After Nabarro
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10/31/2006
3:47 PM
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by Popular Demand! Attention MRS Members Back The Meeting Scene… bringing you the very best of MRS.
Can't attend the 2006 MRS Fall Meeting in Boston? No problem… we’ve got it covered. The MRS “Meeting
Scene” is coming to you!
Check your e-mail daily from November 27 through December 1. We’ll be sending you news and highlights from the preceding day with links back to the meeting Web site. The Plenary and awards sessions. Symposium X talks. Poster award winners. The most exciting technical talks. And so much more.
POSTERMINARIES
After Nabarro With the passing of Frank Nabarro in July of this year, we have lost one of the founding fathers of materials science. His name appears in many of the textbooks from which we train our students today, and also on the spines of several volumes on dislocation theory, including his classic monograph on the subject. He rightly stands among the gods of our field. Ninety years old at his death, he was a sprightly dancer at the frontiers of knowledge, right up to the end. Nabarro was an “old school” materials theorist. He used insight to inform mathematical formulation, then used the mathematical results to develop even deeper insight into the strength of solids, especially in the area of dislocation theory. For him, the details of the mathematics never seemed as important as the underlying principles that they revealed, and by applying the principles, he was able to leapfrog others and quickly identify the solutions to new problems. For those who care to look, his book Theory of Crystal Dislocations (originally published by the Oxford University Press in 1967, then reprinted by Dover in 1987) presciently contains the answers to many questions that have only just begun to be considered by others, just because he thought the topics provided interesting illustrations of the underlying principles. But dislocation theory is a complicated subject, and like many such subjects, it has been studied increasingly through the use of computers. Codes are now in use that can track millions of dislocation segments, or even billions of atoms to find the dislocations. These simulation algorithms allow the researcher to observe how dislocations interact, multiply, and organize themselves during plastic deformation, fatigue, and fracture, and to test how changes in 960
the applied stress or other details of the experiment change its outcomes. They are truly remarkable achievements, and the graphical output is seductive and fascinating. It allows us to see things that cannot be seen using any other tool.
Being able to simulate is not the same as being able to understand. Computer simulation in dislocation theory fits the description of a “disruptive” technology provided by Clayton Christensen of Harvard Business School in his 1997 book, The Innovator’s Dilemma (Harvard Business School Press). A disruptive technology does the same job as an existing tool (for example, pencil and paper) and eventually completely displaces the existing tool. Christensen notes that m
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