FATIGUE DAMAGE OF 2024-T351 ALUMINIUM ALLOY FRICTION STIR WELDING JOINTS. PART 2: FATIGUE DAMAGE
Abstract
The characterisation of micro and macro mechanics in 2024-T351 (Al Alloy) FSW joints was conductedto identify the critical regimes for natural fatigue crack initiation in 2024-T351 Al Alloy FSW weldedjoints and was presented in Part 1. In this Part, the fatigue tests were performed. Scanning electronmicroscopy analysis on fracture surfaces revealed that natural crack initiates from multiple sites andis propagated through different regimes causing coalescence. Replicas of crack images confirmed thatmultiple cracks coalesce. The natural fatigue initiation sites which were found begin from subsurfacedefects rather than form a free surface. For a different applied stress level, the initiation sites werechanged from one regime to another. The number of cracks observed reduces as the applied stressdrops. The fatigue limit of this welded joint was governed by a coalescence of the cracks rather thanby the propagation.
References
ASTM. (1988). Annual Book of ASTM Standards.ASTM International, West Conshohocken,PA, USA.
Bussu, G. and Irving, P.E. (2001). Damage toleranceof welded aluminium aircraft structures.ICAF Design for Durability in theDigital Age. Proceedings of the 21stSymposium of the International Committeeon Aeronautical Fatigue; June 27-29,2001; Toulouse, France, p. 331-350.
Jata, K.V. and Semiatin, S.L. (2000). Continuousdynamic recrystallisation during frictionstir welding of high aluminum alloys.Scripta Materialia, 43:743-749.
Kissell, J.R. and Malloy, B.J. (2001). Makingaluminum more competitive in structuralapplications. In: Aluminium 2001- Proceedingsof the TMS 2001 Aluminum Automotiveand Joining Sessions. Das, S.K.,Kaufman, J.G. and Lienert, T. J. (eds). TMS,Warrendale, PA, USA, p. 283-294.
Mendez, P.F. and Eagar, T.W. (2001). Weldingprocesses for aeronautics. Adv. Mater.Process, 159(5):39-43.
Schmidt, H.J., Van, C., and Hanson, J. (2001).Tango metallic fuselage barrel validationof advanced technologies. ICAF Designfor Durability in the Digital Age. Proceedingsof the 21st Symposium of the InternationalCommittee on Aeronautical Fatigue;June 27-29, 2001; Toulouse, France, p. 273-288.
