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Title: Study of HFQ forming process on lightweight alloy components
Author: Gao, Haoxiang
ISNI:       0000 0004 6496 8096
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2017
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In order to reduce CO2 emissions and improve fuel efficiency for the aerospace industry, a leading edge sheet metal forming technology, namely solution heat treatment, forming and in-die quenching (HFQ) was utilised to form lightweight, complex-shaped components, efficiently and cost-effectively. The work performed in this research project contains two major achievements. The first achievement is successfully forming a complex AA2060 (Al-Li alloy) wing stiffener demonstrator part, and an L-shape AA7075 demonstrator part, without necking or fracture, using HFQ forming technology. The feasibility of forming the aluminium alloys was based on a series of fundamental experimental tests including uniaxial tensile test, isothermal forming limit test and artificial aging test. The second achievement is the development of a novel forming limit prediction model, namely the viscoplastic-Hosford-MK model. This model enables the forming limit prediction of AA2060 and AA7075 alloys under hot stamping conditions, featuring non-isothermal and complex loading conditions. This prediction model fills a significant need in industry for accurately predicting the forming limit of aluminium alloys under such complex forming conditions. The effectiveness of the developed model was analytically verified for AA2060, demonstrating accurate material responses to cold die quenching, strain rate and loading path changes. By applying the developed model to the hot stamping of an AA2060 component, its accuracy was successfully validated. Furthermore, the viscoplastic-Hosford-MK model was also demonstrated for use in industry by determining the optimum initial blank shape of an L-shape AA7075 component. An iterative simulation procedure implementing the forming limit prediction model was used to arrive at an optimum blank shape by the minimisation of the failure criterion. The optimised initial blank shape design was applied in the experimental hot stamping of a demonstrator AA7075 component. The accuracy of the developed model was validated by the successful forming of the component, without necking or fracture.
Supervisor: Wang, Liliang ; Lin, Jianguo Sponsor: Beijing Aeronautical Manufacturing Technology Research Institute (BAMTRI)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral