Issue 48

R. Maciel et alii, Frattura ed Integrità Strutturale, 48 (2019) 269-285; DOI: 10.3221/IGF-ESIS.48.28 284 In the SLJ tensile tests, the load was applied on the advancing side. In the FSW-only joints a trend was observed in respect to the failure modes. As the downward force increased the fracture changed from mode II to mode I which was accompanied by an increase in joint strength. In the Hybrid joints that transition is not as linear and it was verified that when under mode I, the joints tended to fracture with lower applied force, since the adhesive is not as resistance to fracture as it is under pure shear force. This result suggests that higher downward forces, over 500 kgf, tend to degrade the adhesion quality and the adhesive is not as effective under mode I conditions. So, for the hybrid joints, unlike the FSW-only ones, the preferred mode, with better performance, would be mode II. The best results, both for fracture toughness and ductility are therefore obtained with an applied force of 450 kgf which might be considered as an inflection point in joint performance maintaining all the other parameters constant. The hybrid joints present better overall results, the best joint was efficiency achieved with the hybrid joint produced with 450 kgf. The average efficiency value in this case was 73.75%, specimen it reached the value of 85.21%. The from the results it is possible to affirm that the hybridization process confers an improvement between 20-30 % in most cases. A CKNOWLEDGMENTS his work was supported by FCT, through IDMEC, under LAETA, project UID/EMS/50022/2019. Funding provided from NORTE-01-0145-FEDER-000022 SciTech – Science and Technology for Competitive and Sustainable Industries is acknowledged. The authors acknowledge the funding provided by FCT project PTDC/EME-EME/29340/2017 – DisFri. R EFERENCES [1] European Commission (2009). Directive 2009/33/EC - Clean and energy-efficient road transport vehicles, pp. 5–12. Available at: https://eur-lex.europa.eu/legal-content/en/txt/pdf. [2] Peeters, P. M., Middel, J. and Hoolhorst, A. (2005). Fuel efficiency of commercial aircraft. NLR-CR-2005-669, (November), pp. 1–37. http://www.transportenvironment.org/sites/te/files/media/2005-12_nlr_aviation_fuel_efficiency.pdf. [3] Reynolds, C. and Kandlikar, M. (2007). How hybrid-electric vehicles are different from conventional vehicles: The effect of weight and power on fuel consumption. Environmental Research Letters, 2(1). DOI: 10.1088/1748-9326/2/1/014003. [4] Braga D. F. O, Maciel R, Bergmann L., et al. (2018). Fatigue performance of hybrid overlap friction stir welding and adhesive bonding of an Al ‐ Mg ‐ Cu alloy. Fatigue Fract Eng Mater Struct, pp. 1–9. DOI: 10.1111/ffe.12933. [5] Braga, D. F. O. (2018). Innovative structural joining for lightweight design. Submitted for the degree of Doctor of Philosophy in Leaders for Technical Industries of the MIT-Portugal Program. Faculty of Engineering of the University of Porto, Portugal. [6] Marques, E. A. S. et al. (2014). Adhesive joints for low- and high-temperature use: An overview. Journal of Adhesion, 91(7), pp. 556–585. DOI: 10.1080/00218464.2014.943395. [7] Bento, T. J. L. A. A. (2018). Smart Hybrid Friction Stir Welded Joints for Aerospace Design Applications. Submitted to obtain the Master of Science Degree in Aerospace Engineering. Higher Technical Institute of the University of Lisbon, Portugal. [8] Mishra, R. S. and Ma, Z.Y. (2005). Friction stir welding and processing. Materials Science and Engineering: R: Reports, 50(1–2):1 – 78. issn 0927-796X. DOI: 10.1016/j.mser.2005.07.001. [9] Braga, D. F. O. et al. (2015). Aluminum Friction Stir Weldbonding. Procedia Engineering, Elsevier B.V., 114, pp. 223– 231. DOI: 10.1016/j.proeng.2015.08.062. [10] Moreira, P. M. G. P. et al. (2009). Mechanical and metallurgical characterization of friction stir welding joints of AA6061- T6 with AA6082-T6, Materials and Design, 30(1), pp. 180–187. DOI: 10.1016/j.matdes.2008.04.042. [11] Moreira, P. M. G. P. (2008). Lightweight stiffened panels: Mechanical characterization of emerging fabrication technologies. Submitted for the degree of Doctor Philosophy in Mechanical Engineering, Departamento de Engenharia Mecânica e Gestão Industrial, Faculdade de Engenharia da Universidade do Porto, Portugal. [12] Chaves, F. J. P. et al. (2014). Fracture characterization of bonded joints using the dual actuator load apparatus. Journal of Adhesion Science and Technology, 28(5), pp. 512–524. DOI: 10.1080/01694243.2013.845357. T