In today’s Academic Minute, Dr. Antoinette Maniatty of the Rensselaer Polytechnic Institute explains how a better understanding of metal fatigue can increase safety and profitability in the aviation industry.
Antoinette Maniatty is a professor in the Department of Mechanical, Aerospace, and Nuclear Engineering at the Rensselaer Polytechnic Institute in Troy, New York. Her research group works in the broad field of computational solid mechanics with particular emphasis on modeling material deformation. She holds a Ph.D. in mechanical engineering from Cornell University.
Dr. Antoinette Maniatty – Aviation and Metal Fatigue
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.