Ultrasonic welding (USW) of Titanium (Ti) sheets presents several challenges, notably crack formation due to sliding friction. To overcome this problem, the present study applied USW to pure α-Ti ...sheets both with and without different interlayer metals (Al, Ni, and Fe). Al interlayer improved the strength at room temperature significantly to cause base metal fracture (1700 N) by inducing concentrated plastic deformation, facilitating bonding with Ti while minimizing damage. However, its strength decreased significantly at 150–300 °C, suggesting the limitation of using Al interlayer at elevated temperatures. Conversely, the Ni and Fe interlayers led to a two-phase strength development. This enhancement was due to β-phase transformation, which reduces the interfacial defects and generates a more pronounced β-stabilization effect. The Ni interlayer, which has a higher β-transus point (765 °C) and lower molybdenum equivalency, required a higher welding energy (1800 J) and longer diffusion time into Ti, resulting in a gradual increase in strength due to a slower β-Ti transformation. On the other hand, the Fe interlayer with a lower β-transus point relative to Ti (595 °C) achieved peak strength at a lower welding energy of 1200 J. Both Fe and Ni interlayers displayed only a slight decrease in strength (1500–1600 N) at 300 °C with base metal fracture, revealing better joint performance at higher temperatures. These insights suggest a strategical interlayer selection based on the operation temperature, where Al interlayers were advantageous for low-energy welding at room temperature application, Fe and Ni interlayers offer sufficient strength at elevated temperatures by facilitating the β-Ti formation.
•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%.
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.
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 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.
Electrochemical devices such as batteries, fuel cells, and capacitors employing a carbon nanotube (CNT) electrode can be improved by lowering the contact resistance between CNTs and metallic ...contacts. The current work investigates two simultaneous strategies to enhance the contact by using chemical doping of CNTs with potassium tetrabromoaurate (KAuBr4) and ultrasonic welding to a metal foil. The specific contact resistivity was measured using the transfer length method (TLM) to evaluate CNT test structures having ultrasonically welded Cu contacts with and without KAuBr4 doping. Purified CNT-Cu samples had a specific contact resistivity of 5.4 mΩ cm2, whereas the KAuBr4 doped CNT-Cu samples were 2.2 mΩ cm2. Confirmation of selective doping to the weld region was made using measured differences in the emissivity of purified and KAuBr4 doped CNTs, which were 0.84 and 0.56, respectively. The lower contact resistance from KAuBr4 doped CNT-Cu ultrasonic welds also reduced the extent of Joule heating beyond the contact region when applying increasing current to failure in a 2-terminal test structure. The benefit of selectively doped CNT-Cu welds was demonstrated across rectangular ribbon and electrode form factors up to an area of 6 cm × 8 cm (typical of electrochemical pouch-cell current collectors). Each form factor showed a 1.5× reduction in peak temperature when selective doping of the CNTs was performed prior to ultrasonic welding of the Cu contact. Thus, the combination of selective doping and ultrasonic welding demonstrates a viable method to fabricate low electrical resistance between CNT electrodes and metallic contacts for electrochemical devices.
Display omitted
•Novel ribbons with geometrically spaced tabs (RGT) yield comparable specific contact resistivity to standard TLM geometry.•RGT TLM structures enable assessment of selective CNT doping and Cu welding on specific contact resistivity.•Spatially identify dopant location using thermal imaging based on emissivity differences of purified and KAuBr4 doped CNTs.•Selective CNT doping and Cu welding reduces Joule heating beyond the contact region and is scalable in large area designs.
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.
