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JOINing of copper to aluminium by ElectroMagnetic fields

Periodic Reporting for period 1 - JOIN-EM (JOINing of copper to aluminium by ElectroMagnetic fields)

Reporting period: 2015-09-01 to 2017-02-28

Global trends force industry to manufacture lighter, safer, more environmentally-friendly, more performant, and cheaper products. Due to its excellent thermal and electrical conductivity, copper is widely used in heating and cooling equipment and electrical devices. However, the rising demand caused the copper price to increase significantly. Solving the conflict between the technological benefits arising from the excellent properties of copper, on the one hand, and the disadvantages regarding cost and weight, on the other hand, is possible by substituting current full copper parts by copper-aluminium hybrid parts. Within the framework of JOIN’EM, such components are being produced by electromagnetic welding (EMW), a high-speed joining technology using pulsed magnetic fields. The joint is formed due to a high-speed collision of the joining partners without largely heating the parts. Consequently, thermally induced disadvantages associated with conventional technologies are avoided and high-quality dissimilar material combinations can be joined.
In order allow industrial implementation of the process, the aim of JOIN’EM is to develop strategies for the process and tool design. Profile-shaped components as well as sheet metal applications are regarded (see figure). In order to achieve joint optimisation, surface preparation, design of the joint geometry, and other aspects are being investigated. A multi-scale simulation strategy is being developed for determining acting loads, deformation, impacting conditions, joint formation, and load capacity of the joint. Designing durable and efficient tools is an indispensable prerequisite for the industrial implementation of the technology and is therefore addressed in the project, too.
The applicability of the process design strategy is validated based on industrial case studies. Process and equipment design strategies are evaluated in an industrial setting. This includes automation and quality control, economic efficiency calculations, life-cycle, and recycling issues in order to demonstrate and quantify the advantages of EMW.
Specific demonstrators representing applications related to heating and cooling as well as to electrical applications have been selected considering the expected benefit in comparison to the current solution as well as the estimated feasibility. Based on general specimen geometries, a detailed combined numerical and experimental process analysis was performed. In this study, correlations between the adjustable process parameters, the corresponding collision parameters, and weld quality characterising parameters were identified and quantified. On this basis guidelines for the process and joint design were deduced and material combination specific process windows were identified.
With regard to numerical simulation of the process a multi-scale model was developed. Macroscopic coupled electromagnetic and structural mechanical simulation was used to calculate the overall deformation of the joining partners and specifically the collision parameters during impact. These were used as input parameters for a microscopic simulation, which aims at modelling the weld formation.
Moreover, the macroscopic simulation was used to determine the loads acting on the tools in order to numerically predict their lifetime. These investigations were supplemented by experimental durability tests performed on material specimens as well as on the complete tool system. Strategies for optimising the tool durability via improved materials and manufacturing methods were suggested and investigated.
Weld quality was quantified via suitable destructive and non-destructive methods. Here, parameters such as mechanical strength, electrical conductivity, tightness of the weld, and extension and topography of the weld seam were considered. Additionally the corrosion behaviour of the produced material combinations was investigated.
The development of the demonstrators was prepared by a target-oriented re-design of the selected components and a planning of the specific tools required for the manufacturing. Development of a concept for process automation was initiated and standards necessary for industrial implementation of the process were researched. The project was dissiminated via different channels in order to reach a wide audience including students as well as industrial and scientific professionals.
The new joining solutions will help to implement improved lightweight designs with further weight reduction and better performance. This will decrease energy consumption and greenhouse gas emissions, an increasingly significant requirement for industries such as car manufacturing.
The JOIN’EM project will optimise usage of a finite resource –copper –for industry’s benefits
Due to its excellent thermal and electrical properties, copper is the third most frequently used raw material in the world. JOIN’EM directly aims at decreasing the consumption of this high-cost material by partially substituting it with aluminium. At the current level of known reserves and expected consumption, it is expected that copper will become ever more expensive and difficult to obtain, creating an additional cost issue for manufacturers. So, even if the replacement of copper with aluminium can only happen partially, it will have a lasting impact on the targeted industries.

JOIN’EM will:
• Develop innovative methods for joining dissimilar metals, which will allow improved manufacturing of new products. These innovations will also deliver increased product reliability, longer lifetime of the components and welds, combined with a reduction of maintenance costs;
• Facilitate an increased use of dissimilar metal combinations;
• Increase productivity and reduce costs for realising hybrid components using electromagnetic pulse welding: joining operations are performed faster, more efficiently and robustly, with a less expensive production process and better-quality final products;
• Achieve lower product life cycle costs;
• Enable the use of the environmentally-friendly electromagnetic pulse welding process. This process needs no fluxes or shielding gases and produces no harmful smoke, fumes or slag, thus reducing the overall environmental impact.
• Investigate joint performance with conventional as well as novel testing methods.

Looking ahead: The future of electromagnetic welding
Beyond the application of joining copper and aluminium described above, project partners will also look into the transferability of project results to other material combinations of relevance for industrial sectors that deal with multi-material joints. JOIN’EM will develop and demonstrate flexible and cost-effective joining processes for dissimilar metal combinations, for which currently available conventional welding technologies have proved inadequate.