Could engineers have known ahead of time exactly how much pressure the levees protecting New Orleans could withstand before giving way? Is it possible to predict when and under what conditions material wear and tear will become critical, causing planes to crash or bridges to collapse? A study by Weizmann Institute scientists takes a new and original approach to the study of how materials fracture and split apart.
When force is applied to a material (say, a rock hitting a pane of glass), a crack starts to form in the interior layers of that material. In the glass, for example, the force of the striking rock will cause the fracture to progress through the material with gradually increasing speed until the structure of the glass splits apart. The path the forming crack follows and the direction it takes are influenced by the nature of the force and by its shape. As cracking continues, microscopic ridges form along the advancing front of the crack and the fracture path repeatedly branches, creating a lightning bolt or herringbone pattern.
Physicists attempting to find a formula for the dynamics of cracking, to allow them to predict how a crack will advance in a given material, have faced a serious obstacle. The difficulty lies in pinning down, objectively, the fundamental directionality of the cracking process: From any given angle of observation or starting point of measurement, the crack will look different and yield different results from any other. Scientists all over the world have experimented with cracking but, until now, no one has successfully managed to come up with a method for analyzing the progression of a forming crack.
Elizabeth McCrocklin | EurekAlert!
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