Development of multi-container extrusion technique for manufacturing wide-thin aluminium plates with stiffeners
File(s)
Author(s)
Zhang, Zhe
Type
Thesis
Abstract
Wide-thin aluminium plates with stiffeners are extensively utilised in various industries, but their fabrication presents a challenge due to their structural complexity. The multi-container extrusion technology has emerged recently as a promising solution to this predicament with low extrusion force. The work in this thesis focuses on the development of multi-container extrusion in wide-thin stiffened panel manufacturing, including designing and optimising the multi-container extrusion tooling, establishing finite element modelling to optimise the extrusion process, revealing the mechanism of the hot deformation of aluminium alloy, and analysing the performance of extrudates produced by multi-container extrusion.
Two multi-container extrusion dies are developed and compared. Simulation results reveal superior metal flow and welding quality with the modified design, achieving a material savings of 39.5% compared with the initial design. Additionally, the structure of modified die design has a smaller maximum effective stress, effective strain, and displacement.
Thermal-mechanical testing elucidates aluminium alloy behaviour, distinguishing between fully and non-fully homogenised billets. The non-fully homogenised AA6061 billet has a columnar microstructure and displays three unusual characteristics: surface oxidation, different flow stresses, and orange peel surface. Differences in the initial grain morphologies and dislocation density explain the observed behaviours. The fully homogenised billet does not have above abnormal features, having an equiaxed grain structure. The flow stress of fully homogenised billet is lower than that of the non-fully homogenised billet at same testing condition.
The setup of a multi-container extrusion system using the modified die design and fully homogenised billets is detailed. Extrusion experiments under various parameters demonstrate changes in weld appearance and mechanical properties. Specimens with welds typically shown a reduction in hardness, ultimate tensile strength, and elongation, yet they maintain the same yield strength as their counterparts without welds.
Two multi-container extrusion dies are developed and compared. Simulation results reveal superior metal flow and welding quality with the modified design, achieving a material savings of 39.5% compared with the initial design. Additionally, the structure of modified die design has a smaller maximum effective stress, effective strain, and displacement.
Thermal-mechanical testing elucidates aluminium alloy behaviour, distinguishing between fully and non-fully homogenised billets. The non-fully homogenised AA6061 billet has a columnar microstructure and displays three unusual characteristics: surface oxidation, different flow stresses, and orange peel surface. Differences in the initial grain morphologies and dislocation density explain the observed behaviours. The fully homogenised billet does not have above abnormal features, having an equiaxed grain structure. The flow stress of fully homogenised billet is lower than that of the non-fully homogenised billet at same testing condition.
The setup of a multi-container extrusion system using the modified die design and fully homogenised billets is detailed. Extrusion experiments under various parameters demonstrate changes in weld appearance and mechanical properties. Specimens with welds typically shown a reduction in hardness, ultimate tensile strength, and elongation, yet they maintain the same yield strength as their counterparts without welds.
Version
Open Access
Date Issued
2024-02-29
Date Awarded
2024-05-01
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Shi, Zhusheng
Lin, Jianguo
Sponsor
China Scholarship Council
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)