Researchers from Sandia National Laboratories (SNL) and Texas A&M University in the US have observed cracks in a metal becoming shorter. The unexpected finding – cracks normally grow longer – upends theories of fracture in metals and could help in the design of materials that “heal” their own internal damage.
When metals repeatedly undergo stresses and strains, microscopic cracks begin to form. These cracks are a type of fatigue damage, and over time, they grow and spread until they eventually cause the structure to fail – often unpredictably.
Such growth had been assumed to be irreversible, but researchers led by SNL materials scientist and engineer Brad Boyce found that this isn’t necessarily true. In their study, they used a specially modified electron microscope that allowed them to strain nanoscale samples of platinum repeatedly while observing what happens inside them. As expected, they saw nanoscale fatigue cracks appearing early on in the experiment. Unexpectedly, however, they also saw the ends of cracks fusing back together roughly 40 minutes later.
To read more, click here.