Metal Fatigue and You

by Michael Mullaney on April 9, 2012

How can nanotechnology and computer modeling lead to safer air travel?

Mechanical engineering professor Antoinette Maniatty tackled this topic in her recent Academic Minute, which aired last week on NPR affiliates all across the country.

Listen to the excellent 90-second piece here. The local NPR affiliate, WAMC Northeast Public Radio, launched its Academic Minute segment in 2010 to great success. What started as a regional endeavor is now making waves nationally.

The transcript of Maniatty’s Academic Minute is below:

On April 1, 2011, Southwest Airlines Flight 812 made an emergency landing shortly after taking off from Phoenix because a five-foot section of the fuselage tore away and left a gaping hole. The cause of the failure was determined to be metal fatigue in the jets aluminum skin. To avoid such failures, engineers normally use conservative approaches to replacing parts with the vast majority of parts taken out of service with a great deal of remaining life – despite the high cost of parts, labor, and vehicle inactivity. Fatigue failure is very difficult to predict because the number of times a part can sustain repetitive forces that arise in normal use varies tremendously. One part may fail at 100,000 loadings while another identical part may fail at only 10,000 loadings. This wide variability arises because fatigue is a localized degradation process that starts at features in the microstructure of the material, which varies from part to part.

I am working to identify the microstructural mechanisms and features that are associated with early fatigue crack initiation. To do this, we apply fundamental science to develop mathematical models of microstructures subjected to cyclic loads, and solve the resulting equations using high performance computing. At the microstructural level, metals are made up of many crystals. We have found that the orientations of the crystals relative to the loading direction, in regions of high stress and in the presence of very small flaws, have a big effect on the fatigue life in aluminum aircraft alloys, and we have identified orientations leading to a short life.

The goal of this work is to enable engineers to eliminate features in the materials and components associated with early failure, before the components are put into service, which will reduce the risk and cost associated with fatigue.

Read more about Maniatty’s research here and here.

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