F. Abu-Farha, Penn State University/Erie, Erie, PA; M. Nazzal, German-Jordanian University, Amman, Jordan; O. Rawashdeh, Oakland University, Rochester, MI
The increasing interest in lightweight metallic sheets has led to the growing activities on hydro/pneumatic forming operations; particularly at warm and elevated temperatures, provided the limited cold formability of most lightweight alloys. This is most prominent in the case of the superplastic forming (
SPF) technique, which seems to go hand-in-glove with lightweight alloys. However, there is still a lack of accurate models that can describe the behaviour of the formed material, hence adequately predict/control the forming process; a fact that is hampering SPF’s use on a larger scale. One critical problem is the accustomed model validation process, which is predominantly based on a comparison of final thickness distribution in the formed part against FE predictions. While this is a good practice, it is not direct enough to provide an explicit feedback for fine tuning the constitutive model, simply because it is solely based on a post-forming result (
rather than the process itself).
The need for a more direct verification approach provoked this effort, in which simple electrical contact sensors are planted across the surfaces of selected calibration forming dies. The constitutive model for each of the investigated materials is first fed into a FE package, which in turn is used to simulate the forming process corresponding to the die geometry. The contact sensors are then used to monitor the deformation of the sheet, and compare it to the FE predictions. It is shown how monitoring the progress of the forming process provides a significant in situ feedback on the accuracy of the FE generated pressure-time profiles, and hence the accuracy of the adopted material’s constitutive model. The effectiveness of this approach is demonstrate by the presented attempt to generate accurate constitutive/FE models for both the 5083 aluminium and the AZ31 magnesium alloys, at different sets of forming conditions.
This work presents a direct model validation/verification approach, through in situ monitoring of the progress of the hydro or pneumatic (including SPF) forming process. Simple electrical contact sensors are planted across the surfaces of selected calibration forming dies. The constitutive model for each of the investigated materials is fed into a FE package, which in turn is used to simulate the forming process. The contact sensors are then used to monitor sheet deformation and compare it to the FE predictions. It is shown how monitoring the progress of the forming process provides a significant in situ feedback on the accuracy of the FE generated pressure-time profiles, and hence the accuracy of the adopted material’s constitutive model. The effectiveness of this approach is demonstrate by the presented attempt to generate accurate constitutive/FE models for both the 5083 aluminium and the AZ31 magnesium alloys, at different sets of forming conditions.
