The present paper reports the second part of a research carried out by the authors on the application of ultrasonic metal spot welding to lap joints made of AA 6022‐T4 thin sheets. In particular, starting from the findings of Part 1, tensile–shear fatigue experiments are carried out on ultrasonically spot welded lap joints both in single and double spot configurations. The analysis of consequent failure causes and modes and the application of traditional approaches for fatigue assessment of resistance spot welded joints allow then effectively predicting experimental evidences. Furthermore, an optimisation of the fatigue behaviour of double spot joints (longitudinal spots configuration) is achieved in terms of endurable load and distance between spots, with a possible generalisation to multiple spot configurations. Finally, a comparison of the fatigue performance of the ultrasonic technique to other spot joining techniques is presented.
AnnoniM, CarboniM: ‘Ultrasonic metal welding of AA 6022‐T4 lap joints – Part I: technological characterisation and static mechanical behaviour’, Sci. Technol. Weld. Join., 2011, 16, 107–115
2.
DevineJ: in‘ASM handbook’, Vol. 6, ‘Welding, brazing, and soldering’, 324; 1993, Materials Park, OH, ASM International.
3.
RozenbergLD: ‘Physical principles of ultrasonic technology’; 1973, New York, Plenum Press.
4.
ChangUI, FrischJ: ‘On optimisation of some parameters in ultrasonic metal welding’, Weld. J., 1974, 1, 24s–34s.
HarmanGG, AlbersJ: ‘The ultrasonic welding mechanism as applied to aluminum‐ and gold‐wire bonding in microelectronics’, IEEE Trans. Parts Hybrids Packag., 1977, 13, (4), 406–412.
7.
PetersonJM, McKaigHL, de PriscoCF: ‘Ultrasonic welding in electronic devices’, Proc. 1962 IRE National Convention, 1962, 3–12.
8.
HarthoornJL: ‘Ultrasonic metal welding’, PhD thesis, Eindhoven, The Netherlands, Technische Hogeschool, 1978.
9.
WeberA: ‘The economics of ultrasonics. Other joining methods may be cheaper to buy, but none is as cost‐effective to use’, Assembly Mag., Aug. 2003, 44–52.
10.
HetrickE, JahnR, ReatherfordL, SkogsmoJ, WardS, WilkoszD, DevineJ, GraffK, GehrinR: ‘Ultrasonic spot welding: a new tool for aluminum joining’, Weld. J., 2005, 84, (2), 26–30.
11.
de VriesE: ‘Mechanics and mechanisms of ultrasonic metal welding’, PhD thesis, Columbus, OH, USA, Ohio State University, 2004.
12.
RadajD, SonsinoCM, FrickeW: ‘Fatigue assessment of welded joints by local approaches’, 2nd edn, 437; 2006, Cambridge, Woodhead Publishing Limited.
13.
FermérM, SvenssonH: ‘Industrial experiences of FE‐based fatigue life predictions of welded automotive structures’, Fatigue Fract. Eng. Mater. Struct., 2001, 24, 489–500.
14.
PookLP: ‘Fracture mechanics analysis of the fatigue behaviour of spot welds’, Int. J. Fract., 1975, 11, (2), 173–176.
15.
FuM, MallickPK: ‘Fatigue of self‐piercing riveted joints in aluminum alloy 6111’, Int. J. Fatigue, 2003, 25, 183–189.
OverbeekeJL, DraismaJ: ‘Fatigue characteristics of heavy duty spot‐welded lap joints’, Met. Constr., 1974, 6, (7), 213–219.
21.
WangMZ, KassnerME: ‘Tensile and fatigue properties of aluminum alloy sheet 6022’, J. Mater. Eng. Perform., 2002, 11, 166–168.
22.
SoundararajanV, YarrapareddyE, KovacevicR: ‘Investigation of the stir lap welding of aluminium alloys AA5128 and AA6022’, J. Mater. Eng. Perform., 2007, 16, 477–484.
23.
MurakamiY, FukushimaY, ToyamaK, MatsuokaS: ‘Fatigue crack path and threshold in mode II and mode III loadings’, Eng. Fract. Mech., 2008, 75, 306–318.
24.
BerettaS, FolettiS, ValiullinK: ‘Fatigue strength for small shallow defects/cracks in torsion’, Int. J. Fatigue, 2011, 33, 287–299.
25.
BerettaS, CerriniA, DesimoneH: ‘Mixed mode fatigue crack propagation in a ferritic–perlitic cold‐drawn tube’, Eng. Fract. Mech., 2008, 75, 845–856.
26.
MurakamiY: ‘Metal fatigue: effects of small defects and non‐metallic inclusions’, 37; 2002, Oxford, Elsevier Science.
27.
‘Destructive tests on welds in metallic materials – etchants for macroscopic and microscopic examination’, ISO 16060: Geneva, Switzerland, ISO, 2003.
AnnoniM, MoroniF, MussiV: ‘Performance variability of aluminium hybrid LAP-joints obtained by means of adhesives and ultrasonic welding’, Int J Mater Form, 2010, 3 Suppl 1, 1051–1054.
