Simulation of the thermal profile of a mushy metallic sample during tensile tests

Strain measurement is a major challenge in tensile tests performed in a mushy state. While non-contact technique devices like the laser speckle extensometer remain the most reliable facility for this type of measurement, these devices are often not readily available. So the strain measurement is usually performed by determining the length of the ‘‘hot zone’’ of the sample. This is possible with the help of the thermal profile associated with the sample under heating. The purpose of our work is to develop a numerical model to predict the thermal profile of a A356 aluminum alloy sample at high temperature, taking into account the device geometry and characteristics. We simulate the joule heating effect using the FE software Abaqus. Our model takes into account the grips of a Gleeble machine, the thermal contact conductance and electrical contact resistance at the grip-sample interfaces, as well as the convection heat transfer on the free surfaces of the system. These thermo-physical properties have been determined by fitting the experimental thermal profile obtained at 545°C. The model was then used to simulate the temperature profile on the sample at higher temperatures (when the sample is in the mushy state). The thermal profile predicted by our model is in excellent agreement with the profile obtained experimentally

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

Characterization of uniaxial fatigue behavior of precipitate strengthened Cu-Ni-Si alloy (SICLANIC(TM))

Fatigue tests were conducted on cylindrical bars specimens to understand the fatigue behavior of SICLANIC®. Although it displays good resistance in monotonic tension, this material weakens and shows a softening in repeated solicitation. This has been verified through a SEM observation, the Cu-Ni-Si alloy presents transgranular failure by cleavage. The MansonCoffin diagram exhibited the plastic deformation accommodation. The plastic deformation becomes periodic and decreases progressively as the cycle number increases. The approximations of Manson Coffin give fatigue parameters values which are in good agreement with the experience

An anomalous wave formation at the Al/Cu interface during magnetic pulse welding

This paper reports an anomalous wave formation at an Al/Cu bimetallic interface produced by magnetic pulse welding. The mechanism of the anomalous wave formation is investigated using both metallurgical characterization and the interface kinematics. It reveals that the anomalous wave is formed with the combination of the intermediate zone and the interdiffusion zone with a thickness of 70 nm, wherein the intermediate zone is caused by the local melting due to the high shear instability, and the interdiffusion zone is formed below the melting point of aluminum combined with ultrahigh heating and cooling rates of about 1013 °C s−1. A multiphysics simulation of impact welding has been performed, and it is identified that the jetting kinematics and non-uniform distribution of shear strains during high-speed collision enable the formation of the anomalous wave. The numerical and experimental results comprehensively lead to understanding of the mechanism and the characteristics of the anomalous wave produced during an impact welding. This work is supported by the Co-operation Program of UTs and INSAs (France) and funded by the China Scholarship Council (No.201701810138). T. Sapanathan acknowledges F.R.S–FNRS (Belgium) during his postdoc at UCLouvain. The data that support the findings of this study are available from the corresponding author upon reasonable request