Thesis
A study of the forming limits of cold and hot forming of aluminium alloy sheets with multi-point tooling
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2020
- Thesis identifier
- T15795
- Person Identifier (Local)
- 201485827
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Multi-point forming (MPF) is a special category of sheet metal forming techniques with good operational flexibilities due to using two sets of adjustable pins along the machine ram direction. These pins represent the acting points of the desired forming-tool surface contours. Although this technology has already been widely used for the shaping of panel components, it has been little tested for the forming of lightweight metal sheets with high strength. Forming of lightweight metallic materials, such as aluminium alloys, has been widely deployed in the Aerospace and Automotive industry. Nevertheless, some challenges still exist when the forming takes place under different process and machine-set conditions, especially materials such as high strength aluminium alloy sheets. Hot stamping technology is capable of improving the material properties and forming limits while reducing the forming-force requirement and springback. This could be enhanced particularly by integrating an intermediate fast cooling process into the process chain of the forming of aluminium alloys. However the spray cooling that is currently popular in industry cannot achieve the required high cooling rates, while introduction of an intermediate fast cooling process into an industry process is hampered by lack of the industrially viable tooling. To address the issues mentioned above, this PhD research studies the feasibility of combining multi-point forming and hot-forming to shape the high-strength Aluminium alloy sheets. This is done with a view to improving the manufacturing flexibility while the capability of forming high-strength sheet-metals is maintained. This new capability was further enhanced by developing a fast contact-cooling facility and integrating it into a pilot prototype production line. The fundamental and process studies combined with the two test cases, deep drawing and stretch forming with multi-point tooling, suggest a feasible alternative route for the forming of lightweight high-strength sheet-metals. The pilot line established shows that the fast contact-cooling technology is effective for application in an industrial metal forming process. With this pilot line, the aluminium sheets heated up by the electrical furnace were subjected to the intermediate cooling prior to the loading into the multi-point tooling for forming. Different cooling rates, such as 50 °C/s and 100 °C/s, have been tested, and their effects on the forming limits for different component-forms investigated. AA6082 sheet blanks were used as the raw material; several square cups with different depths were formed; and the temperatures of the sheet blanks were monitored during the tests through a built-in monitoring system. The tests conducted demonstrated that the integration of fast contact cooling into a production process is feasible and its associated cost could be relatively low. It also demonstrated that introducing a high-temperature forming configuration into a multi-point tooling forming process is feasible, which extends the existing process capabilities. The test results showed that proper cooling rates, which are achievable easily with the facility developed, could improve forming limits of the high strength aluminium alloys greatly, although, in general, the higher the cooling rate, the better results are obtained. At the same time, the fast-cooling configuration design could, potentially, lead to significant process-time saving, due to the extremely short cooling time involved.
- Advisor / supervisor
- Qin, Li
- Resource Type
- Note
- This thesis was previously held under moratorium between December 2020 and January 2023.
- DOI
- Date Created
- 2020
- Former identifier
- 9912937493302996
Relations
Items
| Thumbnail | Title | Date Uploaded | Visibility | Actions |
|---|---|---|---|---|
|
|
PDF of thesis T15795 | 2021-07-02 | Public | Download |