MODELING OF SINGLE POINT INCREMENTAL FORMING PROCESS FOR METAL AND POLYMERIC SHEET

Incremental Sheet Forming (ISF) is an innovative forming approach for sheet materials. This process has been promising a flexible, short time, and inexpensive way to form sheet products. The requiring equipments for SPIF process include a hemispherical forming tool and very simple frame to hold firmly a forming sheet. The forming tool is moved along a predefined toolpath which is a series of contour constructed a final shape of product by using numerical controlled technology. The sheet is deformed locally and finished in every layer in which is similar to the layered manufacturing principle of rapid prototype approach. Therefore, the process is relative slow and only suitable to small (or medium) production batch and rapid prototype production. Main advantages of SPIF technology are flexible, just-in time, short product development time, and inexpensive die/tooling. Additionally, it can form a product with an unlimited depth and allows high strain in comparison to conventional sheet forming technologies. Realizing advantages of this process in industrial applications, the current study is performed the single point incremental forming process (SPIF) for both sheet metals and sheet polymers into main contents as following: SPIF process is performed with magnesium alloy sheet and aluminum alloy sheet at an elevated temperature. Deforming sheet with SPIF process at a high temperature is to find a high formability in compared with previous researchers of aluminum sheet. Magnesium sheet has important industrial applications with a high ratio of weight/strength; however, it has low formability at room temperature. A heating system based on Joule effect is design to serve for experiments. It allows heating the sheet in very short time, which can avoid oxygenating phenomenon on sheet surfaces. This thesis also investigated FEM simulation to predict the mechanical failures in SPIF. A fully couple thermal analysis is performed with full cone-shaped model which is taken into account of material behaviors such as anisotropy and sensitivity of strain rate and temperature. The speeding up and adaptive meshing technologies for FEM simulation are also discussed in here. The first effort to find an applicability of SPIF for polymeric materials was investigated in the current thesis. Preliminary experiments of SPIF performed on thermoplastic materials at room temperature. An experimental strategy based on DOE technique is designed to evaluate preliminarily the influence of processing parameters on the formability. Then, constitutive material model base on overstress theory (VBO) is developed to implement into FEM simulation for prediction of the thickness and geometric accuracy.