Statistical Physics of Fracture: Scientific Discovery through Advanced Computing
Understanding how materials fracture is a fundamental problem of science and engineering even today, although this problem has been investigated since ancient times. Some of the fundamental questions of material fracture that exist today are: 1) what are the size effects and scaling laws of fracture of disordered materials? and 2) how can the fracture surfaces of materials as different as metallic alloys, glass, wood and mortar (for example) be so similar?
Material disorder and long-range interactions are two of the key components that complicate the study of material failure. From an engineering point of view, understanding the size-dependence of material strength and its sample-to-sample statistical fluctuations is crucial to the design and failure analysis of engineering structures involving quasi-brittle materials such as concrete.
On the other hand, the relation between fracture and phase transitions poses many fundamental questions in statistical physics. Experimental results reveal the existence of an intriguing crackling noise in the acoustic emission and of self-affine fractals in the crack surface morphology. Recent advances in computer power have enabled considerable progress in the understanding of such models and resolved numerous long lasting controversies. Among these still partly controversial issues are the scaling and size effects in material strength, the statistics of avalanches or bursts of microfailures, and the morphology of the crack surface.
Using Oak Ridge National Laboratory’s (ORNL) large scale numerical simulations, which are the largest ever systems analyzed, on Argonne National Laboratory’s IBM BG/L and ORNL’s Cray-XT4, we have developed a novel scaling law for material strength that captures for the first time the experimentally observed crossover from a stress concentration controlled scaling regime to a disorder controlled scaling regime. The scaling law is in excellent agreement with the experimental data on notched paper samples. This universal scaling law extends our understanding of size dependence of material strength, and is relevant for the design and analysis of engineering structures made up of quasi-brittle materials such as concrete.
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