N092-142 TITLE: Advanced Aluminum Cost-effective Joining

TECHNOLOGY AREAS: Materials/Processes

ACQUISITION PROGRAM: CGX Program, PMS 502, ACAT 1

OBJECTIVE: Develop a cost effective mechanically fastened / interlocking / bonded joint for structural aluminum bulkheads and decks using innovative structural shapes, extrusions or connection methods that overcome the limitation of reduced strength from standard weldments.

DESCRIPTION: Aluminum alloys are often considered during material trade studies for topside structures on Navy combatants. However, the severely degraded mechanical properties in the Heat Affected Zone (HAZ) associated with welds occurring at joints are a limiting factor, with strength loss on the order of 50%. This reduction in strength has a direct impact on the potential weight savings of aluminum since the reduced strength in the HAZ is a driving constraint. There are significant benefits (such as reduced weight, production efficiencies, and reduced distortion due to welding) associated with reduction or elimination of the HAZ through the use of either minimal or limited welding in the structural aluminum connections, or through the incorporation of low-cost, low-count fastener systems in aluminum joints.

This topic seeks to explore the use of novel aluminum shapes, extrusions and connection methods to provide a cost-effect method for mitigating the reduced HAZ mechanical properties. Many aluminum alloys are readily extrudable and offer the potential for novel joint details. However, proposers are not limited to extrusions and encouraged to explore shapes that can be made by welding, rolling, casting, forging, flow forming, even machining � the topic focus is overall effectiveness and cost. The proposed joint system should not represent a weight increase over a comparably welded configuration of equal strength. Cost per unit area or length should also be comparable to the welded configuration by a factor of the strength relationship between current and proposed methods. Concepts proposed should take into consideration: method by which foundations, etc would be connected to such a deck or bulkhead system; methods by which the proposed concept(s) would connect to the ship; means of repair; achieving compartment tightness; effects of combat type loads such as shock; life-cycle under operational loads. 5000 series marine grade aluminum alloys should be the primary focus for consideration followed by 6000 series aluminum alloys. Other aluminum alloys series are discouraged.

PHASE I: Demonstrate the feasibility of the use of novel aluminum shapes, extrusions and connection methods to provide a cost-effective method for mitigating the reduced mechanical properties in the HAZ. Develop an initial conceptual design and establish performance goals and metrics to analyze the feasibility of the proposed solution. Perform bench top experimentation where applicable to demonstrate concepts. Provide a Phase II development approach and schedule that contains discrete milestones for product development.

PHASE II: Develop, demonstrate and fabricate a prototype(s) as identified in Phase I. In a laboratory environment, demonstrate that the prototype(s) meets the performance goals established in Phase I. Develop a cost benefit analysis and a Phase III installation, testing, and validation plan.

PHASE III: Working with government and industry, develop production quality, low-cost, and low-maintenance joint system designs for military and commercial implementation onboard naval platforms. Continue to conduct validation testing as appropriate.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: This technology has wide-ranging applicability to both the public and private sectors. Solutions developed here have similar benefits in construction of commercial aluminum boats and pleasure craft, and other industries where stiffened plate construction is required.

REFERENCES:
1. American Bureau of Shipping (ABS) High Speed Naval Craft Guide 2007, http://www.eagle.org/

2. Lincoln Electric Article: "Aluminum: Experience in Application". http://www.lincolnelectric.com/knowledge/articles/content/alumapp.asp

3. Aluminum and Aluminum Alloys: Aluminum and Aluminum Alloys. Joseph R. Davis, J. R. Davis & Associates, ASM International Handbook Committee; Published by ASM International, 1993.

KEYWORDS: aluminum; extrusion; joint; fastener; structure; weld

** TOPIC AUTHOR (TPOC) **

DoD Notice:   Between April 20 and May 17, 2009, you may talk directly with the Topic Authors to ask technical questions about the topics. Their contact information is listed above. For reasons of competitive fairness, direct communication between proposers and topic authors is not allowed starting May 18, 2009, when DoD begins accepting proposals for this solicitation.

However, proposers may still submit written questions about solicitation topics through the DoD's SBIR/STTR Interactive Topic Information System (SITIS), in which the questioner and respondent remain anonymous and all questions and answers are posted electronically for general viewing until the solicitation closes. All proposers are advised to monitor SITIS (09.2 Q&A) during the solicitation period for questions and answers, and other significant information, relevant to the SBIR 09.2 topic under which they are proposing.

If you have general questions about DoD SBIR program, please contact the DoD SBIR Help Desk at (866) 724-7457 or email weblink.