2021 Timoshenko Medal Acceptance Speech

Thank you, Pradeep!First, my hearty congratulations to all the other awardees tonight!I can’t express how thrilled and how excited I am to receive the Timoshenko Medal! I wish to thank everyone involved in the nomination process and the Timoshenko Medal Committee for selecting me for this award. At times like this, my traditional Chinese upbringing would urge me to be so modest that I should politely and humbly decline the medal at least three times before accepting it. But, having lived in America for over 30 years, I am just going to simply say “thank you!” I accept it on behalf of all of my students, postdocs, and collaborators, whose work with me is being recognized here.Prof. Stephen Timoshenko was widely regarded as “the father of applied mechanics” in the United States, and Timoshenko Medal is considered the highest honor of our field. I am most humbled to join the list of prior Timoshenko Medalists who are all highly accomplished members of our community, including many of the legendary figures including Timoshenko himself and many of my mentors and role models who have deeply influenced my career.A year ago, Mary Boyce, the first woman Timoshenko Medalist, started the new tradition of “virtual Timoshenko Medalists”. Today I am very glad to stand with Mary as the second “virtual Timoshenko Medalist.” Mary was also the first recipient of the Applied Mechanics Young Investigator Award in 1998, which later became the Tom Hughes Young Investigator Award. I followed her as the second Young Investigator Awardee in 1999. Today, exactly 22 years later, I am proud to follow Mary in receiving the Timoshenko Medal.From the list of past recipients, I found I am the third Chinese to be awarded the Timoshenko Medal. Prof. C.-C. Lin (林家翘), an applied mathematician and Institute Professor at MIT working in fluid dynamics, a PhD student of von Karman from Caltech, was the first Chinese Timoshenko Medalist in 1975, and Prof. Y.C. Fung (冯元桢), widely credited as the father of biomechanics, became the second in 1991. What an honor for me to join these two legendary Chinese Timoshenko Medalists! I can’t help but observe both Prof. C.C. Lin and Prof. Y.C. Fung received their PhD from Caltech, and as a Harvard graduate, I am now able to add some diversity to this subgroup.When I received the award letter from ASME at the beginning of May this year, one of my colleagues at Nanyang Technological University (NTU) made the observation that this would be the first time Timoshenko Medal has left North America and Europe. As the first person to accept it from an Asian university, I am also pleased to be able to contribute to the geographical diversity of the Medal.Although I have never met Prof. Stephen Timoshenko, I feel connected to him in several ways and owed much to him for my career. Timoshenko grew up in a village in Ukraine, and I spent most of my childhood in countryside in Sichuan, the spicy province of China. Timoshenko had an early ambition to become a railway engineer and pursued his undergraduate study in a college called “the Institute of Engineers of Ways of Communication” at St Petersburg, a place dedicated to the training of “transportation engineers.” The university I attended is called Xi’an Jiaotong University, where the word “Jiaotong” means transportation, and thus, my university can be literally translated as a “university of ways of communication.” It was Timoshenko’s books that inspired me to pursue a career in applied mechanics. I started my academic career in the Division of Applied Mechanics at Stanford, later renamed as Division of Mechanics and Computation, a faculty group founded by Timoshenko in the 1930s. At Stanford, the name Timoshenko was so central to all of our activities that the common room we used for discussions, meetings, seminars, parties, and many other events was called the Timoshenko Room. Timoshenko had also left an endowment called Timoshenko Fund that was and is still being used for many vital programs in applied mechanics at Stanford, including the Timoshenko Visiting Professor and Timoshenko Distinguished Postdoctoral Fellowship.I was born in Chengdu, a city in the middle of China with a population of 16 million people, but considered to be only a medium-sized city in the country! My father worked as an electrical engineer in a research institute that was relocated to a rural and mountainous region for fear of a Soviet nuclear strike in the late 1960s, and thus, I spent most of my childhood in the countryside. Even though my academic strength had been with math and physics, my father encouraged me to study something more practical. When I applied for college in 1978, Xi’an Jiaotong University, a top-tier engineering school half-a-day train ride away in the neighboring province of Shaanxi, with the mission of “learning practical skills, developing industries” seemed particularly appealing. The University was originally established in Shanghai in 1896 to promote engineering education and industrialization of the country after China failed in the Sino-Japanese War of 1895. When I entered college in the Fall of 1978, China had just come out of the cultural revolution and started the process of 改革, 开放, which means reform and opening its door to the world. The whole country was booming with energy and optimism, and we university students were full of enthusiasm and thirst for knowledge. Unlike the liberal arts education in the west, students in China usually submit a wish list of their desired universities and majors according to their grades in a nationwide university entrance exam. They would then be admitted to one of the universities on their wish list and assigned to a class in a particular department. I was admitted to the class of “Applied Mechanics,” which consisted of 35 men and only one woman, which was not atypical of undergraduate mechanics classes at the time.In my final year in college, I took an elective course on fracture mechanics from Prof. Lu Yizhong (陆毅中), who had joined our department two years ago after receiving his PhD from Lehigh University. I found the subject very interesting and was especially fascinated by a story told in the class that China had bought a few airplanes from the United States. After the airplanes were delivered, the Chinese engineers discovered some small cracks. However, the American engineers told them that those cracks were safe according to this new field of fracture mechanics. Since the Chinese engineers did not know anything about fracture mechanics, they had to accept the airplanes, but after that incident, the government regarded sending some students to the United States to learn the subject as a top national priority. Upon graduation, I made up my mind to go to United States to study fracture mechanics. Prof. Lu and my other teachers, including Prof. Ji Xing (稽醒) and Prof. Jiang Yongqiu (蒋咏秋), inspired me to go to Harvard where Prof. Jim Rice and Prof. John Hutchinson, two former Lehigh graduates, had built a powerhouse in fracture mechanics. My teachers also helped arrange a World Bank graduate scholarship for me so I didn’t have to compete for the first-year PhD fellowship at Harvard.When I arrived at Harvard as a fresh PhD student in the fall of 1983, I knew right away I had landed in a gold mine for mechanics. I had great teachers including Jim Rice, John Hutchinson, Bernie Budiansky, Lyell Sanders, George Carrier, Franz Spaepen, and Fred Abernathy. John Hutchinson was my academic advisor during the first year. John gave me a lot of help on course selection while adapting to the new culture and life in the United States. At the end of my first year, John helped arrange a second-year graduate fellowship for me, which was very rare because most students by then would already have found a PhD advisor and started working as RAs. This gave me a whole year of extra time taking additional courses and exploring different research projects, before Jim Rice took me on as a PhD student in the summer of 1985. Jim then taught me how to do research, as well as how to expand my knowledge from mechanics to Materials Science, Applied Math, Applied Physics, and Geological Sciences. Jim had the vision that there will be plenty of opportunities at the cross-disciplinary boundaries between mechanics and other disciplines. With Jim as my advisor, I had a golden key to learn world-class research and jumpstart my career.At Harvard, I had the great fortune to study together with an international group of highly talented students including Yonggang Huang, Zhigang Suo, and Pedro Ponte Castaneda. Yonggang and I became very close friends, and we later started a decade-long research collaboration. Zhigang and I came from the same undergraduate school in Xi’an. Pedro and I now work together as fellow editors for JMPS.Being Jim Rice’s student helped me land my first academic job as an Assistant Professor at Stanford right after graduation. At Stanford, I was humbled to become a colleague with many famous researchers including David Barnett, George Herrmann, Tom Hughes (now at UT Austin), Tom Kane, Joe Keller, Bill Nix, John Spriter, Chuck Steele, Andrew Stuart (now at Caltech), and Juan Simo. At the beginning of my Stanford time, I was still indulged in doing research related to my PhD work. It was largely through the mentoring and guidance of Bill Nix, a giant in material science, that I was able to quickly venture into other topics such as thin-film mechanics and mechanics of indentation size effects. Bill’s amazing ability to break down a seemingly very complex problem into a simple mathematical model using shear physical insights really opened my eyes and fundamentally influenced my approach to science ever since. At Stanford, I also started to collaborate with Yonggang on mechanism-based strain gradient plasticity based on Bill Nix’s experiments on the indentation size effect. Yonggang and I visited each other frequently, each time from a few days to a week. Our collaboration was so intense that I often needed to catch sleep after he left. What an exciting time that was!In 1998, I took a sabbatical leave at the Max Planck Institute for Metals Research as a Humboldt Fellow. My host, Prof. Dr. Eduard Arzt, whom I met in Bill Nix’s office 10 years before, came to me one day and asked me if I would be interested in becoming one of the directors at that institute. Max Planck Society has long been a research powerhouse in Germany and historically had such legendary figures including Max Planck himself and Albert Einstein among its directors. And I was especially interested in the new research direction of Eduard in biological materials. At the time, my interactions with Eduard had mostly been in thin-film mechanics, and he had the vision that there are plenty of new research opportunities at the intersection between mechanics, materials science and biology. I was easily sold on this vision and off I went to the Max Planck Institute on the first day of the new millennium. I had the most productive 5 and a half years of my career at Max Planck. If citation means anything, 6 out of my 10 most cited papers were written during my 5-year-period at Max Planck. I had great colleagues including Eduard Arzt, Helmut Dosch, Manfred Ruehler, Joachim Spatz, and Peter Gumbsch; a great team of students (including Markus Buehler who is also receiving an award tonight), postdocs and visitors, most of whom later became faculty members; and great research topics like mechanics of gecko adhesion, mechanics of receptor-mediated endocytosis, mechanics of nano- and hierarchical structures of biological materials, and mechanics of bionanomaterials such as DNA-CNT assembly. And best of all, all these research projects were supported by the Max Planck Society without me writing a single research proposal! During my 5 and a half years at Max Planck, I only submitted one research proposal to DFG (the German version of NSF), mostly out of my own curiosity, and the proposal was funded! Needless to say, Max Planck Institute really felt like a paradise for fundamental research.My next stop was Brown University. Brown has always had a special place in my heart. Most colleagues I knew in our field had some direct or indirect connections to Brown. When Prof. Ben Freund and Prof. Clyde Briant, then Dean of Engineering at Brown, called me at the beginning of 2005 and asked if I would be interested in a faculty position at Brown, I immediately said yes, went for an interview 2 weeks later, and accepted the job essentially on the spot. I was so proud to join Brown’s solid mechanics faculty group with colleagues including Ben Freund, Rod Clifton, Alan Needleman, Kyung-Suk Kim, Bill Curtin, Pradeep Guduru, Vivek Shenoy, Allan Brower, Janet Blume, Tom Powers and later Christian Franck, David Henann, Haneesh Kesari and Yuri Bazilevs. At Brown, I also found great colleagues in other fields to work with, including Brian Sheldon, Sharvan Kumar, and Nitin Padture from Materials Science, Bob Hurt from Chemical Engineering, and Agnes Kane from Medical School. I enjoyed my next 14 happiest and most fruitful years in the family-like academic environment at Brown!In the summer of 2018, we invited Subra Suresh, a distinguished member of Brown’s extended family, to deliver the inaugural speech for the opening of Brown’s new engineering research building. At the time, Subra had just become the President of NTU in Singapore and was implementing a series of reforms and target hires that aim to further raise the international reputation of the university. I had previously visited the National University of Singapore several times and held a 5-year visiting professor position with the Institute of High Performance Computing (IHPC) in Singapore. But my impression of NTU was relatively vague. During the conversation with Subra, I learned that NTU had become a major research university within a short time period and in fact was considered the world’s best young university. Just as I was becoming quite interested in Subra’s vision, I got a phone call from my long-time friend Ares Rosakis from Caltech that Subra had appointed him as the Chair of a University Search Committee at NTU. Well, one thing led to the other, a year later, I joined NTU as a Distinguished University Professor and was happy to meet many new colleagues as well as a few familiar faces including Prof. Jimmy Hsia who had joined NTU as the Dean of Graduate Study a year before me and Prof. Yongwei Zhang whom I had worked with during my previous visiting appointment at IHPC. I was excited to get involved in a number of research initiatives at NTU such as mechanically adaptive materials, hydrogen tolerant structural materials, and novel drug delivery systems.Today, the field of applied mechanics continues to boom as generations of bright young mechanicians bravely march into new fields and open up new horizons. There are so many exciting developments and new ideas at the boundaries between mechanics, materials, energy, chemistry, physics, biology, medicine, robotics, and artificial intelligence. It seems that we are still right in the middle of an age of multidisciplinary research to address grand challenges such as climate change, pandemics, aging populations, and infrastructure. While our community is actively embracing all these opportunities, I would like to echo advice from Prof. Ben Freund, a former Timoshenko Medalist, who said in his Timoshenko Medal Speech, “It is important that we, as custodians of the discipline, sustain its core structure … this means having a significant number of strong, vibrant graduate programs that offer comprehensive educations spanning theory, computation and experiment.” Indeed, at the time of celebrating the past accomplishments of our colleagues and paying tribute to Prof. Stephen Timoshenko, it is important to remember how we were attracted to the field of applied mechanics ourselves and nurtured by our seniors, and do our own share in making sure that we continue to offer a solid graduate education in applied mechanics, nurturing young colleagues in our field, encouraging them to explore exciting new ideas and new fields, giving them timely recognitions, and having their talents be fully utilized. After all, the vitality of applied mechanics rests on people in our field, as in the saying “mechanics is what mechanicians do.”Throughout my career, I have benefited from collaborations and interactions with so many colleagues and friends that I could not possibly mention all of their names here. Apart from those I already mentioned, I would like to also acknowledge Prof. John Willis from Cambridge University, Prof. K.C. Hwang (黄克智) from Tsinghua University, Prof. Zdenek Bazant from Northwestern University and Dr. Farid Abraham from IBM Almaden Research Center. I would like to express my infinite gratitude to everyone, including all of my colleagues, friends, my family (my wife Joan and son Jonathan), who have guided, supported, and helped me during this journey.Thank you for listening to me, and thanks again for awarding me the Timoshenko Medal.