Creep age forming investigation on aluminum alloy 2219 and related studies

Abstract

By the middle of the 20th Century, traditional mechanical metal forming methods were showing to be inadequate for producing components comprising of large high strength aluminium alloy panels with complex curvatures, such as those used in modern aircraft and aerospace metal structures. To deal with this problem, a new forming method was conceived by Textron, which has proven to be very useful for forming components with these shape characteristics and good mechanical properties. The method is called Creep Age Forming (CAF). The research described in this thesis is a study of CAF of a 2219 aluminium alloy, which is used for fabricating the isogrid structure for fuel tanks of launch vehicles. The main aim of the research is to develop experimental and modelling tools for CAF of AA2219 sheet structures. A series of creep-ageing tests and stress-relaxation tests have been conducted on AA2219 at 175 °C . The age-hardening, creep deformation and stress relaxation behaviour of AA2219 have been investigated. Based on the experimental investigation, a novel set of physically based, unified creep constitutive equations has been established. A small scale CAF test rig was designed to validate the springback prediction from FE simulation. The experimental result and simulation are in good agreement. Development of FE procedures for simulating creep-ageing behaviour of the material and springback has been performed to predict and assess the springback behaviour of metal sheet in typical forming tools.