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Cracks in 3-D.

Cracks in 3-D

For engineers constructing earthquake-resistant buildings, subsurface nuclear waste repositories and other important structures, it's important to know how and why the building materials collapse under force. Now, in an effort to better understand this process, scientists have for the first time developed and tested a method for observing microcracks in three dimensions. Previously, researchers have been able to study the fractures in rocks in only two dimensions.

Neville Cook and Ziqiong Zheng of the University of California at Berkeley added the next dimension by creating a 3-D cast of the cracks. They start by immersing a column of limestone in liquid metal, and then applying up to 10,000 pounds per square inch of force to the ends of the limestone. As the microcracks develop in the rock, the metal seeps into the crack space, and hardens in place when the rock is cooled. The researchers then cut thin sections of the column and apply acid to the surface of the section. The acid etches away the the limestone, but leaves a metal skeleton that represents the actual planes of the cracks. Through a scanning electron microscope, Cook and Zheng have taken stereo 3-D pictures of these metal crack planes and have been able to confirm several theories about crack formation.
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Title Annotation:method for observing microcracks in 3 dimensions to be used in research on earthquake-resistant buildings
Author:Monastersky, Richard
Publication:Science News
Date:Jan 2, 1988
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