Faculty of Engineering


Know, control, and use material defects

In this edition of “Tell Us Teacher,” we spoke with Ryosuke Matsumoto, Associate Professor of the Department of Mechanical and Electrical Systems Engineering at the Faculty of Engineering, who specializes in “computational solid mechanics,” a field that uses calculations to derive the strength of materials such as iron and magnesium.

Q:Did you like science from a young age?

That’s right. I liked science from the time I was in elementary school. In high school, I was particularly fascinated by physics, and my love of cars led me to often tinker with machines. So, it was quite natural for me to pursue a career in science.
When I entered university, many of my classmates chose to study robotic, which was popular at the time, but my love of mechanics led me into the world of physics and the field of “solid mechanics”. My teacher was a witty man who, upon entering the classroom, would write out a difficult problem on the blackboard and say something like, “It would be rude of me to only teach you things that a university student could understand.”

Q:What is “solid mechanics”?

Solid mechanics” is a field that deals with the deformation of solids. In the second year of college, students in departments that concern machinery, including our university, are required to take a course called Mechanics of Materials. While mechanics of materials mainly deals with the deformation of rod-like components, solid mechanics covers the deformation of all solids. On the other hand, there is a field called “computational mechanics,” which involves developing methods to solve mechanical phenomena using computers and using those methods to solve real problems. All of that is done using computer simulations. In my case, when I was assigned to a laboratory in my fourth year of university, I chose to work in the “Computational Solid Mechanics” laboratory, which deals with the deformation of various solids using computer simulations, and I have been moving from one laboratory to another in this field ever since.

I think that many people have probably seen a car crash simulation. In my research, I deal with the deformation of metals, especially on a very small scale, such as on the atomic level. When choosing a laboratory, I visited the “Computational Solid Mechanics” laboratory and found it interesting to learn that there was a field where supercomputers could be used to predict the behavior of unknown materials using only calculations. I remember I was the only one who applied to the Computational Solid Mechanics lab as my first choice, as the most popular labs among students then and now were in the fields of robotics and information.

Q:Please tell us about the research you are currently doing.

My approach has not changed since I was a student: mainly atomic-level simulations, microscopic electron-level calculations using first-principles calculations, and more macroscopic simulation methods, sometimes in combination, to solve various solid mechanics problems. However, the target materials and phenomena have changed. Currently, I am mainly working on “Hydrogen embrittlement” and “Deformation behavior of magnesium alloys”. In this field, computer performance and the use of new computational theories are also important. There are some problems that I once walked away from but am now trying again with the latest computers and theories.

Q:What is “hydrogen embrittlement”?

It has been known for a long time that the strength of metals is greatly degraded when hydrogen enters them during the manufacturing process or in their operating environment. This problem is called the “hydrogen embrittlement problem”. The research on hydrogen embrittlement started with a New Energy and Industrial Technology Development Organization (NEDO) project in which a professor from my laboratory participated when I was invited to Kyoto University from the Kyushu Institute of Technology in 2006. To achieve sustainable development goals, fuel cell vehicles and devices are being developed around the world. As a result, there are concerns about the increase in the number of fracture accidents caused by hydrogen embrittlement, and a major research objective has been to thoroughly elucidate the causes of hydrogen embrittlement so that it can be used for material development and design.

When I started my research, I realized that the problem of hydrogen embrittlement is very difficult and that there are many unknowns. Since then, I have continued to work on research projects funded by Grants-in-Aid for Scientific Research from the Japanese government, and I believe that my role is to unravel the effects of hydrogen one by one from a microscopic perspective.

Q:What kind of research will be done on the other side, the deformation behavior of magnesium alloys?

I started working on research on the deformation behavior of magnesium alloys when I participated in a large project (New Science Field Research) funded by a Grant-in-Aid for Scientific Research from 2011 to 2015. I had never been involved in magnesium research before, but my experience in conducting analyses using atomic simulations was recognized, and I guess I got the nod. Lightness is an extremely important factor in transportation machinery and portable devices. Magnesium is the lightest practical structural metal and is abundant as a natural resource, but it experiences difficulties in terms of strength, workability, high-temperature strength, and corrosion resistance. However, the development of LPSO-type magnesium alloys in Japan around the year 2000 changed the situation completely. Again, my role is to clarify why LPSO-type magnesium alloys have excellent properties and what approaches can be taken to further improve their performance.


Q:What is your motto in research?

The theme of my laboratory is “Knowing, Controlling, and Using Defects”. Metals usually have a crystalline structure. When you hear the word “crystal,” you may imagine that the atoms are lined up in an orderly fashion without any disorder at all. In reality, materials contain countless structures with disordered atomic arrangements, which are called “lattice defects”. Defects in a material are not necessarily weak points, but rather defects that give the material its tenacious properties and strengthen it. All of my research is based on investigating the response of these lattice defects. After 20 years of watching lattice defects move on a screen, I feel as if I understand how they work.

As for my research on magnesium alloys, I have been participating in the CREST (Core Research for Evolutional Science and Technology) project at JST (Japan Science and Technology Agency) as a main researcher since November 2020.

Q:In the future, how do you hope to contribute to society through your research?

There should be no risk to human life due to unexpected damage to machinery or structures. Even in cases where structural failures do not result in the loss of life, such failures always have some degree of economic consequence. Everyone knows that when a large force is applied to a part, it will break, but there are many unknowns about what happens in that process and how the conditions for breaking are determined. In addition, new materials with higher performance are being developed one after another to meet the demand for use in unprecedentedly harsh environments.

The key to developing better materials is to know what is going on inside of them, and to predict and verify hypotheses about the behavior of new materials that have not been used much, or how they will behave in an uncharted operating environment. I would like to contribute to the accumulation of this basic knowledge through computational science, especially electronic and atomic-level simulations, and to contribute to the development of steel materials that are superior in resistance to hydrogen.

Q:Please tell us about your personal life. What are your hobbies and interests, and what were you into during college?

My hobbies are fishing and bicycling. When I was in junior high school, I started going to the nearby ocean by myself to fish. I like both catching and eating fish, so I would go all the time. My father was a fish auctioneer, and I was taught that properly cleaning and eating the fish you have killed is a form of Buddhist “devotion” that honors the life of those fish.

As for bicycling, my wife started to take me out for weekend cycling together when I started gaining a lot of weight after we got married. In 2014, we participated in the All Japan Championships as a couple. Even though dieting was my motivation, I have been able to get to know many people through cycling. I hope to continue to ride from time to time when the opportunity arises.

Q:Before we say goodbye, do you have a message for your students?

First of all, I want you to have a clear idea of what you want to do. If you don’t have a clear idea yet, try all sorts of things. Then, after thinking and struggling, I would like them to focus on and pursue what they think they want to do. I often hear people say, “My parents told me to do it,” or “My uncle recommended it,” but it is difficult to be passionate about something if that is your reason for choosing it. That’s why I would like my students to choose their own path in life, and what they will study at university, according to their own will.

Learn more about Dr. Ryosuke Matsumoto