Advanced Metalworking Solutions for
Naval Systems that Go in Harm's Way
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Portable System to Mitigate Aluminum Cracking to Provide Significant Cost Avoidance

12/06/2016

Success Story Image

Application of a device to mitigate sensitization in aluminum structures will be less labor intensive than the current remove and replace process. NMC photo



S2576 Mitigation of Cracking in Sensitized Aluminum

Problem/Objective:

Cracks in the aluminum superstructure of the CG 47 class cruisers require extensive repairs or replacement (i.e., removing and replacing the affected plate as well as all of the outfitting obstructing the area). The Navy Metalworking Center (NMC) led a project to address the major contributor to the cracking – the sensitized microstructure in the 5456 aluminum-magnesium alloy used in the construction of the structure. An Integrated Project Team (IPT) developed and demonstrated a portable heat treatment system that reverses the sensitization in 5456 aluminum alloy, thereby restoring the affected material in the ship’s superstructure to a stabilized condition, which greatly reduces the propensity for cracking.

Accomplishment/Payoff

Process Improvement:

NMC conducted laboratory tests and finite element simulations to derive the optimized parameters for the reverse sensitization process. Using this data, NMC designed and fabricated a prototype reverse sensitization unit (RSU), which imparts the necessary heat treatment to the aluminum plate in the CG class cruiser superstructure to mitigate the sensitization. The RSU was tested on laboratory sensitized panels, and a mockup of a CG superstructure was designed by NMC. The RSU was then demonstrated onboard two cruisers (one decommissioned, one active duty).

Implementation and Technology Transfer:

The final RSU prototype system was transitioned to PMS 407 for additional evaluation and use during maintenance intervals. A procurement specification was also developed by NMC, so that additional units may be built after successful implementation. Implementation of the new process was initiated in September 2016 with the transition of the equipment to Ingalls Shipbuilding, the planning yard for CG repairs.

Expected Benefits:

Reverse sensitization will give the Navy a low-cost alternative to the current process of cutting out and replacing the sensitized plate.

  • The reverse sensitization repair process can save as much as $2.4M per CG 47 ship availability, resulting in a cost avoidance of as much as $43.2M for 18 ships.
  • The Littoral Combat Ship (LCS) program will also benefit from this improved technology at a conservative estimate of $500K avoidance per hull, resulting in an additional $4M in cost avoidance for the LCS hulls in service over the next five years.

Participants:

  • PMS 407
  • PMS 501
  • SEA 05P2
  • SEA 05D
  • Naval Surface Warfare Center, Carderock Division
  • ElectraWatch
  • DDL OMNI Engineering
  • Serco Inc.
  • NMC
  • ONR Navy ManTech

 

For more information, contact:
Dr. Daniel L. Winterscheidt
Senior Program Director
winter@ctc.com
814-269-6840