Action Of Ultrasonic Vibration Research Articles

Максвеллівська релаксація і внутрішнє тертя в системі полівінілбутираль-полівінілхлорид

The Maxwellian relaxation and internal friction of a mixture of amorphous polymers: polyvinyl butyral (PVB) - polyvinyl chloride (PVC) are studied. It has been found that by changing the temperature (T) and content (j ) of the ingredients, it is possible to control the value of viscoelastic moduli, viscosity, damping force, and energy dissipation due to Maxwellian relaxation caused by the action of ultrasonic vibrations with a frequency (w ) of 0.4 MHz on the composite. The use of computational methods, models, and a phenomenological approach made it possible to differentiate the effects of relaxation and indicate the ways to optimally combine the desired properties of the components in the system.

Strong alternating piezoelectric field enhanced the piezocatalytic degradation of carbamazepine by a 3-chromophore material Cd4BiO(BO3)3 coupled ultrasound in water

How to efficiently treat a type of new emerging organic pollutant, carbamazepine (CBZ), with the features of environmental persistence, toxicity, and bioaccumulation, is now posing a challenge to scientists. Piezocatalysis, through the harvesting of mechanical energy, has a high capacity to degrade organic pollutants and is gaining increasing attention. Herein, a novel piezo material Cd4BiO(BO3)3 (CBB) with a 3-chromophore asymmetric structure showing an excellent CBZ degradation activity has been synthesized. The removal efficiency can reach 96.2% in 60 min, which is 4.13 times that of tetragonal phase BaTiO3 (BTO) under the same conditions. The superior catalytic performance can be attributed to the easily polarized 3-chromophore asymmetric structure units of CBB, d10 Cd2+ ion, stereochemically active lone pair of Bi3+, and π-delocalization of BO3, which can generate a very strong internal alternating piezoelectric field under the action of ultrasonic vibration. Driven by this internal electric field force, the excited free charges can be easily separated and transferred to the surface of the material to take part in the redox reactions. Besides, CBB also exhibits high stability and excellent removal efficiency for rhodamine B (Rh B) and tetracycline (TC). Hydroxylation and aldehyde oxidation are the main processes of CBZ degradation. The eco-toxicity of CBZ and its intermediates was evaluated using T.E.S.T. software. This study shows that the easily strongly polarized borate material has a potential application in the piezocatalytic degradation of organic pollutants.

High-performance piezocatalytic hydrogen evolution by (Bi0.5Na0.5)TiO3 cubes decorated with cocatalysts

Piezocatalysis has great potential in the field of new energy. Developing robust piezocatalyst with high hydrogen evolution reaction (HER) performance is of great significance but still challenging. Here, the hydrothermal-synthesized (Bi0.5Na0.5)TiO3 (BNT) cubes are demonstrated to the excellent piezocatalytic HER performance. Based on the strong piezoelectric property, the BNT cubes allow an efficient water splitting by the action of ultrasonic vibration, with a H2 yield of 0.38 mmol g−1 h−1 and a H2O2 yield of 0.25 mmol g−1 h−1. To further improve the piezoelectric HER efficiency, Ag and CoOx nanoparticles are employed as the cocatalysts through photochemical decoration. Consequently, the HER performance of BNT cubes is significantly enhanced. These cocatalysts provide the unique channels for charge transfer, thus increase the charge separation efficiency, thereby enhancing the piezocatalytic HER performance. This work not only demonstrates the eco-friendly BNT is a promising and superior piezocatalyst for new-energy applications, but also provides a rational strategy to enhance the piezocatalytic performance.

Influence of pre-heating temperature and ultrasonic vibration treatment on the structure and martensitic transformations in NiTi foams produced by SHS

The structure and martensitic transformations in NiTi foams produced by self-propagating high-temperature synthesis under the action of ultrasonic vibrations (USV) at different pre-heating temperatures of the powder mixture are studied. It has been found that with an increase in the pre-heating temperature, the porous structure changes from layered to isotropic one in the NiTi foams, but cavities appear. The USV treatment reduces the number of cavities and increases the maximum pre-heating temperature at which they are not formed. It has been found that the USV treatment reduces the size and volume fraction of precipitates and makes the chemical composition of the NiTi phase more uniform that affects the martensitic transformation. It has been assumed that an increase in the pre-heating temperature compensates the heat transferred from the powder mixture outside the thermal chamber by the titanium waveguide, which increases the length of the reacted zone. This allowed USV to influence the structure formation in the NiTi foams in the same way as it was observed during conventional crystallization of Ti or Al-based alloys.

Microstructure and properties of NiCrBSi coating formed by ultrasonic vibration combined with induction cladding

A new method of ultrasonic vibration combined with induction cladding was used to prepare nickel-based alloy coating on 45 steel to improve the properties of NiCrBSi coating by induction cladding. The temperature field distribution was simulated and analyzed by finite element method, and the optimum process parameters were determined. The transmission mechanism of ultrasonic wave in traditional non-contact ultrasonic vibration composite cladding was revealed. The effects of non-contact and contact ultrasonic vibration on the grain size, element distribution, porosity, and microhardness of the coating were studied. The cross-section of the coating was analyzed by using a scanning electron microscope, energy dispersive spectrometer, and microhardness tester. The results show that the properties of the coating prepared by non-contact ultrasonic vibration combined with induction cladding were not improved because most of the ultrasonic energy was emitted. In contact ultrasonic vibration combined induction cladding, dendrite structure was destroyed, and the coating grains were refined under the action of ultrasonic vibration. The porosity also decreased evidently under the action of ultrasonic cavitation effect. The microhardness of the coating top area been significantly improved in the microhardness test.

ПІДВИЩЕННЯ АДГЕЗІЙНОЇ МІЦНОСТІ ПОКРИТТІВ ПРИ УЛЬТРАЗВУКОВОМУ ШЛІФУВАННІ

Gas-thermal spraying of self-fluxing, ceramic and other powder materials is one of the effective methods of restoring and strengthening machine parts. The paper describes the gas-thermal spraying methods. The reason for the appearance of macrodefects during mechanical processing in the form of microcracks and burns, and during the operation of parts -in the form of delamination of coatings, is the instability of the structure and physical and mechanical properties of coatings, as well as insufficient adhesive strength and significant residual stresses. In turn, the adhesion strength of coatings depends on the level of surface activation of the base material. The analysis of methods of activation of the surface of the part was performed. Different methods are used: shot blasting or sandblasting, spraying the sublayer, forming a "torn" cut. They all have different performance. The main factors that affect the adhesive and cohesive strength are the incomplete connection of the particles forming the coating, the structure of the coating and the residual internal stresses of the coating. The interaction of adhesion strength and residual internal stresses determines the workability of the coating. As the residual internal stresses increase, the adhesive strength decreases. One of the effective methods of reducing residual internal stresses in coatings is the action of ultrasonic vibrations. The paper presents the results of experimental studies of the influence of the amplitude of ultrasonicvibrations on the adhesionstrength of coatings. Adhesive strength was determined by the method of breaking off a conical pin. The authors gave a formula for calculating the adhesion strength of coatings. The analysis of the results of the experiment showed that the replacement of static grinding with vibration significantly increases (by 15-20%) the adhesive strength. This phenomenon is determined by the action of two factors: a decrease in the level of damage to the coating; reducing the yield point of the coating material. It should be noted that the possibility of such a transition is due to the reduction of the fragility criterion to values less than 1. The paper provides a formula for calculating the value of the fragility criterion of coatings, as well as a formula for calculating the length of a critical microcrack. Knowing the length of the critical microcrack makes it possible to diagnose coatings for their performance.

Cavitation Effect in Ultrasonic-Assisted Electrolytic In-Process Dressing Grinding of Nanocomposite Ceramics.

Ultrasonic-assisted electrolytic in-process dressing (UA-ELID) grinding is a promising technology that uses a metal-bonded diamond grinding wheel to achieve a mirror surface finish on hard and brittle materials. In this paper, the UA-ELID grinding was applied to nanocomposite ceramic for investigating the cavitation effect on the processing performance. Firstly, the ultrasonic cavitation theory was utilized to define the cavitation threshold, collapse of cavitation bubbles, and variation of their radii. Next, the online monitoring system was designed to observe the ultrasonic cavitation under different ultrasonic amplitude for the actual UA-ELID grinding test. A strong effect of ultrasonic cavitation on the grinding wheel surface and the formed oxide film was experimentally proved. Besides, under the action of ultrasonic vibration, the dressing effect of the grinding wheel was improved, and the sharpness of grain increased by 43.2%, and the grain distribution was dramatically changed with the increase of ultrasonic amplitude. Compared with the conventional ELID (C-ELID) grinding, the average protrusion height increased by 14.2%, while the average grain spacing dropped by 21.2%. The UA-ELID grinding reduced the workpiece surface roughness Rz and Ra by 54.2% and 46.5%, respectively, and increased the surface residual compressive stress by 44.5%. The surface morphology observation revealed a change in the material removal mechanism and improvement of the surface quality by ultrasonic cavitation effect. These findings are considered instrumental in theoretical and experimental substantiation of the optimal UA-ELID grinding parameters for the processing of nanocomposite ceramics.

Microstructural Evolutions under Ultrasonic Treatment in 304 and 316 Austenitic Stainless Steels: Impact of Stacking Fault Energy

Herein, the influence of ultrasonic treatment (UST) on the microstructure of AISI‐304 and AISI‐316 stainless steels as two common commercial grades with similar properties but different levels of stacking fault energy (SFE) is compared. The softening effect of the ultrasonic wave on the predeformed structure is demonstrated by microhardness measurements, and the relaxation of tensile residual stresses is affirmed through the X‐ray diffraction (XRD) peak shifting. Electron and optical microscopy reveals a significant impact of ultrasound on the reduction of the deformation twins’ fraction. A new mechanism for detwinning under the action of ultrasonic vibration is proposed using electron backscatter diffraction (EBSD) analysis. Reductions of 25% and 34% are detected in dislocation density of the 10% predeformed tensile sample after 300 W UST for the 304SS and 316SS alloys, respectively. The effect of the SFE is discussed, and it turns out that cross‐slip is the main mechanism of dislocation annihilation as a result of UST. Observation of the low‐deformation regions close to the grain boundaries indicates the occurrence of the recrystallization phenomenon during UST. Dislocation annihilation, detwinning, dislocation absorption to grain boundaries, and recrystallization are regarded as the softening and relaxation mechanisms of UST for austenitic stainless steels.

The use of ultrasound to produce metallic powder in the plasma discharge electrolyte

In this work, a new process of plasma-electrolyte sputtering under the action of ultrasonic vibration is proposed, which makes it possible to obtain a finely dispersed metal powder with an average particle diameter of about 100 μm. The process involves irradiation with a high-power continuous laser on a consumable metal substrate vibrating at an ultrasonic frequency. The burning of a gas discharge around the vibrating electrode causes the surface to melt and small droplets are ejected. Preliminary results of spraying stainless steel 12X18H9T with a discharge power of 800 W and an ultrasonic vibration frequency of 20 kHz are presented. Vibration displacement does not significantly affect average particle size and size distribution according to capillary wave spray theory. The microstructure of the larger atomized particles exhibits a fine dendritic structure on the surface and shrinkage porosity at the center of the particles, indicating multiple surface nucleation for solidification.

Effects of Excessive Zr Content and Ultrasonic Treatment on Microstructure and Mechanical Properties of Al-Zn-Mg-Cu Alloy

The Zr element is one of the important grain refiners for 7xxx series Al-Zn-Mg-Cu alloys, but the effect of Zr content more than 0.15 wt.% needs to be deeply investigated under the action of ultrasonic vibration. In this study, the effects of Zr contents (0.1 to 0.25 wt.%) on microstructure and mechanical properties of Al-Zn-Mg-Cu alloy were studied. The results showed that Zr element could refine grains, but when the Zr content was greater than 0.15 wt.%, the grain size was not uniform, the number of second phase particles increased, and the segregation of components became more serious. It was found that after ultrasonic treatment, the grain-size inhomogeneity was greatly improved, and the Zr content could be added up to 0.2 wt.%. When the Zr content is equal or lower than 0.2 wt.%, ultrasonic treatment can effectively improve the mechanical properties of materials by refining grains and weakening segregation. However, when the Zr content is up to 0.25 wt.%, the effect is getting worse.

Influence of ultrasonic vibration on keyholing/penetrating capability in plasma arc welding with controlled pulse waveform

Ultrasonic vibration-assisted plasma arc welding with controlled pulse current waveform was developed to weld the 8 mm thick stainless steel plates. Both bead-on-plate and butt welding experiments were carried out with open-loop and closed-loop control strategies under different welding conditions. The signals of welding current and efflux plasma voltage and the images of keyhole exit were sensed to monitor the keyhole status during the welding process. It was found that the ultrasonic vibration-assisted plasma arc can completely penetrate the stainless steel plates with the thickness of 8 mm in a single pass with higher welding speed or lower peak welding current in controlled pulse keyhole mode. By continuous real-time adjustment of welding current waveform in closed-loop strategy, the “one-pulse-one-open keyhole” mode was achieved successfully with lower welding heat input. Due to the reduction of heat input and further constriction of plasma arc under the action of ultrasonic vibration, the weld was narrowed and the depth-width ratio was raised.

ПОЛУЧЕНИЕ ГРАФЕНОВЫХ СТРУКТУР И НАНОПОЛИМЕРОВ С ИСПОЛЬЗОВАНИЕМ УЛЬТРАЗВУКОВЫХ КОЛЕБАНИЙ

Graphene-based polymer nanocomposites are considered a promising class of future materials. The degree of filling, the filler and binder nature, and the shape, size, and mutual arrangement of filler particles determine the properties of a polymer composite material. The destruction of nanoparticles aggregates occurs most effectively in liquid media under the action of ultrasonic vibrations. The authors proposed the technique and designed laboratory equipment for ultrasonic treatment of the finely-dispersed graphite suspension, carried out the ultrasonic treatment (UST) of finely-dispersed graphite powder. The suspensions based on graphite with a solvent were obtained. The authors carried out the experiments on producing graphene using the graphite liquid-phase exfoliation method at the ultrasonic treatment with different ultrasonic treatment times, analyzed experimental data, and selected the UST optimal time. The paper contains the results of the study of the effect of the graphite suspension base on the degree of ultrasonic liquid-phase exfoliation of graphite. The most effective synthesis of graphene structures using UST is synthesis from graphite suspensions based on dichloroethane, benzol, and dichlorobenzene. Graphene structures’ output ratio amounts to up to 66 %. The authors developed the technology for producing polymers modified with graphene structures using ultrasonic dispersion. Based on graphene synthesized by the graphite liquid-phase exfoliation, the authors obtained nanopolymers using ultrasonic vibrations, carried out DSC measurements, and studied their strength properties. The limit strength of elastic polymers is from 1.9 to 3.6 MPa at different concentrations of graphene inclusions. The residual elongation of samples within the deviation did not change and amounted to 200 %.

Визначення залишків пестицидів хроматографічними методами для безпечності харчової продукції

The paper presents the methodology of preparation of samples of oilseeds, lettuce, apples for research by chromatographic control of xenobiotics of the following chemical groups of pesticides: benzimidazole derivatives, anilinopyrimidine derivatives, bipyridylium derivatives. The implementation of the following processes is considered: homogenization of the sample, purification of the extract by solid-phase or liquid-liquid extraction, obtaining a plant extract, obtaining an extract of analytes. For fine-grained homogenized samples of sunflower seeds, the optimal ratio of raw material -extragent is 1:20, for pasty homogenized samples of apple fruit - 1:10, for liquid samples of homogenized lettuce - 1: 5. Analysis of the distribution of xenobiotics in the system octane/water, the dipole moment of solvents allowed to determine the extractants that are able to dissolve and remove xenobiotics from raw materials. It was found that a mixture of acetonitrile and methanol (4: 1) should be used to remove benzimidazole derivatives and anilinopyrimidine derivatives, bipyridylium derivatives are best extracted with methanolic trifluoroacetic acid (9.5: 0.5). Quantitative analysis of xenobiotics content in extracts obtained from samples artificially enriched with xenobiotics was performed. The most complete xenobiotics were removed from samples of plant products containing traces of fat. The most difficult process of sample preparation is the process of obtaining sunflower seed extract. The content of xenobiotics in extracts obtained from samples artificially enriched in analytes is influenced by the temperature at which the process takes place and the duration of extraction. Based on the chemical composition of the sample matrix and the list of analytes, the conditions of the variable component of the methodology are proposed: obtaining plant extract under the action of selective solvents, homogenized raw material-solvent with constant stirring of the extraction system at 180-200 rpm, or under the action of ultrasonic vibrations with a frequency of 37 kHz from 4°C to 25°C for 5-25 minutes. The control of the qualitative and quantitative composition of the studied plant extracts and analyte extracts was investigated by the methods of high-performance liquid and gas chromatography (liquid and gas) with mass-selective detectors.

Raising the Efficiency of Coagulation of Dispersed Particles by the Action of Ultrasonic Vibrations on Gas-Dispersed Flows in Inertial Dust Collectors

The authors have presented results of experiential investigations of the process of ultrasonic coagulation of dispersed particle in a swirling flow. The investigations were conducted using the proposed and developed test bed implementing a two-stage removal of fi ne particles. At the first stage (agglomeration), the formation of a swirling flow and the ultrasonic pre-coagulation of fi ne particles are ensured. At the second stage, high-efficiency trapping of particles preformed at the first stage is attained using a cyclone. As a result of the experimental investigations, the authors have established the prospects of using a two-stage removal of fi ne particles and have revealed the optimum conditions of ultrasonic action on a swirling gas-dispersed flow that ensure an enlargement of 4.5 times of particles in the range of RM2.5 particle sizes which is the most hazardous for humans.

Thermo-mechanical coupling effect on surface residual stress during ultrasonic vibration-assisted forming grinding gear

Abstract Gears are important motion and power transmission components and enhancing their machining accuracy and performance. In this work, a novel processing of ultrasonic vibration-assisted forming grinding gear (UVAFGG) is proposed, which involves the superimposition of ultrasonic vibration on the gear, and the thermo-mechanical coupling effect on surface residual stress is explored as well. Firstly, based on the local contact geometry relationship for forming grinding, the three-dimensional (3D) distribution model of the heat flux density along the tooth profile is established. In addition, the mathematical relationship models between the grinding force, grinding heat, residual stress, and grinding parameters are also given. Then, the effect of grinding parameters such as spindle speed and ultrasonic amplitude for the characteristics of residual compressive stress accumulation is obtained by comparing the single factor experimental and finite element simulation results. It is found that under the action of ultrasonic vibration, the grinding heat and grinding force reduce by 38.7% and 40.5 % and 40.5 %, respectively. The surface residual compressive stress gradually decreases with the increase in spindle speed, while with the increase in ultrasonic amplitude, it increases first and then decrease. Comparing with the conventional grinding gear (CGG), the average rate of increase of the surface residual compressive stress under the both parameters is 17.8 %–31.3 % and 20 % respectively. Meanwhile, the residual compressive stress along involute shows a negative correlation with the increase in the rolling angle. At the same time, the experimental and simulation results agree well with the theoretical model. In conclusion, the results of this study provide a novel process technology for gear machining, and a reference for the investigation on residual stress during UVAFGG.

Spreading and Wetting Behaviors of Sn2.5Ag0.7Cu0.1RE0.05Ni Solder on the Surface of Cu Substrate under Ultrasonic Vibration

The spreading and wetting behaviors of Sn2.5Ag0.7Cu0.1RE0.05Ni lead-free solder on the surface of Cu substrate under ultrasonic vibration were studied by SEM, EDS and other methods. The ultrasonic time was 1, 2, 3, 4, 5 s, respectively and was compared with the spreading of solder in the condition of soldering flux. The results showed that the Sn2.5Ag0.7Cu0.1RE0.05Ni solder was forced to spread instantly on the base metal surface under the action of ultrasonic vibration, and the ultrasonic cavitation can crush the oxide film on the surface of solder and base metal, resulting in the wetting of liquid solder and base metal. When the ultrasonic time was 3 s, the spreading area and spreading ratio of the solder achieved the maximum, and the ultrasonic cavitation could break the β-Sn and eutectic structure of the solder during solidification, refining the microstructure and improving the hardness of the solder matrix.

Microcrack Growth Properties of Granite under Ultrasonic High-Frequency Excitation

The failure of most rock materials is essentially a process of crack initiation and propagation. It is of great significance to study the microcrack growth characteristics of granite under ultrasonic high-frequency excitation for understanding the failure mechanism of rock under ultrasonic vibration. In this paper, the experimental and numerical simulation methods are used to study the propagation characteristics of rock cracks under ultrasonic vibration. Scanning electron microscopy (SEM) was used to observe the growth of microcracks in granite samples after ultrasonic vibration for 0 min, 2 min, and 4 min. A discrete element software PFC2D was used to simulate and solve the cracking mechanism of rock cracks under ultrasonic vibration. Also, it is found that the action of ultrasonic vibration can effectively promote the development of microcracks in the granite samples. The main three cracks causing the failure of quartz under the ultrasonic high frequency are intragranular cracks, transgranular cracks, and grain boundary cracks. The breakage of transgranular cracks usually contributes a shell-like fracture, that is, a regular curved surface with a concentric circular pattern appears on the fracture surface, which is a typical quartz brittle fracture mode. In addition, the feldspar grain failure is mainly caused by intragranular crack and transgranular crack. Microcracks are wavy expansion in feldspar grain. Mica failure is mainly caused by grain boundary crack, and the effect of lamellar cleavage on the failure of mica is significant. Moreover, it is also found that the mechanism of microcrack propagation is tensile failure. The failure of feldspar grains is mainly contributed to the failure of granite.

Effect of Parameters of High-Velocity Collision on the Structure and Properties of Joints upon Explosive Welding with Simultaneous Ultrasonication

This paper presents the comparative results of the study of the influence of the parameters of high-velocity collisions of metals upon explosive welding with the simultaneous action of ultrasonic vibrations on the structure and properties of the welded joints. The effect of the impact velocity on the strength, microhardness, and formation of the structure of explosively welded joints of copper, aluminum, and steel under the influence of ultrasound has been shown.

CFD simulation and experimental studies of suspension flow field in ultrasonic polishing

With the rapid development of science and technology, hard and brittle materials with high performance have been widely used. Meanwhile, it necessitates the development of compatible machining techniques. As the final processing step of precision component, polishing plays a decisive role. Ultrasonic polishing is a powerful method for improving polishing efficiency and surface quality, especially for hard and brittle materials. In this paper, effects of ultrasonic vibration on suspension flow field have been specifically studied in ultrasonic polishing. At micro level, a mathematical model for analyzing the effects of ultrasonic vibration on the velocity and stress of the inner microelement in polishing suspension flow filed was established. CFD simulation was adopted to study the behavior of polishing suspension flow filed under the action of ultrasonic vibration. It was proved that periodic dynamic changes occur and turbulence form in suspension flow field which are positive for polishing, suspension flow field velocity in x direction near workpiece surface could reach a maximum of about 2.3 m/s, while that in z direction is 0.13 m/s. Material removal thus mainly depends on generated transverse shear flow. And a surface rough change rule was summarized. At macro level, monocrystalline silicon polishing experiments have verified the positive role of ultrasonic vibration, within the same polishing time and polishing head rotation velocity, the surface roughness without ultrasonic vibration reduced from 102 nm to 15 nm, while that with ultrasonic vibration reduced from 109 nm to a minimum of 4 nm, only with ultrasonic amplitude of 15 μm, surface roughness reduced from 98 nm to 27 nm, with the rotation of polishing head and ultrasonic amplitude of 9 μm, 15 μm and 21 μm respectively, the surface roughness reduced to 6 μm, 4 μm and 4 μm respectively. The changes of surface roughness in all experiments were consistent with the summarized rule.

Effect of a Nanodisperse Graphite on the Viscoelastic Properties of Polyvinyl Chloride

In the absence of segregation of nanodisperse graphite particles, obtained by electrolysis as a new filler of polyvinyl chloride (PVC), the viscoelastic phenomena dependent on the structural changes of a composite are investigated. The shear modulus and the volume compressibility caused by deviations of elements of the structure from the quasi-equilibrium state under the action of ultrasonic vibrations (ω = 0.4·106 0.4 · 10 s–1) are calculated at filler concentrations 0 ≤ φ ≤ 10.0 vol.% and temperatures 298 K ≤ T ≤ (Tg + 10) K. It is shown that the volume density of internal energy depends on the expectation time for the transition of structural elements through the energy barrier, the dynamic viscosity of the material, and temperature. The results of calculations serve as the basis for producing PVC systems with controllable of properties.