Ultrasonic welding of carbon fiber reinforced thermoplastic (CFRTP) has attracted increased attentions from researchers in the automotive and aerospace industries. This paper proposes a novel ...ultrasonic welding method for focusing the welding energy at the desired location without using the energy director (ED). An anvil with a spherical surface is used in the welding system instead of a conventional flat anvil. Short carbon fiber reinforced polyether ether ketone (CF/PEEK) is employed as the research material. The effects of spherical radius and welding energy on the weld formation are investigated. The microstructure, tensile-shear property, and fracture characteristics of the joints are also analyzed. The results show that the using of a spherical surface anvil can effectively concentrates the welding energy and therefore, reduces the scattered welds.
Ultrasonic-assisted soldering welding is widely applied for joining difficult materials. The cavitation phenomenon in liquid always occurs during the ultrasonic excitation. Base metals are striked by ...ultrasonic cavitation, creating erosion on the surface. The soft solder materials are penetrated on the rough surface, generated inter-metallic compounds. This work expresses the design of ultrasonic soldering machine using 20 kHz source and steel sonotrode. The curvature of reflecting plates with specific radius and their location are also condidered. The major technological parameters of ultrasonic soldering welding such as ultrasonic exciting time, power and curvature radii of reflecting plate are discussed. Tin soldering material is utilized for joining copper wires and plates are investigated. SEM images on the surface of tin soldering on cooper plates and tensile strength are investigated.
Multi-layered aluminium (Al) tabs to copper (Cu) busbar joints are increasingly being used for electric vehicle (EV) battery applications. Being a solid-state joining process, ultrasonic welding ...(USW) offers several benefits including less intermetallic or no porosity formation and larger weld area compared to fusion type welding, especially for highly conductive/reflective multi-layered dissimilar materials welding. In spite of being a suitable joining process, the impact of ultrasonic process parameters needs in-depth analysis for multi-layered stack-up where the process parameters play a pivotal role to join the layers of weldments. In this study, three layers of 0.3 mm Al tabs were welded to 1.0 mm single Cu busbar for the investigations of multi-layered Al–Cu dissimilar joints. Joint macro and microstructures, welding mechanism, layer-wise micro-hardness and grain formation were studied to understand the flow of material, the formation of grains and mixing of the Al and Cu for under-weld, good-weld and over-weld categories. The effects of amplitude of ultrasonic vibration, welding pressure and welding time were investigated to produce the satisfactory tab-to-busbar connection. The layer-wise microstructural study revealed the welding mechanism, propagation of micro-bonds and flow of material. The micro-hardness study unveiled different weld zones indicating the area of material mixing and the affected region whereas the crystallographic orientation maps disclosed the grain formation and recrystallization after the welding. The results showed that interfacial material mixing, wave-like material flow and interfacial micro-bonds formation were the prominent reasons for the satisfactory ultrasonic weld.
•Layer-wise weld microstructure was studied for multi-layered Al–Cu ultrasonic joint.•Material flow and mixing were analysed for under-, good- and over-weld categories.•In-depth layer-wise micro-hardness illustrated the cold work and thermal softening.•EBSD maps revealed grain formation and recrystallization for each weld categories.•Fractography and tensile strength were correlated with the weld microstructure.
•Ultrasonically welded ageing resistant Al/CFRP-joints with ultimate lap shear forces of up to 8300 N.•Insulating character by glass fiber surface ply of all hybrid joints proven.•A metallographic ...characterization of the joining zone shows adhesive (between aluminium and polymer) as well as cohesive (between aluminium and glass fibers) components of bonding.•Analysis of bond formation with the aid of process data recording.
Ultrasonic metal welding is a promising process for joining light metals with fiber-reinforced thermoplastics. The technique is characterized by high reproducibility, short process times, low energy input, no additional filler materials and finally the possibility of extensive process data logging. With this process, dissimilar aerospace materials are ultrasonically welded and the applied process parameters are optimized by statistical methods. A prediction of ageing resistance is possible by the evaluation of the electrical resistivity of the multi-material-joints. With the help of detailed process parameter recording and microscopic investigations, the bonding mechanism of hybrid AA5024/(GF-)CF-PEEK joints is explained and the kinematics of bonding formation is presented in detail.
•Ultrasonic welding of austenitic steel and 7075 aluminum alloys was conducted.•Local melting of aluminum alloy occurred when temperature is higher than 470 °C.•A unique ∼ 1-μm precipitate layers of ...Al18Mg3Cr2 and Al6(Cu, Fe) formed.•Strength saturation (2.75 kN) due to stress concentration at the precipitation layer.
This study elucidated the ∼ 1-μm precipitate layers of Al18Mg3Cr2 and Al6(Cu, Fe) formed apart from the interface when the interfacial temperature is higher than 470 °C during ultrasonic welding of steel/7075 Al alloy. The formation of continuous precipitate layers was induced by local melting, leading to strength saturation (2.75 kN).
Breakthrough of glass forming ability limitation has been a longstanding pursuit in metallic glasses. In present work, an ultrasonic welding technology was used to achieve this goal. The ...La55Al25Ni5Cu10Co5 rods were bonded together. Results of computed tomography and scanning electron microscope show that the weld seam tends to narrow gradually and disappear with the increase of welding energy. X-ray diffraction indicated that it preserves completely amorphous structure. In addition, the hardness of the weld position increased with the increase of energy, showing the interfaces bonded together.
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•Ultrasonic welding of Cu-Ti with Al interlayer was studied.•Interfacial strength evolved from plastic flow and mechanical interlocking.•Large plastic strain caused interface-adjacent cracks, ...reducing strength.•Introduced Al interlayer prevented base metal damage, improving weld quality.•Al interlayer increased interfacial strength by 26% via enhanced frictional heat.
This study investigated the ultrasonic welding of Cu-Ti joints, revealing that the interfacial strength originated from mechanical interlocking. However, strength was diminished owing to interface-adjacent crack initiation due to excessive plastic strain. Introducing an Al interlayer prevented base metal damage with more frictional heat, and enhanced interfacial strength by 26%.
Although ultrasonic welding of dissimilar metals has been widely applied in the automotive and electronic industries, the dynamic weld evolution, including deformation, breakage, and attachment, is ...still in a conjecture stage because of the short welding time, thin reaction layer and complex thermomechanical behavior. In this study, dissimilar welds of aluminum (Al) alloy 1060 to T2 copper (Cu) were comprehensively investigated via microstructural characterization, molecular dynamics simulations, and mechanical tests. It was found that micro-welds first formed at high asperities. Subsequently, the continuous relative friction at the interface induced severe plastic deformation on the Al side, resulting in the alternating fracture and formation of micro-welds, flattening of asperities, and attachment of Al on the Cu surface. The lap shear failure loads for the joints gradually increased with increasing welding time. The failure loads reached the maximum values of 0.9 ± 0.03 kN after a welding time of 0.29 s. Furthermore, the Cu asperities completely sunk into the Al matrix, presenting a macro-interlocking morphology at the interface. A swirl-like grain morphology with no deformation texture appeared simultaneously on the Al side. Analysis of the weld formation indicated that microstructural evolution of the joint, including material flow, grain morphology, and grain orientation, was mainly concentrated on the softer material side, providing a new understanding of the ultrasonic welding of dissimilar metals.
•Three stages of dynamic weld evolution for Cu–Al joints were proposed.•The material flow, grain morphology and grain orientation were observed by SEM and EBSD analysis.•Micro-weld formation process and uneven deformation were further proved by MD simulation.•The changes on failure loads at different stages were discussed.
In this study, ultrasonic welding (USW) of lap joints of polyetherimide (PEI) plates (adherends) with carbon fiber (CF) prepregs impregnated with PEI was investigated. No energy director (ED) was ...used, so binder contents were varied in the prepregs to compensate for the lack of the polymer in the fusion zone. In addition, the effect of the USW parameters on the structure and the mechanical properties of the lap-joints were analyzed. The most homogeneous macrostructure, the maintained structural integrity of both the CF-fabric in the prepregs and the lap-joined PEI adherends, as well as the maximum strength properties (tensile strength) were revealed for the USW joints with the minimum polymer content in the prepreg. In this case, rising the USW time from 400 up to 800 ms radically changed the macrostructure of the fusion zone, while the strength properties did not vary significantly (shear stresses were 42–48 MPa). Computer simulation of the influence of the PEI/CF-fabric ratios in the prepregs on the deformation response of the USW joints showed that the prepreg thicknesses and, accordingly, the PEI/CF ratios did not exert a noticeable effect on the strain–stress (tensile) diagrams, while the determining factor was the adhesion level.
Repair is a common process to extend the service life of composite structures, and there is a need for techniques compatible with thermoplastic composites (TPCs). As the assembly of TPC joints ...through welding is gaining importance, evaluating their potential for repairability is essential. This work aims to develop novel techniques to repair welded TPC joints: 1) Successive repair (three cycles) of broken joints by ultrasonic-assisted method with neat and nanocomposite films, and 2) one-step repair using ultrasonic welding (USW) and resistance heating. It was found from tensile testing that multi-walled carbon nanotube/polypropylene (MWCNT/PP) films partially restored the lap shear strength (LSS), but pure PP films enabled significant recovery of the LSS as 94.5%, 89.4%, and 86.7% after the first, second, and third repair cycle, respectively. Nanocomposite films were however promising for monitoring the initiation and propagation of the damage occurring within the repaired joints, even after three repair cycles. Moreover, results from one-step repair using USW revealed that a stronger and more uniform repair interface was obtained, compared to resistance heating. Overall, the repair methods developed in this study exhibited promise for TPC joint repair, with strength recovery between 63.8% and 94.5%.
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