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The main objective of this project is to develop and enhance the computational tools necessary to model the plastic deformation of thin aluminum metals that have been deformed by the use of electromagnetic forces. The models developed are intended to provide insight into the experimentally observed plastic anisotropy of various sized rings and tube...
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In this paper, a previously developed viscoelastic-viscoplastic behaviour model for short fibre-reinforced thermoplastics (SFRT) is enriched with matrix ductile damage and fibre/matrix interfacial debonding constitutive laws. Aiming at industrial applications, model development takes special care to ensure a relatively easy characterisation of mate...
Citations
... For the development and validation stage of the solver, it is recommended to choose a study case that can be easily analyzed through analytical formulations. Fenton [8] proposed the ring expansion experiment as the easiest model to perform plasticity characterization on metal specimens submitted to high speed loading. ...
... For this reason we have selected the electric current to be one of the first observables from the simulation. In Figure 5 we compare the resulting electric current to the analytic solution (refer to [8] for details on the equations)., Globally the agreement between both is good, having just a 5% difference on the peak value. Looking at the evolution of the discharge potential at the capacitor level Figure 6, the curves fit almost perfectly. ...
In this paper, we review the latest developments on high-speed forming at the Centre for Material Forming (CEMEF). We have developed a 3D finite elements analysis toolbox for the simulation of Electromagnetic forming (EMF) within the frame of the software FORGE. At the same time, we have recently acquired an EMF machine to study the behaviour of materials at high deformation speeds. We describe the modelling strategy for the simulation package together with some results for a ring expansion case. We also present the experimental settings and some preliminary results for a direct free forming of flat metal sheet.
... As computing power progressed over more recent decades, researchers were able to use more robust algorithms and computers to solve complicated forming processes. Since the late 1980's electromagnetic metal forming researchers like Takatsu et al. [15], Gourdin et al. [26,27], and Fenton [5], took into account the magnetic field evolution with material deformation. ...
... Fenton [5] used the results from the experimental work of Gourdin to to serve as benchmarks for validating the predictability of a high performance computer code which is explained in more depth later. The computer code was used to model the expanding ring experiments of Gourdin. ...
The intent of this paper is to show that a two-dimensional (2D) arbitrary Lagrangian Eulerian (ALE) finite-difference computer code can accurately predict the dynamics of the electromagnetic sheet metal forming process. The challenging aspect of simulating the deformation of thin metal parts which have been loaded by magnetic forces is solving a highly coupled system of partial differential equations. The material motion and the magnetic physics require two drastically different time steps to maintain numerical stability. The CALE computer code has the ability to solve such challenging problems. This paper highlights the CALE modeling of a number of electromagnetic sheet metal forming operations.
The car industry is currently working to integrate the conflicting requirements of environmental legislation and customer demands for high-performance and safety by developing lightweight vehicles. To meet these very different goals, automotive components are being manufactured from alloys that include including lightweight materials such as aluminum and magnesium. However, existing welding and forming processes such as fusion welding, any that use heat in general, and low-velocity press forming can all cause defects. Therefore, Electromagnetic pulse technology has become the focus. Electromagnetic pulse technology is a high-velocity process that uses electromagnetic forces for welding and forming processes. In particular, because of its good flexibility, environmentally friendly process, and high-quality dissimilar weldment, the technology can potentially resolve the challenges in welding and forming processes for lightweight materials that have low weldability and formability. In particular, Korea’s research on electromagnetic pulse technology was started in 2008 by KITECH. These studies include the basic theory, crafting of applications, and simulation. Currently, electromagnetic pulse research has focused on the dissimilar sheets and tubular workpieces for applications in the automobile industry, which includes the propeller shaft. Although electromagnetic pulse technology research remains limited compared to other manufacturing processes, with the continuous increase in market demand in the automobile and electronics industries, interest in electromagnetic pulse technology research will also continue to increase
Nowadays, with the continued technological advances, traditional sheet metal forming
processes face more and more challenges in both forming quality control and forming cost control. These challenges are especially serious for extreme manufacturing areas, such as aviation and aerospace industries. In aviation and aerospace industries, there are lots of sheet metal parts with characteristics of large-size, thin-walled, deep-cavity, complicated curved-surface. The increasing forming cost and the difficult forming quality control in manufacturing of these sheet metal parts nearly pushes the traditional sheet metal forming processes to their limits.
Lots of researches indicated that, electromagnetic forming (EMF)—as one of high energy rate and high speed forming process shaping sheet metal with high pulsed Lorentz force—has lots of advantages over the traditional quasi-static forming process, such as enhanced forming flexibility, improved forming limit, inhibited wrinkling, reduced spring-back, and effectively lowered forming cost. Therefore, EMF is one of the most promising forming technologies that can break through the abovementioned challenges. However, the high complexity of the EMF process leads to the lack of effective design criterion for EMF; meanwhile, the high electromagnetic and mechanical loadings in EMF process put forward high requirements on the forming facility. These two reasons significantly limit the widespread applications of EMF in sheet metal forming.
In order to overcome these obstacles, this dissertation proposed a multi-space-time
high pulsed magnetic field based electromagnetically sheet metal forming method. From
methodology aspect, the new method introduces a multi-stage (in time dimension) and
multi-direction (in space dimension) pulsed Lorentz force to flexibly alter the deformation
behavior of the workpiece, thus accurately controlling the forming quality. And from
technological realization aspect, high magnetic field pulsed magnet and high energy pulsed power source technologies were introduced to develop high performance EMF system with multiple driving coils and multiple power sources, thus producing the multi-stage and multi-direction pulsed Lorentz force. Based on this method, the dissertation systematicallyinvestigates the design and implementation of the multi-stage and multi-direction pulsed Lorentz force, and the mechanism of the multi-stage and multi-direction force on driving and altering the workpiece deformation behavior. These investigations establish key foundations to realize the manufacturing of sheet metal parts with extremely large size and complicated shape.
Firstly, the dissertation developed a circuit-magnetic-structure coupled numerical
model of EMF. This model is the foundation to analyze the complicated dynamic
deformation behavior driven by multi-space-time magnetic field, and is also the key to
optimize the EMF system. In this coupled model, the electromagnetic model was realized
based on equivalent circuit method. The structure model was realized with finite element
software ANSYS. And the coupling between the electromagnetic and structure models was realized with a data interface program. Compared with most of the existing EMF numerical models which simulate electromagnetic field with finite element method, the proposed model need not to update the air mesh. As consequences, the simulation is more effective; and more importantly, this enables the structure model to handle the high speed impact between the workpiece and the die, conveniently and effectively. Therefore, the proposed model can simulate the complicated dynamic deformation behavior of the workpiece-die system more effectively and more accurately.
Secondly, aim at the state of art that EMF is hard to form sheet metal part with
complex shape, due to the onefold spatial distribution of the generated Lorentz force, the
dissertation proposed the process of axial-radial Lorentz force driven EMF method with a
dual-coil EMF system. Different to the traditional EMF, which can be regarded as axial
Lorentz force driven EMF, the proposed method introduced an additional radial inward
Lorentz force on the sheet flange to enhance the plastic flow of the sheet flange, therefore
introducing the deformation mode of deep drawing. In this dissertation, theoretical analysis, experimental investigations, and numerical simulations were conducted to prove the feasibility of the method, to demonstrate the flexibility of the method on altering the
deformation behaviors of the workpiece, and to reveal the underlying mechanism of the
radial and axial Lorentz forces on driving the changes of the deformation behaviors.
Thirdly, aim at the state of art that EMF is hard to shape large size sheet parts, due to
the limitations of the forming equipment and other reasons, the dissertation proposed alight-weight and flexible EMF method capable of shaping large size sheet metal. In this
study, this method was applied to form an aluminum alloy sheet with a diameter of
1378 mm into partial-ellipsoid shape. The numerical simulations were carried out to
optimize the forming coil system. The design and implementation of the forming facility
was discussed in detail. The fabricated forming facility is very light-weight, the
characteristic length of which is 1840 mm, only 1.34 times of the workpiece diameter,
which is much lighter than those of traditional quasi-static forming equipment. An
experiment was performed to evaluate the forming quality obtained by the proposed facility. The workpiece to be formed was with thickness of 3.945 mm, the manufacturing of which is very difficult with traditional forming process, due to the thickness-diameter ratio is lower than 0.3%. The experimental results show sound forming quality. The maximum thinning over the ellipsoid surface of the formed sheet was only about 9.5%. The maximum deviation between the deformed sheet and the die is about 4.2 mm. The results show the great advantages of the proposed method on improving the forming quality in large-scale sheet metal forming, providing a new approach for integrated manufacturing of large-scale light-weight alloy sheet parts in aviation and aerospace industries.
The aim of this paper is to carry out an analysis of the electromagnetic (EM) aspects involved in magnetic forming processes. Moreover, we shall address two specific issues: 1) modeling of Maxwell equations and comparison between the classical quasi-static approach and the full dynamic model (inclusion of displacement currents) and 2) modeling the electric circuit parameters involved in a typical EM forming process. In order to carry out this work, a 3-D finite-element model has been developed in our laboratory. This model can also be used for benchmarking an EM solver aimed at magnetic pulse forming applications.
최근 금속가공산업은 자동차, 조선 기계, 전자 등의 부품소재 제조에 있어 핵심적인 산업으로 자리하고 있다. 특히 가장 많은 비중을 차지하고 있는 용접산업은 저임금을 바탕으로 한 중국기술의 추격과 선진국의 고품질화에 직면하고 있으며 이러한 문제를 해결하기 위하여 친환경 공정기술의 개발과 신기술을 통한 제품의 부가가치 제고가 요구된다. MPW는 자기장에 의한 전자기력을 사용하므로 물리적인 접촉 없이 금속을 가공하는 방법으로서, 용접(brazing과 soldering 포함), 금형 및 소성가공공정에서 환경오염 발생원인 용접재료, 가스, 용가재, 플럭스, 윤활유 및 세척유 등이 필요 없이도 고품질의 제품을 생산할 수 있는 친환경적인 공정기술이다. 그 외에도 도금된 상태에서 작업이 가능하여 기존의 공정에서 결함이 발생되었을 때 재도금을 실시하는 후공정이 생략되어 도금공정에서 배출되는 오염물질도 줄일 수 있고, 작업이 수 μs 하에서 이루어지기 때문에 전력소모가 매우 적으며 작업시간을 절약할 수 있는 장점을 갖고 있다
The electromagnetic forming (EMF) process relies on a driving force that is induced by eddy current and magnetic field, both of which are generated in the workpiece by a transient current in a nearby coil. The high deformation rates achievable using this forming method enhances the formability of materials such as aluminum. Also, the dynamics of contact with the forming die can eliminate springback, an undesired effect that can be problematic in other forming techniques such as stamping. The advancement of the EMF technology is currently awaiting rigorous numerical modeling capabilities that can adequately simulate the forming process and be used to design the forming system. Such capabilities must be based on physical models that address the strong coupling between the electromagnetic, deformation and thermal response of the deforming workpiece and other system structure. In this paper, a brief exposition of the EMF method and its applications and a review of the existing models are given. In addition, a mathematical framework, which can be further developed numerically for the purpose of process simulation, is outlined. Finally, the paper discusses the challenges to advancing the EMF technology.
A series of high-rate electromagnetic-forming experiments are presented that consider free-forming and two configurations of cavity fill operations, one with a flat-bottomed die and the other with a hemispherical protrusion on the bottom of the die cavity. The experiments are performed on 1 and 1.6 mm AA5754 and 1 mm AA5182 aluminum alloy sheet; all of which are candidates for lightweight automotive structural applications. Increasing energy levels of discharge resulted in increased cavity fill and strain level in the formed parts. The effect of die geometry on formability, strain state and location of failure is examined.Numerical simulations of the high-rate deformation and structural impact that occur during electromagnetic forming are presented, and provide insight into the physics of the problem and the transient nature of this high-rate deformation process. A transient electromagnetic finite-element code is used to model the time-varying currents that are discharged through the coil in order to obtain the transient magnetic forces that are imparted to the workpiece. The body forces generated by electromagnetic induction are then used as the loading condition to model the high-rate deformation of the workpiece using an explicit dynamic finite-element code. A “two-way, loose coupling” of the electromagnetic analysis with the elastic-plastic structural analysis is utilized to account for the effect of changing workpiece geometry on the transient body forces. Validation of the numerical model is performed through comparison between predicted and measured strain distributions within the formed parts.
