A modification of the multicomponent Armstrong–Frederick model with multiplier for the enhanced simulation of aerospace aluminium elastoplasticity. (August 2018)

• Record Type: Journal Article
• Authors: Agius, Dylan; Kourousis, Kyriakos I.; Wallbrink, Chris
• Is Part Of: International journal of mechanical sciences. Volume 144(2018)
• Page Start: 118
• Page End: 133
• Publication Date: 2018-08
• Subjects: Cyclic plasticity -- Kinematic hardening -- Hysteresis loops -- Mean stress relaxation -- Multiplicative AF model -- Aerospace aluminium; Mechanical engineering -- Periodicals; Génie mécanique -- Périodiques; Mechanical engineering; Maschinenbau; Mechanik; Zeitschrift; Periodicals; 621.05
• DOI: 10.1016/j.ijmecsci.2018.05.036
• Languages: English
• ISSNs: 0020-7403

Abstract

Highlights: The proposed modification improved the mean stress relaxation capability of the MAFM model. The decaying feature of the MAFM coefficients used to simulate the initial monotonic loading branch has resulted in significant improvement of hysteresis loop shape. A novel memory parameter algorithm incorporated in the model allowed the re-emergence of the monotonic behaviour from overloads in variable loading cases. Experimental data from two widely used aerospace aluminium alloys were successfully simulated with the new model. Overall, the modified model has improved the original MAFM model prediction capabilities. Abstract: The Multicomponent Armstrong–Frederick (AF) model with Multiplier (MAFM) has demonstrated high simulation accuracy for uniaxial and multiaxial loading conditions for a number of different materials. In this study the MAFM model is modified to improve the phenomenological modelling of aerospace aluminium alloys 7075-T6 and 7050-T7451 under uniaxial constant and variable amplitude loading. In order to recognise the experimentally observed strain amplitude dependency of mean stress relaxation rate, the coefficient of the linear kinematic backstress was modified from a constant to a strain amplitude dependent dynamic term. This modification improved the mean stress relaxation capability of the MAFM model. Additionally, the hysteresis loop evolution has been enhanced via further modification of the MAFM model by improving the monotonic stress-strain evolution of the initial loading branch of cyclic load cases by separating the kinematic backstress coefficients into two parts, the contributions from cyclic and monotonic micro-mechanisms. The monotonic coefficients were allowed to decay with continued cycling, which captured the monotonic to cyclic transition of stress-strain development. Finally, the experimentally observed reversibility of the monotonic stress-strain evolution has been also incorporated successfully through the introduction of a decaying strain range memory parameter, which improved the variable amplitude hysteresis loop evolution. Overall, the modified MAFM model has been successful in improving simulation accuracy of the cyclic elastoplastic response exhibited by both aluminium alloys examined. Graphical abstract: Image, graphical abstract