Yip-Wah Chung Reflects on Storied Career
Chung, who joined Northwestern in 1977, is retiring having made a significant impact on tribology and other fields
In the 1970s, tribology was mainly a mechanical engineering discipline focused on contact stresses and lubricant film thickness under varying loads and speeds. With growing computing power, researchers began modeling complex contact geometries and using molecular dynamics simulations. Zinc dialkyl-dithiophosphate (ZDDP) was widely used to reduce wear, though its mechanism remained unclear. Interest in surface science grew, and studies emphasized tribology’s economic importance, prompting the US National Science Foundation to establish a dedicated tribology research program.
By the 2000s, tribology had become a multidisciplinary field spanning materials science, physics, and chemistry. Industry-university collaboration became the norm, though this blurred traditional disciplinary lines. The NSF eventually dissolved its dedicated tribology program, instead funding tribology research through broader areas like materials, chemistry, and surface engineering — encouraging interdisciplinary exploration.
Today, advanced testing tools and computational resources are widely available, enabling nanoscale research that was once unimaginable. Without much fanfare, the magnetic storage community quietly achieved major nanotribological advances before the term existed, increasing magnetic storage density by 10,000 times compared with the early 1990’s.
Northwestern Engineering’s Yip-Wah Chung has seen all of that happen.
Chung, who joined Northwestern in 1977, is retiring having made a significant impact on tribology and other fields. In this Q&A, Chung looks back on his accomplishments, what’s coming next for tribology, and more.
Where do you expect the field of tribology to go in the next five years?
As the baseball legend Yogi Berra famously said, “It’s tough to make predictions, especially about the future.” With that caveat, I will venture to make some extrapolations. Tribologists are tasked with solving problems in engineering systems, often under various constraints. Addressing these issues goes beyond mere firefighting. For instance, if threads are being stripped from a jackscrew during service, a tribologist should immediately recognize that either the alloy chosen for the jackscrew is inappropriate, the applied stress exceeds specifications, or lubrication is inadequate. This requires a multidisciplinary knowledge base and analytical skills to understand the problem and, more importantly, to develop solutions that prevent it from recurring.
As we strive for better performance under more extreme conditions, engineering systems face unprecedented challenges. Solutions to these challenges cannot be found simply by consulting a handbook, database, or software. The best steels or coatings to use, the most appropriate surface treatments, or optimal lubricant packages may have to be invented. We will often be operating in uncharted territories. Drawing expertise from multiple disciplines is crucial, giving us the confidence to “boldly go where no one has gone before.”
How can the field support a more sustainable future?
Sustainability is no longer just a buzzword; it is an all-hands-on-deck existential challenge. At the annual Society of Tribologists and Lubrication Engineers conferences over the past few years, sessions related to electric vehicles have been standing-room only. High voltages and large electromagnetic fields alter the wear resistance of materials and the lubrication characteristics of conventional lubricants. This exemplifies the uncharted territory we are navigating.
Another emerging challenge in the coming decade is bio-lubricants, such as vegetable oils, and biofuels, such as ethanol and biodiesel. While these are viable replacements for petroleum-derived products, they behave differently in drive- and power-train systems. For example, ethanol is more viscous and hydrophilic than gasoline, causing it to flow differently in the fuel system and potentially making the system more susceptible to corrosion. As we transition to carbon-neutral methods to produce these essential products, we need to develop new additives and tribological materials to operate in these new environments.
In what ways will AI and machine learning change the field going forward?
There has been a lot of buzz about machine learning and AI lately. A tribological interface involves materials in contact (often steels), lubricants and additives, contact stress, temperature, and sometimes electromagnetic fields. The complex interplay among these components, possible catalytic reactions, phase changes, evolution of surface topography, and introduction of third bodies due to wear makes ab initio prediction of tribological performance virtually impossible.
On a positive note, we have vast tribology databases derived from research studies over the past 50 years. In the coming years, I am confident that one or more groups will develop new design tools trained on these databases. Such tools may help us take the first steps in designing and developing complex mechanical components with robust performance. Indeed, my colleague, Professor Q. Jane Wang, and her team at the Center for Surface Engineering and Tribology are working along these lines.
Which moments from your career bring you the most pride?
Thanks to my former students, postdocs, and visiting scholars, I take pride in the discoveries and new materials developments achieved over nearly 50 years. These include unraveling the mechanism of strong metal-support interaction in heterogeneous catalysis, developing superlattice coatings with hardness rivaling that of diamond, inventing protective overcoats for computer disk drives, debunking myths, and discovering new alloys for various applications. However, there have been far more poignant moments along the way.
Years ago, I saw a bank commercial on TV where a father reminisced in a bittersweet moment at the end of a wedding reception. Flashbacks filled the screen: the birth of his daughter, her first time learning to bike, her first day of school, going to prom, heading off to college, and now getting married to her college sweetheart. In many ways, we as research advisers are given an amazing privilege and responsibility — to nurture a graduate student into an independent and responsible researcher and a contributing member of society. Every time one of my PhD students completes his or her thesis, I experience similar flashbacks as the father in that commercial. It fills me with pride and a bittersweet feeling as I wish the student could stay a bit longer, even though I know it’s time for him or her to move on.
It has been my privilege to work with so many talented students over the years, despite my own shortcomings as an adviser. After all, there is no manual for being a good father or a good adviser — we are all learning as we go along!
What impact has Northwestern’s culture of interdisciplinary collaboration had on your research?
I had the fortune to begin what eventually turned into lifelong collaborations with Professor Morrie Fine on environmental effects and the design of steels, and Professor Herbert Cheng on surface chemistry effects on friction and wear, within a few years of my arrival at Northwestern. Before my fateful encounters with them, I knew absolutely nothing about steels and tribology. These initial collaborations were followed by more joint research activities with colleagues in materials science and engineering, mechanical engineering, civil engineering, chemistry, and physics. Except for my first funded project, all my other research studies have been conducted with one or more colleagues, either at Northwestern or elsewhere. My research journey would not have been nearly as enjoyable without these interdisciplinary collaborations.
This is not surprising, as many of the research problems we have explored are intertwined and cannot be easily dissected into neat, standalone packages. The tight coupling among different components of these problems makes interdisciplinary collaboration and sharing of insights not just an option, but a standard operating procedure. This mindset extends beyond research; it is about fostering a culture of learning from one another, where colleagues, research group members, and staff treat one another with kindness and respect. It’s about exploring bold ideas together, celebrating each other's successes, and forming lifelong friendships. This culture is what binds us – it makes the department not just a place to work, but a place to belong. It truly is our home away from home! I feel deeply grateful and privileged to be part of this amazing family!