Spatial Mechanical Response and Strain Gradient Evolution of Friction Stir Welded Aluminum-2139

Report No. ARL-TR-5892
Authors: Brian Justusson; Jessica Medintz; Jian Yu; Constantine Fountzoulas; Chian-Fong Yen
Date/Pages: February 2012; 30 pages
Abstract: With current involvements of the U.S. Military in various peace-keeping and combat operations throughout the world, there is an increase in the deployment of armored military vehicles. Traditional armoring techniques have performed well against particular threats, but, in the recent combat operations, a new threat of improvised explosive devices, the vulnerability of the undercarriage, is being exposed. While thick, steel-structural members have been used in the past, an effort to make them more agile and deployable has caused a push toward lightweight materials. Advanced aluminum alloys, such as AA-2139, are attractive candidates because of their high strength and lower density than steel. Single-body construction can eliminate joint failure but requires a new joining technique. Friction stir welding (FSW) is a solid-state joining technique that combines extreme plastic deformation coupled with localized heat flux to create unique microstructure joints. In general, the mechanical properties are dependent on the formation of the microstructure. To the best of our knowledge, these microstructural zones and the quality of the weld have not fully been characterized under blast loading. Finite-element simulations have been used to predict the mechanical response of blast loading, but the effects of the microstructural zones on blast loading are not fully understood. In the present work, the spatial mechanical response of a FSW joint is analyzed to determine the spatial mechanical properties.
Distribution: Approved for public release
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Last Update / Reviewed: February 1, 2012