Improving the absorption of copper for near-infrared laser beams to optimize laser spot welding quality of copper to aluminum

Scientific Conference (2023, June 29)

Laser spot welding of copper-aluminum has gained significant attention thanks to the unique properties of these metals in addition to the capabilities of laser welding. Applying the laser on the aluminum ... [more ▼]

Laser spot welding of copper-aluminum has gained significant attention thanks to the unique properties of these metals in addition to the capabilities of laser welding. Applying the laser on the aluminum side in an overlap configuration is well-studied in the literature however, directing the beam from the copper may bring some advantages to better control the final microstructure of the weld and minimize the formation of intermetallic compounds. The issue to be addressed is the considerable reflectivity of copper surfaces for well-established near-infrared laser sources. In this paper, the absorption of copper is improved by implementing laser-based surface structuring. The absorption of copper is tracked with online temperature measurement and offline microscopic observation. In addition, the mechanical performance (shear load) of welded copper-aluminum samples with different copper surface conditions and laser powers was considered to explain the absorption of the laser beam and optimize the microstructure of the weld zone regarding the formation of intermetallic compounds. [less ▲]

Digital twin of end-of-life process-chains for a circular economy adapted product design - A case study on PET bottles

in Journal of Cleaner Production (2023), 382

The concept of Circular Economy (CE) is gaining increasing attention as an indispensable renewal of linear economy without neglecting sustainable development goals. Closing resource loops and keeping ... [more ▼]

The concept of Circular Economy (CE) is gaining increasing attention as an indispensable renewal of linear economy without neglecting sustainable development goals. Closing resource loops and keeping resources in the system at the highest level of use for as long as possible are cited as the main goals of CE. However, due to missing information exchange, the lack of consistency between the existing end-of-life (EOL) infrastructure and the respective product designs hinders a successful circularity of resources. This research presents a method to collect, process, and apply EOL process data to provide the beginning-of-life (BOL) with important EOL-knowledge through a CE-adapted product design assessment. EOL-data is collected using a Circular Value Stream Mapping (C-VSM), EOL-information is processed using a digital state flow representation, and EOL-knowledge is applied by providing a decision-support tool for product designers in the context of a PET bottle case study in Luxembourg. The goal is to anticipate a circular flow of resources by reflectively aligning product design with the relevant EOL infrastructure. In contrast to the linear economy, the developed method makes it possible to consider not only the requirements of users but also the actual end users, the EOL process chains, when designing products. [less ▲]

PROCESS INNOVATION FOR SENSORS IN MOBILE APPLICATIONS BASED ON LASER ASSISTED METAL-POLYMER JOINING

Doctoral thesis (2021)

The laser joining of metals to polymers is currently an interesting research area thanks to the capability of developing lightweight structures. Considering their miscellaneous applications in the ... [more ▼]

The laser joining of metals to polymers is currently an interesting research area thanks to the capability of developing lightweight structures. Considering their miscellaneous applications in the automotive industry, aluminum and polyamide are chosen as the material combination for this study. There are three main challenges regarding laser joining of metals to polymers in general: significant difference between the melting points of the materials, adhesion at the interface, and the mechanical properties of the assembly. The first challenge is addressed by in-situ heating observation and temperature measurement during the joining process. Therefore, polyamide thermal pyrolysis is effectively avoided by optimizing the laser joining parameters and employing power modulation. The second one is studied by applying different surface treatments on the materials (laser-based and abrasive-based). The surfaces were tested by several characterization techniques before and after each surface treatment. The modification of the surface structure through an appropriate surface treatment leads to the improvement of wetting and adhesion between the melted polyamide and aluminum surface. Therefore, the alteration of a mixed failure (adhesive/cohesive) to a fully cohesive failure is the major step to enhance the mechanical properties of the assemblies. However, in the absence of bubbles, the structural modification of polyamide during the joining process is responsible for the failure. Energy-dispersive X-ray1 mapping and Time-of-Flight Secondary Ion Mass Spectrometry2 shows the physicochemical bonding between aluminum oxide and the polyamide at the interface. To further enhance the mechanical properties of the assemblies, the structure of the polyamide near the interface of metal/polymer is addressed. For this purpose, laser treatment of polyamide, post-heat treatment, and joining with different feed rates were implemented. Finally, the shear strength of approximately 45 MPa on average is achieved for the assembly of laser-polished aluminum laser-joined to the polyamide with 2 and 5 mm/s feed rate. [less ▲]

The effect of temperature and joining speed on the joining quality for conduction laser joining of metals to polymers

Scientific Conference (2021, June 24)

Laser joining of metals to polymers offers several advantages to produce lightweight hybrid assemblies. An important one is the exceptional control over the heat input which defines the temperature at the ... [more ▼]

Laser joining of metals to polymers offers several advantages to produce lightweight hybrid assemblies. An important one is the exceptional control over the heat input which defines the temperature at the interface of the materials. Initially, the in-situ heating observation of PA inside ESEM is considered. Then, aluminum and polyamide are joined in an overlap configuration while the temperature was recorded simultaneously at different areas between the materials. The results show that due to excessive heat input, polyamide degrades and leaves bubbles in the melted area. Finally, the materials are laser joined with several joining speeds to investigate different cooling rates of the polyamide during the joining process. It is concluded that joining with high cooling rates generates an amorphous melted layer of the polyamide which is different from the semi-crystalline structure of the bulk. This difference acts as a stress concentration zone and reduces the shear strength of the assembly. [less ▲]

Pre and post-treatments to improve weldability and mechanical properties of Aluminum-Polyamide laser welded specimens

in Procedia CIRP (2020), 94

The laser polishing surface treatment is a prerequisite for enhanced weldability that is enabled by superior adhesion between the weldments. The paper describes the laser polishing process of the aluminum ... [more ▼]

The laser polishing surface treatment is a prerequisite for enhanced weldability that is enabled by superior adhesion between the weldments. The paper describes the laser polishing process of the aluminum surface to develop a relatively thick and porous artificial aluminum oxide layer. Microscopic observation shows the laser polishing process significantly improves the adhesion of molten polyamide to the aluminum surface. Besides, the shear load of the pretreated joints is much higher than that of as-received ones. However, for the majority of the welded samples, the failure happens at the polyamide near the interface of aluminum/polyamide due to the thermal effect and structural changes of polyamide during the welding process. By applying the post-treatment of the welded specimens with different cycles, the mentioned failure mechanism is not observed anymore. Therefore, the mechanical properties of the joint will be improved and reach to the limits of the base materials. [less ▲]

Dissimilar Laser Micro-Welding of Nickel Wire to CuSn6 Bronze Terminal

in Transactions of the Indian Institute of Metals (2018)

In the present study, the laser welding of wire to flat geometry for miniature electromechanical hybrid components has been investigated. Considering the geometry of parts to be welded and also ... [more ▼]

In the present study, the laser welding of wire to flat geometry for miniature electromechanical hybrid components has been investigated. Considering the geometry of parts to be welded and also requirement of mechanical properties, spatial modulation of the laser beam was needed to be implemented to achieve a sound joint. Tensile-shear test and optical microscopy were employed to represent the mechanical properties and melt pool geometry of the joints. All welds were done by power modulation of the laser beam to better control the energy input at several feed rates and three different beam trajectories. Results showed that the shear load of the joint could be controlled by feed rate and the trajectory of the laser beam. Considering the material combination of the study that were nickel and CuSn6 bronze, which represented solubility in solid state, a joint stronger than base wire metal was achieved by defining a proper spatial modulation and feed rate of the laser beam. [less ▲]