Investigation into Interface Lifting Within FSW Lap Welds

Conference · Sun Jun 01 00:00:00 EDT 2008

OSTI ID:969507

Miller, K S; Tolle, C R; Clark, D E; Nichol, C I; McJunkin, T R; Smartt, H B

Friction stir welding (FSW) is rapidly penetrating the welding market in many materials and applications, particularly in aluminum alloys for transportation applications. As this expansion outside the research laboratory continues, fitness for service issues will arise, and process control and NDE methods will become important determinants of continued growth. The present paper describes research into FSW weld nugget flaw detection within aluminum alloy lap welds. We present results for two types of FSW tool designs: a smooth pin tool and a threaded pin tool. We show that under certain process parameters (as monitored during welding with a rotating dynamometer that measures x, y, z, and torque forces) and tooling designs, FSW lap welds allow significant nonbonded interface lifting of the lap joint, while forming a metallurgical bond only within the pin region of the weld nugget. These lifted joints are often held very tightly together even though unbonded, and might be expected to pass cursory NDE while representing a substantial compromise in joint mechanical properties. The phenomenon is investigated here via radiographic and ultrasonic NDE techniques, with a copper foil marking insert (as described elsewhere) and by the tensile testing of joints. As one would expect, these results show that tool design and process parameters significantly affect plactic flow and this lifted interface. NDE and mechanical strength ramifications of this defect are discussed.

• Research Organization: Idaho National Laboratory (INL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC07-05ID14517
• OSTI ID: 969507
• Report Number(s): INL/CON-08-14900
• Conference Information: Trends in Welding, The 8th International Conference,Pine Mountain, Georgia USA,06/02/2008,06/05/2008
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALLOYS
ALUMINIUM
COPPER
DEFECTS
DESIGN
DETECTION
DYNAMOMETERS
FRICTION
friction stir welding
MARKET
MECHANICAL PROPERTIES
non-destructive evaluation
PROCESS CONTROL
TESTING
TORQUE
ULTRASONIC WAVES
WELDED JOINTS
WELDING