Fatigue Machine Honored     image of PDF button

An SwRI machine designed to study metal fatigue is named one of the 100 most significant developments of the year.

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The award-winning high-cycle fatigue machine designed and built at SwRI allows engineers to observe the high-frequency stress process and resulting fatigue using a scanning electron microscope. The technology was developed by (front to back) Andrew Nagy, Dr. David Davidson, and Dr. Thomas Owen. John Campbell is not pictured.

An instrument built at Southwest Research Institute (SwRI) to study high-cycle fatigue has earned the Institute its 21st R&D 100 award. The awards are given annually by R&D Magazine to recognize the 100 most significant technologies of the year.

Retired Institute Scientist and consultant Dr. David L. Davidson is the principal developer of the machine, along with Staff Engineer Andrew Nagy and Engineering Technologist John B. Campbell (all of the SwRI Mechanical and Materials Engineering Division), and Institute retiree and consultant Dr. Thomas E. Owen.

The high-cycle fatigue (HCF) machine, developed using internal research funds, combines a high-frequency machine with a scanning electron microscope to help engineers understand metal fatigue, a potentially catastrophic phenomenon that can affect high-performance aircraft engines. (See "Cracking the Fatigue Mystery" in the Fall 1998 issue of Technology Today®). A patent for the machine is pending.

The HCF machine is currently in use on a major program sponsored by the U.S. Air Force Research Laboratory at Wright-Patterson Air Force Base, Ohio. A national team comprised of the University of Dayton Research Institute, Purdue University, several U.S. engine manufacturers, and SwRI is working together to develop an improved design methodology to alleviate high-cycle fatigue problems in military jet engines. The five-year research effort, which began in early 1997, is applicable to a range of jet aircraft in use by the U.S. Air Force.

Dr. Stephen J. Hudak Jr., an Institute scientist in the Mechanical and Materials Engineering Division and project manager for the Air Force program, says that three concerns of the jet engine study are being evaluated at SwRI -- foreign object damage, interactions between fatigue cycles of different magnitudes, and fretting fatigue, which typically occurs where the turbine blade attaches to the disk.

"These phenomena occur in a frequency regime where we are now able to test because of the high-cycle fatigue machine," says Hudak. "We can put 10 million cycles on a test sample in about an hour and a half using the machine. Conventional test methods would take nearly a week."

The second phase of the program recently began, and the HCF machine is expected to play a role there as well. "We're extending a derivative of the machine to allow overall temperatures of 1,900°F. This will allow us to simulate the hot section components of the aircraft engines."

The high-cycle fatigue machine is the third in a series of innovative and successful instruments built in support of a broad historical program for fundamental research on fatigue and fracture. It complements a cyclic loading machine, built in 1978, which operates at tensile loads up to 1,000 pounds, and a high-temperature machine, built in 1985, that operates at the same loads and at temperatures up to 850°C.

Comments about this article? Contact Hudak at (210) 522-2330 or shudak@swri.org.

Published in the Fall 1999 issue of Technology Today, published by Southwest Research Institute. For more information, contact Maria Stothoff.

Technics Fall 1999 Technology Today
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