Cracks: More Than Just a Clean Break

The complexity of materials has long thwarted efforts to understand their failure. But evidence that defects--microscopic impurities and dislocations in a material9s crystal structure--play a key role in the evolution of cracks has led computer modelers to believe that defects may be the key to predicting when, where, and how materials will fail. These efforts to model cracks have been hampered by a shortage of computer power, as simulating a crack that spawns a complex, three-dimensional network of defects around itself requires scientists to model hundreds of millions of interacting atoms--many more than are necessary for a crack that cleaves a material cleanly. Over the past few years, however, several groups have reported computer simulations that come closer to mimicking physical reality.