05-27-04

IOWA STATE AWARDED $6.5 MILLION U.S. AIR FORCE RESEARCH CONTRACT TO STUDY AGING MILITARY AIRCRAFT

AMES, Iowa -- The Center for Nondestructive Evaluation at Iowa State University has won a $6.5 million contract toresearch nondestructive evaluation techniques for assessing the aging of military aircraft. The award, from the AirForce Research Laboratory, Wright-Patterson Air Force Base, Ohio, is the most recent in many collaborations between thecenter and the U.S. Air Force.

Nondestructive evaluation tests a structure's ability to perform a function and prevent failure without destroying thesample. The Air Force project focuses on improving non-destructive evaluation techniques and applying them to thechallenges presented by the military branch's aging fleet, much of which is at least 25 years old.

"[The contract] is part of a national response to increased need for military readiness," said R. Bruce Thompson, CNDEdirector and Anson Marston Distinguished Professor in Engineering at ISU. "The ultimate benefit to the Air Force is afleet of aircraft that is available for use a large percentage of the time, and will perform reliably at a minimumcost."

The center and the Air Force have reviewed more than 20 different non-destructive evaluation technologies to determinewhich are best suited to meet the Air Force's inspection challenges. For instance, one project goal is to extend thelife of critical components such as jet engines; their parts can cost tens of thousands of dollars.

"Clearly, if you don't have to throw away a $20,000 part because its useful life is extended, that's significant costsavings," Thompson said.

Jet engine components such as turbine blades are strengthened with a process called shot peening. Small beads are shotat the part during fabrication, which builds in residual stresses that impede the growth of cracks. Over time, however,the high temperatures and stresses of jet engine operation may cause this residual stress protection to diminish.

Existing methods for assessing residual stress only measure it in a very thin layer near the surface of a component.Part of the center's research looks at developing improved techniques to measure the stress at a greater depthcomparable to that of the shot-peened region.

"You need to be able to measure that stress to know how much of the life of the component remains," Thompsonsaid.

Researchers also will study how to apply simulation techniques to the Air Force's nondestructive evaluation needs. Withthis approach, computers are used to simulate how to best inspect components for defects.

"Simulation allows you to have a rational basis for designing new inspections when a new problem presents itself,"Thompson said. "It also provides a much faster way to respond to problems."

Simulations also can help assess how well a technique might work.

"No technique is perfect, so you always miss some defects, but you want the number you miss to be sufficiently low,"Thompson said.

Since 1985, the center has worked with the Air Force, Federal Aviation Administration, NASA and industry to apply itsexpertise to the aerospace industry. The most recent project will involve 15 to 20 center investigators and 10 to 15graduate and post-doctoral students each year. The majority of the work will be done at ISU, although somesubcontractors may be used. Lisa Brasche, center associate director, is the co-leader of the Air Force project.

The Center for Nondestructive Evaluation is a National Science Foundation Industry/University Cooperative ResearchCenter. It focuses on the research and development of new theories and techniques for use in quantitativenondestructive evaluation. The center applies its expertise to aerospace, nuclear energy, automotive, materialsmanufacturing and other industries. The center is member of the Institute for Physical Research and Technology, anetwork of scientific research centers at ISU. More information on the center can be found on the Web athttp://www.cnde.iastate.edu/.

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