Aircraft turbine engines are prone to ingesting pebbles and other debris that can damage jet engine fan blades, dramatically reducing the longevity of the components - sometimes catastrophically. Failures associated with such "foreign object damage" cost the aerospace industry an estimated $4 billion a year. Studies at SSRL have helped show how and why fan blades - which normally experience significant stresses during flying - fatigue sooner than expected from foreign object damage. Brad Boyce of Sandia National Laboratories, Apurva Mehta of SSRL and their collaborators simulated the damage by firing small steel balls onto a titanium alloy commonly used in fan blades. They examined the resulting damage with the unique abilities of synchrotron mesodiffraction (X-ray diffraction in the sub-millimeter scale, in this case 0.3 mm to match the size scale of the damage).

The team made spatial maps showing the magnitude and distribution of residual stresses from the damage, as well as maps of the corresponding elastic and plastic strains (a measure of the degree of deformation). The measurements also demonstrated the validity and limitations of calculations that engineers have been using to estimate the residual stress state. This new understanding has been incorporated into a mathematical model of failure to help design new blades to prevent failures from foreign object damage. This example illustrates the utility of a synchrotron x-ray source to solve real-world engineering problems.

This research was carried out at the Stanford Synchrotron Radiation Laboratory, a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.