PSI - Issue 17

Ashu Garg et al. / Procedia Structural Integrity 17 (2019) 456–463

463

Ashu Garg et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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The fractographic analysis of notch tensile specimen prepared with TIF tool pin is shown in Fig. 7(c). It may be noted from Fig. 7(c) that the fracture surface examined near the notch tip (crack initiation site) the region exhibit significant amount of shear failure marks with some fine dimples. This indicates that the material endures reasonable plastic deformation and failed both under shear and ductile failure. However, fractograph taken from center of fracture surface, the surface exhibit numerous shallow dimples with some shear failure marks indicates that the joint failed under ductile fracture with relatively small elongation. From the present experimental study, it was observed that the FSW joint between AA6061-T6 and AA7075 T651 obtained with CYL tool pin under the tested process conditions, tunnel/void was observed in SZ and under tensile loading the crack initiated from the vicinity of such tunnel region and propagated through the boundary of SZ and TMAZ. FE results also indicated that the stresses and strain were confined near tunnel region which acted as crack initiation site. For joints obtained with TIF tool pin, sample failed from HAZ region on AS of the joint when no tunnel/void was observed in the SZ. FE results also indicated that the crack initiated and propagated through HAZ region from the AS of the workpiece. From elemental stress distribution it was also be observed that for joint made with CYL tool pin more stresses were generated with a sharp rise and less elongation at failure. However, for joint obtained with TIF tool pin higher stresses are confined in HAZ region and exhibited higher elongation at failure. For notch tensile specimen, notch strength ratio was found greater than unity thus indicated that the joint was notch insensitive. Moreover, the notch opening was observed from the bottom of the weld nugget and propagated towards the weld center through dynamically recrystallized zone. Fractographic studies revealed the presence of dimples, micro-voids for all joints indicating the ductile failure of the joints. Ajri, A., Shin, Y.C., 2017. Investigation on the Effects of Process Parameters on Defect Formation in Friction Stir Welded Samples via Predictive Numerical Modeling and Experiments. Journal of Manufacturing Science and Engineering 139, 111009-1 – 111009-10. Đurđević, A., Živojinović, D., Grbović, A., Sedmak, A., Rakin, M., D ascau, H., Kirin, S., 2015. Numerical Simulation of Fatigue Crack Propagation in Friction Stir Welded Joint Made of Al 2024-T351 Alloy. Engineering Failure Analysis 58, 477 – 484. Ilangovan, M., Boopathy, S.R., Balasubramanian, V., 2015. Effect of Tool Pin Profile on Microstructure and Tensile Properties of Friction Stir Welded Dissimilar AA6061-AA5086 Aluminium Alloy Joints. Defence Technology 11, 174 – 184. Moreira, P.M.G.P., de Jesus, A.M.P., de Figueiredo, M.A.V., Windisch, M., Sinnema, G., de Castro, P.M.S.T., 2012. Fatigue and fracture behavior of friction stir welded aluminium-lithium 2195. Theoretical and Applied Fracture Mechanics 60, 1 – 9. Moreira, P.M.G.P., Santos, T., Tavares, S.M.O., Richter-Trummer, V., Vila ҫ a, P., de Castro, P.M.S.T., 2009. Mechanical and Metallurgical Characterization of Friction Stir Welding Joints of AA6061-T6 with AA6082-T6. Materials and Design 30, 180 – 187. Rajakumar, S., Muralidharan, C., Balasubramanian, V., 2011. Influence of Friction Stir Welding Process and Tool Parameters on Strength Properties of AA7075-T 6 Aluminium Alloy Joints. Materials and Design 32, 535 – 549. Raturi, M., Garg, A., Bhattacharya, A., 2019. Joint Strength and Failure Studies of Dissimilar AA6061-AA7075 Friction Stir Welds: Effects of Tool Pin, Process Parameters and Preheating. Engineering Failure Analysis 96, 570 – 588. Reza-E-Rabby, M., Tang, W., Reynolds, A.P., 2018. Effects of Thread Interruptions on Tool Pins in Friction Stir Welding of AA6061. Science and Technology of Welding and Joining 23, 114 – 124. Yan, J., Sutton, M.A., Reynolds, A.P., 2006. Notch Tensile Response of Mini-Regions in AA2024 and AA2524 Friction Stir Welds. Materials Science and Engineering A 427, 289 – 300. Yokoyama, T., Nakai, K., Katoh, K., 2018. Tensile Properties of 6061-T6 Friction Stir Welds and Constitutive Modelling in Transverse and Longitudinal Orientations. Welding International 32, 161 – 171. 4. Conclusions Acknowledgements Authors acknowledge the Science and Engineering Research Board (SERB) - DST, New Delhi, India for the support (YSS/2015/000085). References