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JOINing of copper to aluminium by ElectroMagnetic fields

Periodic Reporting for period 2 - JOIN-EM (JOINing of copper to aluminium by ElectroMagnetic fields)

Reporting period: 2017-03-01 to 2018-08-31

Global trends force industry to manufacture lighter, safer, more environmentally-friendly, more performant, and cheaper products. Due to excellent thermal and electrical conductivity, copper is widely used in heating and cooling equipment and electrical devices, but due to the rising demand the copper price increased. Solving the conflict between the technological benefits and the disadvantages regarding cost and weight is possible by substituting current full copper parts by copper-aluminium hybrid parts. In JOIN’EM, such components were produced by electromagnetic welding (EMW). In this process the joint is formed due to high-speed collision of parts without largely heating them, so that thermally induced disadvantages of conventional technologies are avoided and high-quality dissimilar material combinations can be joined.
In order to allow industrial implementation of the process, strategies for the process and tool design were developed for tubular and sheet metal parts (see figure). Designing durable and efficient tools is an indispensable prerequisite for the industrial implementation of the technology and is therefore addressed in the project, too. A multi-scale simulation strategy supporting the process and tool design was developed. It allows determining acting loads on workpiece and tool coil, deformation of the workpieces, impact conditions, joint formation, and fatigue of the most relevant coil components.
The applicability of the process design strategy is validated on industrial case studies from different application fields. 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. It was shown the EMW parts are absolutely comparable with current state of the art solutions in terms of technical properties, while they even feature advantages in terms of costs and environmental impact.
Specific demonstrators representing applications related to heating and cooling and to electrical applications were selected considering the expected benefit compared to the current solution and the estimated feasibility. Based on general specimens, a combined numerical and experimental process analysis was performed. 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.
A multi-scale model for the numerical process simulation was developed. Macroscopic coupled electromagnetic and structural mechanical simulation was used to calculate the deformation of the workpieces and the locally and temporally varying collision parameters during impact. The latter serve as input parameters for a microscopic simulation modelling the weld formation. A user-friendly interface was programmed as part of the development of an industrial simulation tool.
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 and on complete tool systems. Strategies for optimising the tool durability via improved materials and manufacturing methods were investigated.
Weld quality was quantified via suitable destructive and non-destructive methods. Here, parameters such as mechanical strength, electrical conductivity, tightness, and extension and topography of the weld seam were considered. The corrosion behaviour of the joined parts was investigated. To enable non-destructive evaluation of the joint quality in the complete welding zone a technique based on measurement of laser ultrasound signals was developed. The setup was optimised for automated operation e.g. in the field of quality control.
Three full industrial demonstrator parts – a refrigerant circuit, a flat condenser, and a pouch cell component – as well as three partial demonstrators – a refrigeration circuit component of a compressor dryer, a loop heat pipe flat evaporator, and a battery connector – were developed. After re-designing the parts considering the EMW specific process characteristics and designing and building the necessary tools, the manufacturing of the demonstrators was investigated in multi-step investigations continuously increasing the intricacy until full complexity of the industrial components was reached. Technological testing of the joints was investigated and for the full demonstrators application related performance parameters were tested, too.
Industrial implementation was considered for the full demonstrators by designing automation concepts. Additionally, economic efficiency calculation in terms of determination and comparison of the costs of the process chain and a cradle-to-grave Life-cycle Analysis was done.
The project was disseminated via different channels in order to reach a wide audience including students as well as industrial and scientific professionals. Dedicated technology training was done by integrating EMW into standard training modules and creating a unique training module focusing on EMW.
JOIN’EM has developed methods and guidelines for process and tool design, a verified numerical simulation approach, demonstration of technological feasibility and benefits regarding costs and environment, validated destructive and non-destructive testing methods and training material for EMW. These results provide an indispensable basis for implementing the technology in industrial production and allow exploiting the process advantages and benefits. This paves the way for the realisation of new lightweight design solutions via implementing multi-material concepts, which in turn decreases energy consumption and greenhouse gas emissions, an increasingly significant requirement for industries. Specifically, JOIN’EM allows reducing the use of copper. Due to its excellent properties, copper is the third most frequently used raw material in the world, but it is also a high cost heavy metal and at the current level of reserves and expected consumption the price is expected increase further. JOIN’EM aims at decreasing its consumption by substituting full copper solutions with hybrid copper aluminium parts, which allow exploiting the advantages of copper without fully accepting the corresponding disadvantages. Beyond this specific material combination, the consortium also analysed the transferability of the results to other dissimilar metal combinations, for which conventional welding technologies are inadequate such as e.g. aluminium steel joints. Independent from the material combination the EMW process developed in JOIN’EM
• allows improved manufacturing of new products with increased use of dissimilar metal combinations,
• increases productivity and reduces costs for realising hybrid components,
• allows achieving lower product life cycle costs, and
• avoids fluxes or shielding gases and produces no harmful smoke, fumes or slag, thus reducing the overall environmental impact and improving health conditions of the workers.