Arlington, VA—On November 27, the U.S. Office of Naval Research (ONR) honored two engineers who patented a nondestructive method for detecting flaws and anomalies in composite materials. Rear Admiral William E. Landay, Chief of Naval Research, presented the 2006 Vice Admiral Harold G. Bowen Award to Dr. Colin P. Ratcliffe and Dr. Roger M. Crane for their “Nondestructive Method for Detecting Structural Anomalies in Composites,” also known as Structural Irregularity and Damage Evaluation Routine or SIDER (U.S. Patent 6,799,126).
Ratcliffe is a professor of Mechanical Engineering at the U.S. Naval Academy and Crane is a senior composites materials engineer in the Structures and Composites Division at the Naval Surface Warfare Center, Carderock Division.
The Bowen Award is named for Vice Admiral Harold Gardiner Bowen, the first Chief of Naval Research, and it recognizes inventions that have been patented by current or former civilian or military Navy personnel, and that have been of great benefit to the Navy. This benefit may be related to the extent of the invention’s use, the cost savings it produces, or its contribution to increased military capabilities or quality of life.
Crane and Ratcliffe developed SIDER, a method for testing composite materials to detect flaws, damage, and other structural anomalies. The method is rapid, accurate, and easy to perform and interpret. Additionally, the method does not damage or destroy the material being tested, and it can be used anywhere, eliminating the need to cut samples from the material and send them to a laboratory.
The method involves tapping a composite structure with a specially designed “hammer” and recording data from the resulting mechanical vibrations. Changes in the vibrational properties may indicate flaws or damage in the material. Transducers measure the force of the taps, and accelerometers measure the interactions between the composite material and the vibrations caused by the hammer’s tapping. Vibrational readings can be mapped with great precision onto an image of the structure, allowing an engineer to locate anomalies quickly.
Crane and Ratcliffe have used SIDER to check composite materials in the vertical stabilizers of the F-18 Super Hornet aircraft, the twisted rudder on the DDG guided missile destroyer, and a road bridge on Route 896 in Delaware. Crane noted that the entire bridge test was completed in about six hours, about the same amount of time that it takes to complete a ship hull inspection. A similar inspection could take up to two days using conventional ultrasound methods.
Another advantage over ultrasound is that the vibrational readings can be mapped with great precision onto an image of the structure. When an anomaly appears, you can point to an exact location on the ship’s hull or other structure and say, “Here’s where the flaw is.” Adm. Landay noted during the award presentation that detecting damage early on, before a structure fails, has the potential to save lives.