African Journal of Basic & Applied Sciences 7 (2): 116-124, 2015 ISSN 2079-2034 © IDOSI Publications, 2015 DOI: 10.5829/idosi.ajbas.2015.7.2.22285 Corresponding Author: Y. Kambouz, University of SidiBel-Abbes-ALGERIA, Materials and Reactive Systems Laboratory 116 Numerical Study of Fatigue Behaviour for AA6082-T6 Aluminium Alloy Friction Stir Welds under Monotonic and Variable Amplitude Loading Y. Kambouz, M. Benguediab, B. Bouchouicha and M. Mazari University of SidiBel-Abbes-ALGERIA, Materials and Reactive Systems Laboratory Abstract: In addition to uncertainty such as material strength, notch geometries, defect contents and residual stresses, welded components are often subjected to variable amplitude service loads. The objective of this investigation is to determine the fatigue strength of friction stir welds in AA6082-T6 under constant and variable amplitude loading and analyse the validity of Miners rule in this specific welding process. Microhardness tests were performed to characterize the Vickers hardness profile in the vicinity of the weld area. Friction stir welding process leads to a decrease of the static mechanical properties relatively to base material. Detailed examination revealed a hardness decrease in the thermo mechanically affected zone and the nugget zone average hardness was found to be significantly lower than the base alloy hardness. Welded specimens show significantly lower lives than base material specimens. Key words: Friction Stir Welding Aluminium alloy Fatigue Variable amplitude loading INTRODUCTION The objective of this work is to study the fatigue Friction stir welding (FSW) is a relatively new amplitude loading and analyse the validity of Miners´s solid-state joining process and is very energy rule for this specific welding process. efficient, environment friendly and versatile, being considered to be the most significant development in Presentation of the Material: The material used is an metal joining in a decade. Since its invention in 1991 at the aluminum alloy 6000 series subjected to T6 treatment, Welding Institute (TWI) of UK [1], a large amount of which will help the investigation of the various research was carried out in several fields and different phenomena that occur during welding with involving the materials precipitation phenomenon. Aluminium alloys are the materials more often studied This aluminum alloy is a high strength Al-Mg-Si alloy and where this technique has shown a better performance. that contains manganese to increase ductility and Comparative mechanical properties studies of base toughness. The T6 condition is obtained through artificial material and welded specimens, including fatigue strength ageing at a temperature of approximately 180°C [8]. tests have been performed by several authors [2-6]. In addition to uncertainty such as material strength, Hardness Profile and Mechanical Properties of the notch geometries, defect contents and residual stresses, Material: The most commonly used practice is the welded components are often subjected to variable measurement of microhardness which gives a first amplitude service loads. The lack of Miner´s validity evaluation of the mechanical properties in different areas accumulation rule [7] has been demonstrated in many of the weld, in order to obtain a profile across it and to applications and, in consequence, its usage will introduce establish the weld zones. It is a direct result of the uncertainties which must be compensated by safety change in the microstructure caused by the welding factors. In the case of friction stir welding (FSW) no data process. is available concerning fatigue behaviour under variable The optimization of the weld process FSW requires amplitude loading. the mechanical characterization of the weld bead. strength of friction stir welds under constant and variable