Investigation of creep age forming of high strength Al-Li alloy AA2060
File(s)
Author(s)
Wang, Xi
Type
Thesis
Abstract
Panels are critical structural components for aircraft serving as the load-bearing structures and forming the aerodynamic shape. Creep-age forming (CAF), as a well-adopted technology specially invented for fabricating large-scale panels, has attracted much attention since its invention, especially in the recent two decades. Concurrently, continuous efforts have been made to create new generations of Al-Li alloys with advanced performances in strength and weight reduction. Characterised with superior synergy of strength, corrosion resistance, and weight reduction, as one of the newest 3rd generation Al-Li alloys, AA2060 is viewed as the ideal substitution for its predecessors. However, little study has been conducted regarding adopting this newly introduced Al-Li alloy in CAF. On the other hand, with the evident promotion of the strength of the material, the creep resistance of the high strength Al-Li alloys is increased especially in the T8 temper which is the mostly adopted finish temper for the Al-Li alloys. Hence, challenges exist in adopting AA2060-T8 in CAF and relative investigation is still lacking and urgently required.
Aiming at filling this research gap, this thesis presents a comprehensive investigation on adopting AA2060-T8 in CAF. A general review of the background and previous investigations regarding to the CAF and Al-Li alloys has been conducted. To fully understand the micro and macro material behaviours in CAF, a series of experiments have been systematically designed and conducted with corresponding results summarised and discussed. Based on the obtained experimental results, modelling works have been conducted including establishing a constitutive model for describing the stress-creep strain relationship in the uniaxial loading case, as well as extending the established model into the multiaxial case and implementing in the numerical simulations for the conducted CAF fabrication tests of four-point bending and adopting the flexible tool for verification. Lastly, a closed-form springback prediction solution and compensation method covering constitutive relations from elastic to plastic in CAF is developed and verified with the conducted CAF fabrication tests. With the conducted investigation works in this thesis, the basic knowledge of the material behaviours of AA2060-T8 in CAF has been gained and the subsequent forming issues induced by the high creep resistance of this alloy have been solved, which hopefully can shed a light on the future studies of adopting the high strength Al-Li alloys in CAF.
Aiming at filling this research gap, this thesis presents a comprehensive investigation on adopting AA2060-T8 in CAF. A general review of the background and previous investigations regarding to the CAF and Al-Li alloys has been conducted. To fully understand the micro and macro material behaviours in CAF, a series of experiments have been systematically designed and conducted with corresponding results summarised and discussed. Based on the obtained experimental results, modelling works have been conducted including establishing a constitutive model for describing the stress-creep strain relationship in the uniaxial loading case, as well as extending the established model into the multiaxial case and implementing in the numerical simulations for the conducted CAF fabrication tests of four-point bending and adopting the flexible tool for verification. Lastly, a closed-form springback prediction solution and compensation method covering constitutive relations from elastic to plastic in CAF is developed and verified with the conducted CAF fabrication tests. With the conducted investigation works in this thesis, the basic knowledge of the material behaviours of AA2060-T8 in CAF has been gained and the subsequent forming issues induced by the high creep resistance of this alloy have been solved, which hopefully can shed a light on the future studies of adopting the high strength Al-Li alloys in CAF.
Version
Open Access
Date Issued
2022-10-31
Date Awarded
01/03/2023
Advisor
Lin, Jianguo
Shi, Zhusheng
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)