 C, whereas others are not lubricated and operate at temperatures up to 800 C. An example of the former would be the bearing system, whereas the latter includes the variable geometry and wastegate systems.
It is vital, therefore, to determine the tribological behavior of the various interfaces within a turbomachine, in order to generate a product that is both robust and reliable.
TLT: What test methods do you use to evaluate the tribological performance of materials intended for use within a turbocharger?
Burkinshaw: As a result of the multitude of tribosystems and operating environments observed within a turbocharger, numerous test methodologies are employed when characterizing the tribological performance of materials intended for use within a turbocharger.
However, in order to simplify the process, significant effort has been placed into ensuring that no matter the test methodology, a defined and documented five-step process is followed when evaluating new material combinations. Such can be observed in Figure 1. Included within this process are steps to define the tribosystem and characterize the materials under evaluation prior to tribological testing on various turbocharger-level platforms, namely gas stand or engine system.
Figure 1. Cummins Turbo Technologies tribological test and analysis process.
Laboratory-based tribological testing is conducted using a range of tribometers, located at various worldwide locations, which have been developed in combination with specific turbocharger applications. Such equipment is used to evaluate the friction and wear performance of materials and surface treatments according to tests that have been developed to replicate particular tribosystems with the turbocharger. All relevant tribological interfaces and the majority of their associated operating environments can be replicated. Analysis of test samples is comprehensive in order to determine the fundamental behavior of the substrates. Indeed, numerous techniques are employed to characterize the topography, surface chemistry and wear type on worn samples.
Within academic research, it would be at this stage when the tribological performance of materials would be concluded. However, tribometer-based testing is well-known to neglect particular variables experienced by a real-world application. Therefore, turbocharger-level testing is conducted—on gas stand and on an engine system—in order to ensure that the friction and wear behavior has translated from laboratory to the real world. Subsequently, performance information and other relevant test data is sent to the tribology laboratory in order to improve correlation and therefore, where possible, afford mitigation of future turbocharger-based experimentation.
TLT: What advances in turbocharger tribology do you picture in the next five years?
Burkinshaw: Two main requirements within the industry are to improve product durability and reduce product cost. Therefore, when relating this requirement to tribology, there are key turbocharger tribology developments that will need to be introduced in the next five years.
Namely, greater levels of analysis-led design will be developed in order to understand the fundamental friction and wear behavior of materials and tribosystems. This will involve the development of novel tools that will model tribological behavior and improve correlation between tribometer-based and turbocharger-based experiments. Subsequently, this approach will result in greater technical proficiency, ultimately improving product durability and decreasing testing costs.
In addition, surface-treated, lower-cost base materials will be developed, which afford at least transparent tribological performance when compared to significantly more expensive exotic materials. This will ensure that product cost is minimized, and—when used in combination with other technological advances—will create more durable products.
TLT: Do you think that the principles of tribology are understood sufficiently throughout relevant industries?
Burkinshaw: Not really. Peter Jost’s revolutionary document from 1966 regarding tribology is still pertinent. Indeed, even though significant improvement has been made since the aforementioned article was published, in some relevant industries, tribology is still not understood to the appropriate level. A greater focus on education and research into the topic should be implemented so that the benefits of the correct application of tribology are experienced by such industries.
TLT: What trends have you observed and do you picture for industry-based tribology testing?
Burkinshaw: Due to the previously discussed industry trends, I have witnessed and expect to observe further research into the analysis-led design aspect of tribological testing. This will afford the negation of expensive and unnecessary system-level experiments, while maximizing technical knowledge and efficiency.
You can reach Michael Burkinshaw at michael.burkinshaw@cummins.com.