Comparative Study of Incremental Forming and Elevated Temperature Incremental Forming Through Experimental Investigations on AA 1050 Sheet

Unlike conventional forming processes, incremental forming (IF) does not require any part-specific tooling. It is a flexible forming process that is suitable to form user-specific shapes and for low volume production. The IF process has been recognized as a promising manufacturing process over conventional forming for the materials having decent formability. However, it does not give reliable results while forming hard to form materials. A few investigations revealed that heat plays a vital role in enhancing the formability. On heating, the yield stress of the materials gets reduced, the ductility increases, and hence the formability improves. Thus, for the materials having poor formability, an advance IF technique, elevated temperature incremental forming (ET-IF), has been developed. ET-IF involves incremental forming of the sheets while being heated by an external heat supply. This research study focuses on the execution of the ET-IF process and its comparison with the conventional IF process. A radiation type heating device to perform the ET-IF process is designed and fabricated. The experimental investigations were carried out on 1 mm thick AA 1050 sheets by carrying out the IF process at room temperature and enhanced temperatures. Experimentation was initiated with performing straight grove tests, which were later extended to form a few more shapes. Experimental results confirm the delay in fracture and intensification of formability with the ET-IF process in comparison to that of the IF process at room temperature. The work overcomes the limitation and enlarges the scope of application of the IF process.

Thickness control in a new flexible hybrid incremental sheet forming process

Incremental sheet forming is a cost-effective process for rapid manufacturing of sheet metal products. However, incremental sheet forming also has some limitations such as severe sheet thinning and long processing time. These limitations hamper the forming part quality and production efficiency, thus restricting the incremental sheet forming application in industrial practice. To overcome the problem of sheet thinning, a variety of processes, such as multi-step incremental sheet forming, have been proposed to improve the material flow and thickness distribution. In this work, a new process has been developed by introducing multi-point forming as preforming step before conducting incremental sheet forming processing. Employing an established hybrid sheet forming system and the corresponding thickness prediction model, the preform shape can be optimized by employing a two-step optimization approach to improve the sheet thickness distribution. In total, two case study examples, including a hemisphere part and an aerospace cowling part, are fabricated using the developed hybrid flexible process in this study. The experimental results show that the hybrid flexible forming process with the optimal preform design could achieve sheet parts with more uniform thickness distribution and reduced forming time.

Importance of Feature Sequencing in Incremental Forming

Incremental Sheet Forming (ISF) is a flexible forming process suitable for low volume production of sheet metal components. Single Point Incremental Forming (SPIF), which has only one tool forming the geometry, is the simplest variant of incremental forming. Bending of sheet between the component opening and the fixed boundary is unavoidable in SPIF due to the absence of support/backup. Double Sided Incremental Forming (DSIF) has two tools which can be used interchangeably for forming and providing local support. The accuracy of parts formed using DSIF is superior to those formed using SPIF as the unwanted bending is substantially reduced by providing local support. In addition DSIF is capable of forming components with features on both sides of the initial plane of sheet and convex and concave features without additional setup. In ISF, as the deformation progresses, the intended geometry slowly develops, this increases the stiffness of the sheet. While forming multiple features, the forming sequence greatly affects the way stiffness builds-up, which further affects the geometry of formed components. In the present work, an experimental investigation is carried out to demonstrate the affect of forming sequence on the geometries and accuracy of formed component. Results presented show that the feature sequencing greatly affects the geometry and accuracy of formed components.

The Effect of Loading Path on Forming Results in Multi-Gripper Flexible Stretch Forming

Multi-gripper flexible stretch forming (MGFSF) is a recent technological innovation of sheet metal flexible forming process. Straight jaws in traditional stretch forming machine are replaced by a pair of opposed clamping mechanisms which can move relative to each other. Taking the case of forming a sheet metal into spherical surface by stretching the sheet in two opposite directions, the finite element models of MGFSF under various loading paths were established and the effects on stretch amount, strain and thickness of the simulated parts were analyzed comparatively. It is founded that compared to the horizontal-tilting (HT) and horizontal-vertical (HV) loading paths, the horizontal-tilting-vertical (HTV) loading path would result in more uniform stretch amount, strain and thickness distributions also with lower strain and thickness reduction, which improves the forming quality significantly. Finite element simulations also revealed that the material flow state in the transition zone can be improved effectively and the local strain concentration can be greatly suppressed with reasonable loading path, which would decrease the possibility of material failure.

Investigation of Sheet-Titanium Forming with Flexible Tool – Experiment and Simulation / Badanie Kształtowania Blach Tytanowych Z Wykorzystaniem Elastycznego Narzędzia - Doświadczenie I Symulacja

In the paper the results of investigation of sheet-titanium forming with flexible tool are presented. Titanium alloy sheets belong to a group of materials which are very hard to deform at ambient temperature. To improve sheet formability forming technology using a semi-flexible tool was implemented. Experiments were carried out on a specially designed for this purpose device. Due to the application of a rubber pad the stress state similar to triaxial compression was produced in the deformed material. Such a stress state made it possible to obtain higher material deformation without risk of fracture. The numerical simulations were used for analysing the flexible forming process. The ADINA System basing on the Finite Element Method (FEM) was applied.