# Predicting the probability of fracture

march 2012

It doesn't happen often, but structures like bridges, airplanes and buildings do fail, sometimes catastrophically. What are the odds, and how can it be prevented ?

IENI-CNR researchers obtained new theoretical insights into the probability of structural failures, based on hundreds of thousands of computer simulations.

Traditionally, engineers have calculated the odds of failure by relying on mathematical theorems that allow extrapolation independent of the details of how and why individual structural components, like beams in a bridge, fail. IENI-CNR researchers, joined by colleagues in Finland and USA, assert that their calculations provide a much more specific and accurate way to predict structural failure. Their models are based on how different sizes and shapes of cracks, even microscopic ones, form and grow.

They focused mainly on a class of materials considered brittle, a classic example being glass. They used a computer program to model billions of cracks, which allowed them to predict how structural elements -- such as the bridge beams -- would hold up under different stresses and loads.

Comparing their results with the traditional way of extrapolating failure rates, they found that they could far more accurately predict when and how the material would fail.

The picture shows the strain field due to cracks present in a material.

Reference:

Claudio Manzato, Ashivni Shekhawat, Phani K. V. V. Nukala, Mikko J. Alava, James P. Sethna and Stefano Zapperi*Strength of Disordered Media: Universality, Interactions and Tail Asymptotics*Phys. Rev. Lett. 108, 065504 (2012)