Ultrasonic spot welding of Al-Cu sheets: A comprehensive study

Energy crisis poses a major challenge in the modern industrial scenario. A critical aspect of the shop floor work includes the welding of dissimilar metal sheets which require the right amount of energy. In order to tackle these challenges, a conservative and energy efficient method are necessary. Recently, automotive industries have been widely adopted the ultrasonic metal welding process for assembling lithium-ion battery packs and its modules. The joining of these dissimilar metals using any other conventional welding process is extremely challenging due to varying physical, chemical, thermal properties, the formation of the heat affected zone and lesser bond strength. However, ultrasonic metal welding yields better quality welds under the influence of optimal parametric conditions. In this research, the weld quality of two dissimilar materials, namely, aluminum (AA1060) with cupronickel (C71500) sheets investigated at different welding time, vibration amplitudes and welding pressures with a fixed ultrasonic frequency of 20 kHz. Experimental results show the tensile shear strength of the weld is maximum at the highest vibration amplitude with a moderate amount of weld pressure and weld time. Additionally, the joint quality and its associated microstructure at the weld region are analyzed by scanning electron microscopy (SEM) to reveal the bond strength with the interlocking feature.

Ultrasonic spot welding of Al/Mg alloys: A state-of-the-art review

Ultrasonic welding is a solid-state joining process that produces joints by the application of high-frequency vibratory energy in the work pieces held together under pressure without melting. In electronic and automotive applications, copper wires are connected to the equipment (alternator/rectifier) by a solid state joining process. For such an application ultrasonic metal welding is useful. The dominant problem faced by industry dealing with ultrasonic metal welding process is the poor weld quality and strength of the weld due to improper selection of weld parameters. In this work welding parameters like welding pressure, weld time and amplitude of the vibration are considered while producing ultrasonically welded joints of copper whose thickness is 0.2 mm. If other modes of joining are used, this size being very small, it may damage the weld. A suitable experimental design based on Taguchi’s robust design methodology was designed and executed for conducting trials. The analysis of variance (ANOVA) and signal to noise ratio analyses are employed to investigate the influence of different welding parameters on the weld strength and to obtain the optimum parameters.

Ultrasonic metal welding (USMW) has received noteworthy attention during recent years for its application to join lightweight materials. To improve the understanding of USMW process and to enhance the weld strength as well as quality, the present work is focused on the parametric study and its influence on the weld strength with various types of anvil tip geometries. It is observed that at higher weld time, an excessive amount of heat is produced at weld zone. Thus, a heavy plastic deformation occurs which is the major reason for over welding and lowering the weld strength. The temperature profiles for different types of anvils during the welding process are also examined at various weld conditions. The numbers of critical weld attributes are also identified to characterise the quality of weld formation over time. Microstructure study and microhardness measurement also have been employed to prove the severe plastic deformation in the interface layer as well as to establish a relationship between weld performance and physical weld attributes. As the weld time increases, the weld interface has been changed from planner to wavy morphology and the SEM micrographs proved the weld strength increments with the increase of waviness of the interface.

This paper presents some preliminary results in ultrasonic joining of ferrous and non-ferrous metals, which has recently been adopted to manufacture micro-welded parts. The effects of ultrasonic welding parameters such as vibration amplitude, weld time and weld pressure were compared through tensile shear and T-peel tests with microstructural analysis. These mechanical tests revealed that the maximum weld strength was obtained at the highest vibration amplitude. The temperature generated at the weld zone is lower than the aluminium melting temperature, which is consistent with solid state welding. Microhardness tests were also carried out to show the plastic deformation. The grain deformations, phase transformation, and aluminium diffusion were also examined through SEM and EDS analysis.

Ultrasonic spot welding of aluminum-copper dissimilar metals: A study on joint strength by experimentation and machine learning techniques

This paper gives a description of an experimental study on the ultrasonic welding of metals. In ultrasonic metal welding, high frequency vibrations are combined with pressure to join two materials together quickly and securely, without generating large amount of heat. Horn, a key part of ultrasonic welding machine, should be designed very accurately to get the natural frequencies and vibration mode required. In this study, a horn is designed and developed for ultrasonic welding of Cu sheets. The tensile strength of welded parts is investigated for evaluation of weldability. Experimental parameters of welding test is set as follows; welding time 0.4s ~ 3.4sec. and vibration amplitude 40%, 60%, 80% and welding pressure 1.5bar, 2.0bar, 2.5bar. Samples are Cu sheets of 0.1mm thickness. Experimental results showed that the tensile strength increase as welding parameters increase, but when welding pressure is excessive, the tensile strength decrease due to fracture of the Cu sheets caused by over-welding. These results could be successfully applied for ultrasonic metal welding in various fields of manufacturing industry.

Article history: Ultrasonic metal welding, unlike the conventional welding techniques, does not require an external heat source, welding rod, or filler metal. Therefore, ultrasonic metal welding is not only economical but also environment-friendly, and hence, it has been receiving much attention. In ultrasonic welding, heat is generated because of the plastic deformation and the friction between both surfaces of the welded materials. It is important to identify the heat-affected zone by measuring the temperature generated at the weld. In this study, the effects of the welding pressure, welding time, and vibration amplitude on the temperature distribution in the weld were evaluated by performing a transient thermal analysis of the heat generated during ultrasonic metal welding. The experimental results indicated that the temperature of the weld tends to increase with the welding time and vibration amplitude. However, an increase in the pressure does not affect the temperature of the weld largely.

Investigation of mechanical properties and microstructure characteristics on ultrasonic metal welding of aluminum alloy 8011 sheets

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.

Ultrasonic welding (USW) is a solid-state joining process in which the joint is created between the workpieces by the application of high frequency ultrasonic waves under pressure. Poor weld strength is one of the major problem experienced in the application of such weldments. It is mainly due to improper selection of process parameters. In order to achieve satisfactory weld strength optimization of welding process parameters is indeed essential. In this present context, the USW has been carried out to join dissimilar materials like A1100 aluminum alloy and CuZn37 brass plates of thickness 0.1 mm using Taguchi’s L16 orthogonal array design of experiments. The process parameters like amplitude, weld pressure and weld time have been taken into consideration. Taguchi’s S/N ratio concept has been employed to study the effect of different process parameters on the response like tensile strength; and finally, the optimum setting of process parameters has been decided in view of maximizing tensile strength. The predicted result of the optimized tensile strength has been validated by conducting a confirmatory test. This analysis shows that the high quality and efficient joints can be generated by exploring optimized setting of process parameters which is fruitful in mass production as well as off-line quality control of such a welding practice.

Investigation of process parameters of ultrasonic welding of copper using Taguchi and grey relational analysis

Ultrasonic metal welding is often used as a rapid and effective technique for joining sheet metals without causing them to melt. Precise management of the welding process parameters is crucial for achieving excellent joint quality. However, modeling the behavior of the weld material and the welding process is still very challenging. This study aimed to create 3D finite element models that accurately simulate the ultrasonic metal welding process. The proposed material model integrates frictional heat and ultrasonic softening, as well as the cyclic plasticity model. A friction law incorporating a variable friction coefficient is examined to investigate surface impacts. This coefficient is influenced by contact pressure, slippage, temperature, and the number of cycles. The findings of this study demonstrate that the oscillation frequency significantly influences both the temperature fluctuation and the extent of the heat-affected zone. Increased frequencies lead to accelerated temperature fluctuations and expanded heat-affected. Furthermore, ultrasonic welding combined with preheating led to a much wider heat-affected zone than ultrasonic welding without heating. The minimum preheating temperature required for ultrasonic welding of aluminum is 150 °C. This model can predict the relative displacement between welded plates. Assessing the oscillations that arise during the ultrasonic welding process is beneficial in selecting suitable welding settings to prevent excessive heating. This aids engineers in choosing appropriate welding parameters to avoid excessive heat generation during ultrasonic welding, hence limiting the reduction in tensile strength of the weld. Consequently, it can decrease the expense of the experimental methodology.

Modeling and optimization of ultrasonic metal welding on dissimilar sheets using fuzzy based genetic algorithm approach

Ultrasonic Metal Welding is a green manufacturing technique and one of the most advanced solid state welding processes in which similar or dissimilar metallic components are joined by the application of high frequency vibrations (> 20 kHz) and pressure. Ultrasonic metal welding is accompanied by slip and plastic deformation so that the base metals being welded will not melt and in turn forms a homogenous coalescence of two metals at the joining area so that the joint retains the parent metal properties. The major problem faced by the industries using ultrasonic metal welding process is the poor weld quality and weld strength. The design of acoustic horn or sonotrode plays a dominant role in producing quality welds. The primary function of sonotrode is to vibrate at a level required for welding and also to transmit the vibration energy to the point where welding of metals takes place. For producing quality welds, the vibration energy is to be transmitted to the weld interface without much loss. Therefore, there is a need for accurate design of sonotrodes in ultrasonic metal welding process. This work focuses on designing a stepped sonotrode used for joining metallic wire with metallic sheet based on significant design parameters such as amplitude gain and von Mises stress factor using modal and harmonic analysis. Experimental trials are conducted using the stepped sonotrodes and the effectiveness of the designed sonotrodes is evaluated based on improvement of strength of the joint in tension.