Special Issue: Ships Navy Experts Explain the Newest Material & Structural Technologies AMPTIAC is a DOD Information Analysis Center Administered by the Defense Information Systems Agency, Defense Technical Information Center The issue you hold in your hands has been 14 months in the color reproduction. You also have probably noticed that we are making. It began with a simple idea: turn the spotlight on the publishing these large special issues fairly often. It is all a part age-old art of building ships. We wanted to show the exciting of our mission to bring you the most in-depth, focused, and new technologies that are offering novel materials for ship con- technologically exciting coverage of Defense materials and pro- struction, changing the way ships are built, and indeed creating cessing advances available anywhere. one of the most fundamental shifts in Navy combatants since But the side effect of the more noticeable and attention- steel replaced wood. grabbing Quarterly, is that This simple mission turned AMPTIAC itself has lost some out to be much more complex. attention. The reality is that the The project underwent a num- Editorial: center has grown with numer- ber of different iterations, but ous projects, focused reports, finally settled in and came There’s More to AMPTIAC and database efforts over the together. It has been a labor of than the Quarterly past few years, but there are love for yours truly, for I really many out there that may read do believe that even though air- this publication and not even planes and tanks often grab the know that the center exists. spotlight, Navy ships are still the most challenging structural We want to put more emphasis on the other efforts and materials engineering systems fielded in today’s military. AMPTIAC is involved in, and let our customers and potential Nothing has the complexity, impact, size, and sheer force of a customers know that we are here for you. We help with ques- fighting vessel, nor can many things capture the imagination in tions, assist in materials selection, and provide consultation on quite the same way. a variety of materials and processing-related issues. We have So here it is, finally, and I am thankful that it is done. Not more than 210,000 DOD technical reports in our library and just because it is off my desk and I can get on to the next proj- direct access to hundreds of thousands more throughout DOD, ect, but we are proud because AMPTIAC has compiled some- DOE, NASA, and other US Government agencies. We have thing that probably has not existed before: an overview of the dozens of focused reports tailored to specific technology areas newest technologies being incorporated into structures and and many more compiling vast amounts of data into hand- materials for use aboard Navy combatants. And the people pro- book-style resources. viding the perspective are the experts at the Office of Naval The basic message here is to take note of this magazine, read Research, NSWC-Carderock, and the Naval Research Lab. You it, and enjoy. But if you think AMPTIAC is just the Quarterly, won’t find this level of detail, variety, and expert content Think Again. focused on this subject anywhere else. That all being said, there is one critical feature of this publi- Wade Babcock cation that needs some attention: the DOD center behind it. Editor-in-Chief Some of you out there have been reading this publication for seven years now. You undoubtedly remember about two years ago when we shifted over to our current layout format and full http://iac.dtic.mil/amptiac Editor-in-Chief The AMPTIAC Quarterly is published by the Advanced Materials and Processes Technology Information Wade G. Babcock Analysis Center (AMPTIAC). AMPTIAC is a DOD sponsored Information Analysis Center, administratively managed by the Defense Information Systems Agency (DISA), Defense Technical Information Center (DTIC). Creative Director The AMPTIAC Quarterly is distributed to more than 15,000 materials professionals around the world. Cynthia Long Inquiries about AMPTIAC capabilities, products and services may be addressed to Information Processing David H. Rose Judy E. Tallarino Director, AMPTIAC 315-339-7023 Patricia McQuinn EMAIL: [email protected] Inquiry Services URL: http: //amptiac.alionscience.com David J. Brumbaugh We welcome your input! To submit your related articles, photos, notices, or ideas for future issues, please contact: AMPTIAC Product Sales ATTN: WADE G. BABCOCK Gina Nash 201 Mill Street Rome, New York 13440 Training Coordinator PHONE: 315.339.7008 Christian E. Grethlein, P.E. FAX: 315.339.7107 EMAIL: [email protected] Maria Posada, Jennifer P. Nguyen, David R. Forrest, Johnnie J. DeLoach Welding and NDE Branch Robert DeNale Metals Department Survivability, Structures, and Materials Directorate Carderock Division, Naval Surface Warfare Center West Bethesda, MD INTRODUCTION plates to be joined. A vertical force (z-axis load) is applied per- Lighter, stronger, faster: This mantra drives structural materials pendicularly to the joint line, driving the rotating pin into the research and development for Navy systems. Ships that can be work piece. Frictional heat is generated at the top surface of the quickly deployed, carry larger payloads, reliably withstand the workpiece under the FSW tool shoulder, and in the base mate- assaults of high sea states, and travel safely through harm’s way rial at the interface with the pin. For steels and other higher are the ultimate goal of the scientists and engineers working on melting temperature alloys, a small-diameter hole is pre-drilled advanced materials and the technologies for building them. One in the joint line to lessen the forces acting on the welding tool means of achieving lighter, stronger, and faster ships and sub- during the plunge. marines is through the introduction of materials with specific After sufficient dwell time to allow for homogeneous heating property improvements including titanium and aluminum and softening of the material, a lateral force (x-axis load) is alloys, and higher strength steels. Effectively exploiting these applied in the direction of travel. Both z- and x-axis loads act advanced materials for ship construction requires developing on the rotating welding tool as it traverses along the joint line, effective joining technologies, and friction stir welding (FSW) is sweeping the softened material along the periphery of the pin an important part of this program. and depositing it in the tool’s wake. This “stirring” action, along FSW is a rapidly maturing solid state joining process that with the pressure and restraining forces induced by both the offers significant benefits over conventional joining processes. tool and fixturing, creates a heavily deformed region of materi- Invented by The Welding Institute (TWI) in 1991, FSW uses a al which upon cooling defines a strong, metallurgical joint that combination of frictional heating and compressive loading to is fine-grained with no entrapped oxides or gas porosity. join metal plates that are butted against each other and tightly Characteristics that make solid state joining attractive are clamped to the anvil of the machine. included in Table 1. The process, shown schematically in Figure 1, is initiated by Friction stir welding of relatively low-melting temperature rotating a welding tool (consisting of a shoulder and pin assem- materials, such as alloys of aluminum and magnesium, has X bly) at speeds up to several matured significantly and is being adopted by the aerospace hundred revolutions per community. For example, NASA’s Marshall Space Flight Center minute (rpm) before it is low- plans to use FSW for constructing Al-Li external fuel tanks, and Y ered into contact with the Eclipse Aviation has used FSW in the fabrication of jet aircraft. The Navy is interested in extending this a technology to shipbuilding and optimiz- b ing it for joining naval materials, such as carbon steels, stainless steels, titanium alloys and nickel aluminum bronze. Z FSW FOR SHIPBUILDING c d For future naval construction, emerging higher strength, stiffness, and toughness steels and stainless steels are of interest. High strength, low alloy (HSLA) steels and AL-6XN are currently being investi- gated. HSLA-65 steel is an alternative to Figure 1. Schematic of FSW Process (left) and a Photo of an Actual FSW Tool (right) DH-36 for aircraft carrier construction. (Photo courtesy of University of South Carolina) The AMPTIAC Quarterly, Volume 7, Number 3 13 Table 1. Characteristics of Solid State Joining. • Minimization of fume generation since the heat generated during this process remains below the melting temperature of the material • Reduced distortion • The ability to form strong joints without filler wire • Reduced joint preparation and post-weld clean-up • Reduced post-weld inspection and rework • Various inherent user- and environmentally-friendly properties, such as the ability to be automated Figure 2. USS Arleigh Burke (DDG 51). With improved property-to-weight ratios, HSLA-65 will theo- requirement could reach $80M per year for US Navy ship con- retically enable thinner-gauge sections to be used, resulting in struction after a one time $30M implementation cost. lighter weight designs. (Please see the accompanying article by Czyryca, et. al. in this issue.) AL-6XN is a high-toughness, non- THE R&D PROGRAM magnetic, super-austenitic stainless steel being evaluated as a In response to these challenges, the Navy is investigating structural material for Advanced Double Hull (ADH) surface advanced joining methods, including FSW for joining of carbon combatants. (Please see the accompanying article by Beach in and austenitic stainless steels. The overall program includes sci- this issue.) ence and technology directed toward advanced equipment devel- In order to exploit the improved properties of these advanced opment, tool design and tool material development, welding steels, advanced joining technologies will also be required.