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Title: Superplastic Forming of Aluminum Multisheet Structures Fabricated Using Friction Stir Welding and Refill Friction Stir Spot Welding

Abstract

Superplastically-formed structural panels are growing in their applications in aerospace, aircraft, automotive, and other industries. Generally, monolithic sheets are employed, limiting the size and complexity of the final part. However, more complex and larger final geometries are possible if individual sheet materials can be joined together through an appropriate joining technology, then SPF formed to final shape. The primary challenge in this type of SPF fabrication has been making a joint between the sheets that will survive the SPF forming event and display the correct amount of elongation in the joint relative to the base materials being formed. Friction Stir Welding is an ideal joining technology for SPF applications because the forming response of the weld metal at SPF conditions is adjustable by selecting different weld process parameters during initial joining. This allows the SPF deformation in the weld metal to be “tuned” to the deformation of the parent sheet to prevent early failure from occurring in either the weld metal or the parent sheet due to mismatched SPF flow stresses. Industrial application of the concept of matching flow stresses is currently being pursued on a program at the Pacific Northwest National Laboratory on room temperature formed friction stir weldedmore » tailor welded blanks for heavy truck applications. Flow stress matching and process parameter “tuning” is also important in the fabrication of SPF multisheet structural panels. These panels are fabricated by joining three sheets together with alternating welds top and bottom, so that each weld penetrates only two of the three sheets. This sheet pack is then sealed with a weld seam around the outside and hot gas is introduced between the sheets through a welded tube. Under SPF conditions the sheet pack inflates to produce an internally supported structure. In this paper we presents results on an investigation into using FSW and Refill Friction Stir Spot Welding to fabricated 5083 aluminum multisheet packs that can be SPF formed into 3-D structural or integrally stiffened panels. Several configurations of 3-sheet egg crate and truss structures were friction stir welded and hot gas SPF formed in a parallel-platen SPF press. Data on weld conditions for optimum SPF forming as well as pre- and post- forming microstructures will be presented. It is found that FSW process conditions are a key feature of a successful SPF forming operation and the nugget microstructures and other features of the weld zone can be optimized to produce a wide range of weld region elongations. Friction Stir Welding may prove to be the enabler that allows aluminum to be considered in multisheet and integrally stiffened SPF Aluminum structures.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
960335
Report Number(s):
PNNL-SA-53238
VT0502020; TRN: US200923%%319
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Conference
Resource Relation:
Conference: 6th International Symposium on Friction Stir Welding, October 10-13, 2006 Saint-Sauveur, Canada, 52(4)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 42 ENGINEERING; ALUMINIUM; DEFORMATION; ELONGATION; PANELS; FABRICATION; FLOW STRESS; FRICTION; STRESSES; WELDING; PLASTICITY; WELDED JOINTS; Friction Stir Welding; Superplastic Forming; Aluminum Forming; SPF

Citation Formats

Grant, Glenn J., Herling, Darrell R., Arbegast, William J., Allen, Casey D., and Degen, Cassandra M.. Superplastic Forming of Aluminum Multisheet Structures Fabricated Using Friction Stir Welding and Refill Friction Stir Spot Welding. United States: N. p., 2006. Web.
Grant, Glenn J., Herling, Darrell R., Arbegast, William J., Allen, Casey D., & Degen, Cassandra M.. Superplastic Forming of Aluminum Multisheet Structures Fabricated Using Friction Stir Welding and Refill Friction Stir Spot Welding. United States.
Grant, Glenn J., Herling, Darrell R., Arbegast, William J., Allen, Casey D., and Degen, Cassandra M.. Wed . "Superplastic Forming of Aluminum Multisheet Structures Fabricated Using Friction Stir Welding and Refill Friction Stir Spot Welding". United States. doi:.
@article{osti_960335,
title = {Superplastic Forming of Aluminum Multisheet Structures Fabricated Using Friction Stir Welding and Refill Friction Stir Spot Welding},
author = {Grant, Glenn J. and Herling, Darrell R. and Arbegast, William J. and Allen, Casey D. and Degen, Cassandra M.},
abstractNote = {Superplastically-formed structural panels are growing in their applications in aerospace, aircraft, automotive, and other industries. Generally, monolithic sheets are employed, limiting the size and complexity of the final part. However, more complex and larger final geometries are possible if individual sheet materials can be joined together through an appropriate joining technology, then SPF formed to final shape. The primary challenge in this type of SPF fabrication has been making a joint between the sheets that will survive the SPF forming event and display the correct amount of elongation in the joint relative to the base materials being formed. Friction Stir Welding is an ideal joining technology for SPF applications because the forming response of the weld metal at SPF conditions is adjustable by selecting different weld process parameters during initial joining. This allows the SPF deformation in the weld metal to be “tuned” to the deformation of the parent sheet to prevent early failure from occurring in either the weld metal or the parent sheet due to mismatched SPF flow stresses. Industrial application of the concept of matching flow stresses is currently being pursued on a program at the Pacific Northwest National Laboratory on room temperature formed friction stir welded tailor welded blanks for heavy truck applications. Flow stress matching and process parameter “tuning” is also important in the fabrication of SPF multisheet structural panels. These panels are fabricated by joining three sheets together with alternating welds top and bottom, so that each weld penetrates only two of the three sheets. This sheet pack is then sealed with a weld seam around the outside and hot gas is introduced between the sheets through a welded tube. Under SPF conditions the sheet pack inflates to produce an internally supported structure. In this paper we presents results on an investigation into using FSW and Refill Friction Stir Spot Welding to fabricated 5083 aluminum multisheet packs that can be SPF formed into 3-D structural or integrally stiffened panels. Several configurations of 3-sheet egg crate and truss structures were friction stir welded and hot gas SPF formed in a parallel-platen SPF press. Data on weld conditions for optimum SPF forming as well as pre- and post- forming microstructures will be presented. It is found that FSW process conditions are a key feature of a successful SPF forming operation and the nugget microstructures and other features of the weld zone can be optimized to produce a wide range of weld region elongations. Friction Stir Welding may prove to be the enabler that allows aluminum to be considered in multisheet and integrally stiffened SPF Aluminum structures.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Dec 20 00:00:00 EST 2006},
month = {Wed Dec 20 00:00:00 EST 2006}
}

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