Magnetic Pulse Welding: An Innovative Joining Technology for Similar and Dissimilar Metal Pairs

Once it was widely thought to be an exceptional innovative welding solution, the magnetic pulse welding, dragged the related manufacturing industries and particularly automobile companies for its complex assembly solutions in early 2000s. Although this technique has been implemented by some giant manufacturers for various joining tasks, the process still has not been well adopted by industries. However, in recent years, many researchers turned their attention to the potential applications and insight investigations of this process due to the existence of bottlenecks and the prime novelty of this technique. This chapter clearly highlights the process, applications, requirements, interfacial kinematics of the welding, numerical predictions of interfacial behaviours and multi-physics simulations. This chapter recommends that the overall outlook of the process is promising while it requires extra attention in the individual welding cases and its material combinations

Effect of Conductivity of the Inner Rod on the Collision Conditions During a Magnetic Pulse Welding Process

The Magnetic Pulse Welding (MPW) process involves a high speed collision between the flyer and inner rod. Conductivity of the inner rod may play a significant role in the collision speed and collision angle. The collision conditions were investigated with varying conductivity of the inner rod in this study. Coupled mechanical-electromagnetic 3D simulations were carried out using LS-DYNA package to investigate the effect of conductivity of the inner rod on the collision patterns during the MPW process. The simulation involves a welding process with a tube and a rod using a one turn coil with a separate field shaper. The electrical conductivity was varied to a wide range to investigate the influence on the collision condition. Moreover, in order to verify the independency of the collision condition with the mechanical properties of the inner rod, two cases including aluminum alloy AA2024-T351 and copper with appropriate Johnson-Cook parameters were used for the rod. In the entire simulations aluminum alloy was used as the tube material. It was identified that the impact velocity is almost consistent for each case and the impact angles vary between negative and positive values according to the angular measurement convention used in this study. Although, influence of the conductivity of the inner rod is not significant for the investigated current flow while it may sometime delay the incidence of collision at lower frequencies than the critical frequency (FCrit). Optimizing the collision conditions in the MPW process can help to identify the suitable materials for prescribed welding conditions

Heterogeneous deformation during electromagnetic ring expansion test

High speed forming methods become attractive in manufacturing and it significantl reduces the cost and energy requirements. Conventional manufacturing processes such as forging, forming, stamping and cutting of metals typically involve a strain rate of 10 2 – 10 4 s-1 which includes high energy rate fabrication (HERF) methods [1]. During advanced manufacturing methods such as high speed forming and high speed welding processes, certain local regions (e.g. interfaces) of materials could also experience significantly high strain rate (> 10 4 s-1). In order to understand the physical behaviours of materials and to design/control/optimise, such manufacturing processes that require an appropriate technique to capture the material’s viscoplastic property under the high strain rate deformation. Therein, the electromagnetic ring expansion test becomes a promising method to characterize the material behaviours under the high strain rate deformation. The ring expansion is caused by Lorentz force that is generated due to the magnetic induction on the ring. However, the realistic nature of the electromagnetic ring expansion test is quite complex because of the coupling physics between electromagnetic-thermal-mechanical components. Therefore, in this study we evaluate certain controlling parameters which govern the fundamental behaviour of the electromagnetic ring expansion test. Particularly the rotation and inhomogeneous deformation of the ring are noticeably observed and these phenomena require extra attention

Development of Vibration During the Electromagnetic Ring Expansion Test

Magnetic pulse forming (MPF) techniques work on the principle of Lorentz force induced by eddy current which can cause plastic deformation in a metal workpiece. Lorentz force depends on parameters such as frequency and amplitude of input current, electromagnetic properties of materials and distance between the work piece and coil. The development of vibration as a consequence of elastic strain recovery in a ring expansion process using a MPF technique has been identified and presented in this paper. Coupled mechanicalelectromagnetic 3D simulations were carried out to investigate the effect of various magnetic pulse currents in the development of reversal of motion during the MPF process using LS-DYNA package. Ring expansion using a multi-turn helix coil with an applied pulse current, with the rings made of aluminum alloy AA6061 –T6 is investigated for the effect of vibration during the process. The numerical results show good agreement with the experimental work for various currents. The underlying principle of vibration and formability has respectively been studied using force analysis and stress analysis. The results also show that the 5.6kJ energy already increased the formability by ~66 percent in comparison with the quasi-static formability value from the literature

Assessment of Gap and Charging Voltage Influence on Mechanical Behaviour of Joints Obtained by Magnetic Pulse Welding

This work investigates the study of the experimental weldability in magnetic pulse welding process of a one material assembly (aluminium AA6060T6) and a dissimilar metal couple (aluminium6060T6/copper). The weld quality is defined using a destructive process allowing measuring the weld dimension. A diagram charging voltage-air gap is used to establish the variance of weldability. With the criterion of width of the weld, this representation is able to determine the operational weldability window. The lower boundary is defined by the case of bad weld, i.e. an insufficient bonding, and the upper boundary by defective welds, i.e. a weld susceptible to crack. The weld is able to undergo a plastic deformation prior to failure. A large weld is more potentially ductile. A numerical modelling of a mechanical destructive push out test could be helpful to characterise the weld in a quantitative manner. Finally, the material dissymmetry as considered in this study notably reduces the weldability window because of intermetallic phase at the welded interface. For this case, the weld is found to have a rather brittle behaviour

A multiscale model for magneto-elastic couplings

At the macroscopic scale two different phenomena illustrate the couplings between the elastic and magnetic behaviours of ferromagnetic materials : first, magnetisation induces a deformation mechanism called magnetostriction, and, second, stresses have an effect on the magnetic behaviour. The complexity of the non-linear relations between these phenomena is such that few realistic macroscopic constitutive equations have been proposed to model the coupled magneto-elastic behaviour of magnetic materials. Magnetisation and magnetostriction are macroscopic manifestations of the complex magnetic domain structure that is modified by applied mechanic and magnetic loads. Herein, it is proposed to use homogenisation methods to deduce the macroscopic behaviour of single crystals and polycrystals from a statistical description of the magnetic domain structure. Therefore, the macroscopic couplings naturally arise from the expression of the free energy written at the level of the magnetic domains