A Study on Contour of Workpiece According to the Shape of Forming Coil in EMF Process

Aluminium alloys is desirable for the automotive and electronic appliances industries due to their high strength-to-weight ratio, corrosion resistance and weldability. However applications of the aluminium alloys were very difficult because aluminium alloys formability is very low at room temperature, despite their advantages. One of the high speed forming technologies is Electromagnetic Metal Forming (EMF), which can be useful forming method for low formability light-weight materials such as aluminium, magnesium alloys in overcoming the limitations of conventional forming methods. EMF process refers to the high velocity and high strain rate deformation of low-formability materials driven by electromagnetic forces that are generated by the rapid discharge current through forming coil. This technology depends on the properties of the sheet metal, as well as the process factors such as electromagnetic force in a practical forming operation. Moreover selection of proper shape of forming coil is most important to achieve the desired deformation using the EMF process. Therefore, the purpose of this study is to analyse of the dynamic behaviours on workpiece according to various forming coil shape with aluminium alloys. To achieve these objectives, a magnetic pulse forming system consisting of a 24kJ electromagnetic power source and a bar-type and helical-type forming coil was employed in an experiment. Then, deformation depth was measured for analyse dynamic behaviours on workpiece. The results showed that as the electromagnetic force increases, surface damage to part of the workpiece will increase and according to the shape of forming coil, distribution of electromagnetic force applied on workpiece is changed in EMF process