Presence Of Ultrasonic Vibration Research Articles

Revealing nanoscale material deformation mechanism and surface/subsurface characteristics in vibration-assisted nano-grinding of single-crystal iron

Ultrasonic vibration-assisted grinding (UVAG) has attracted extensive attention as it can significantly improve the surface integrity of the machined workpiece. However, the atom-scale material deformation mechanism with the presence of ultrasonic vibration is still unclear, which hider the application of the UVAG to the ultra-precision machining process. To fill this gap, we present a molecular dynamics (MD) model for the vibration-assisted nano-grinding process (VANG) of single-crystal iron. The characteristics of the material deformation process induced by ultrasonic vibration are studied, including material accumulation, temperature, dislocation, subsurface damage (SSD), contact area, and grinding force. The results show that vibration changes the dislocation distribution in the plastic zone, forms the phenomena of expansion and contraction and causes the fluctuation of SSD depth. Due to the different distribution of stress and temperature during VANG, the details of plastic deformation, such as dislocation movement, dislocation nucleation and phase transformation, change with the varying vibration frequency. In addition, the reduction of the projected contact area is the main reason for the reduction of grinding force. However, dislocation pileup in the grinding zone and chips further increase the grinding hardness. This research could enrich the understanding of nano-scale deformation mechanisms in vibration-assisted processing of metallic materials.

Elevation of the Operating Efficiency of Plate-Like Heat Exchangers in the Presence of Ultrasonic Vibration

Elevation of the Operating Efficiency of Plate-Like Heat Exchangers in the Presence of Ultrasonic Vibration

Influence of Ultrasound Vibrations on the Corrosion Resistance of Heat-Exchange Plates Made of AISI 316 Steel

The corrosion resistance of plates 0.4 mm in thickness made of AISI 316 stainless steel is studied under the conditions of ultrasonic vibration with a frequency of 28 kHz and a power of 50 W applied to the end of the sample. The tests are performed by the methods of potentiodynamic and galvanostatic polarization in 10 g/liter and 35 g/liter NaCl solutions at the standard temperature. According to the results of electrochemical studies, in the presence of ultrasonic vibration, the rate of dissolution of steel becomes 30 times lower as compared with the sample not subjected to vibration. These results are confirmed by the analysis of morphology of the specimen surface after testing in a scanning electron microscope. The mechanism of suppression of pitting by ultrasound is proposed. It can be described as the removal of the layer of corrosion products in the stage of formation of metastable pits with their subsequent repassivation. Ultrasound vibration proves to be a promising method for increasing the corrosion resistance of stainless steels. This method can be used to protect the plates of heat exchangers in the heat-and-water supply systems.

Ultrasonic-vibration-assisted laser annealing of fluorine-doped tin oxide thin films for improving optical and electrical properties: Overlapping rate optimization

An ultrasonic-vibration-assisted laser annealing method was developed to enhance the performance of fluorine-doped tin oxide (FTO) thin films. The influences of ultrasonic vibration, laser scan line overlapping rate (LOR) and laser spot overlapping rate (SOR) on surface morphology, FTO layer thickness, RMS roughness, crystal structure and photoelectric properties of the FTO films were investigated. The results indicated that the presence of ultrasonic vibration during laser annealing could significantly enhance the film compactness, and using moderate LOR and SOR values resulted in significantly decreased FTO layer thicknesses and RMS roughnesses as well as slightly increased crystallite sizes, thus yielding significantly improved optical transmittance values and slightly enhanced electrical conductivity values. It was found that the optimal LOR and SOR values for ultrasonic-vibration-assisted laser annealing of the FTO films were 80% and 90%, respectively. The as-obtained film possessed the best overall photoelectric property with an average transmittance (400–800 nm) of 85.9%, a sheet resistance of 8.7 Ω/sq and a figure of merit of 2.51 × 10–2 Ω–1. This work may be of great significance in terms of performance optimization of transparent conducting oxide (TCO) thin films.

Remediation of Sulfidic Wastewater by Aeration in the Presence of Ultrasonic Vibration

Remediation of Sulfidic Wastewater by Aeration in the Presence of Ultrasonic Vibration

Remediation of Sulfidic Wastewater by Aeration in the Presence of Ultrasonic Vibration

In the current study, the aerial oxidation of sodium sulfide in the presence of ultrasonic vibration is investigated. Sulfide analysis was carried out by the methylene blue method. Sodium sulfide is oxidized to elemental sulfur in the presence of ultrasonic vibration. The influence of air flow rate, initial sodium sulfide concentration and ultrasonic vibration intensity on the oxidation of sodium sulfide was investigated. The rate law equation regarding the oxidation of sulfide was determined from the experimental data. The order of reaction with respect to sulfide and oxygen was found to be 0.36 and 0.67 respectively. The overall reaction followed nearly first order kinetics.

Mitigation of hot cracking in Inconel 718 superalloy by ultrasonic vibration during gas tungsten arc welding

In the present study, Gas Tungsten Arc Welding (GTAW) of Inconel 718 alloy has been carried out at different welding currents with and without ultrasonic vibration. In the absence of ultrasonic treatment, samples welded with a current of 80 A have shown a crack length of 15 mm which is found to increase to 35 mm for a welding current of 120 A. The slow solidification rate associated with high welding current causes increase in hot cracking length. Non-equilibrium Scheil solidification simulation of Inconel 718 based on CALPHAD approach suggests that the long freezing range of more than 175 °C, small fraction of eutectic, i.e., less than 10% in susceptible freezing range (SFR) and segregation of low melting point Laves and γ′′ (Ni3Nb) phases play critical roles in hot cracking behavior of Inconel 718 alloy. Ultrasonic treatment during solidification of weld metal has decreased the crack sensitivity and dendritic arm length of Inconel 718 alloy from 47.5% to 13.3% for the welding current of 120 A. There was a corresponding reduction in dendritic arm length from 1256 to 89 μm. Further, it was observed that the welding current has very limited role in the hot cracking behavior of Inconel 718 alloy in the presence of ultrasonic vibration. Dendritic fragmentation, grain refinement and reduction in solute segregation are recognized as the main factors that mitigate hot cracking tendency of Inconel 718 alloy by ultrasonic vibration.

Analytical and experimental approaches to study elastic deflection of thin strip in ultrasonic-assisted drilling process

During machining of thin material, workpiece endures deflection due to cutting forces that negatively influence dimensional tolerances and machined surface quality. An applicable method for the restriction of such problems is machining in the presence of ultrasonic vibration. However, understanding of how this improvement is caused by this type of vibration needs extensive studies. This paper presents a workpiece deflection model for conventional drilling and ultrasonic-assisted drilling of 1 mm thickness aluminum 7075. The workpiece considered was a thin beam and the deflection was determined by the use of beam vibration theory in continuous system. The deflection of workpiece during both the conventional and ultrasonic-assisted drilling processes were determined by means of developed model and compared with those derived from experiments. It was found that the average prediction error in worst case was less than 20%. Also, it is observed from both the experimental and theoretical approaches that applying ultrasonic vibration to drilling tool significantly reduces the workpiece deflection. Furthermore, from both approaches, it is identified that increase in vibration amplitude causes a decrease in beam deflection. Restriction of beam deflection by exerting high-amplitude ultrasonic vibration causes elimination of cap burr in the exit hole due to enhancement in the rigidity of workpiece.

Effects of high power ultrasonic vibration on temperature distribution of workpiece in dry creep feed up grinding

Temperature history and distribution of steel workpiece (X20Cr13) was measured by a high tech infrared camera under ultrasonic assisted dry creep feed up grinding. For this purpose, a special experimental setup was designed and fabricated to vibrate only workpiece along two directions by a high power ultrasonic transducer. In this study, ultrasonic effects with respect to grinding parameters including depth of cut (ae), feed speed (vw), and cutting speed (vs) has been investigated. The results indicate that the ultrasonic vibration has considerable effect on reduction of temperature, depth of thermal damage of workpiece and width of temperature contours. Maximum temperature reduction of 25.91% was reported at condition of vs=15m/s, vw=500mm/min, ae=0.4mm in the presence of ultrasonic vibration.

Fundamental Machining Characteristics of the In-base-plane Ultrasonic Elliptical Vibration Assisted Turning of Inconel 718

Inconel 718 has been widely used in aerospace, petroleum and nuclear industry because of its excellent mechanical properties such as high fatigue strength, good corrosion resistance and strong creep resistance. However, these properties in turn are leading to high cutting force and heavy tool damage in the turning process. Against these problems, the ultrasonic assisted machining was a potential technique since the presence of ultrasonic vibration could decrease the cutting force and cutting temperature, and therefore reduce the tool damage. Nevertheless, in conventional ultrasonic assisted turning, the ultrasonic vibration was superimposed in a single direction along the cutting speed which resulted in the existence of a critical cutting speed and thus limited to the material removal rate. Therefore, this study proposed a novel ultrasonic assisted tuning method in which an ultrasonic elliptical vibration was superimposed to the tool in the base plane. In order to validate the proposed method, experiments were carried out on a CNC lathe attached with an ultrasonic cutting unit involving a rod-shaped Inconel 718 specimen. In addition, a dynamometer was positioned under the cutting unit for measuring cutting forces. A coated carbide insert was installed at the tip of the cutting unit as the cutting tool. The experimental results showed that the cutting force and cutting temperature with ultrasonic vibration were smaller than those without ultrasonic vibration. Particularly, even the cutting speed was beyond the maximum vibration velocity, the cutting force and cutting temperature with vibration were still much lower than those without vibration. In other words, the application of ultrasonic elliptical vibration in the base plane still benefited to the turning of Inconel 718 even when the cutting speed exceeded the max ultrasonic vibration speed.

Deformation analysis of brass in micro compression test with presence of ultrasonic vibration

The application of ultrasonic vibration in metal forming is attracting more attention due to the better performance of ultrasonicassisted process. By adding small vibration amplitude on tools, the plastic deformation behavior of metal material would differ from the static process. In this study, ultrasonic-assisted compression test was carried out to investigate the influences induced by ultrasonic systematically. Ultrasonic influences on material flow stress, friction and temperature were analyzed. Acoustic softening effect was found size dependent and a new model on basis of surface grain model was proposed to explain it. Numerical simulations were carried out to validate and compare with experimental results.

Influence of Ultrasonic Vibration on Metal Foils Surface Finishing with Micro-forging

Traditional processes used for surface finishing such as polishing, grinding, finishing or laser irradiation could produce quite smooth surface. However, it is not convenient to apply these processes in micro manufacture due to the small size of product. In this study, micro forming process with presence of ultrasonic vibration was introduced for metal foils surface finishing. Influences of ultrasonic vibration on surface roughness were obtained at different conditions and a surface grain model was employed to clarify mechanism of improvement by ultrasonic. Results showed that surface roughness reduction is linear to ultrasonic vibration amplitude and static stress. The large surface roughness reduction was believed to have close relation with surface / total grain ratio, which is a function of dimension.

Ultrasonic Nanofabrication with an AFM

Ultrasonic AFM may improve fabrication technologies on the nanometer scale. In the presence of ultrasonic vibration, hard surfaces can be indented and scratched with the tip of a soft cantilever, due to its inertia. Ultrasound reduces or even eliminates friction, and hence modifies the tip-nanoparticle-surface interactions in AFM manipulation. The subsurface sensitivity of the technique makes feasible the purposed manipulation of subsurface nanoscale features by ultrasonic actuation.

Evaluation of the secondary consolidation of columns for liquid chromatography by ultrasonic irradiation

The consolidation of packed analytical chromatography columns was carried out under ultrasonic irradiation. Columns were first packed using a conventional high pressure downward slurry method. Then, they were subjected to further bed consolidation in the presence of ultrasonic vibration. This process of further bed consolidation is referred to as secondary consolidation. Secondary consolidation was observed to occur more readily in solvents of low viscosity and at low flow-rates (low pressures). Column efficiency was not observed to be a factor affecting the process of secondary consolidation of the packed bed.

Electroinitiated polymerization of butadiene sulfone

AbstractElectroinitiated polymerization of butadiene sulfone was achieved by direct electron transfer in acetonitrile—tetrabutylammonium fluoroborate system by controlled potential electrolysis technique. High conversions were obtained at reasonable temperatures and polymerization times. The polymer was found to be composed of linear segments along with some cyclic units. The effect of monomer concentration, temperature, and polymerization potential on the rate of polymerization was investigated. Temperature and polymerization potential have positive effects on the rate of polymerization. The effect of ultrasonic vibration was also investigated by conducting electrolyses at different monomer concentrations in the presence and absence of ultrasonic vibration. It was observed that the rate of polymerization increases significantly in the presence of ultrasonic vibration. The inverse relationship between the rate of polymerization and monomer concentration was observed in presence and absence of ultrasonic vibration.

Effect of ultrasonic vibration on the turning process

A magnetostrictive transducer is used to vibrate a carbide-tipped cutting tool while turning is taking place. The tool can be vibrated either in the horizontal direction (parallel to the workpiece axis) or in the vertical direction (tangential to the workpiece surface). Two components of the cutting force can be measured using strain gauges mounted on the transducer stub. Cutting force components are found to be less than with a static tool, particularly at low cutting speeds, a phenomenon which has been observed by other workers. It has been suggested that such reductions may be due to a reduction in the mechanical strength of the workpiece material in the presence of ultrasonic vibration. In an attempt to observe such a reduction, tensile and torsion tests to fracture are performed on a specimen of the workpiece material while it is being subjected to ultrasonic vibration. No reduction of mechanical strength under these conditions is observed and it is concluded that the effect is a purely frictional one. The effect of the vibration on surface finish when turning is also studied.