In this paper, dissimilar aluminum (Al) and copper (Cu) metals were joined together using ultrasonic metal welding (USMW), a solid-state welding technology. From the perspective of increasing the ...base metal welding contact area, the Cu/Al mating surface was innovatively prepared and ultrasonically welded. A comprehensive analysis was carried out on the forming quality, welding process temperature, interface structure, and mechanical properties of the welded joint. Defect-free and squeezed welds were successfully achieved by machining novel patterns especially C4-2. The results indicated that the reference joint can withstand higher loads, but its failure mode is very unstable. Failure may occur at welded interface and on the aluminum plate which is not good for actual production applications. Welded strength of reference joint was 4493 N, and the welded strength of C4-2 joint was 3691 N. However, microscopic analysis discovered that the welded joint internal morphology in C4-2 was more stable and hardest. C4-2 joint has successfully achieved higher tensile strength and stability under failure displacement of 38% which is higher than C4-1 joint. All welded joint failures occurred on aluminum plate, indicating that the joint strength is higher than that of bottom plate. This is attributed to unique structural design of chiseled joint and lesser thickness. SEM–EDS results investigated that the C4-2 joint can transfer more energy to area under welding head which provides welded joint with robust diffusion capacity. The transition layer has a higher thickness while the energy transferred to area away from welding head was smaller. Thickness of transition layer is significantly reduced and reference joint has similar diffusion characteristics. Conversely, the thickness of the transition layer at the corresponding position is smaller than that of pattern morphology. This is due to overall smaller thickness of the pattern joint which is more conducive to the transfer of welding energy. The surface-conformed approach and comprehensive temperature analysis provide a new understanding of USMW in dissimilar welded metals.
This study aimed to develop robust thermoplastic-to-thermoset composite joints upon an ultrasonic welding process. The carbon fiber/epoxy composite was topped with a layer of polyetherimide (PEI) ...film by a co-curing process, making it “weldable” with the carbon fiber/PEI composite. The effects of welding displacement and thickness of the energy director (ED) on the welding process of the epoxy-to-PEI hybrid composite joints were investigated. The experimental results demonstrated that an optimal welding displacement existed for the best welding quality, whose value depended on the ED thickness. Given a certain ED thickness, the lap-shear strength (LSS) of the hybrid joints increased to a maximum value and then decreased as the welding displacement increased. By optimizing the displacement and ED thickness, a maximum LSS of 39.4 MPa was obtained for the hybrid joints. In which case, the level of the defects within the welding line was minimized, and the joints failed cohesively within the composite substrates.
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•A layer of PEI film was co-cured onto a carbon fiber/epoxy composite to make it weldable.•The best quality welding line was obtained by optimizing the welding displacement and ED thickness.•A maximum lap-shear strength of 39.4 MPa was achieved for the epoxy-to-PEI composite hybrid joints.•The defects within the welding line was eliminated and the joint failed within the composite substrates.
In this study, the weldability of single-sided ultrasonic welding of 4-mm-thick carbon fiber/Nylon 66 composite was studied. Extensive welding was performed, and the weld microstructures, ...fractographies, and appearances of welded joints were examined and analyzed. It was found that the strengths of single-sided ultrasonic welded (SSUWed) joints made with proper welding variables are comparable to that of the ultrasonic welded joints. The solid SSUWed joints with introducing a gap of 1.0 mm can be produced with the use of double-pulse ultrasonic vibration schedule. The robust welding variables include a weld pressure of 0.17 MPa and a weld time of 1.3 s for the first vibration pulse, 5-s cooling, and a weld time of 1.3 s for the second vibration pulse. Microstructure analyses and mechanical testing of the welds revealed that the application of second ultrasonic pulse caused the melting of the materials at periphery of the existing weld, and consequently resulted in an increase in weld area. The use of the second vibration pulse not only improved the strength but also decreased the scatter in strength of the ultrasonic welded 4-mm-thick carbon fiber/Nylon 66 composite. The double-pulse vibration schedule improves the robustness of the SSUW and increases the flexibility of product designs that rely on the ultrasonic welding for assembly.
Ultrasonic wire welding is considered a method of choice for creating reliable interconnects in electronics industry including aerospace, batteries and electric vehicles. In this paper, ultrasonic ...welding tests between EVR252 copper wire and substrate are carried out. Novel pattern morphologies are machined on substrates to explore its influence on mechanical properties of welded joint. Patterns are divided into three different categories e.g., original surface, vertical and horizontal shapes. Cracks, microstructure strength and tensile properties of welded joint are studied and its joining mechanism is analysed. Compared with the reference substrate (S1), the welded joint performance of the longitudinal patterns (S2, S3, S4) has been improved, among which the longitudinal pattern (S4) has the most significant improvement (+ 15%). Likewise, the performance of transverse pattern (S5) welded joints is relatively poor (− 16%). The microstructural analysis using SEM has revealed predominant joint strength on Cu wire surface while maintaining rock-like and compact properties of S4 substrate. Upper side of wire-harness compactness is frequently observed due to vertical direction of patterns on substrate and also increases the strength of welded joint. Values of failure load, failure displacement and failure energy absorption were increased by 7.9%, 72% and 35% for S2, 6.1%, 75% and 42% for S3 and 15%, 87% and 113% for S4 compared to S1. Failure modes of welded joints are mainly characterized into: 1-poor ductility or rupture (no deformation) failure in vertical 3-line pattern joints 2-cylindrical deep holes failure in vertical 3-line zigzag pattern joints and 3-bulging effect failure in horizontal 3-line zigzag pattern joints. Point and line scans EDS measurement were performed to investigate weaker and stable trends of different locations in welded joints. In S4 substrate, 17.9% carbon content at the position of welded joint was investigated, leading to content of less oxides and fraction impurities. However, S1 weld zone contains 38.7% carbon content which can weaken welded joint and reduce durability.
Graphical Abstract
This work focuses on ultrasonic (US) welding of CF/PEEK composite containing a PEI layer at the interface. Welding time, load and amplitude are defined as the welding parameters. The influence of ...each parameter is assessed by temperature measurement and mechanical tests on US welding specimens. 80-μm diameter thermocouples are integrated into the interfacial polymer layer for in-situ monitoring of the maximum temperature profile during the welding phase. Only welding time and welding load have an influence on both temperatures and lap shear strengths (LSS). The highest LSS are close to 50 MPa, and the temperature achieved in those cases is around 580°C. Interfacial fractures occur in both PEI and PEEK. PEI-based fracture is mostly brittle whereas PEEK-based fracture is a competition between brittle and ductile fracture. Finally, a fracture within the PEI/PEEK blend can occur. Raman spectroscopy is effectively used to quantify the thickness of this blend zone, it is about 0.075 mm.
Ultrasound welding technology is widely applied in the field of industrial manufacturing. In complex working conditions, various factors such as welding parameters, equipment conditions and ...operational techniques contribute to the formation of diverse and unpredictable line defects during the welding process. These defects exhibit characteristics such as varied shapes, random positions, and diverse types. Consequently, traditional defect surface detection methods face challenges in achieving efficient and accurate non-destructive testing. To achieve real-time detection of ultrasound welding defects efficiently, we have developed a lightweight network called the Lightweight Attention Detection Network (LAD-Net) based on an attention mechanism. Firstly, this work proposes a Deformable Convolution Feature Extraction Module (DCFE-Module) aimed at addressing the challenge of extracting features from welding defects characterized by variable shapes, random positions, and complex defect types. Additionally, to prevent the loss of critical defect features and enhance the network's capability for feature extraction and integration, this study designs a Lightweight Step Attention Mechanism Module (LSAM-Module) based on the proposed Step Attention Mechanism Convolution (SAM-Conv). Finally, by integrating the Efficient Multi-scale Attention (EMA) module and the Explicit Visual Center (EVC) module into the network, we address the issue of imbalance between global and local information processing, and promote the integration of key defect features. Qualitative and quantitative experimental results conducted on both ultrasound welding defect data and the publicly available NEU-DET dataset demonstrate that the proposed LAD-Net method achieves high performance. On our custom dataset, the F1 score and mAP@0.5 reached 0.954 and 94.2%, respectively. Furthermore, the method exhibits superior detection performance on the public dataset.
•Designed DCFE-Module for complex defect extraction in welding dataset.•LSAM-Module is designed with SAM-Conv for improved defect perception in welding.•Integration of EVC and EMA enhances defect detection by balancing information.•New LAD-Net enables fast, accurate defect detection across two datasets.
The combination of alkali metal electrodes and solid-state electrolytes is considered a promising strategy to develop high-energy rechargeable batteries. However, the practical applications of these ...two components are hindered by the large interfacial resistance and growth of detrimental alkali metal depositions (e.g., dendrites) during cycling originated by the unsatisfactory electrode/solid electrolyte contact. To tackle these issues, we propose a room temperature ultrasound solid welding strategy to improve the contact between Na metal and Na
Zr
Si
PO
(NZSP) inorganic solid electrolyte. Symmetrical Na|NZSP | Na cells assembled via ultrasonic welding show stable Na plating/stripping behavior at a current density of 0.2 mA cm
and a higher critical current density (i.e., 0.6 mA cm
) and lower interfacial impedance than the symmetric cells assembled without the ultrasonic welding strategy. The beneficial effect of the ultrasound welding is also demonstrated in Na|NZSP | Na
V
(PO
)
full coin cell configuration where 900 cycles at 0.1 mA cm
with a capacity retention of almost 90% can be achieved at room temperature.
The ultrasonic welding technology is widely promoted as a new connection approach in the field of current energy vehicle wiring harness connection. In this paper, three kinds of 25mm2 copper wire ...harnesses with different wire diameters and T2 copper terminals with different surface roughness were welded by ultrasonic welding. The mechanical properties of the joints were investigated by tensile experiments and the microstructure of joints was characterised using SEM and EBSD techniques. Excessive roughness increases plastic deformation at the weld interface during ultrasonic welding. This increases the dislocation density at the weld interface and refines the grain size. However, at the same time it inhibits recrystallisation to a certain extent. The lower roughness facilitates recrystallisation, but the low density of HAGBs makes the interface susceptible to slip in extended crystallographic plane and direction. Appropriate roughness allows the weld interface to generate fine equiaxed grains and a high density of HAGBs. This facilitates the obstruction of dislocation movement and improves the strength of joint. In addition, the high porosity of a longitudinal cross-section of the conductor with its small diameter was investigated. This results in a large number of wires remaining on the terminals when force is applied. It was determined that the larger a diameter of wire, the higher a cross-sectional porosity. The copper wire breaks at a weak point in cross-section when the force is applied, resulting in the entire wire being left on terminal. At a wire diameter of 0.2 mm, the porosity of a cross-section reaches an equilibrium and the strength of joint is even higher than the strength of material itself, resulting in the joint pulling off. The maximum strength reaches 4703.77 N.
•Copper wires were soldered to terminals with right roughness and improved mechanical properties and stability of joints.•Observation of the transverse and longitudinal interfaces of the joints revealed opposite moulding effects.•Joint strength has achieved peak with balanced transverse and longitudinal porosity for 0.2 mm wire diameter.•EBSD analysis explored, how terminal surface roughness affects recrystallization and mechanical properties.•Three connector failure modes are outlined and the cause of the failure is investigated and explained.
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