Vibration Measurements Performed on Carrier Sea Trials to Support CVN Design
Mr. Jim Gardner, Northrop Grumman Newport News

Abstract:

Excessive vibration in surface ships is a design concern that affects equipment and sailors.   NIMITZ class ships have reached their weight service life allowance (SLA) far earlier in their 50 year design service life than predicted, thereby imposing operational restrictions on the ships.  The new CVN 78 class ships have an aggressive weight reduction goal to restore margin in weight SLA, while integrating more advanced and weight intensive technologies and constraining the hull form to similar to the NIMITZ class.  These constraints and advanced requirements pose a significant challenge to the ship designers.  To meet these weight reduction
goals, significant integration of higher strength, lighter weight, and more efficient structures are being employed throughout the design by comparison to the NIMITZ class.   The NIMITZ class design has proven through experience that the vibration levels using typical mild steel and higher strength steel designs are adequate and establis!
hes a baseline for CVN78 to meet.  Integration of more HSLA steels in the design to reduce weight raises concerns for acceptable vibration performance in the CVN 78 design by comparison to NIMITZ.

During several ship trials of CVN76, vibration measurements were performed on the engine rooms, machinery flats, decks, platforms, and hull girder.  These measurements were done to support CVN78 design and finite element model predictions of vibration levels. 

This presentation reviews the various vibration measurements performed and discusses the rationale for the measurement.  The presentation further addresses how information from the CVN 76 testing is used to develop an analytical approach for predicting response in the CVN 78 design.

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