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CHIPS Articles: New prototype enhances ship-testing capability at NSWC Carderock Division

New prototype enhances ship-testing capability at NSWC Carderock Division
By NSWC Carderock Division Public Affairs - March 9, 2016
WEST BETHESDA, Md. -- A new 1,000-pound inertial actuator, the AMA1000, is giving engineers at Naval Surface Warfare Center, Carderock Division (NSWCCD) unprecedented capability in full-scale testing.

Dr. John Miesner, an engineer assigned to Carderock Division’s Acoustic Signatures Technology Division, said the Navy has used actuators like the AMA1000 in a wet environment for many years, but the shakers, as they are called, were not capable of producing high forces at a broad range of frequencies until 2014. That is when the Carderock Division Shaker Lab developed a wet-capable shaker called the MA400 specifically for this purpose. The installed MA400s are performing well and produce about 400 pounds of force.

Dr. Miesner recognized that the MA400 design could be improved to produce 1,000 pounds within the same volume by replacing the rectangular magnetic laminations with axisymmetric components that better fill the cylindrical vessel. This also reduces the number of parts required and simplifies the manufacture and assembly of the shaker. “This shape naturally fills the cylindrical volume and allows all of the moving mass to be used for generating magnetic forces for higher acceleration of the inertial mass and increased output force” Miesner said.

Shakers are rooted in Isaac Newton’s second law of motion (F=MA) and researchers use them at Carderock Division to predict how a ship will respond to vibration sources including motors, pumps and other rotating equipment. The shaker does this by exciting the ship structure allowing the dynamic properties to be measured by an array of accelerometers.

The Navy submitted a patent application for the AMA1000 on May 6, 2015, and Miesner completed it July 7, 2015, with the assistance of Signature Measurement Technologies and Systems Division employee Matthew Willey, who did the detailed design drawings and oversaw the manufacture and assembly, and his fellow Acoustic Signatures Technology Division employee Richard Cohen, who did most of the machining.

“Dr. Miesner's patent application underscores the Acoustic Signatures Technology Division's reputation for technical excellence and innovation,” said Marylou McNamara, division head, Acoustic Signatures Technology Division. “The development of the AMA100 and the completion of the patent application process are incentives for my employees and for all potential Carderock inventors.”

The prototype AMA1000 is currently being tested at the Carderock Division Shaker Lab at up to 1,200 pounds of force output and meets or exceeds design requirements.

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