Brittle Fracture and Propagation of Crack in a Box Girder

<p>[[Video(http://www.youtube.com/watch?v=dnCJ8682ldY)]]</p>

<p>This video illustrates a brittle fracture which occurs in a laboratory test of a bridge girder from a retired railroad flat car. The girder was notched and cooled using liquid nitrogen to well below -100F to ensure the steel was on the lower shelf. Load was applied to produce the fracture. Later in the video, images that were captured using a high-speed camera show the actual fracture propagation through the depth of the girder. At 10,000 frames per second, still only 3 to 5 frames capture the entire fracture event, illustrating the extremely fast crack propagation rate of such an event.</p>