NUMERICAL & EXPERIMENTAL INVESTIGATION OF EFFECTS OF PROCESS PARAMETERS ON ELECTROMAGNETIC FORMING OF METALS

Abstract

Electromagnetic forming is a highspeed forming process in which a metallic sheet is driven by the impulsive magnetic force generated by transient induced current. In this type of forming there is no mechanical contact between the workpiece and tool. The deforming force is attributed to the Lorentz force produced due to a transient current passing through the coil. This technique can be used to achieve a wide range of operations such as compression and expansion of metallic tubes using helical coils, flat sheet forming into three-dimensional shapes using flat spiral coils. The technique can also be used for other operations like cutting, welding, hemming, joining, and crimping. The technique is used to deform metals with low electrical conductivity using aluminium as a driver. Due to growth in industrial applications, the demand for better-simulating tools and parametric analysis of process parameters to improve the electromagnetic forming process is also increasing. The present research aims to provide detailed parametric analysis and an efficient Finite Element (FE) model for the analysis of the electromagnetic forming process. A 2-D symmetric FE model has been developed and compared with the experimental data. The model consists of three main modules which are fully coupled namely electrical circuit, magnetic field and solid mechanics. In this work, particular attention is assigned to the study of the most relevant process parameters, focusing on their significance, effects and mutual interaction. To evaluate the performance of the proposed approach, numerical results were compared with experimental results and those proposed in the literature, to assess the robustness and accuracy of the proposed model. The obtained results show a good correlation between numerical and experimental results. The effect of sheet deformation on changing magnetic flux and system inductance was considered in the numerical model. A good agreement with experimental results was observed. The effect of varying parameters on the deformation, change in sheet thickness and the velocities of equidistant points were numerically calculated. The maximum error observed in numerical and experimental deformation was 4.9%. A Taguchi L9 array is used for the Design of Experiments (DoE). Three parameters such as Input voltage, sheet thickness, coil parameter. These sets of experiments were performed on AA6061-T6 to check the deformation and thickness variation response by changing process parameters. The most significant parameter during sheet deformation was estimated using ANOVA technique. It was observed that the effect of coil turns was negligible as compared to the input voltage and sheet thickness on sheet deformation. The contribution ratio of input voltage in sheet deformation was 46.21% while that of sheet thickness was 45.13%. The same technique was used to analyse the effects of process parameters (input voltage, driver sheet thickness, driven sheet thickness) on the deformation of non-magnetic stainless-steel sheets (SS304) using AA6061-T6 sheets as a driver. The results revealed that all three process parameters (i.e. input voltage, driver sheet thickness, driven sheet thickness) are significant. The contribution ratio of input voltage in sheet deformation was 23.98%, the contribution ratio of driver sheet thickness was 19.07% while that of driven sheet thickness was 51.6%. A numerical investigation of driven sheet dynamics and deformation was carried out. A good agreement with experimental results was observed with a maximum error in deformation of less than 5%. The proposed method is very useful to industries and provides a better understanding of the important parameters using simulation tools without wasting time and energy on experimental trials.