New approach to understanding cracks

Feb 03, 2006

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.

Prof. Itamar Procaccia and research students Eran Bouchbinder and Shani Sela of the Chemical Physics Department set out to find a way of analyzing data from experiments in cracking that would avoid the direction problem. First, they divided the cracks' ridged surfaces up into mathematically-determined sectors. For each sector they were able to measure and evaluate different aspects of the crack's formation and to assign it simple directional properties. After some complex data analysis of the combined information from all the sectors, the team found their method allowed them to gain a deeper understanding of the process of cracking, no matter which direction the measurements started from. The team then successfully applied the method to a variety of materials – plastic, glass and metal.

From the concrete in dams and buildings, to the metal alloys and composites in airplane wings, to the glass in windshields, many of the materials we depend on daily are subject to cracking. The team's method will give engineers and materials scientists new tools to understand how all of these basic materials act under different stresses, to predict how and when microscopic or internal, unseen fractures might turn life-threatening, or to improve these materials to make them more resistant to cracks' formation or spread.

Source: American Committee for the Weizmann Institute of Science

Explore further: Occam's razor redux: A simple mathematical approach to designing mechanical invisibility cloaks

Related Stories

Nepal quake could have been much worse: Here's why

13 hours ago

The structural engineer strides through Kathmandu's old city, past buildings reduced to rubble, buildings whose facades are cracked in dozens of places, like the fractured shell of a hardboiled egg. But it's ...

Bendable glass devices

Apr 27, 2015

A special class of glass materials known as chalcogenide glasses holds promise for speeding integration of photonic and electronic devices with functions as diverse as data transfer and chemical sensing. ...

More than 2,200 confirmed dead in Nepal earthquake

Apr 26, 2015

A powerful aftershock shook Nepal on Sunday, making buildings sway and sending panicked Kathmandu residents running into the streets a day after a massive earthquake left more than 2,200 people dead.

Nepal quake: Nearly 1,400 dead, Everest shaken (Update)

Apr 25, 2015

Tens of thousands of people were spending the night in the open under a chilly and thunderous sky after a powerful earthquake devastated Nepal on Saturday, killing nearly 1,400, collapsing modern houses and ...

Recommended for you

Efimov state in the helium trimer observed

Apr 30, 2015

A quantum state predicted by the Russian theoretician Vitaly Efimov 40 years ago has been discovered by physicists of the Goethe University in a molecule consisting of three helium atoms. The molecule is ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.