Experimental investigation and numerical simulation of creep age forming with aluminium-copper-lithium alloy 2050

Abstract

This thesis presents a comprehensive research on experimental investigation and numerical modelling of the creep-ageing behaviour of a newly developed Al-Cu-Li alloy, AA2050-T34, building a solid foundation for the alloy to be manufactured through creep age forming (CAF) technology for panel products in the aerospace industry. An experimental programme has been designed and carried out to investigate the creep deformation and age hardening behaviours of the alloy at 155 ºC under both tension and compression conditions, including creep-ageing and tensile tests and microstructural observations. An asymmetric tension and compression creep-ageing behaviour and a particular double primary creep feature of the alloy have been first-time observed and the relevant mechanisms have been revealed through the microstructural analysis. A new unified constitutive model has been developed and calibrated with the experimental results. The model can well capture these microstructure-controlled mechanisms and accurately predict the asymmetric creep-ageing behaviour with the double primary creep feature of AA2050-T34. The developed constitutive equations have been implicitly resolved and implemented into the finite element (FE) software, PAM-STAMP, for CAF process simulation. CAF experiments were carried out to form some singly-curved and doubly-curved AA2050-T34 plates with different thicknesses. The simulation results of yield strength evolution during CAF and springback properties of the formed plates from CAF FE models correspond well with experimental results, validating the effectiveness of the developed FE model for CAF process simulation and prediction. The CAF FE model for AA2050-T34 developed in this thesis can now be used to assist the yield strength prediction and tool shape compensation for CAF manufacture of particular products.