Sunday, March 05, 2006

Researcher Spotlight: Professor Lambert Ben Freund (LBF)

Notes of AMR Administrators: This article is an adapation of a biography that appeared in the Journal of Mechanics and Physics of Solids, 51, (2003), the proceedings of a symposium, held at Caltech and organized by Ares Rosakis, G. Ravichandran and Subra Suresh, on the occasion of the 60th birthday of Professor L.B. Freund.

Lambert Ben Freund (LBF) was born on November 23, 1942, in Johnsburg, Illinois, a tiny rural community of a few hundred people in the northeast corner of the state. This part of the Midwest was opened to European settlement by the Black Hawk War of the 1830s. A small delegation of his ancestors arrived in the area in 1841. The enthusiastic letters they wrote to relatives waiting in Bavaria and the Rhineland resulted in rapid settlement of the area by immigrant families in the mid-1800s. The farm that would become the Freund family farm was deeded to one of the settlers through an 1820 Act of Congress for the sale of public lands by the government. It was subsequently purchased by LBF's great-grandfather who passed on one quarter section (160 acres) to each of four sons, one of whom was LBF's grandfather. The land was then passed on to the only surviving son, Bernard Freund. The third of four children, LBF was raised by his parents, Bernard and Anita Freund, on the family dairy farm. The responsibilities for managing a dairy farm took precedence over social activities and school sports. At the same time, it provided a vigorous outdoor life with exposure to the cycles of nature, the art of breeding livestock and an appreciation for the value of hard work. He attended St. John the Baptist Elementary School and the McHenry Consolidated High School where he demonstrated a talent for mathematics and science.

Upon graduation from secondary school, LBF followed the advice of his father to continue his education in order to qualify for a good job. In 1960, he enrolled at the University of Illinois at Urbana-Champaign in order to study electrical engineering. The standard curriculum of the day included a required course on statics and dynamics, taught in the Department of Theoretical and Applied Mechanics, in the second year. Through this course, he discovered a natural interest and appreciation for the field of mechanics. Consequently, he changed his major area of study to a relatively new program at the U. of I. in Engineering Mechanics. In addition to broad exposure to the branches of mechanics, the program offered the opportunity to study to some depth in mathematics. The program also required a sequence of courses in the practice of engineering and, to fulfill the latter objective, he followed the sequence of courses in machine design in the Department of Mechanical Engineering. The mechanics program also required a senior thesis, and this turned out to be an entirely experimental project on creep rate acceleration in lead subjected to cyclic loading. The experience of experimental work and study of machine design proved to be useful in the course of four summers and university holidays spent in the research and development division of the Frank G. Hough Co. of Libertyville, Illinois, manufacturer of rubber tired earth moving equipment. This practical work experience provided the opportunity to do experimental instrumentation, data reduction from field testing and management of testing programs to certify new designs of transmission clutches or axles, for example. In the course of this work, he also learned the rudiments of operating heavy equipment.

LBF receive the Bachelor of Science and Engineering Mechanics in 1964 from the University of Illinois. In order to become eligible for more attractive professional opportunities in engineering, he decided to continue his studies toward a master's degree at the same institution. It was during this period that graduate courses on energy methods in applied mechanics and wave motion provided the inspiration to pursue the subject of mechanics much more deeply. In 1965, he enrolled in the program in theoretical and applied mechanics within the Department of Civil Engineering at Northwestern University as a National Defense Education Act fellow. Many fellowships of this kind had been created in response to the launching of the Sputnik satellite in 1957 by the Soviet Union. He was assigned to work with a relatively new faculty member at Northwestern, Professor Jan D. Achenbach, who proved to be a superb research advisor. The association was productive and it resulted in a lifelong professional friendship.

While an undergraduate at the University of Illinois, LBF was introduced to Colleen Hehl, an undergraduate art student at Illinois State University in Normal, Illinois, by a mutual friend. Following completion of his master's degree at Illinois and her bachelor's degree at Illinois State, LBF and Colleen were married in 1965. As they began their new life together in Evanston, Illinois, Colleen taught art in secondary school in Wheeling, Illinois, while LBF pursued his graduate study at Northwestern. He also participated actively on the Civil Engineering intramural basketball team.

LBF finished his Ph.D. research at Northwestern in less than two years, with a thesis entitled Diffraction of Elastic Waves by Semi-Infinite Plane Barriers at the Interface of Elastic Media. Based on the advice of faculty members at Northwestern, LBF decided to pursue postdoctoral research in order to gain exposure to branches of mechanics not included in his graduate education. In 1967, an opportunity for relatively unrestricted research became available within the Materials Research Laboratory at Brown University, and he elected to pursue that possibility without hesitation. The position offered the opportunity to study plasticity and the mechanics of large deformation phenomena. In 1969, he was invited to join the regular faculty as Assistant Professor in the Division of Engineering at Brown University.

The year 1969 also marked a major change in the personal lives of LBF and his wife Colleen, namely, the birth of their first son, Jonathan. Thereafter, family became a central focus for them, a perspective that provided strength and motivation throughout their lives. The family expanded again four years later with the birth of twin sons, Jeffrey and Stephen, in 1973.

By 1970, the research area of dynamic fracture mechanics was emerging throughout the international research community. By this time, Elizabeth Yoffe in the United Kingdom and Bertram Broberg in Sweden had publish their pioneering mathematical solutions of problems in fracture dynamics, and others were beginning to devote their attention to the subject. Significant work was produced at a time by J. D. Eshelby, Jan Achenbach and others. With research funding provided by The Office of Naval Research and the National Science Foundation, LBF undertook a program of research focused on several fundamental issues in the area of fracture dynamics. The field was given major impetus by a series of his papers, published in the Journal of the Mechanics and Physics of Solids between 1972 and 1974. This work provided, for the first time, a complete mechanics of elastodynamic crack growth that could be applied without a priori assumptions on the nature of that growth. Through that work, equations of motion for growth of tensile and shear fractures became available for interpretation of laboratory experiments and field failures. The work stimulated an international research effort focused on the study of fracture initiation, crack propagation and crack arrest under dynamic conditions. Over the next 30 years, this work and its consequences inspired a number of breakthroughs in both theory and experiment and it broadened the scope of fracture mechanics through the active involvement of his former students, postdoctoral researchers and other coworkers.

In addition to his fundamental scientific contributions to dynamic fracture mechanics, LBF's work has had a profound impact on a broad range of other areas within the area of fracture mechanics. On the side of practical applications, his work on elastic-plastic fracture of pipelines and pressure vessels contributed to the understanding of failures in practice, the interpretation of field experiments intended to improve the quality of pipelines steels, the design of mechanical crack arresters for buried pipelines and the design and interpretation of laboratory experiments on characterizing the dynamic fracture behavior of engineering materials. More recently, he has pursued an understanding of the observed fragmentation of ductile materials when deformed at very high rates. Explanation of this phenomenon had remained an open problem in the field for half a century until it was resolved through its treatment as a dynamic plastic bifurcation phenomenon by LBF and postdoctoral associates Vijay Shenoy and Pradeep Guduru. His work has also shown how the addition of a relatively soft, light-weight material to the surface of a ductile structural material can have a marked effect in suppressing the onset of ductile fracture.

In the areas of seismology and seismic source modeling within geophysics, LBF's work on dynamic shear provided timely quantitative guidance toward the understanding of the ruptures in the crust of the earth that give rise to earthquakes. In particular, his prophetic papers on intersonic shear rupture examined the theoretical possibility of such highly dynamic scenarios. Thirty years later, laboratory experiments and geophysical field evidence verified his theoretical predictions to a surprising degree of accuracy through the work of his former student Ares Rosakis and others. His contributions on dynamic failure of materials culminated with publication of a monograph by Cambridge University Press in 1990. This book, entitled Dynamic Fracture Mechanics, continues to be the major reference on the subject, not only within the engineering sciences but also in other branches of physical science which have developed an interest in dynamic fracture phenomena.

While still deeply involved in work on dynamic fracture, LBF became interested in the subject of deformation and failure of thin film materials. He began his pursuit of this area, which was new not only to him but to the mechanics community, with the characteristic enthusiasm and rigor that has governed his entire research career. Indeed, for the years that followed much of his research effort was devoted to various aspects of thin-film research. His work in the area began with development of an understanding at a basic mechanistic level of the nucleation, propagation and blocking of threading dislocations in thin films. His series of papers on the subject forms the foundation of understanding the micromechanics governing this complex phenomenon which is crucial to the fabrication of high quality semiconductor films for microelectronic devices. His research further led to the study of diffusion assisted roughness evolution on film surfaces and on the analysis of morphology evolution of semiconductor islands, or quantum dots, during deposition under high vacuum conditions. He also provided insights into the failure of thin-film conducting materials, particularly through the modeling of void nucleation and stress-driven void growth in passivated interconnect lines in microelectronic devices and the modeling of electromigration failure of conducting lines.

LBF and his students provided the first integration of quantum mechanics into mechanical deformation to assess the role of residual strain fields on charge carrier transport in quantum devices. This work, which evolved in parallel with an experimental study of the problem at Brown University, added a new dimension to the field of mechanics and has inspired a number of young people to pursue similar studies spanning the domains of traditional mechanics and modern electronics. In very recent work, LBF and Vivek Shenoy have established a connection between surface energy of small single crystals of semiconductor materials and mechanical strain that arises naturally in the fabrication of small semiconductor heterostructures. This discovery has provided the means to understand experimental observations that defied interpretation for years, particularly the persistence of the surface orientations not regarded as low-energy orientations. The stabilization of these surface orientations is due solely to mechanical strain. In addition, through this study, a new variational approach for analyzing the evolution of surfaces of small strain structures in during their formation was introduced. The new methodology provides an effective and efficient way to analyze these systems.

This body of work, spanning the scale from wafer curvature methods for stress measurement, through fracture and buckling of stressed thin films, down to surface phenomena on the nanoscale, was summarized in a book entitled Thin Film Materials, co-authored with Subra Suresh of the Massachusetts Institute of Technology and published by Cambridge University Press in 2003.

Although a significant number of LBF's research papers have been solely authored, he has also pursued productive collaborations with many graduate students, postdoctoral researchers, Brown University colleagues and colleagues at other institutions. He has spent sabbatical/research leaves at Stanford University (1974-75 and again in 1995), Harvard University (1983-84), California Institute of Technology (1988, 1999 and again in 2003), University of California at Berkeley (1995) and the University of Illinois (2003).

LBF's impact on the engineering sciences has been significant and permanent. He has served as the nucleus for the evolution of new fields and as a source of inspiration for an entire generation of scientists and engineers. While these new areas of research have sustained a life of their own outside of his direct involvement, LBF has continued to find new ways to use his sense of opportunity and need to shape the field of mechanics for the future. He is currently cultivating an interest in the adhesion of biological materials and the generation of intermolecular interaction forces related to such processes. Among the goals of work in this area is to understand cell motility in biological functions and, further, to develop strategies for modifying that motility.

LBF has taken seriously his responsibilities as teacher and mentor throughout his career. His lecturing skills and classroom presentations are legendary among Brown graduates. The clarity and transparency of underlying thought processes, as well as an acute sense of organization of course material, makes his teaching style an experience to remember.

In addition to being an accomplished teacher and researcher, LBF has another side to his professional persona that is devoted to the service of the community. He has served as chairman of the Division of Engineering at Brown University, as Treasurer of the International Union of Theoretical and Applied Mechanics (IUTAM), currently as President of IUTAM and as Chairman of the Applied Mechanics Division of the American Society of Mechanical Engineers (ASME). He has also had long and successful tenures as technical editor of the Journal of Applied Mechanics, as coeditor (with John Willis) of the Journal of the Mechanics and Physics of Solids, and as associate editor of the Proceedings of the National Academy of Sciences. Service in these positions reflects a desire to foster a high standard for the field, to guide the development of younger researchers, and to encourage broad interaction within the engineering and scientific communities. Aptly recognized for his contributions by many professional societies, LBF has been the recipient of a number of principal awards in the field, including the George R. Irwin Medal (American Society for Testing and Materials), the William Prager Medal (Society of Engineering Science) and the Stephen P. Timoshenko Medal (American Society of Mechanical Engineers). He has also been elected to membership in the American Academy of Arts and Sciences (1993), the National Academy of Engineering (1994) and the National Academy of Sciences (1997).

LBF has pursued a number of interests beyond scholarly and professional activities. He has found relaxation in playing the guitar since his undergraduate student days, an interest that has been passed on to his eldest son. He enjoys a large collection of recorded music containing mostly baroque and classical works of the Masters of those periods, as well as a selection of blues and American folk music. He is an avid reader with particular interests in biography and American history, particularly the eras of the US Civil War and World War II. He is a lifelong admirer of Abraham Lincoln and an interested student of Lincoln's published speeches and correspondence.

At the time of this writing, LBF and Colleen, his spouse of more than 40 years, reside in Barrington, Rhode Island. Their family continues to be a focal point in their lives. The eldest son Jonathan is a professor of mechanical and aeronautical engineering at the University of Illinois; he and his wife Amy have contributed four grandchildren to the family. Jeffrey is the cofounder and chief technology officer of the small company Clickability, based in San Francisco and a developer of Internet software; he and his wife Megan will be contributing a grandchild of their own to the family in the near future. Jeffrey's twin brother Stephen is a professor of computer science at Williams College in Massachusetts.


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