Continuous ultrasonic welding is a promising high-speed and energy-efficient joining technique for thermoplastic composite structures. However, in the current state-of-the-art research on the topic ...numerous deconsolidation voids could be identified at the welding interface, which results in a strength knock-down. The aim of this study is, therefore, to improve the quality of continuous ultrasonically welded joints by adding a consolidation shoe to the welding setup. To determine the required consolidation pressure, the size of the shoe, and its distance from the sonotrode a stepwise approach was followed based on the static ultrasonic welding process. The closest consolidation distance, best representing the static welding conditions, did not improve the weld quality as significant porosity was still found in the weld line and in the adherends. However, for the furthest consolidation distance high-quality continuous welds were obtained with almost no porosity and a high strength.
Abstract
There are several possibilities for establishing a cohesion joint between dissimilar metals. In the case of thin sheets, the ultrasonic welding process is suitable. This process can ...establish a cohesion joint rapidly, with a low heat input between the thin sheets. The authors have tried to determine the optimal ultrasonic welding parameters for copper and austenite stainless steel joining by using an experimental method of joining. Suitable results were obtained by welding tests due dissimilarities in the chemical, physical and mechanical properties of the copper and stainless steel. A standard size sheet thickness and test sample was used for the welding by different parameters. The parameters were refined based on the theoretical and practical knowledge during the experiments. The experimental welding was made by a Branson L20 type welder machine. The joint made by the different parameters was inspected by shearing-tensile tests (maximal force level).
The shear and tensile strengths of carbon fiber-reinforced thermoplastic (CFRTP) laminate joints by ultrasonic welding were investigated by lap shear tests (LSTs) and cross tensile tests (CTTs). The ...adherends were the cross-ply and the twill woven CFRTP laminates, and the flat energy director (FED) was used to clarify its effectiveness. A modified jig and testing method for CTTs were newly proposed. In each test, the strengths were calculated in two ways: by indicators of “welding efficiency” and “welding quality.” From the experimental results, the strengths of the cross-ply laminate joints were saturated at high welding energy, and the “welding quality” was improved by FED. On the other hand, higher strengths of the twill woven laminate joints were obtained as the welding energy increased, and the effectiveness of FED was confirmed mainly for the “welding efficiency.” The fracture surfaces were then observed to clarify the fracture mechanisms of the joints.
Ultrasonic welding is a joining technology suitable for carbon-fiber-reinforced thermoplastic (CFRTP) components because of its high throughput, and ease of automation. An effective online ...weld-quality inspection technology can promote the industrial application of ultrasonic composite welding. Literature focused on the quality inspection of ultrasonic composite welding is scarce. To address this, the present study proposes an online weld-quality inspection method for ultrasonic composite welding by combining artificial intelligence (AI) technologies with welding process signatures. The failure load in a tensile-shear test and the weld quality level (i.e., under weld, normal weld, and over weld) are predicted simultaneously using artificial neural network (ANN) and random forest (RF) models. Eight features consisting of the duration and energy at each welding stage are extracted from the process signatures as independent variables. The results indicate that both the ANN and RF models exhibit high prediction accuracies. The weld quality can be assessed comprehensively and reasonably by considering both the failure load and weld quality level. The findings of this study demonstrate the feasibility of online weld-quality inspection for ultrasonic composite welding.
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•A quality inspection method for ultrasonic composite welding by combining AI technologies with process signals is proposed.•The failure load and weld quality level are predicted simultaneously by artificial neural network and random forest models.•The weld quality can be assessed more comprehensively by considering both the failure load and the weld quality level.
Ultrasonic welding has become a key joining approach in batteries and energy vehicles. This work reports the optimization in static property and stability of self-piercing riveting joints which is ...becoming the most versatile way to join microstructures. Tool heads of three different knurling profiles (e.g., A, B, and C) are used to perform ultrasonic composite with riveting. Based on tensile-shear tests, SEM, EDS, XRD, and Vickers microhardness analysis were conducted to investigate the comparative study of the fracture morphology, element distribution, phase structure, and hardness. The results indicated that all three types of knurling generate solid phase welding at the sheet joints. Thus, it improved the forming quality and mechanical properties of self-piercing riveting joints. The C-shaped welding tool head has advantageous effect on optimizing the mechanical properties of joints. Further, it enhanced the average peak load by 25.6%, the average failure displacement by 31.1%, and the average energy absorption by 88.8%. The microscopic results showed that a large amount of oxides are precipitated at the edge of welding joints when the B-shape knurling tool is used. The distribution of the hardness value of joints horizontal line is “M” shape. Besides, the coarse grains in the joint area and the interplanar space increase significantly after ultrasonic welding which softens the sheet.
The rapid and solid joining of thermoplastic to metal is of great significance for structural lightweighting. A thermoplastic acrylonitrile butadiene styrene (ABS) and laser textured 5052 Al is ...joined by ultrasonic welding with longitude wave in this study. Influence of the texturing type on microstructure and joint strength are investigated. Experimental results showed that the texturing type was a major factor in joint strength, and the mesh array was superior than circular hole array in terms of joint strength. The maximum joint strength of 17.87 MPa was obtained in L1, which was about 2.4 times and 3.6 times of these other two cases. Interfacial and cohesive failure mode was observed, and the fracture surface can be divided into four different parts: light black mark Region Ⅰ, transitional Region Ⅱ, Region Ⅲ with dense residues, and porous structure Region Ⅳ. The joint strength increased with the increase of Regions Ⅱ and Ⅲ while dropped with the occurrence of Region Ⅳ. Thermal decomposition of ABS composite resulted from the high temperature during welding process was responsible for the formation of Region Ⅳ. The joining mechanism in UW of ABS to laser textured 5052 Al was mechanical interlocking. Successful joining of ABS/Al hybrid structure by ultrasonic welding appears to be a reliable and potential technique for industrial applications.
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•New concept of resistance heat assisted ultrasonic welding (RUSW).•6061 Al and pure Cu were successfully welded by RUSW.•The output power of transducer and the temperature of the ...interface are increased significantly in RUSW.•The microstructure and the mechanical properties of the RUSW joints were improved.
This paper proposes a new welding method for joining non-ferrous metals: resistance heat assisted ultrasonic welding. Resistance heat generated by the electric Joule effect is used as an additional electrical energy source to assist ultrasonic welding process. A comparison is conducted between two dissimilar Al–Cu joints, one produced by ultrasonic welding and the other by resistance heat assisted ultrasonic welding. In the resistance heat assisted ultrasonic process, the peak power of ultrasonic vibration increases significantly. The interfacial reaction between aluminum and copper is studied as a function of the current. The thickness of the intermetallic compound layer, which is predominantly composed of CuAl2, increases with the current. At a relatively high current (1500A), resistance heat assisted ultrasonic welding produced a dendritic solidification microstructure at the interface, due to the occurrence of a eutectic reaction, α-Al+θ→L, during the welding process. The influence of current on the mechanical properties of the joints is also discussed.
Magnesium alloy, copper and other light alloys are widely used in aerospace, new energy vehicles, lightweight manufacturing and other fields due to their excellent mechanical properties, but the ...connection between light alloys has always been a challenge. Ultrasonic welding is an advanced manufacturing technology that can realize high-strength connection between heterogeneous light alloys. In this study, ultrasonic welding between AZ31B magnesium and pure copper are carried out. The fracture, microstructure and tensile properties of the joint are studied, and its connection mechanism is analyzed. The finite element analysis model of magnesium-copper ultrasonic welding process is established. The fracture mode of magnesium-copper ultrasonic welded joint is interface-type fracture. The joint strength reaches the maximum value of 3798 N. The ultrasonic connection between magnesium alloy and copper is mainly realized by the interface diffusion layer formed in the welding process. The main component of the interface diffusion layer is Mg2Cu. The growth trend of interface diffusion layer is revealed. During welding, heat is generated in the central area of the solder joint, and then transferred around. The maximum temperature at the interface can reach 550 °C. The distribution law of temperature field and plastic deformation field of joint are revealed.
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