Ultrasonic Welding Technology Research Articles

Experimental study under thermal shock environment to investigate effect of welding width on properties of ultrasonically welded joints of multiple copper cables

Based on the ultrasonic welding technology, this study uses three different welding widths to weld copper cables with different specifications. The influence of welding width on the mechanical properties and microstructure of each group of welded joints was systematically studied for the first time. The thermal shock test was carried out for each group of welded joints under optimum welding width to simulate the influence of severe temperature change environment on joint performance. It is found that the cross-sectional area of joint is 20 mm2 and optimal welding width of joint composed of two and three cables is 7 mm. The optimal welding temperature of the joint composed of four cables is 5 mm. Under the optimal welding width, the average shear strength of two-cable joint reaches 309.4 N. The four-cable joint is only 232.2 N. Moreover, the welding strength weakens significantly as the number of cables and the peak temperature decreases. The high temperature of bonding interface is the key factor to form a good weld. The peak temperature during welding is negatively correlated with the porosity of joint and positively correlated with peeling strength of joint. In addition, the morphology of ultrasonically welded joints has changed obviously after thermal shock test. With the participation of oxygen, the surface of welded joint is gray and bright brass, while the interior of joint is purple due to lack of oxygen. Moreover, the phenomenon of atomic diffusion and thermal expansion generates joints which were initially in a mechanically interlocked form and welding interface of the metallurgical bond under the action of high temperature. So the maximum joint peel strength is slightly improved.

Orthogonal experiments and bonding analysis of ultrasonic welded multi-layer battery foils and tabs

The motivation for this research stems from the growing demand for solid-phase welding technology to join multilayers metals, particularly in green electric vehicles. Welding of foils and tabs inside battery is a challenging task due to poor joint formation at the interface and low strength. Ultrasonic welding is an efficient, reliable and environmentally friendly bonding method to firmly connect multi-layer copper foils and tabs. Therefore, this is used to achieve electrical bonding within the lithium-ion batteries. This is widely used in production of new energy vehicle batteries. In this work, 40 layers of copper foil were bonded to 0.3 mm nickel-plated copper tabs using ultrasonic metal welding technology. The effect of ultrasonic welding parameters on T-peel strength of joints was systematically investigated by orthogonal experimental design. The maximum T-peel strength of 359.17 N was obtained under optimal parameters (e.g., welding energy 600 J, pressure 0.3 MPa and amplitude 55 %). The variation of welding temperature and amplitude under different welding parameters was measured using infrared thermometer and laser vibrometer. Moreover, the surface, cross-sectional and failure fracture analysis and characterization of specimens with different weld qualities were performed using optical microscopy and scanning electron microscopy (SEM). In addition, the state of Ni layer in cross-section was analyzed using the energy dispersive spectroscopy (EDS) technique after ultrasonic welding. This approach can be straightforward and more appropriate to the development of solid-phase welding method for automotive industry.

Microscopic mechanism of ultrasonically welded joints: The role of terminal roughness and wire diameter

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.

Development of an inline non-destructive monitoring method for ultrasonically welded seams during a continuous joining process

The welding manufacturing process is increasingly being used as an alternative joining method to sewing for functional textiles including for medical and protective wear, high-performance reinforcement textiles for fiber-reinforced plastics, film materials, and smart textiles. Ultrasonic (US) welding technology is a universally applicable cost-effective joining method for thermoplastic membranes. A key issue with the quality of the welded seam is that many of the faults are not visible on the membrane surface. The traditional quality control of the seam cannot be performed because it is done by destructive testing methods. Therefore 100% assurance of compliance of product safety produced at a production scale is not possible. The objective of the study is to develop a nondestructive (NDT) inline testing method for the quality control of welded seams during the continuous ultrasonic welding process. Currently, the quality control of Ultrasonic (US) welded seams is performed based on sample destructive standard tests, where the quality control of complete welded seams is not ensured. The air-coupled US sensors are used to detect imperfections in the welded seam. A variety of membrane materials with base fabric made of polyester and coated with PVC coating were tested during this research. A superimposed type of seam was produced longitudinally by PVC-coated textiles with smooth surfaced anvil wheels and was welded using a welding width of 10 mm. These coated materials were provided by industrial partners and are used in diverse technical textile applications. A process-integrated NDT test method was developed. The imperfections in welded seams were identified during a continuous US welding procedure with the help of air-coupled ultrasonic sensors by developing an inline test method. A prototype to realize inline monitoring during continuous ultrasonic welding was developed and tested. Faults of different widths were artificially produced during welding. The inline monitoring of welded seams with faults was successfully performed and analyzed. The developed process can further pave the way for the development of inline monitoring of welding seams with US sensors for textile membranes joined with a continuous US welding technology.

Tubular cubic polynomial sonotrode for green and sustainable ultrasonic welding technology

Ultrasonic Welding has emerged as a sustainable, green, and efficient manufacturing technology. This technique joins unique and advanced materials quickly, with good welding quality through high-intensity vibrations. Ultrasonic welding uses relatively low energy and incurs lower costs compared to various conventional welding systems. One of the key aspects to ensure high welding quality and strength, along with the transmission of high forces, is the design of an efficient ultrasonic sonotrode. This research study is aimed at proposing, evaluating, and testing the design of a tubular cubic polynomial sonotrode using finite element analysis. This novel ultrasonic welding sonotrode operates with low stresses and high displacement amplification. The performance of the proposed ultrasonic welding sonotrode design was compared with the commercially popular sonotrode, as well as cubic Bezier, exponential, and conical designs. This comparison was done in terms of harmonic excitation response, stresses, axial stiffness, displacement amplification, and factor of safety. The performance characteristics were also evaluated along the sonotrode length. The proposed sonotrode was found to be superior in terms of high vibration amplification and axial stiffness within safe stress limits. The benefits of the flexible design as per requirement to attain a higher displacement amplitude at the output end; consequently, lower welding forces were also realized. The proposed design is an improvement towards an efficient and green manufacturing technology involving reduced cost, energy consumption, use of consumables, effort, waste generation, and harm to the environment.

Morphological Characterization and Failure Analysis of the Ultrasonic Welded Single-Lap Joints.

Ultrasonic welding technology represents an advanced method for joining thermoplastic composites. However, there exists a scarcity of systematic investigations into welding parameters and their influence on the morphological characteristics and quality of the welded regions. Furthermore, a comprehensive experimental understanding of the welded joint failure mechanisms remains deficient. A robust model for simulating the failure behavior of welded joints under loading has yet to be formulated. In this study, ultrasonic welded specimens were fabricated using distinct welding control methods and varied parameter combinations. Diverse experimental methodologies are employed to assess the morphological features of the welded areas, ascertain specimen strength, and observe welding interface failure modes. Based on a cohesive model, a finite element model is developed to predict the strength of the ultrasonic welded joints and elucidate the failure mechanisms. The results showed that, under identical welding parameters, the specimens welded with a high amplitude and low welding force exhibit superior welding quality. The specimens produced under displacement control exhibit minimal dispersion in strength. The proposed finite element model effectively prognosticates both welded joint strength and failure modes.

A Driving Power Supply for Piezoelectric Transducers Based on an Improved LC Matching Network

In the ultrasonic welding system, the ultrasonic power supply drives the piezoelectric transducer to work in the resonant state to realize the conversion of electrical energy into mechanical energy. In order to obtain stable ultrasonic energy and ensure welding quality, this paper designs a driving power supply based on an improved LC matching network with two functions, frequency tracking and power regulation. First, in order to analyze the dynamic branch of the piezoelectric transducer, we propose an improved LC matching network, in which three voltage RMS values are used to analyze the dynamic branch and discriminate the series resonant frequency. Further, the driving power system is designed using the three RMS voltage values as feedback. A fuzzy control method is used for frequency tracking. The double closed-loop control method of the power outer loop and the current inner loop is used for power regulation. Through MATLAB software simulation and experimental testing, it is verified that the power supply can effectively track the series resonant frequency and control the power while being continuously adjustable. This study has promising applications in ultrasonic welding technology with complex loads.

Why do cracks occur in the weld joint of Ti-22Al-25Nb alloy during post-weld heat treatment?

Ultrasonic pulse frequency tungsten inert gas welding technology was adopted to join Ti-22Al-25Nb alloy. There were some cracks in the Ti-22Al-25Nb alloy weld joint after post-weld heat treatment. The hardness and Young’s modulus of α2, O, and β/B2 phases in Ti-22Al-25Nb alloy were examined with an in situ nanoindentation technique. The phase transition stresses of three different phases in the weld joint of Ti-22Al-25Nb alloy were analyzed to explain why cracks occur in the weld joint of Ti-22Al-25Nb alloy during post-weld heat treatment. The results show that mean hardness is highest for the α2 phase, second-highest for the O phase, and lowest for the β/B2 phase; the mean Young’s modulus has the same trend in Ti-22Al-25Nb alloy. Phase transition stress results in cracks in the weld joint of Ti-22Al-25Nb alloy during post-weld heat treatment. By improving post-weld heat treatment, the ultimate strength of the Ti-22Al-25Nb alloy weld joints reaches 750 MPa, which is 72.5% that of the base material.

Less Waste, More Efficiency

Reduce scrap rates with ultrasonic welding technology

Evaluation of Arc Signals, Microstructure and Mechanical Properties in Ultrasonic-Frequency Pulse Underwater Wet Welding Process with Q345 Steel

The ultrasonic-frequency pulse underwater wet welding (UFP-UWW) process was achieved through a constant-voltage-mode power source connecting an ultrasonic-frequency pulse power source in parallel. The arc voltage and welding current waveforms, sound signal variations, microstructural characteristics and mechanical properties at different parameters were investigated. The results showed that the ultrasonic-frequency pulse voltage and current of the UFP-UWW process displayed a periodic high-frequency oscillation on the based values of the conventional UWW process. The arc stability of the UFP-UWW process improved owing to the fact that the proportions of the unstable arc burning region could be reduced to 1.56% after the introduction of the ultrasonic-frequency pulse current. No significant changes in weld width and penetration were observed while the weld dilution rate increased to 54.2% for the combination of 40 V–30 kHz, compared with the results of the conventional UWW process. The flux-cored arc (FCA) welding arc in the air had the same frequency response to the ultrasonic excitation signal, which verified the existence of the ultrasonic-frequency vibration induced by the periodic high-frequency electromagnetic forces. The application of the ultrasonic-frequency pulse produced finer columnar grains in the welds with an average length of 315 μm, although the amount of pro-eutectoid ferrite and acicular ferrite varied little. The mechanical properties of the welded joints were also noticeably enhanced with the application of different ultrasonic excitation frequencies. The optimum tensile strength and impact toughness of the welded joint were improved by 6.7% and 21.7% when the applied ultrasonic excitation voltage was 40 V for a pulsed frequency of 30 kHz. These results facilitate the application of ultrasonic arc welding technology in the marine field.

Joints formation and bonding mechanism of ultrasonic welded multi-strand single core copper cables with copper terminals

• Metallurgical bonding of multi-strand single core copper cables with copper terminals was achieved by ultrasonic welding technology. • Formation of bonding interfaces involved plastic deformation, dynamic recrystallization, and dynamic recovery. • Fine equiaxed grains at the bonding interfaces were beneficial to increase the strength of the joints. The metallurgical bonding of multi-strand single core copper cables with copper terminals was achieved by ultrasonic welding technology. The joint forming process and bonding mechanism that involved plastic deformation, dynamic recrystallization and dynamic recovery were clarified. The necklace-like fine grains structures observed in the central areas of the bonding interfaces would significantly improve the T -peel strength of the joints.

Investigation of the ultrasonic welded stainless steel corrosion resistance

This article will present the ultrasonic welding technology of the stainless steel sheets, the joining with agreeing of the material science theory and metal-working rules-based executed experiments. Fusion welding is well understood and investigated in the case of steel. The ultrasonic welding in the case of metals causes different changes in the metals structure. The ultrasonic welding cause complex effect during the welding process. These effects are plastic deformation, heat, and ultrasound vibration. The goal of this research is to show the case of the experimented welded stainless steel (X5CrNi18-10) to determine the corrosion behaviour by non-destructive (visual test and microscopy) inspections. The stainless steel is sensible for all processes even that the cold working, heating and ultrasound effect. These effects can cause a decrease in the corrosion resistance of stainless steel.

Fusion Bonding Possibility for Incompatible Polymers by the Novel Ultrasonic Welding Technology: Effect of Interfacial Compatibilization.

Fusion bonding for polymers has been successfully welded for the same and dissimilar materials. However, it is difficult to bond incompatible polymers due to poor interfacial adhesion. Usually, interfacial compatibilization can resolve this problem. According to the mechanism, an interlayer solder sheet (ISS) consisting of maleic anhydride-functionalized polypropylene (PP-g-MAH) and polyamide6 (PA6) was introduced into the ultrasonic welding (USW) device. In this way, it successfully realized the weldability between PP and PA6. The welding strength of PP–PA6 reached 22.3 MPa, about 84% welding strength for the PP body and 63% tensile strength for PP. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM) showed the formation of PP-g-PA6 copolymer in blends. This copolymer played the role of an emulsifier, which enhanced the interfacial adhesion between PP and PA6 in two phases, leading to micron-scale homogeneity. In the USW process, the copolymer could act as a bridge between PP and PA6 molecular chains to realize the fusion bonding of incompatible polymers. Finally, we proposed the fusion bonding model for PP–PA6 interfaces.

Precise and Safe Battery Welding

Ultrasonic spot welding technology provides battery manufacturers with a fast, controlled, and gentle process even at low forces

Energy Direction in Ultrasonic Impregnation of Continuous Fiber-Reinforced Thermoplastics

As a new and innovative processing method for fabrication for fiber-reinforced thermoplastic composites (CFRTs), the feasibility of ultrasonic welding technology was proven in several studies. This method offers potential for the direct manufacturing of CFRT–metal structures via embedded pin structures. Despite the previous studies, a deeper understanding of the process of energy input and whether fibers work as energy directors and consequently can, in combination with chosen processing parameters, influence the consolidation quality of the CFRTs, is still unknown. Consequently, the aim of this work is to establish a deeper process understanding of the ultrasonic direct impregnation of fiber-reinforced thermoplastics with an emphasis on the fiber’s function as energy directors. Based on the generated insights, a better assessment of the feasibility of direct, hybrid part manufacturing is possible. The produced samples were primarily evaluated by optical and mechanical test methods. It is demonstrated that with higher welding time and amplitude, a better consolidation quality can be achieved and that independent of the process parameters chosen in this study, no significant fiber breakage occurs. This is interpreted as a sign of a gentle impregnation process. Furthermore, based on the examination of single roving and 5-layer set-ups, it is shown that the glass fibers function as energy directors and can influence the transformation of sonic energy into thermal energy. In comparison to industrially available CFRT material, the mechanical properties are weaker, but materials and processes offer potential for significant improvement. Based on these findings, proposals for a direct impregnation and joining process are made.

Ultrasonic Metal Welding of Multilayered Copper Foils to Nickel-Plated Copper Sheet in Lithium-Ion Battery Cell

The battery performance of electric vehicles depends on the density and capacity of the battery; thus, the battery cells must be assembled in as many layers as possible. Electric vehicle batteries are typically composed of several cells which form modules connected by busbars, with dozens of modules manufactured as battery packs. The ultrasonic metal welding (UMW) technology is applied to such multilayered foil welding. This study analyzed UMW to ensure the weldability of multilayered Cu foils and a Ni-plated Cu strip in lithium-ion battery cells through various approaches. In UMW, the effect of the alignment on weld production and quality were examined through the energy and mechanical performance of the weld by conducting comparative experiments on the alignment of the horn and anvil. Additionally, the effects of UMW process parameters, such as the welding pressure, amplitude, and welding time, were statistically analyzed. The weldability evaluation and characteristic analysis were performed based on these variables. Furthermore, the cross-sectional shapes and microstructure behavior of the Ni layers were analyzed based on the weld quality.

Orbital Ultrasonic Welding of Ti-Fittings to CFRP-Tubes

Hybrid structures are important for the automotive and aeronautical industry as they have the potential to reduce vehicle or aircraft weight and to improve fuel efficiency. Continuous ultrasonic metal welding is a promising technique for hydraulic applications in aircraft to realise tubular metal/fiber reinforced polymer (FRP) hybrids. Fluid proof connections between dissimilar components can be joined by continuous welding seams. Tubular metal/FRP hybrids, produced by a new advanced variant of ultrasonic metal welding, are investigated as a potential substitute for metallic hydraulic tubes. The oscillating welding system moves around the tubular joining partners to generate a sealed orbital connection. Homogeneous joint quality is required to assure the requested component strength. Therefore, the amplitude of sonotrode displacement and the welding force are controlled to keep the induced welding energy constant and the joint quality uniform. High mechanical strength is required for a safe application in the 5000 psi hydraulic system of current and future aircraft concepts. For this study metal injection molded (MIM) titanium fittings (TiAl6V4) and carbon fiber reinforced PEEK (CF-PEEK) tubes were investigated. Process parameters for metal/FRP hybrid joining were evaluated considering their mechanical and technological properties, as well as the microstructure of the hybrid interfacial area. The entire joining area of tubular joining partners has to be in close contact before welding to assure a continuous tight joint. Hence, the titanium fitting is thermally shrunk onto the CFRP tube before ultrasonic welding. The presented orbital ultrasonic welding technology was developed for prospective industrial use and future applications of ultrasonically welded tubular multi-material-components.

Research status and future perspectives on ultrasonic arc welding technique

In recent years, ultrasonic arc welding technology, a novel and promising welding process, has been widely applied in the welding of steel, aluminum alloy, titanium alloy, nickel base alloy and composite materials to improve the welding efficiency and quality of the welded joints. This paper reviews the research status of ultrasonic arc welding technology, systematically classifies and summarizes the process of ultrasonic arc welding in terms of different ultrasonic energy forms, and evaluates the limitations of the processes. Based on the experiment and simulation results, this paper summarizes the effect mechanisms of ultrasonic on the arc characteristics and molten pool behaviors during arc welding, namely the theories of ultrasonic vibration and electromagnetic field, and briefly discusses the association mechanism of ultrasonic vibration and electromagnetic field. Finally, we summary the systematic results supporting the association mechanism. On the one hand, ultrasonic energy leads to arc compression, which can effectively improve the arc stiffness, arc pressure and energy density, thus improving the arc thermal efficiency and welding efficiency. On the other hand, the ultrasonic stirring and mixing effects as well as the high-frequency pulsed electromagnetic field force introduced by the ultrasonic energy accelerate the thermal convection circulation and the flow of the molten pool, and affect the solidification and crystallization behavior of the molten pool, thus improving the formation, microstructure and mechanical properties of the weld. The paper aims to comprehensively review the ultrasonic arc welding process and mechanisms, and provide guidance for the future research and development in ultrasonic arc welding technique.

Research into the Textile-Based Signal Lines Made Using Ultrasonic Welding Technology

Abstract The article describes research into the transmission properties of textile signal lines (TSLs) made using ultrasonic welding technology. The presented TSLs are made from electroconductive, nickel coated, fabric strips welded between non-conducting textile layers. The article presents an analysis of the usability of the ultrasonic welding method for creating TSLs. This analysis shows that direct welding of an electroconductive path with the substrate increases its linear resistance, making it impossible to create a properly functioning line. This article presents an alternative method of creating the line using ultrasound welding technology.

Cold joining to fabricate large size metallic glasses by the ultrasonic vibrations

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.