Ultrasonic Welding of Glass Fiber Reinforced Polypropylene

Shear strength and meltdown behavior of reinforced polypropylene assemblies made by resistance welding

Ultrasonic welding is one of the most popular techniques for joining thermoplastics because it is fast, economical, and easily automated. In near‐field ultrasonic welding, the distance between the horn and the joint interface is 6 mm or less. This study investigated the near‐field ultrasonic welding of amorphous (acrylonitrile‐butadiene‐styrene and polystyrene) and semicrystalline (polyethylene and polypropylene) polymers. High frequency ultrasonic wave propagation and attenuation measurements were made in order to estimate the dynamic mechanical moduli of the polymers. The estimated moduli were entered into a lumped parameter model in order to predict heating rates and energy dissipation. Experimental results showed that variations in the welding pressure had little effect on energy dissipation or joint strength; Increasing the amplitude of vibration increased the energy dissipation and the weld strength. For the semicrystalline polymers, increasing the weld time improved strength up to weld times greater than 1.5 s, where strength leveled off. For the amorphous polymers, the weld strength increased with Increasing weld time up to times of 0.8 s; for longer weld times, the power required was too high, causing overloading of the welder. Monitoring of the energy dissipation and static displacement or collapse provided valuable information on weld quality.

In this paper, the dissimilar joining of Poly Lactic Acid (PLA) with Cork Wood (CW) particles reinforced Poly Lactic Acid (CW/PLA) was made by using an Ultrasonic Welding (UW) process. The single lap joint was made to analyse the better joining with good adhesion between the neat polymer and Cork PLA polymer composite. The objective of this study is to formulate a good bonding of neat biodegradable polymeric material with Cork wood particles reinforced composite with concern to the UW factors like Ultrasonic Amplitude (UA), Welding Pressure (WP), and Welding Time (WT). The experimental trial was carried out by altering the levels of UW factors such as UA (25, 28 and 31 µm), WP (0.10, 0.15 and 0.20 MPa), and WT (1, 1.3 and 1.5 sec) with respect to attainment the higher lap shear strength. The statistical optimization methods, including Taguchi and Analysis of Variance, are employed to identify the optimum factors for the welding process and evaluate the proportional impact of the UW factors. The results revealed that the UA of 28 µm, WP of 0.15 MPa, and WT of 1.5 sec exhibits the higher lap shear strength of 24.16 MPa. For the optimized condition, the interface hardness was measured using the Shore D hardness method. The results imply that the maximum interface hardness of 75 was observed at the weld centre. Fractured samples clearly show that interfacial failure is absent, this dictates the weld regions are strong enough to hold the applied load. The developed regression model for the present UW process on the PLA and Cork wood PLA composite is significant and has an R2 value of 92.8%. So, the developed model is suitable for converting into large-scale industrial production and applications.

Ultrasonic welding is a welding method that has been applied for welding nonwoven fabrics, with many advantages such as fast speed, high reliability, easy automation and especially less pollution to the environment. This paper studies the optimization of technological parameters in the welding process such as welding time, pressure, and weld shape on the breaking strength of ultrasonic welding of Polypropylene (PP) nonwovens. To evaluate the influence level and find the reasonable technological parameters domain in the paper, the Taguchi method is used in combination with the face-centered central composite design (FCCCD) response surface method. The research results have determined the regression equations used to calculate the breaking strength for each weld shape as well as the optimal domain for the main technological parameters, ensuring the breaking strength of the weld. There are different degrees of influence of technological parameters (shape of the weld zone, welding time and welding pressure) on the breaking strength of ultrasonic welds. Among them, the influence level of welding time t is 45.31 %, the weld shape is Pattern 2 with the rate of 30.03 %, and the welding pressure is 24.66 %. Carrying out a verification test with the welding parameters: t=1.6 s, p=3.1 kgf/cm2, two patterns ( Pattern 2 and Pattern 3), the result of breaking strength for patterns was achieved. Pattern 2 has a difference of 1.19 % between the regression equation results and the actual experimental results, while the figure for Pattern 3 is 0.77 %. From these results, it is possible to select the appropriate technological parameters for ultrasonic welding equipment when processing products from nonwoven fabrics to ensure the highest quality and productivity

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

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

Ultrasonic metal spot welding (USMW) is a well-known solid-state joining process for bonding non-ferrous metals without using any filler materials. The joining of dissimilar materials such as aluminum, nickel, copper, magnesium is difficult by fusion welding processes due to its higher thermal, chemical, and physical properties. However, USMW yields better quality of joints under the influence of optimal parametric conditions. The flexibility of using this method is still restricted because of insufficient scientific understanding and unwanted intermetallic compound formation in the weld interface. The current study is focused on the weld strength and failure behavior of ultrasonic spot-welded aluminum (AA1100) and pure nickel joints at different weld parametric conditions, i.e., weld time, weld pressure, and vibration amplitude. From the mechanical analysis, the tensile shear failure load of the welded specimen is highest at the maximum vibration amplitude with a balanced amount of weld pressure and weld time. It is also noticed that these joint strengths decreased with the further increase of weld time or weld pressure because of excessive interface temperature rise. It results in the softening of base material and more amount of interfacial diffusion occurred in the weld region. The microstructural morphologies at the weld region disclose various types of weld characteristics such as mechanical interlocking zone, wavy pattern region, and swirling like diffusion area at the weld interface.

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.

Ultrasonic welding is becoming an essential technique for joining of thin and dissimilar materials in battery electric vehicle manufacturing because of consumption of less power, unmatched weld quality, high production rate, excellent efficiency, etc. The process control parameters in welding play a vital role in getting a good quality weld. In this study, AA1100 aluminum and UNS C10100 copper are utilized for experimentation by controlling three input parameters such as weld pressure, weld time, and vibration amplitude. The effects of these control parameters on the responses like tensile shear and T-peel failure loads of joints with microstructures are revealed. Furthermore, a three-dimensional thermo-mechanical finite element (FE) model with the relevant welding mechanics is proposed for this dissimilar material combination to predict the temperature distribution in its interface, sonotrode, and anvil. The simulation results are validated by comparing the experimental temperature values, and they are showing good agreement with each other. It provides a significant insight of thermal softening phenomenon in ultrasonic welding process and demonstrates the relationship between physical attributes and the interface temperature.

ABSTRACTUltrasonic spot welding (USW) is a solid-state joining process which is preferably adopted in the joining of lithium-ion battery tabs for hybrid electric vehicles. It has several benefits over traditional fusion welding techniques like shorter weld time, no formation of the heat-affected zone (HAZ), less energy consumption and lower operating cost. The present research work explores the effect of various welding factors like weld time, weld pressure and vibration amplitude on the tensile shear strength for joining aluminum (AA1060) with cupronickel (UNS C71500) sheets. The results indicated that tensile shear load raised with grow in weld time and achieved the peak value of 809 N. The various types of weld qualities were also identified such as ‘under weld’, ‘good weld’ and ‘over weld’ based upon the nature of bond formation at several weld parametric conditions. The detailed microstructural investigation on the welding region revealed the bonding mechanism with the mechanical interlocking feature and the correlation between the weld strength and the bond density was also established.

Welding via bond exchange reactions has provided advances in obtaining high-quality joining performance. However, the reported welding method requires a relatively high press force, and challenges are still encountered in welding hard vitrimer. In this work, a facile surface depolymerization strategy was introduced to weld high-performance epoxy vitrimer. The vitrimers were firstly dissolved into ethylene glycol for depolymerization based on the solvent-assisted bond exchange reactions. Then, the depolymerized vitrimers were welded under heat and press force. The effect of the depolymerizing time, welding pressure, welding temperature and welding time on the welding strength were further investigated. It was found that there were optimal values for the depolymerizing time, welding pressure, and welding temperature, respectively, for the welding strength, while the welding strength increased with increasing welding time. Through facile surface degradation, the welding pressure was highly reduced, while the welding strength was increased. With surface depolymerization, the welding strength was 1.55-times higher, but the magnitude of press force was 1/1000-times than that with no surface depolymerization. It is elucidative that surface depolymerization can be used to weld hard vitrimer composites alongside reducing the press force effectively.

Sn-3.0Ag-0.5Cu lead-free solder, PCB copper clad laminate and copper thin film substrate were used as experimental materials and the Cu/SAC305/Cu interconnection plate-level structure micro-solder joint was prepared by pulsed hot-pressing welding test. The author aimed at investigating the pulse welding time, pulse welding temperature and welding pressure which influence on the microstructure of solder joint and the pattern of the interface and obtained the optimum range of welding parameter, as well as analyzed the difference of the microstructure and interface pattern between the two methods of pulse hot-pressing welding and reflow welding under the same welding temperature. The results show: When the welding temperature and welding pressure were the same and the thickness of Cu/SAC305/Cu solder joint IMC layer increased with the welding time, the size of the primary crystal phase of the β-Sn in the brazing filler metal increased with the extension of the welding time at the same time. When the welding time and welding pressure were the same, the thickness of Cu/SAC305/Cu solder joint IMC layer increased with the welding temperature increased. When the welding temperature and welding time were the same, the pressure was not applied and pulse heat welding could not form effective solder joint. When the pressure was 20N ∼40N, the solder joint IMC layer was continuous and almost uniform. When the pressure reached 60N, the pattern of IMC solder joint distribution was not smooth. Under the condition of same temperature, the thickness of the solder joint IMC of the pulsed hot-pressing welding was thinner than that of the reflow soldering point. At a temperature of 260 °C, the thickness of the solder joint IMC of pulse hot-pressing welding was only 40% of the reflow soldering joint and at the same time reflow soldering reaction could not occur wetting reaction to form effective solder joints at 240°C, but pulse hot-pressing welding could form valid solder joint.

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.

An energy director is widely used in ultrasonic welding to increase the welding speed and quality. In the present work, three different types of energy directors were studied—namely, a triangular, a rectangular, and an innovative semicircular energy director. Experiments were performed using far‐field test samples made of amorphous‐type (ABS) and semicrystalline‐type (PE) thermoplastics. It was found that the weld time is an important parameter of ultrasonic welding for the three types of energy directors studied. Weld pressure has different effects for the types of plastics tested. Increasing the weld pressure will decrease the welding efficiency for ABS. But for PE, increasing the weld pressure to four bars will increase the welding efficiency. The shape of the energy director was found to significantly affect the welding efficiency. In comparison, a semicircular shape was found to yield the highest welding efficiency under the same welding conditions and the triangular shape the lowest. Temperature measurements at the triangular energy director during the welding process indicate that the energy director absorbed 48.5% of the welding energy for ABS and 21.1% for PE. The different energy absorption rates are probably due to the difference in elasticity and viscosity between amorphous (ABS) and semicrystalline (PE) plastics.

Diffusion welding of copper to aluminum has been carried out in vacuum. The microstructure of the bonding zone was examined in detail with several metallographic methods to make clear the important factors which affect the mechanical properties of the joint. Results obtained are summarized as follows:1) An intermetallic compound layer was observed which could be devided into characteristic region I, II, and III. The intermetallic compounds of θ and γ2 formed in I and III region, respectively. The hardness of II region is the highest of the regions.2) The growth of the intermetallic compound layer is considered to be controlled by the atomic diffusion and the increase in the intimate contact area between the faying surfaces. The diffusion process became more important with the increase in welding temperature and time.3) At shorter welding time, the tensile strength of joints increased with the rise of welding temperature, time, and pressure. This stage is considered to be a process where the intimate contact between the faying surfaces was developed.4) At longer welding time, the tensile strength of joints approached to a saturated value (2.3 kg/mm2) much lower than that of aluminum base metal. This tendency was observed for the thickness of the intermetallic compound layer greater than 15-20μm. In this case, fracture was developed in the intermetallic compound layer, but not at the welding interface. The strength of these joints is considered to be controlled by the intermetallic compound layer.5) Oxide film of aluminum delayed the real metallic contact between the faying surfaces at shorter welding time.