Vertical Ultrasonic Vibration Research Articles

Characterization of PEDOT:PSS Nanofilms Printed via Electrically Assisted Direct Ink Deposition with Ultrasonic Vibrations.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has emerged as a promising conductive polymer for constructing efficient hole-transport layers (HTLs) in perovskite solar cells (PSCs). However, conventional fabrication methods, such as spin coating, spray coating, and slot-die coating, have resulted in PEDOT:PSS nanofilms with limited performance, characterized by a low density and non-uniform nanostructures. We introduce a novel 3D-printing approach called electrically assisted direct ink deposition with ultrasonic vibrations (EF-DID-UV) to overcome these challenges. This innovative printing method combines programmable acoustic field modulation with electrohydrodynamic spraying, providing a powerful tool for controlling the PEDOT:PSS nanofilm's morphology precisely. The experimental findings indicate that when PEDOT:PSS nanofilms are crafted using horizontal ultrasonic vibrations, they demonstrate a uniform dispersion of PEDOT:PSS nanoparticles, setting them apart from instances involving vertical ultrasonic vibrations, both prior to and after the printing process. In particular, when horizontal ultrasonic vibrations are applied at a low amplitude (0.15 A) during printing, these nanofilms showcase exceptional wettability performance, with a contact angle of 16.24°, and impressive electrical conductivity of 2092 Ω/square. Given its ability to yield high-performance PEDOT:PSS nanofilms with precisely controlled nanostructures, this approach holds great promise for a wide range of nanotechnological applications, including the production of solar cells, wearable sensors, and actuators.

The effects of scratching speed in ultrasonic vibration-assisted single diamond scratching process

Ultrasonic vibration-assisted machining has been widely used in manufacturing hard and brittle materials. Previous studies have shown that the vertical ultrasonic vibration in ultrasound-assisted single diamond scratching can affect the scratching forces, surface quality, and material removal mechanism by two mechanisms: changing the contact mode between the single diamond and the workpiece and increasing the speed of the single diamond relative to the workpiece. However, some studies point out that increasing the speed has little effect on the scratching force and material removal mechanism. Therefore, it is necessary to conduct an investigation that takes into account the effects of both scratching velocity and ultrasonic vibration on scratching force, surface quality, and material removal mechanisms. In this study, the single diamond conventional scratching (CS) and ultrasonic vibration-assisted scratching (UAS) experiments have been conducted at different scratching speeds to investigate the material removal mechanism of ultrasonic vibration-assisted machining. The effects of increasing the scratching speed on cutting forces, material removal mechanism, and machined surface quality are investigated. The results show that in both CS and UAS processes with low to medium scratching speeds (less than1000 mm/s), increasing the scratching speed leads to more brittle material removal and lower surface quality. At the same time, the scratching speed has almost no effect on the scratching speed force.

Thermodynamic simulation modeling analysis and experimental research of vertical ultrasonic vibration assisted EDM

Compared with traditional EDM, ultrasonic vibration assisted EDM (UEDM) shows better performance in machining efficiency and surface quality. However, the material removal process of UEDM is complex, and there are many influencing factors. It is difficult to describe the material removal process accurately. In this study, based on the voltage variation during UEDM processing and combined with the heat transfer theory, the material removal model of TC4 titanium alloy under the condition of single pulse vertical UEDM is established. The material removal process of UEDM under different amplitudes is analyzed. The machining efficiency and surface quality of UEDM with different amplitude of ultrasonic vibration under the condition of vertical ultrasonic vibration are verified by UEDM experiments. The best material removal rate (MRR) can be obtained by adjusting the current and ultrasonic amplitude, which can improve the efficiency of UEDM.

Surface Integrity of Ultrasonically-Assisted Milled Ti6Al4V Alloy Manufactured by Selective Laser Melting

The Ti6Al4V parts produced by the existing selective laser melting (SLM) are mainly confronted with poor surface finish and inevitable interior defects, which substantially deteriorates the mechanical properties and performances of the parts. In this regard, ultrasonically-assisted machining (UAM) technique is commonly introduced to improve the machining quality due to its merits in increasing tool life and reducing cutting force. However, most of the previous studies focus on the performance of UAM with ultrasonic vibrations applied in the tangential and feed directions, whereas few of them on the impact of ultrasonic vibration along the vertical direction. In this study, the effects of feed rate on surface integrity in ultrasonically-assisted vertical milling (UAVM) of the Ti6Al4V alloy manufactured by SLM were systemically investigated compared with the conventional machining (CM) method. The results revealed that the milling forces in UAVM showed a lower amplitude than that in CM due to the intermittent cutting style. The surface roughness values of the parts produced by UAVM were generally greater than that by CM owing to the extra sinusoidal vibration textures induced by the milling cutter. Moreover, the extra vertical ultrasonic vibration in UAVM was beneficial to suppressing machining chatter. As feed rate increased, surface microhardness and thickness of the plastic deformation zone in CM raised due to more intensive plastic deformation, while these two material properties in UAVM were reduced owing to the mitigated impact effect by the high-frequency vibration of the milling cutter. Therefore, the improved surface microhardness and reduced thickness of the subsurface deformation layer in UAVM were ascribed to the vertical high-frequency impact of the milling cutter in UAVM. In general, the results of this study provided an in-depth understanding in UAVM of Ti6Al4V parts manufactured by SLM.

Study on the effective discharge energy mechanism of vertical ultrasonic vibration assisted EDM processing

Compared to traditional EDM processing, UEDM (Ultrasonic Vibration Assisted EDM) have a great improvement in optimizing discharge environment. In this study, ultrasonic vibration is attached to the electrode. According to the relative positional relationship between the movement path of the electrode tip and the discharge gap, four working states of UEDM are defined. The four working states are the path within the discharge gap, the path in contact with the edge of the discharge gap, part of the electrode end path outside the discharge gap, and the path in contact with the workpiece, respectively. States are analyzed from the effective discharge energy and discharge frequency. A mathematical model for effective discharge energy and surface roughness is established for two conventional working states. The correctness of the theoretical research is verified by experiments. As the experiment results shown, the influence of ultrasonic amplitude on the energy of UEDM is primary, while frequency is secondary. A working state with better discharge stability and higher discharge energy when the electrode end path is in contact with the edge of the discharge gap. In the first three conventional machining states, the surface quality of the workpiece increases with the increase of ultrasonic amplitude and frequency. The study can provide scientific guidance for parameter matching of UEDM.

Research on the promotion mechanism of surface burnishing process by two-dimensional ultrasonic vibration

Abstract Tangential ultrasonic vibration and vertical ultrasonic vibration are applied in the surface burnishing process (SBP) to study the improvement mechanism of both on the machining performance. The force in the machining process is collected by a Kistler force sensor. The surface roughness (Sa, Sq, Ssk, and Sku) and cross-section hardness of the machined samples are characterized. A molecular dynamic model is established to discuss the acoustic softening effect. Experimental results show that the vertical ultrasonic can reduce the normal force (Fz) value in the machining process. Meanwhile, the tangential ultrasonic vibration can suppress the volatility of the X-axis direction force (Fx) and Y-axis direction force (Fy) while reducing the tangential force (Ft) value. Compared with SBP treated samples, the two-dimensional ultrasonic vibration-assisted surface burnishing process (2D-USBP) can better improve the surface properties of the sample, such as improving the surface roughness, the surface hardness, and the thickness of the strengthening layer. Molecular dynamic results show the introduction of ultrasonic vibration to change the microstructure in the sample. Under the excitation of ultrasonic vibration, the dislocation density and potential energy are increased, and the plastic deformation force is decreased.

Research on the machining characteristics of vertical ultrasonic vibration assisted WEDM-LS

ABSTRACT In this paper, a novel composite process technology – Low Speed Wire Electrical Discharge Machining (WEDM-LS) with Vertical Ultrasonic Vibration (VUV) assisted is put forward to improve the performance of traditional WEDM-LS. First, a fluid-solid coupling model of interelectrode flow field and workpiece is established. The simulation result reveals that under the assistance of Vertical Ultrasonic Vibration of workpiece, the velocity of deionized water near the wall of discharge craters is much higher than traditional WEDM-LS or WEDM-LS with the assistance of wire ultrasonic vibration (Wire USV). Therefore, Vertical Ultrasonic Vibration is helpful to the removal of residual debris from the craters. Second, the multiphase flow model of debris, deionized water, and bubbles between electrodes was constituted, and it shows that workpiece vibration frequency is positively correlated with the movement intensity of bubbles and debris, which promotes debris removal throughout the whole processing area. Finally, based on the Taguchi method, the experiments of traditional WEDM-LS, Wire USV assisted WEDM-LS and VUV assisted WEDM-LS were conducted. The workpiece was selected as TiNi-01 shape memory alloy (SMA). The experimental results reveal that under the large electrical machining parameters, Vertical Ultrasonic Vibration assisted WEDM-LS can achieve excellent machining efficiency and quality.

The effects of elliptical ultrasonic vibration in surface machining of CFRP composites using rotary ultrasonic machining

Compared with conventional surface grinding (CSG) process, surface machining of carbon fiber-reinforced plastic (CFRP) composites using rotary ultrasonic machining (RUM) with vertical ultrasonic vibration generates smaller cutting forces because of improved machining performance and more damages to the machined CFRP surface due to the intermittent knocking induced by vertical ultrasonic vibration. It is reported that surface quality can be improved when the ultrasonic vibration is parallel to the feeding direction. In addition, elliptical ultrasonic vibration can be formed by the combination of horizontal and vertical ultrasonic vibrations. However, the effects of elliptical ultrasonic vibration in RUM surface machining of CFRPs are still unknown. This paper will study the influences of elliptical ultrasonic vibration on the machining performance and machined surface quality in RUM surface machining of CFRPs. The comparisons of output variables (including cutting forces, surface roughness, and machined surface topography) between RUM surface machining with elliptical ultrasonic vibration and the CSG process as well as RUM surface machining with vertical ultrasonic vibration will be conducted under different levels of input variables (including depth of cut, feedrate, and tool rotation speed). The abrasive-grain trajectory and the tool-workpiece contacting modes in these three machining processes are analyzed. It is found that RUM surface machining with elliptical ultrasonic vibration produced smallest feeding-direction cutting force, smallest vertical-direction cutting force, best morphology of machined surface, and smallest surface roughness among these three kinds of machining processes.

A novel investigation on horizontal and 3D elliptical ultrasonic vibrations in rotary ultrasonic surface machining of carbon fiber reinforced plastic composites

Carbon fiber reinforced plastic (CFRP) composites were attractive in lots of applications, in which surface machining processes were always needed after molding fabrication processes to achieve the final functional surface geometry with desired accuracy. To improve the effectiveness and efficiency, rotary ultrasonic surface machining (RUSM) had been applied in processing CFRP composites. With the assistance of vertical ultrasonic vibration in RUSM, cutting forces were significantly reduced, but the surface roughness was increased. To improve the surface conditions and additionally reduce the cutting force for RUSM, the applied ultrasonic vibration should be aligned with surface generation direction (namely horizontal feeding direction). Up till now, there were no reported investigations on RUSM with horizontal vibration and 3D elliptical ultrasonic vibration, formed from the combination of horizontal and vertical ultrasonic vibrations. In this investigation, the horizontal and 3D elliptical ultrasonic vibrations were applied in RUSM. The comparisons among RUSM with 3D elliptical ultrasonic vibration, RUSM with horizontal ultrasonic vibration, and the surface machining without ultrasonic vibration on machining performance and surface quality were conducted. Experimental results showed that RUSM with horizontal ultrasonic vibration reduced both cutting force and surface roughness. With the application of 3D elliptical ultrasonic vibration, both cutting force and surface roughness can be further decreased. The critical horizontal ultrasonic frequency for the overlapping of abrasive grains’ trajectories was analyzed. The mechanisms of RUSM with both horizontal and 3D elliptical ultrasonic vibrations and the reasons for both cutting force decreasing and surface roughness decreasing were also investigated.

Effects of lateral and vertical ultrasonic vibrations on the microstructure and microhardness of Stellite-6 coating deposited on Inconel 718 superalloy through laser metal deposition

In this research work, Stellite-6 was deposited on an Inconel 718 substrate via laser metal deposition (LMD) process. Lateral and vertical ultrasonic vibrations were applied during the LMD process at 150 W and 250 W to achieve improved properties. The resultant coatings were evaluated by scanning electron microscopy (SEM) equipped with an energy dispersive spectroscopy (EDS) analyzer and optical microscopy. Also, the microhardness values of two samples (without vibration and with vertical vibration) were measured. The results showed that applying ultrasonic vertical vibrations led to significant changes in the microstructure of the coatings and the coating/substrate interface i.e. a better distribution of alloying elements of the coating was achieved, the number of the secondary arms increased, and the porosity percentage decreased significantly. Moreover, the microhardness value in the sample synthesized at 150 W and under vertical vibrations were higher than that in the sample produced without vibrations.

High stress-driven voltages in net-like layer-supported organic–inorganic perovskites

Huge mechano-electrical performance obtained from net-like PVDF composites infiltrated with methylammonium lead iodide under vertical ultrasonic vibration, without additional poling.

A mechanistic model on feeding-directional cutting force in surface grinding of CFRP composites using rotary ultrasonic machining with horizontal ultrasonic vibration

In surface grinding of carbon fiber reinforced plastic (CFRP) composites, cutting force is a key factor that controls surface damage, tool wear, cutting temperature, delamination, etc. Surface grinding of CFRP composites using rotary ultrasonic machining (RUM) with vertical ultrasonic vibration has been proven to be an effective method to reduce cutting force. However, the machined surface quality is lowered due to the knocking effects on the machined surface resulted from up-and-down vertical vibration. It has been proven that to decrease cutting force and simultaneously improve surface quality, ultrasonic vibration aligning with surface generation direction (feeding direction) is needed. However, there are limited investigations on RUM surface grinding of CFRP composites with horizontal ultrasonic vibration, and the mechanistic model on cutting force in such a process is not explored. This paper, for the first time, establishes a mechanistic model on feeding-directional cutting force in RUM surface grinding of CFRP composites with horizontal ultrasonic vibration. This modeling development is based on the assumption of brittle fracture material removal mechanism, which is the dominant removal mechanism in such a process. The predicted trends in this model agree well with those in experimentally measured results. This modeling will provide a guidance for the mechanistic modeling development to predict other output variables through the cutting force in RUM surface grinding of CFRP composites.

Rotary ultrasonic surface machining of CFRP composites: Effects of horizontal ultrasonic vibration

Abstract Carbon fiber reinforced plastic (CFRP) composites are popular in many industries due to their superior properties. However, many problems, including high cutting forces, high tool wear, high surface roughness, etc., are generated in conventional surface grinding (CSG) processes, due to the carbon fibers’ abrasive property as well as the inhomogeneous and anisotropic properties of CFRPs. Rotary ultrasonic surface machining (RUSM) with vertical ultrasonic vibration has been proven to be effective to reduce cutting forces. However, this process produces larger surface roughness than CSG because of vertical ultrasonic vibration. To solve this issue, RUSM with horizontal ultrasonic vibration is developed in this investigation. The comparisons between CSG and RUSM with horizontal ultrasonic vibration are conducted. The kinematic motions of abrasive grains in both processes are discussed and analyzed. Effects of input variables (including tool rotation speed, feedrate, and depth of cut) on output variables (including cutting forces and surface roughness) are also investigated in both CSG and RUSM processes. RUSM with horizontal ultrasonic vibration is proven to be an effective machining method for reducing cutting forces and simultaneously improving machined surface quality.

Effect of ultrasonic vibration-assisted laser surface melting and texturing of Ti-6Al-4V ELI alloy on surface properties

Ultrasonic vibration-assisted laser surface processing that involves application of vertical ultrasonic vibrations to the Ti-6Al-4V alloy substrates while being irradiated with a CO2 laser was performed for the development of laser melted and textured surfaces with potential applications in biomedical implants. The laser processing resulted in very consistent repeating undulating grooved surfaces, and the undulations were significantly more pronounced in the samples processed with higher ultrasonic power outputs. The phase evolution, studied by x-ray diffraction, confirmed that the laser processing triggered transformation of globular α → acicular α and martensitic α' as well as increased amounts of retained β phases, which were also reflected in the microscopic analysis. The surface texture developed by laser processing resulted in increased surface wettability with increasing ultrasonic power output. The textured surfaces exhibited marked decrease in coefficients of friction during sliding wear testing performed under simulated body fluid due to lubricant entrainment within the textured grooves. The texturing also resulted in significant reduction in surface contact area during the wear process, which considerably reduced the overall wear rates due to abrasive wear.

Effects of Flux Activator Addition in Nanofiber/Solder Anisotropic Conductive Films (ACFs) on the Solder Wettability of Flex-on-Flex (FOF) Assembly

The advanced electronic packaging trends are changing to be more light weighted and miniaturized. Demands for flexible packaging are rapidly growing due to the rapid growth of wearable electronic industries, and advanced flexible interconnection methods are required. In order to satisfy these needs, fine pitch flex-on-flex (FOF) assembly has been introduced. FOF assembly can provide smaller package size, lower contact resistance, higher power handling capability, and flexibility. Anisotropic conductive films (ACFs) are interconnection materials, which have been widely used for the FOF assembly due to their simple and low-temperature processes. Previously, nanofiber ACFs were introduced by our research group, which showed remarkable capability of enhancing the conductive ball capture rate and preventing short circuit in the fine pitch assembly by suppressing the movement of conductive particles during the bonding process. Conventionally, an ultrasonic bonding method was used for a solder ACF bonding, because native solder oxide layer around solder balls can be physically broken by applying vertical ultrasonic vibrations, resulting in excellent solder metallurgical joints between electrodes. However, there are potential misalignment and damage issues generated by vertical ultrasonic vibrations. Therefore, the alternative bonding method is needed that can remove solder oxide layer to obtain excellent solder wetting without misalignment and damage issues by the ultrasonic bonding method. In this paper, thermocompression (TC) bonding and nanofiber/solder ACFs with addition of flux activators were used to chemically eliminate solder oxide. For the formation of stable intermetallic compounds, the contents of flux activators in nanofiber/solder ACFs were optimized. To investigate the flux effect during the TC bonding process, cross-sectional transmission electron microscopy was performed to analyze whether solder oxide layer is certainly removed by the flux. With the TC bonding and nanofiber/solder ACFs with addition of flux activators, stable solder wetting and excellent alignment were demonstrated for the fine pitch FOF assembly.

Understanding Spray Coating Process: Visual Observation of Impingement of Multiple Droplets on a Substrate

Spray coating is a facile deposition process with numerous existing and emerging applications. However, spray coating is a stochastic process comprising impingement of many droplets which upon impact on a heated substrate may dry or solidify individually or coalesce first to form a thin liquid film and then dry to yield a thin solid film. There is very limited knowledge on how this process occurs; therefore in this work, high speed imaging is used to visualize the spray coating process. Two model solutions including food-dye with properties like those of water, and poly (3, 4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS), a polymeric solution, are sprayed onto permeable glossy paper and regular impermeable glass substrates. Substrates are kept at room temperature and 80 °C elevated temperature. In some cases, a vertical ultrasonic vibration is imposed on the substrate to study its effect on the coating process. It is observed that the spray coating process is highly random and stochastic. A higher substrate temperature results in a better coating process in that a more uniform and defect-free coating forms. Imposed vibration in the case of glossy paper substrates results in better droplet spreading and more uniform coating. The results also show that under the conditions of these experiments, impinged droplets dry individually or as islands of multiple coalesced droplets to form a coating. In other words, at used spray flow rate and spray droplet size, a continuous thin liquid film does not form prior to drying even at room temperature. Further systematic studies and high magnification lenses are required to visualize and understand the details of the process.

Impact dynamics and deposition of pristine and graphene-doped PEDOT:PSS polymeric droplets on stationary and vibrating substrates

In this work, using high speed imaging, the impingement of water as the reference liquid, polymeric PEDOT:PSS and graphene-doped PEDOT:PSS droplets onto bare glass and FTO-coated glass substrates with varying contact angles (surface energy) is studied, in an attempt to understand the process of drop casting, spray coating and inkjet printing frequently used for the fabrication of polymeric thin films in thin film devices. The effect of imposing lateral and vertical ultrasonic vibration on the substrate on impinging droplets and deposition is also studied, and unprecedented results are obtained, and discussed. It is concluded that, when the substrate is fully cleaned and exposed to UV light, droplet contact angle significantly decreases because of an increase in the surface energy, resulting in an effective deposition process and suppression of receding. It is also demonstrated that imposing vertical ultrasonic vibration on the substrate increases spreading of PEDOT:PSS-based droplets. The enhanced spreading asa result of surface treatment and imposed vibration is of great importance for the fabrication of solution-processed thin films by droplet-based coating methods. It is also observed that imposed ultrasonic vibration results in a decrease in the roughness of the resulting thin solid films.

Stability of thin liquid films subjected to ultrasonic vibration and characteristics of the resulting thin solid films

Thin solid films have ubiquitous presence in many existing and emerging technologies. Solution-processed thin solid films may be fabricated by casting a thin liquid film followed by a drying step. It has been shown that by imposing a low-amplitude ultrasonic vibration on the substrate, the physical and structural characteristics of the resulting thin solid films is improved, significantly. Therefore, in this study, to investigate and rationalize the aforementioned findings, the evolution and stability of thin and ultrathin films of Newtonian liquid solutions, subjected to vertical and horizontal ultrasonic vibration is studied, using the long-wave approximation and negligible inertia forces. An explicit criterion is obtained for the film instability. Consistent with established theories, it is found that the vertical vibration tends to destabilize the thin liquid film, although for ultrasonic vibrations with low-amplitude, the term contributing to the perturbation growth rate decays rapidly with time and the film may remain stable. However, the vertical ultrasonic vibration is found as a significant destabilizing force, if the film thickness is near a critical value in which case the destabilizing van der Waals and stabilizing gravity and surface tension forces balance one another. To validate the model, experiments on thin liquid films of dilute polymeric solutions are performed. It is found that while imposing ultrasonic vibration may potentially destabilize and breakup the thin film, imposing a low-power vibration can significantly improve the homogeneity, electrical properties, and uniformity of the film, whereas a large-amplitude vibration may have a detrimental effect, because of excessive mixing and agitation of the liquid film or cracking of the resulting thin solid film.

Finite Element Simulation Analysis of Thin-Wall Parts Ultrasonic Vibration Turning Device

Based on the thin-wall parts easily deformed difficult processing characteristics, design the vertical ultrasonic vibration turning device which is suitable for thin-wall parts precision machining utilizing the superiority of ultrasonic vibration turning processing.This device mainly includes piezoelectric transducer, composite horn, tool, tools folder body and the installation device part, carry on the finite element simulation for transducer, solid horn and the entire device system and compare with the resonance frequency of practical requirements, thus proving the reliability of the thin-wall parts ultrasonic vibration turning device we designed.

Effect of vibration on surface and tool wear in ultrasonic vibration-assisted scratching of brittle materials

The purpose of this paper is to investigate the effects of vibration on the surface and tool wear in scratching of brittle materials. In the past, research methodology of vibration cutting has mainly involved vibrating tool parallel to cutting direction. In this paper, a new approach is proposed by an elliptic ultrasonic vibrating workpiece. It presents the fundamental principles and mechanism of ultrasonic machining together with experimental results of scratching of polysilicon with parallel and vertical ultrasonic vibration assistance. With the elliptic ultrasonic vibration assistance, the brittle material would be more likely to be ductilely removed than in conventional condition, and tool wear could be decreased in scratching of brittle materials.