Failure modes of friction stir spot welds in cross-tension specimens of dissimilar aluminium 5754-O and 7075-T6 sheets are investigated. Experimental results show that the failure loads of friction stir spot welds in cross-tension specimens are much lower than those in lap shear specimens. Optical micrographs of the 5754/7075 and 7075/5754 welds before and after failure under quasistatic loading conditions are examined to understand the failure modes of the welds in cross-tension specimens. The micrographs show that the 5754/7075 and 7075/5754 welds in cross-tension specimens mainly fail from the fracture along the interfacial surface and then from the fracture surface through the upper sheet material. The failure modes of the welds in cross-tension specimens are quite different from those in lap shear specimens. Finally, the paper presents discussion of the load carrying capacities and fatigue data of the welds in lap shear and cross-tension specimens based on the linear elastic stress intensity factor solutions.
ThorntonP. H., KrauseA. R. and DaviesR. G.: ‘The aluminum spot weld’, Weld. J., 1996, 75, 101s–108s.
2.
GeanA., WestgateS. A., KuczaJ. C. and EhrstromJ. C.: ‘Static and fatigue behavior of spot-welded 5182-O aluminum alloy sheet’, Weld. J., 1999, 78, 80s–86s.
3.
SakanoR., MurakamiK., YamashitaK., HyoeT., FujimotoM., InuzukaM., NagaoY. and KashikiH.: ‘Development of spot FSW robot system for automobile body members’, Proc. 3rd Int. Symp. on ‘Friction stir welding, Kobe, Japan, September 2001, TWI.
4.
IwashitaT.: ‘Method and apparatus for joining’, US patent 6601751 B2, 2003.
5.
PanT.: ‘Friction stir spot welding (FSSW)—a literature review’, SAE Technical Paper no. 2007-01-1702, Society of Automotive Engineers, Warrendale, PA, USA, 2007.
6.
NandanR., DebRoyT. and BhadeshiaH. K. D. H.: ‘Recent advances in friction-stir welding – process, weldment structure and properties’, Prog. Mater. Sci., 2008, 53, 980–1023.
7.
BakavosD. and PrangnellP. B.: ‘Effect of reduced or zero pin length and anvil insulation on friction stir spot welding thin gauge 6111 automotive sheet’, Sci. Technol. Weld. Join., 2009, 14, 443–456.
8.
GerlichA., SuP. and NorthT. H.: ‘Peak temperatures and microstructures in aluminium and magnesium alloy friction stir spot welds’, Sci. Technol. Weld. Join., 2005, 10, 647–652.
9.
SuP., GerlichA., NorthT. H. and BendzsakG. J.: ‘Material flow during friction stir spot welding’, Sci. Technol. Weld. Join., 2006, 11, 61–71.
10.
SuP., GerlichA., NorthT. H. and BendzsakG. J.: ‘Energy utilisation and generation during friction stir spot welding’, Sci. Technol. Weld. Join., 2006, 11, 163–169.
11.
SuP., GerlichA., NorthT. H. and BendzsakG. J.: ‘Intermixing in dissimilar friction stir spot welds’, Metall. Mater. Trans. A, 2007, 38A, 584–595.
12.
GerlichA., SuP., YamamotoM. and NorthT. H.: ‘Material flow and intermixing during dissimilar friction stir welding’, Sci. Technol. Weld. Join., 2008, 13, 254–264.
13.
FujimotoM., KogaS., AbeN., SatoY. S. and KokawaH.: ‘Microstructural analysis of stir zone of Al alloy produced by friction stir spot welding’, Sci. Technol. Weld. Join., 2008, 13, 663–670.
14.
TozakiY., UematsuY. and TokajiK.: ‘Effect of processing parameters on static strength of dissimilar friction stir spot welds between different aluminum alloys’, Fatigue Fract. Eng. Mater. Struct., 2007, 30, 143–148.
15.
TweedyB. M., WidenerC. A., MerryJ. D., BrownJ. M. and BurfordD. A.: ‘Factors affecting the properties of swept friction stir spot welds’, SAE Technical Paper no. 2008-01-1135, Society of Automotive Engineers, Warrendale, PA, USA, 2008.
16.
TranV.-X., PanJ. and PanT.: ‘Effects of processing time on strengths and failure modes of dissimilar spot friction welds between aluminum 5754-O and 7075-T6 sheets’, J. Mater. Process. Technol., 2009, 209, 3724–3739.
17.
HanL., BlundellN., LuZ., ShergoldM. and ChrysanthouA.: ‘Fatigue behaviour of friction stir joined aluminum alloy NG5754 and AA6111 sheets’, SAE Technical Paper no. 2007-01-1704, Society of Automotive Engineers, Warrendale, PA, USA, 2007.
18.
UematsuY., TokajiK., TozakiY., KuritaT. and MurataS. : ‘Effect of re-filling probe hole on tensile failure and fatigue behaviour of friction stir spot welded joints in Al-Mg-Si alloy’, Int. J. Fatigue, 2008, 30, 1956–1966.
19.
UematsuY. and TokajiK.: ‘Comparison of fatigue behaviour between resistance spot and friction stir spot welded aluminium alloy sheets’, Sci. Technol. Weld. Join., 2009, 14, 62–71.
20.
LinP.-C., PanJ. and PanT.: ‘Failure modes and fatigue life estimations of spot friction welds in lap-shear specimens of aluminum 6111-T4 sheets, Part 1: welds made by a concave tool’, Int. J. Fatigue, 2008, 30, 74–89.
21.
LinP.-C., PanJ. and PanT.: ‘Failure modes and fatigue life estimations of spot friction welds in lap-shear specimens of aluminum 6111-T4 sheets, Part 2: welds made by a flat tool’, Int. J. Fatigue, 2008, 30, 90–105.
22.
TranV.-X., PanJ. and PanT.: ‘Fatigue behavior of aluminum 5754-O and 6111-T4 spot friction welds in lap-shear specimens’, Int. J. Fatigue, 2008, 30, 2175–2190.
23.
WangD.-A. and ChenC.-H.: ‘Fatigue lives of friction stir spot welds in aluminum 6061-T6 sheets’, J. Mater. Process. Technol., 2009, 209, 367–375.
24.
MallickP. K. and AgarwalL.: ‘Fatigue of spot friction welded joints of Mg–Mg, Al–Al and Al–Mg alloys’, SAE Technical Paper no. 2009–01–0024, Society of Automotive Engineers, Warrendale, PA, USA, 2009.
25.
UematsuY. and TokajiK.: ‘Comparison of fatigue behaviour between resistance spot and friction stir spot welded aluminium alloy sheets’, Sci. Technol. Weld. Join., 2009, 14, 62–71.
26.
TranV.-X., PanJ. and PanT.: ‘Fatigue behavior of spot friction welds in lap-shear and cross-tension specimens of dissimilar aluminum sheets’, Int. J. Fatigue, 2010, to be published.
