Abstract
This study aims to investigate the formability of the AA2198-T3 Al-Li alloy in hydro-mechanical deep drawing (HMDD), through experimentation and finite element simulation. The effects of the most critical factors were studied: die cavity pressure and forming temperature; the forming temperature is selected at 298K and 423K. The Gurson−Tvergaard−Needleman model (GTN model) was employed to analyze the formability of AA2198-T3 Al-Li alloy and predict the fracture in the hydroforming of a cylindrical part. Both the numerical and experimental results showed that the increase of the pressure inside the liquid chamber, within a certain range, contributes to improve the formability of the alloy. Increasing the temperature would reduce the required pressure for sheet hydroforming. Notably, the appropriate chamber pressure was beneficial to form good quality parts with a relatively uniform wall thickness. By analyzing the fracture morphologies, the brittle fracture of AA2198-T3 plays a main role at room temperature, but the ductile fracture was shown at the elevated temperature.
Highlights
With the rapid development of the aerospace industry, modern military and civilian aircraft have developed towards high-speed overload, long life and flight safety
The distribution of the equivalent plastic strain predicted by the FE simulation model under different hydraulic pressures at 298 K and 423 K are depicted in Figs. 4b and 4c respectively
The hydrodynamic deep drawing (HMDD) process with proper fluid pressure can improve the formability of the alloy
Summary
With the rapid development of the aerospace industry, modern military and civilian aircraft have developed towards high-speed overload, long life and flight safety. The materials and weight requirements of aircraft structural parts have become increasingly stringent. Aluminum-lithium (Al-Li) alloys offer great superiority for use in aircraft structure since they reduce the density, increase stiffness, increase the resistance to fracture toughness and fatigue crack growth, and enhance the corrosion resistance [1,2]. With the addition of lithium, the weight (density) of the alloy reduces approximately 3% for each 1% lithium addition to aluminium, while Young’s modulus increases about 6% [1,3]. AA2198-T3 Al-Li alloy, as the third generation of damage-tolerant Al-Li alloys, is considered as one of the most competitive lightweight and high strength structural materials in the aerospace industry [4,5,6,7]. The application of formed parts in critical structures is still restricted by the material low formability at ambient temperature [8,9,10]
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