Emerging Materials Technology: Front Page
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Symposium Honors Accomplishments of Carlos Tomé
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By Lynne Robinson
Posted on:
9/1/2010 12:00:00 AM...
On muddy rugby fields in Argentina, Carlos Tomé experienced how being open to an opportunity could yield a big benefit—and even a win. The perseverance, teamwork, and resourcefulness that he displayed for 20 years with his rugby club are also hallmarks of the scientific accomplishments he is being recognized for at Polycrystal Modelling with Experimental Integration: A Symposium Honoring Carlos Tomé, to take place at the TMS 2011 Annual Meeting, February 27-March 3, San Diego.
“I have been lucky to be often in the right place at the right time, which has given me the opportunity to get acquainted and work with very bright researchers,” said Tomé, technical staff member at Los Alamos National Laboratory. “Each of them shared with me their knowledge, their passion, and their personal style of reasoning. This, plus the fact that I developed good friendships with most of them, has leveraged my scientific experience.”
Influential Collaborations
It was through early collaborations while a doctoral student at the National University of Rosario in Argentina that Tomé first began to appreciate the possibilities in materials science and engineering. “I was doing my dissertation on the subject of ‘irradiation produced defects.’ There was a small research group at the university doing experimental characterization of the mechanical response of metals and I thought that I could complement their research by providing them with theoretical and numerical support. As a consequence, I decided to focus my postdoctoral studies on crystal plasticity,” he said.
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(Click on image to enlarge.) Tomé delivering a lecture at a conference in Belgium.
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While pursuing research into the mechanical properties of crystals and polycrystals as a fellow of the National Research Council of Argentina, Tomé began working with two key mentors in his professional life—Fred Kocks, a now-retired fellow of Los Alamos National Laboratory, and Stuart MacEwen, Atomic Energy of Canada. “From Fred Kocks, I learned plasticity and to exert a critical view over my and others’ research conclusions” said Tomé, “and from Stuart MacEwen I learned to use experimental evidence as guidance for my theoretical work.”
Tomé has since specialized in the analysis and simulation of the constitutive behavior of low symmetry metals, such as magnesium, zirconium, and uranium, as well as geologic materials, such as olivine and calcite. “These materials deform via a complex combination of slip and twin modes and are characterized by a very anisotropic mechanical response,” said Tomé. “As a consequence, more sophisticated and mechanism-based models and techniques are required than the ones used for understanding cubic materials.”
This search for understanding led Tomé and his collaborators to develop sophisticated polycrystal modeling techniques and numerical codes that are now considered the gold standard of predictive tools for parameter identification, interpretation of experiments, and multiscale calculations.
“Carlos Tomé is one of the pioneers of the self-consistent method for the modelling of the plastic deformation of polycrystalline materials. More in particular, he has been the first to develop it for some of the materials which are of interest in the nuclear sector, namely zirconium,” said Paul Van Houtte, professor, Mechanical Metallurgy Section, Katholieke Universiteit Leuven, Belgium.
In describing Tomé as “the leading scientist worldwide in multi-level modelling of the plastic deformation of HCP metals,” Van Houtte also noted, “Carlos is not working alone. He has done remarkable scientific work with the help of a series of students whom he has put on the path of science. Most of them have become excellent researchers and several of them already enjoy high esteem at the international level. Guiding junior scientists towards such excellence is indeed one Carlos Tomé’s most important achievements.”
Scientific Generosity
One such scientist is Ricardo Lebensohn, researcher in the Materials Science and Technology Division of Los Alamos National Laboratory, and organizer of Tomé’s 2011 honorary symposium. Now a co-worker, Lebensohn was one of Tomé’s undergraduate students in Rosario. Later, Tomé became his Ph.D. thesis supervisor, as well as a colleague and collaborator on a number of projects.
“Along his career, Carlos has pioneered the theoretical and numerical development of physically based modelling of mechanical behavior of polycrystals, with emphasis on the role played by texture and microstructure on the anisotropic properties of engineering materials,” said Lebensohn. “His many contributions have been critical to establishing a strong connection between models and experiments, and to bridge different scales in pursuit of multiscale formulations with experimental integration.”
While a goal of the symposium is to recognize Tomé’s pioneering contributions to polycrystal modeling, Lebensohn observed that the robust number of abstract submissions from throughout the world indicates that the symposium is “a necessity for the TMS community and the broader mechanics of materials international community.”
“Since most materials are polycrystals, they exhibit significant directional properties related to the anisotropic behavior and the preferential orientations of the constituent single crystals. The development of fully anisotropic approaches—in which Carlos and his group in Los Alamos are major international players—is enabling revolutionary changes in the way simulations and interpretation of measurements on mechanical behavior of materials are performed,” Lebensohn said. “The interplay between microstructure and properties can now be explicitly considered through fully directional physically based laws, instead of the simplistic, purely phenomenological and isotropic relations employed in the past.”
Many of those who will be presenting and attending the symposium note that Tomé is admired as much for his generosity as his scientific accomplishments. Frédéric Barlat, professor at Pohang University of Science and Technology, Republic of Korea, recalled meeting Tomé at a conference and asking permission to use his viscoplastic self-consistent (VPSC) code. “Dr. Tomé is kind enough to give copies of his code to anyone who requests it,” said Barlat. “I worked with the VPSC code quite a bit, and during that time, Dr. Tomé helped me solve issues that I had with the code, while also giving me advice on my project. Although very busy, he was always getting back to my messages in a timely manner and with excellent suggestions.”
Rob Wagoner, George R. Smith Chair, Department of Materials Science and Engineering, Ohio State University, echoed these observations. “Like many, many others internationally, my group has used his codes with his unfailing assistance and without any kind of cost or obligation,” he said. “I think it is this unselfish, caring attitude that sets Carlos apart from his peers, even more so than his tremendous technical achievements in creating and using VPSC.”
Stepping Stones
Looking ahead, Tomé said that he regards “the linking of length scales and the description of mechanical response using probabilistic approaches as two exciting future possibilities in the field of material simulation.
“The challenge is to find ways to transfer the knowledge from the microscopic to the macroscopic level, while preserving what is relevant,” Tomé continued. “The ongoing improvements in some very powerful characterization techniques, such as in-situ TEM, high resolution EBSD, and x-ray synchrotron diffraction, support the possibility of succeeding in this quest.”
While acknowledging that being honored with the symposium indicates he has helped lay a stepping stone to this greater understanding, Tomé said, “I would feel very uneasy if anyone perceives this recognition as a certification of scientific truth. While we always try to get our science ‘right,’ we have limitations and the knowledge that we produce will be revised in the future. Hopefully, my scientific production will encourage a critical view and will elicit the right questions from my colleagues.”
Visit the TMS 2011 Annual Meeting website for additional information on the Carlos Tomé honorary symposium, as well as other programming, events, and networking opportunities.
Lynne Robinson is a news and feature writer with TMS.
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