A team of researchers discovered a new way to test metals at the microscopic scale to rapidly apply repetitive loads on materials while analyzing how damage accrues and evolves into cracks in real-time, according to a new study published in Science.
New method reveals how cracks propagate before catastrophe
When metallic parts installed in bridges, airplanes, and other structures give way and crack, the results are often disastrous. The new study from Johns Hopkins University outlines a new method of reliably predicting the vulnerabilities at earlier stages of decay than earlier tests can.
"We're able now to have a more fundamental understanding about what leads up to cracks," said El-Awady, one of the study authors. "The practical implication is that it will allow us to understand and predict when or how the material is going to fail."
Studying cracks is crucial for saving expenses
This happens when vehicles take a pounding on bridges, or when air pressure shifts around airplanes, like when, for example, a continuous change known as "cyclic loading" induces slips in the internal molecular structure of metals with the highest durability — until cracks happen that experts may have seen long before they became a danger.
"Fatigue failure plagues all metals and mitigating it is of great importance," added El-Awady. "It is the leading cause of cracks in metallic components of aircraft."
This is why the airline industry must submit to regular (and expensive) replacement schedules for numerous parts. But the life of each component might be more accurately predicted with better intelligence regarding the origins of cracks. Investigators in France called for design reviews of the Airbus A380 — to examine the company's ability to take precautions against the risks of metal fatigue, reports Phys.org.
Knowing crack origins is crucial for expenses
"With the lack of understanding of the mechanisms that lead to crack initiation, it has been difficult to predict with any reasonable accuracy the remaining life of a cyclically loaded material," said El-Awady. "The component could actually be fine and never fail but they throw it away anyway solely on the basis of statistical arguments. That's a huge waste of money."
Most present-day tests to capture the origins of crack initiation typically focus on the moments just before and after cracks happen — to see how the metal's makeup is affected. Many such tests use much larger samples to preclude tracking the beginning of damage — which is a feature of the sub-micrometer scale. This new method narrows the observational lens to the smallest feasible scale, and starts when metals are initially exposed to loads of the precise excess where localized damage may grow into catastrophic cracks.