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To conduct the ultrasonic weld inspection of polyethylene pipes, it is necessary to use low-frequency transducers due to the high sound energy attenuation of polyethylene. However, one of the challenges in this process is that the blind zone of the ultrasonic transducer may cover a part of the workpiece being tested. This leads to a situation where if a defect appears near the surface of the workpiece, its signal will be buried by the blind zone signal. This hinders the early identification of defects, which is not favorable in such a scenario. To address this issue, we propose a new approach to detect and locate the near-surface defects. We begin by performing a synchro-squeezing transform on the original A-scan signal to obtain an accurate time-frequency distribution. While successful in detecting and localizing near-surface defects, the method alone fails to identify the specific type of defect directly: a limitation shared with other signal processing methods. Thus, an effective and lightweight defect identification model was established that combines depth-wise separable convolution and an attention mechanism. Finally, the performance of the proposed model was compared and visually analyzed with other models. This paper successfully achieves the detection, localization, and identification of near-surface defects through the synchro-squeezing transform and the defect identification model. The results show that our model can identify both general and near-surface defects with an accuracy of 99.50% while having a model size of only 1.14 MB. [ABSTRACT FROM AUTHOR]

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Deck structures subjected to drop-weight low-velocity impact are critical safety elements for ships and offshore structures. Therefore, the aim of the present study is to propose experimental research on dynamic responses of deck structures composed of stiffened plates subjected to drop-weight impact of a wedge impactor. The first step was to fabricate a conventional stiffened plate specimen and a strengthened stiffened plate specimen, as well as a drop-weight impact tower. Then, drop-weight impact tests were carried out. Test results show that local deformation and fracture occurred in the impact area. A sharp wedge impactor caused premature fracture, even under relative low impact energy; the permanent lateral deformation of the stiffened plate was reduced by 20–26% by the strengthening effect of a strengthening stiffer; residual stress and the stress concentration of the cross-joint caused by welding may cause undesired brittle fracture. The present investigation provides useful insight for improving the crashworthiness design of the deck structure of ships and offshore structures. [ABSTRACT FROM AUTHOR]

Ultrasonic metal welding (USMW) is widely used in assembling lithium-ion (Li-ion) battery packs due to its advantages in joining dissimilar and conductive materials in the solid state. However, the welding process and mechanisms are not yet clearly understood. In this study, dissimilar joints of aluminum alloy EN AW 1050 to copper alloy EN CW 008A were welded by USMW to simulate the tab-to-bus bar interconnects for Li-ion battery assembly. Qualitative and quantitative investigations were carried out on plastic deformation, microstructural evolution, and the correlated mechanical properties. During USMW, the plastic deformation concentrated on the Al side. The thickness of Al was reduced by more than 30%; complex dynamic recrystallization and grain growth occurred near the weld interface. The mechanical performance of the Al/Cu joint was evaluated with the tensile shear test. The failure load gradually increased until a welding duration of 400 ms, and then remained almost constant. The obtained results showed that the mechanical properties were greatly influenced by plastic deformation and microstructure evolution, which provides guidance for improving the weld quality and the process in general. [ABSTRACT FROM AUTHOR]

Recently, battery capacity and performance improvements have become the most important issues for improving the performance of electric vehicles. Improvement of the aluminum and copper junctions used as battery tab materials is also required. The dissimilar tab materials are connected either in series or parallel to deliver the required battery power and capacity to the vehicle. Ultrasonic welding is increasing in popularity for joining dissimilar materials, and the automotive industry is likely to benefit the most. However, the industry is dealing with variations in joint quality due to the numerous welding parameters involved, such as the welding time, vibration amplitude, welding pressure, etc. Therefore, in this study, an appropriate design-of-experiment method was used to optimize the selected welding parameters with a reduced number of tests in terms of weld strength quality (either under lap-shear or T-peel tests) and electrical joint resistance. The signal-to-noise ratio and strength-reduction ratio analyses were employed to investigate the influence of different welding parameters for each joint-quality category and to predict the optimum welding parameters within the limits of the parameters studied. The analyses were successful and effective in identifying the most influential welding parameter for each category. The results of analyses and predictions generated were satisfactorily comparable with the validation experiment results. [ABSTRACT FROM AUTHOR]

Ultrasonic welding (UW) is a well-established technique for joining thermoplastic composites and has recently been utilized in the aerospace and automotive industries. In the case of thermoset composites (TSCs), a polymer-based material placed at the welding interface called an energy director (ED) is required. The choice of the coupling layer material is linked to several requirements, such as processing temperature, high adhesion to the thermoset composites (TSCs) adherend and mechanical strength of the resulting welded joints. In this work, the authors investigated the possibility of using Poly-vinyl-butyral (PVB) reinforced with graphite nanoplatelets (GNPs) as a coupling layer in the UW of TSC adherents. The effect of GNPs aspect ratio and content on the weldability of carbon fiber-reinforced plastics (CFRP) has been investigated. PVB/GNPs nanocomposites with different filler contents (from 0.5 wt% to 2 wt%) and different aspect ratios (100 and 2100) have been fabricated. The influence of the viscoelastic properties of the flat EDs on weldability has been assessed. Finally, an improvement of lap shear strength (LSS) of 80% was found for nanocomposites with 0.5 wt% of high-aspect-ratio GNPs with respect to neat PVB. The use of high damping nanocomposites as coupling materials for TSCs paves the way for a new generation of EDs in UW. [ABSTRACT FROM AUTHOR]

The usage of natural fiber–reinforced composites (NFRCs) may help the global fraternity in achieving their long-term goal of developing sustainable products having minimum effect on ecosystem, during and at the end of their service life. The primary manufacturing processes such as injection molding, hand-layup, and compression moulding have been extensively used to fabricate products with simpler profiles. However, the fabrication of complex products necessitates secondary manufacturing processes. In current investigation, the short fiber (banana and bagasse)–based polypropylene composites (10, 15, and 20 wt.%) were fabricated using extrusion-injection moulding process. Banana fiber–based composites recorded 1.8%, 4.7%, and 3.25%, higher tensile strength than bagasse fiber–based composites at 10, 15, and 20 wt.% fiber loading, respectively. However, bagasse fiber–based composites performed distinctly better in flexural properties. Field emission scanning electron microscopy and thermogravimetric analysis were employed to analyze the failure mechanisms and thermal degradation behavior (analyzed at 5%, 25%, 50%, and 75% weight loss) of the fabricated composites. The ultrasonic welded joints of banana fiber–based composites recorded higher failure load prior to the fracture as compared to bagasse fiber–based composites upto 15% fiber loading. It was established that ultrasonic welding can be successfully employed for joining of NFRCs.

A servo-driven ultrasonic welding (USW) offers a good control for joining carbon fiber reinforced thermoplastic composites (CFRTP) with a constant plunging speed, a dynamic applied force and adjusting power in real time. This study focuses on the process and strength analysis during servo-driven USW of CF/PA6 composites without energy director (ED) to obtain the correlation between the operation parameters and joint strength. The results show that a servo-driven welder benefits in USW without ED due to the initial intimate contact between workpieces without horn retraction. It is also found that a typical vibration process can be divided into four stages following the heat evolution and characteristic temperature of CFRTP, i.e., “initial stage”, “soften stage”, “melting stage” and “steady stage”. High energy and amplitude bring enough total energy and high power to melt materials; while a low trigger force and a slow plunging speed can mitigate the excessive squeeze-out with a result of the increase in weld strength. Thus, as the melted material remained in the weld region decides the bonding efficiency, the desired joints can be obtained under the enough welding energy (≥400 J) and amplitude (≥80%), not too high welding force (≤800 N) and plunging speed (≤0.8 mm/s). Meanwhile, weld quality can be online inspected and judged based on welding force evolution, and the measured displacement relative to the set value. This work contributes to the optimal parametric selection for USW of CFRTP plates without ED applying a servo-driven welder.

This investigation deals with the study of the effect of environmental parameters viz dew point temperature, relative humidity, ambient air temperature, and job surface temperature on robotic MAG (Metal active gas) welded joint quality. Weld samples taken were mass manufacturing welded structures of a heavy-large scale industry, which were further subjected to semi-automatic ultrasonic testing to assess defects within welded joints. The trend of defects observed and recorded after ultrasonic testing of weld joints was co-related with the trend of atmospheric parameters for a span of four years to establish a linear empirical relationship. It has been established that variations in atmospheric parameters resulted in variations in the trend of weld defects. These variations were studied to get the empirical relationship to establish the effect of variation in atmospheric parameters on weld quality or defects in joints. It has been observed that whenever there was a drop in the "difference in ambient air temperature & dew point temperature, especially less than 5," a drop in ultrasonic testing straight pass % was observed than the average value. [ABSTRACT FROM AUTHOR]

In view of the complex multi-scale target detection environment of ultrasonic atlas of weld defect and the poor detection performance of existing algorithms for the multiple small target defects, the Faster RCNN convolution neural network is applied to weld defect detection, and a Fast RCNN deep learning network is proposed in combination with an improved ResNet 50. Based on the coexistence of multiple small targets and multi-scale target detection, this paper proposes to combine deformable network, FPN network and ResNet50 to improve the detection performance of the algorithm for multi-scale targets, especially small targets. Based on the efficiency and accuracy of candidate frame selection, K-means clustering algorithm and ROI Align algorithm are proposed, and the anchors points and candidate frames suitable for weld defect data sets are customized for accurate positioning. Through the self-made ultrasonic atlas data set of weld defects and experimental verification of the improved algorithm in this paper, the overall mean average precision has reaches 93.72%, and the average precision of small target defects such as "stoma" and "crack" has reaches 92.5% and 88.9% respectively, which is 4.8% higher than the original Faster RCNN algorithm. At the same time, through the ablation experiments and comparison experiments with other mainstream target detection algorithms, it is proved that the improved method proposed in this paper improves the detection performance and is superior to other algorithms. The actual industrial detection scene proves that it basically meets the requirements of weld defect detection, and can provide a reference for the intelligent detection method of weld defects. [ABSTRACT FROM AUTHOR]

The optimal mode for ultrasonic welding (USW) of the "PEEK–ED (PEEK)–prepreg (PEI impregnated CF fabric)–ED (PEEK)–PEEK" lap joint was determined by artificial neural network (ANN) simulation, based on the sample of the experimental data expanded with the expert data set. The experimental verification of the simulation results showed that mode 10 (t = 900 ms, P = 1.7 atm, τ = 2000 ms) ensured the high strength properties and preservation of the structural integrity of the carbon fiber fabric (CFF). Additionally, it showed that the "PEEK–CFF prepreg–PEEK" USW lap joint could be fabricated by the "multi-spot" USW method with the optimal mode 10, which can resist the load per cycle of 50 MPa (the bottom HCF level). The USW mode, determined by ANN simulation for the neat PEEK adherends, did not provide joining both particulate and laminated composite adherends with the CFF prepreg reinforcement. The USW lap joints could be formed when the USW durations (t) were significantly increased up to 1200 and 1600 ms, respectively. In this case, the elastic energy is transferred more efficiently to the welding zone through the upper adherend. [ABSTRACT FROM AUTHOR]

Copyright of New Building Materials / Xinxing Jianzhu Cailiao is the property of New Building Materials Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The feasibility of using laser-generated ultrasonic Total Focusing Method (TFM) was assessed for guided ultrasonic waves in finite plates. The application under consideration is for inspection of ultrasonically welded battery tab-to-electrode foil stack joints. The testing constraints for this weld necessitate couplant-free, remote, guided-wave conditions making laser ultrasonic TFM an ideal inspection technique. It was determined that laser-generated guided wave TFM can be used to remotely assess defects in a finite plate when the defects are strong reflectors in the plane of wave propagation. The finite dimensions of the tab require a strong understanding of the edge reflection effects on the TFM image. The guided wave modes used in this study were strongly affected by scattering due to the complex weld geometry, which most resembles that of a periodic triangular grated wave guide. Future work will investigate methods to compensate for the strong scattering/guided wave effects, the use of other guided wave geometries, out of plane TFM reconstruction for other weld defect types, as well as apodization effects. [ABSTRACT FROM AUTHOR]

In this research, the effect of resistance spot welding (RSW) parameters including current intensity, welding time and welding force (coded by A, B and C) on the radius, thickness and area of the nugget and the radius of the heat affected zone(HAZ) of transformed induced plasticity (TRIP) steel joints was investigated by design of experiment(DOE) and response surface methology (RSM). A 3D coupled thermal-electrical-structural FEM was used to model RSW. To validate the FE model, two TRIP steel sheets were welded experimentally. During welding, the temperature was measured and the results were compared with the FE results and a good agreement was obtained. The boundaries of the welding zones were determined according to the critical temperatures and the responses in all samples were calculated. Using analysis of variance, direct, quadratic and interaction effects of parameters on the responses were studied and a mathematical model was obtained for each response. The direct linear effect of all parameters on all responses were significant. But among the interaction effects, the effect of B×C on the nugget radius, the effect of A×B on the nugget thickness, the effect of A×B on the nugget area and the effects of A×B and B×C on the HAZ radius were significant. Also, current intensity had the greatest effect on all responses. [ABSTRACT FROM AUTHOR]

Polymer parts often replace traditional metallic parts in load-bearing applications due to their high strength-to-weight ratio, with thermoplastics at the forefront. Conventional manufacturing processes rely on using fasteners or adhesives to hold composite assemblies together, but thermoplastics can be welded together. Ultrasonic welding is widely used but becomes challenging for complex geometries, and new parameters need to be developed for different polymers and specimen geometries. In this work, we developed a closed-loop welding machine that employs the recent discovery of radio-frequency (RF) heating of carbonaceous materials. The machine is successfully able to weld polylactic acid (PLA) coupons with graphitic RF susceptors at the bondline in less than 2 min and using less than 50 W of input RF power. We found that a higher areal density of the graphitic paint lowers the mechanical properties of the weld because the carbonaceous materials hinder polymer chain diffusion. A significant change was not observed in weld properties for welding pressure ranges between 0 and 0.3 MPa. However, increasing out-of-plane welding displacement increased the modulus and strength of the weld. This work provides an interesting new automated system for welding polymer composites using RF fields, with potential applications in various manufacturing industries. [ABSTRACT FROM AUTHOR]

When working with thin layers of comparable and/or different metals, resistance welding and conventional welding each have their own set of limits that they must overcome. When the input parameters include a high-frequency vibration, proper weld duration and pressure, ultrasonic metal welding performs at its highest level of efficiency. Ultrasonic welding uses a lot of power, force and energy, and if the right input parameters aren't chosen, the quality of the weld and its durability suffer. This study takes into account the relationships between the input process parameters of welding pressure, welding time and vibration amplitude and the output responses of power, force and energy in ultrasonic metal welding (UMW). For multilayer AL-8011 foils, the author utilized UMW has experimented with central composite design by design professionals. The response surface approach, often known as RSM, has been used to improve the process parameters to get the best possible welding connections. [ABSTRACT FROM AUTHOR]

Previously, we developed an instrument to evaluate the heel fat pad (HFP) two-layer structure, under varying loading conditions, with ultrasonography from the plantar surface through a polymethylpentene resin plate; the measured values were equivalent to those obtained without this plate. The study described here aimed to determine the intra- and inter-examiner reliabilities of the HFP thickness measurements and the agreement between long- and short-axis measured values using this instrument. Two examiners successively recorded the HFPs of 40 healthy adults twice under the no loading and loading conditions on the long- and short-axis scans. The HFPs were classified into two layers, and their thicknesses were measured. Short-term intra- and inter-examiner reliabilities were determined using the intraclass correlation coefficients. Measurements were repeated 1 mo later to determine the long-term intra-examiner reliability. The agreement between the measured long- and short-axis values was investigated by calculating the minimal detectable changes. The determined short- and long-term intra-examiner reliabilities ranged from 0.750 to 0.999 and from 0.765 to 0.952, respectively. Inter-examiner reliability ranged from 0.765 to 0.997. Differences may occur between the values measured at different axes. The measurements using this evaluation instrument were reliable, and it is best to unify the measurement axis for quantitative research. [ABSTRACT FROM AUTHOR]

The laser welding efficiency of stainless steel is high, but the welding quality is still insufficient. In order to improve the welding performance of stainless steel, a controllable ultrasonic laser welding system was designed in the paper. Through numerical simulation and experimental test, the influences of ultrasonic vibration on the mechanical properties of weld were obtained. For the simulation study, the sound vibration coupling scheme was applied to the welding model. The closed environment model was established, and the characteristic frequency and sound pressure distribution of ultrasonic were simulated and analyzed by COMSOL software. In the aspect of performance test, through the real-time monitoring of the welding system, the effect of ultrasonic on the molten pool area, molten pool flow rate and metal vapor pressure is obtained. Under different ultrasonic excitation frequencies, the changes of weld microstructure, wear morphology, hardness and oxidation were studied. The results show that ultrasonic vibration can significantly improve the wear resistance, hardness and corrosion resistance of stainless steel welds. The ultrasonic energy efficiency at the second-order characteristic frequency is higher, the flow rate in the molten pool is low, and the joint quality is better. [ABSTRACT FROM AUTHOR]

The use of welded joints in composite structures with reinforced fibers has rapidly increased owing to their advantages in terms of strength-to-weight ratio, design flexibility and ease of production. Herein, the generalized progressive damage model is numerically and experimentally studied to predict the degradation process in end notch flexure (ENF) composite specimens welded by the ultrasonic method. In numerical modeling, a trapezoidal traction-separation model that expresses the embedded process zone (EPZ) is developed using three data reduction methods of the compliance calibration method (CCM), classical beam theory (CBT) and compliance-based beam method (CBBM), and formulated by combining failure and damage mechanics. Finally, the force-displacement diagrams obtained from experimental investigations and the force-displacement diagrams extracted from numerical modeling are compared. The results demonstrate that the models extracted using CBBM and CBT methods make accurate predictions compared to the CCM method. [ABSTRACT FROM AUTHOR]

Galvanic corrosion of AZ31B joined with bare or Zn-coated DP590 steel by ultrasonic spot welding or linear friction stir welding was quantitatively studied by pre-defining anode and cathode in the lap joint samples. Corrosion volume and depth from Mg anode surfaces exposed to 0.1 M sodium chloride solution was analyzed as functions of cathode surface type and welding method. Characterization of as-welded joints was performed to identify any microstructural feature of the bonding zone that could impact galvanic corrosion behavior. COMSOL modeling with modified user subroutine was conducted to simulate the progression of Mg corrosion in the same joint and electrode configurations used for the corrosion experiments. The experimental results indicated that Zn-coated cathode surface can reduce Mg galvanic corrosion significantly as galvanic polarization and cathodic current on Zn-coated surface remained relatively low for Mg in the weld joints. COMSOL modeling described the growth of Mg galvanic corrosion in a reasonable manner but showed limitation by underestimating the corrosion volume as it did not capture self-corrosion. [ABSTRACT FROM AUTHOR]

Ultrasonic welding (USW) is a solid-state welding process based on the application of high frequency vibration energy to the workpiece to produce the internal friction between the faying surface and the local heat generation required to promote the joining. The short welding time and the low heat input, the absence of fumes, sparks or flames, and the automation capacity make it particularly interesting for several fields, such as electrical/electronic, automotive, aerospace, appliance, and medical products industries. The main problems that those industries have to face are related to the poor weld quality due the improper selection of weld parameters. In the present work, 0.3 mm thick copper sheets were joined by USW varying the welding time, pressure, and vibration amplitude. The influence of the process variables on the characteristics of the joints and weld strength is investigated by using the analysis of variance. The results of the present work indicate that welding time is the main factor affecting the energy absorbed during the welding, followed by the pressure and amplitude. The shear strength, on the other hand, resulted mostly influenced by the amplitude, while the other parameters have a limited effect. Regardless the welding configuration adopted, most welds registered a failure load higher than the base material pointing out the feasibility of the USW process to join copper sheets. [ABSTRACT FROM AUTHOR]

The thermoplastic polymer polyether ether ketone (PEEK) offers thermal and mechanical properties comparable to thermosetting polymers, while also being thermally re-processable and recyclable as well as compatible with fused filament fabrication (FFF). In this study, the feasibility of joining additively manufactured PEEK in pure and short carbon-fiber-reinforced form (CF-PEEK) is investigated. Coupon-level samples for both materials were fabricated using FFF with tailored integrated welding surfaces in the form of two different energy director (ED) shapes and joined through ultrasonic polymer welding. Using an energy-driven joining process, the two materials were systematically investigated with different welding parameters, such as welding force, oscillation amplitude and welding power, against the resulting weld quality. The strengths of the welded bonds were characterized using lap-shear tests and benchmarked against the monotonic properties of single 3D-printed samples, yielding ultimate lap-shear forces of 2.17 k N and 1.97 k N and tensile strengths of 3.24 M Pa and 3.79 M Pa for PEEK and CF-PEEK, respectively. The weld surfaces were microscopically imaged to characterize the failure behaviors of joints welded using different welding parameters. Samples welded with optimized welding parameters exhibited failures outside the welded region, indicating a higher weld-strength compared to that of the bulk. This study lays the foundation for using ultrasonic welding as a glue-free method to join 3D-printed high-performance thermoplastics to manufacture large load-bearing, as well as non-load-bearing, structures, while minimizing the time and cost limitations of FFF as a fabrication process. [ABSTRACT FROM AUTHOR]

This paper explains the use of remote ultrasound vibration at the optimum position and frequencies to vibrate plates under welding, with the aim of initiating cavitation in the molten pool area. It has been shown in the literature that ultrasound cavitation changes microstructure morphology and refines the grain of the weld. In practice, the plates are excited through narrow-band high-power ultrasound transducers (HPUTs). Therefore, a theoretical investigation is carried out to identify the plate-mode shapes due to the ultrasound vibration aligned with the frequency bandwidth of HPUTs available in the marketplace. The effect of exciting the plate at different locations and frequencies is studied to find the optimum position and frequencies to achieve the maximum pressure at the area of the fusion zone. It was shown that applying the excitation from the side of the plate produces an order of 10 3 higher vibration displacement amplitude, compared with excitation from the corner. The forced vibration of cavitation and bursting time are studied to identify vibration amplitude and the time required to generate and implode cavities, hence specifying the vibration-assisted welding time. Thus, the proposed computational platform enables efficient multiparametric analysis of cavitation, initiated by remote ultrasound excitation, in the molten pool under welding. [ABSTRACT FROM AUTHOR]

Lithium-ion battery (LIB) remanufacturing holds great potential for CO 2 savings, but there are challenges to productive disassembly. The demand to increase productivity in LIB production has resulted in a number of assembly methods and LIB designs that are unfavorable for automated disassembly. Disassembly by automation must handle a large number of variants. Automated disassembly processes must disassemble LIB and replace cells in a fully automated and non-destructive manner. The development of automated remanufacturing solutions is inevitable in order to repair and reuse LIB components in closed loops, and enable multiple life cycles for remanufactured LIBs. This paper proposes an automated remanufacturing process for LIBs. The proposed concept includes process and remanufactured product design for LIB packs. The proposed LIB pack design enables the separation of ultrasonic wire bonds to replace and reconnect defective cells from wire-bonded LIB packs. Both the process and LIB pack designs are evaluated using a use case, and the stability of cell separation and reconnection with ultrasonic welding is demonstrated. [ABSTRACT FROM AUTHOR]

This study investigates the effects of fabric properties and ultrasonic welding on the performance of surgical gowns. For this purpose, eight spunlace fabrics with different structural properties were provided. 100% polyester, 100% viscose, and their blends were used as test materials. First, the fabrics' thickness, breaking force, elongation at break, air permeability, drape behavior, and surface friction properties were investigated. Then the fabrics were sewn with the ultrasonic sewing machine. Afterward, the sewn fabrics' seam strength, air permeability, and drape behavior were tested. The results were statistically evaluated. A detailed comparison was made based on the data obtained. The higher the polyester content in the fabric, the higher the fabric strength, seam strength, and air permeability. However, viscose-rich fabrics have a softer feel and are easier to drape compared to polyester fabrics. Moreover, the sewing process leads to a reduction in the air permeability of the fabrics. [ABSTRACT FROM AUTHOR]

As a solid-state bonding technology, ultrasonic welding (USW) has the characteristics of green energy saving and environmental friendliness. It is more suitable for joining dissimilar metals than other welding technologies. The aluminum-to-steel USWed joint has been widely used in the automotive and aviation industries. Currently, there is no review literature report on aluminum-to-steel USW. The main physical phenomena of the USW process include interface temperature increase, ultrasonic softening, plastic deformation, formation and growth of the IMCs, and dynamic recrystallization. Hence, the microstructures and mechanical properties of aluminum-alloy-to-low-carbon-steel, aluminum-alloy-to-stainless steel, and aluminum-alloy-to-galvanized-steel-joints by USW are reviewed. Moreover, the effect of interface temperature, interface plastic deformation, and interface macrostructure and microstructure is explored. Lastly, tensile-shear and fatigue strength of joints and numerical simulation of the USW process are also discussed. In addition, some new application types of aluminum-to-steel USW are introduced. Finally, the future trends of aluminum-to-steel USW with guidance are provided. [ABSTRACT FROM AUTHOR]

In order to improve the Cu/Cu joint quality, the bottom Cu sheet surface to be welded was dampened by a drop of absolute ethyl alcohol before the welding. Then, the ultrasonic spot welding (USW) was utilized to join a 0.5 mm thick Cu sheet to a 1.0 mm thick Cu sheet. The results demonstrated that, due to the action of the alcohol, obvious changes of the welding interface temperature, effective thickness, bond density, interface microstructure, joint resistance, micro-hardness, lap shear strength and fracture mode occurred in comparison with the joint without alcohol. Discontinuous dynamic recrystallization took place at the welding interface and facilitated the migration of grain boundaries across the contact interface, leading to the formation of the metallurgical bonding between the two Cu sheets. [ABSTRACT FROM AUTHOR]

One of the basic trends in the automotive industry today is to achieve the most acceptable ratio between the total weight of the car to its overall performance and utility properties. Reducing the weight of cars is largely due to the use of new materials, where composite materials offer a wide space for their application. Composite materials have their specific properties which is very beneficial in reducing the total weight. Another advantages is strength, stiffness, low fiber density, the ability to form them into any shape based on the required applications. One of the challenges associated with the use of composite materials is the search for new technological possibilities of joining composite materials with metals. These include technologies as for example riveting, ultrasonic welding, but especially gluing. Bonding is currently one of the most preferred ways of joining composite materials. The paper deals with testing of technology of bonding composite materials with metals used in the manufacture of automobiles and a comparison of individual results obtained from the experiment. [ABSTRACT FROM AUTHOR]

Ultrasonic welding is a fast and promising joining technique for thermoplastic composite parts. Understanding how changing the part thickness affects the process is crucial to its future upscaling and industrialization. This article presents an initial insight into the effect of the adherend’s thickness on the near-field ultrasonic welding of CF/LMPAEK thermoplastic composites. Different thicknesses of the top and bottom adherend were welded and analyzed using the output data of the welding equipment, temperature measurements, and other visual characterization techniques. Increasing the thickness of both the top and the bottom adherends showed to increase the power consumed during welding. An overshoot in the power needed at the onset of the welding process for increased thickness of the top adherend precluded welding beyond a threshold thickness of 4.72 mm. In the case of the thicker top adherends, there was also melting of the energy director and early fiber squeeze-out within the top adherend as a result of increased bulk heating. Increased bulk heating was hypothesized to be caused by increased hammering, as indicated by the amplitude readings for thicker adherends. Welding with a higher force, which is known to reduce hammering, corroborated this hypothesis as fiber squeeze-out within the top adherend was not observed. It is believed that hammering contributes to heating by causing an oscillatory impact excitation that is close to the natural frequencies of the system, which would result in amplification of the cyclic strain and subsequent increase in the viscoelastic heating in the adherend.

Ultrasonic spot welding (USW) represents one of the unique solid-state joining methods for lightweight materials such as magnesium alloy and aluminum alloy. However, the sonotrode vibration may have a detrimental impact on the sheet material and the existing welds, depending on the component geometry and vibration frequency. In this study, a modal analysis tool based on steady-state dynamics was developed for ultrasonic spot welding which features a cyclic load applied to the sheets during the joining process. Through predicting relative motion and shear stress at the faying surfaces, coupon geometry and weld spacing are identified as two major factors that affect the welding reliability and joint quality in USW. The model was validated via welding experiments on aluminum alloy and magnesium alloy and relevant characterization of temperature distribution, joint strength as well as fracture location.

In multilayer ultrasonic welding, the sonotrode presses on metal sheets and drives the sheets to produce ultrasonic vibration. Then, each contact interface generates heat, produces plastic deformation, and forms solid-state bonding. However, the load distributes unevenly in each sheet, which results in the uneven friction state and inconsistent welding quality. Hence, it is necessary to reveal the mechanism of frictional state and energy dissipation based on the load distribution in each sheet. A finite element model of 5-layer copper sheets is established using Abaqus and considering the Cattaneo-Mindlin contact theory. The clamping force and ultrasonic vibration in each interface is simulated. The slip-stick state of each interface is obtained and the effect of the clamping force are analyzed. The frictional energy dissipation and proportion of each interface are calculated, the influencing factors of frictional energy dissipation are summarized, and the optimization of input clamping force is discovered, which can provide theoretical guidance for the improvement of multilayer ultrasonic welding.

Abstract This paper presents a new design approach for two main components of an ultrasonic plastic welding machine, booster and horn, based on an analytical model. The design procedure is developed due to the lack of a comprehensive and precise analytical model for rapid design and analysis of these components. The previous analytical models use the one-dimensional wave equation that causes significant errors in designing components with large lateral dimensions. Three-dimensional vibrations are considered for developing an analytical model using the apparent elasticity method. In this way, longitudinal frequency equations are coupled with radial frequency equations by mechanical coupling coefficients. Also, the damping of materials is taken into account. The model can be adapted to calculate the resonant length of the components or calculate the resonant frequency. To verify the model, the results are compared to a numerical simulation. The difference between analytical and numerical resonance frequency is less than 0.02%. Moreover, an experimental modal analysis is performed, which shows 0.9% error with analytical results. Article highlights A new design approach for boosters and horns has been developed based on an analytical model. Three-dimensional vibrations are considered in the model using the apparent elasticity method. The accuracy of calculating resonant frequencies is more than one-dimensional design method.

The usage of natural fiber–reinforced composites (NFRCs) may help the global fraternity in achieving their long-term goal of developing sustainable products having minimum effect on ecosystem, during and at the end of their service life. The primary manufacturing processes such as injection molding, hand-layup, and compression moulding have been extensively used to fabricate products with simpler profiles. However, the fabrication of complex products necessitates secondary manufacturing processes. In current investigation, the short fiber (banana and bagasse)–based polypropylene composites (10, 15, and 20 wt.%) were fabricated using extrusion-injection moulding process. Banana fiber–based composites recorded 1.8%, 4.7%, and 3.25%, higher tensile strength than bagasse fiber–based composites at 10, 15, and 20 wt.% fiber loading, respectively. However, bagasse fiber–based composites performed distinctly better in flexural properties. Field emission scanning electron microscopy and thermogravimetric analysis were employed to analyze the failure mechanisms and thermal degradation behavior (analyzed at 5%, 25%, 50%, and 75% weight loss) of the fabricated composites. The ultrasonic welded joints of banana fiber–based composites recorded higher failure load prior to the fracture as compared to bagasse fiber–based composites upto 15% fiber loading. It was established that ultrasonic welding can be successfully employed for joining of NFRCs. [ABSTRACT FROM AUTHOR]

The diagenesis of welded tuffs is a process in which volcanic debris undergoes degassing, compaction, and quenching, and vitreous rheologic, which indicates that the welding occurred in a high-temperature, high-pressure diagenetic environment and that different temperatures and pressures result in different degrees of welding in the welded tuffs, which can also result in differences in the mechanical properties of the rock. In this study, based on petrographic identification, mineral composition analysis, and pore structure characterization, uniaxial compression combined with linear accelerator CT and Brazilian splitting tests was carried out to investigate the influence of the welding degree on the strength and failure modes. The test results showed that although they had almost similar mineral composition and porosity, the uniaxial compression strength and tensile strength of the strongly welded tuffs were greater than that of the weakly welded tuffs. Their failure modes were also different. Fractures in the weakly welded tuffs developed gradually, while the strongly welded tuffs showed a higher brittleness with sudden failure. The results of this study shed light on the influence of the diagenetic environment on the mechanical properties of rock from a geological perspective and can provide a mechanical basis for rockfall risk evaluation in scenic areas of welded tuff. [ABSTRACT FROM AUTHOR]

The present study focuses on multi-criteria optimization of pulse current tungsten inert gas (TIG) welding process parameters using technique for order of preference by similarity to ideal solution (TOPSIS) based Taguchi approach to enhance quality and productivity characteristics. The tig welding process is controlled by the input parameters, and optimization of process parameters is, therefore, useful for metallurgical advancements, which improve weld quality and enhance weld life. The work material used for the investigation are SAILMA 450 and EN 14B which find huge application in manufacture of rear axle in high-tech automobile industries. These materials have not been given much attention in the past but find a range of applications and hence need to be investigated.Taguchi’s L25 experimental design is used to investigate the influence of process parameters like peak current (Ip), base current (Ib), pulse frequency (F) and shielding gas flow rate (Q) on properties like yield strength (YS), ultimate tensile strength (UTS), flexural strength (FS) and microhardness (H) of the welded joints. The tensile property testing and characterization of welded sub-surface has been done to improve the weld quality and investigate the effect of welding phenomena on tensile steels. To understand the impact of pulse tig welding process parameters, analysis of variance has been used. Confirmatory tests show an improvement of 0.5457 in the preference values. The recommended settings of process parameters is found to be Ip=220A, Ib =120A, F=5Hz and Q=17l/min. Microstructure analysis of optimal sample shows absence of welding defects and crack formation in the fusion zone. [ABSTRACT FROM AUTHOR]

An engineering method is proposed for determining the amplitudes of vortex-induced vibrations, which accounts for the dependence of the excitation force coefficient, the Strouhal number, and the logarithmic decrement on the vibration amplitude of a structure, as well as the correlation distribution of aerodynamic force pulsations along the length of a structure. This method also includes the Eurocode method as a special case and, in contrast to the known ones, makes it possible to more reliably calculate the amplitudes of vortex-induced vibrations of span structures. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study of the morphology and structure at the weld interface in a brass–Invar bimetal, which belongs to the class of so-called thermostatic bimetals, or thermobimetals. The structure of the brass–Invar weld interface was analyzed using optical microscopy and scanning electron microscopy (SEM), with the use of energy-dispersive X-ray (EDX) spectrometry and back-scattered electron diffraction (BSE) to identify the phases. The distribution of the crystallographic orientation of the grains at the weld interface was obtained using an e-Flash HR electron back-scatter diffraction (EBSD) detector and a forward-scatter detector (FSD). The results of the study indicated that the weld interface had the wavy structure typical of explosive welding. The wave crests and troughs showed the presence of melted zones consisting of a disordered Cu–Zn–Fe–Ni solid solution and undissolved Invar particles. The pattern quality map showed that the structure of brass and Invar after explosive welding consisted of grains that were strongly elongated towards the area of the highest intensive plastic flow. In addition, numerous deformation twins, dislocation accumulations and shear bands were observed. Thus, based on the results of this study, the mechanism of Cu–Zn–Fe–Ni structure formation can be proposed. [ABSTRACT FROM AUTHOR]

Due to the high degree of dissimilarity in physicochemical properties between metal and carbon fiber, it presents a tremendous challenge to join them directly. In this paper, cold rolled steel (SPCC) and carbon fiber reinforced thermoplastic (CFRTP) chopped sheet hybrid joints were produced with the addition of Nylon 6 (PA6) thermoplastic film as an intermediate layer by the ultrasonic plastic welding method. The effect of ultrasonic welding energy and preheating temperature on the hybrid joint microstructure and mechanical behavior was well investigated. The suitable joining parameters could obtain a strong joint by adding the PA6 film as an intermediate layer between the SPCC and bare carbon fibers. Microstructural analysis revealed that the interface joining condition between the PA6 film and the SPCC component is the primary reason for the joint strength. The crevices generated at the interface were eliminated when the preheating temperature arrived at 200 °C, and the joint strength thus significantly increased. The lap shear test results under quasi-static loading showed that the welding energy and preheating temperature synergistically affect the joint performances. At 240 °C, the joint strength value reached the maximum. Through the analysis of the microstructure morphology, mechanical performance, and the failure mechanism of the joint, the optimized joining process window for ultrasonic plastic welding of SPCC-CFRTP by adding an intermediate layer, was obtained. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]