Ultrasonic Vibration Frequency Research Articles

Influence of optimal conditions of ultrasonic dispersion on the stability of suspensions of finely ground slags

The preparation in the jet mill of finely ground slag (FGS) from the waste of metallurgical production granulated blast-furnace slag, the obtaining of slag suspensions, and the behavior of FGS particles in an aqueous dispersion medium are considered in the paper. It was found that FGS particles in the suspension form micelles of two types with negative (micelle 1) and positive (micelle 2) charges of FGS surface. To increase the aggregative and sedimentation stability of FGS particles in suspensions, studies were carried out using ultrasonic dispersion. The results of investigations on the detection of optimal dispersion parameters for slag suspensions are presented. It was found that in the absence of temperature control, the process of coagulation of slag particles is accelerated and aggregative and sedimentation stability of suspensions of FGS is reduced. The slag particles in the suspension form aggregates that lead to a deterioration of the strength characteristics of the cement stone using suspensions of FGS. Optimal parameters of ultrasonic dispersion of slag suspensions are established: the frequency of ultrasonic vibrations is equal to 44 kHz; the dispersion temperature is 25 ± 2 °C; the dispersion time is 15 min. It was found that the application of ultrasonic dispersion to slag suspensions with the observance of dispersion conditions can increase the aggregative and sedimentation stability of FGS suspension by 2-3 times in comparison with the mechanical mixing of suspensions. The strength of samples with suspensions of FGS prepared using UST under the recommended dispersing conditions increased by 19 to 39% in the first day; for 28 days of hardening - by 19 - 36%, which allows using slag suspensions in the production of cement composite materials and concretes based on them.

Modelling of MRR and hole taper for ultrasonic assisted jet electrochemical micro-drilling process using Buckingham's <i>π</i> theorem

Ultrasonic assisted jet-electrochemical micro-drilling (UAJet-ECMD) process integrates ultrasonic vibrations and jet electrochemical micro drilling process. In the present study, Buckingham's π theorem has been employed to model the process responses namely material removal rate (MRR) and hole taper of the UAJet-ECMD process with continuous DC voltage. The model has been formulated taking into account the experimental parameters namely voltage, electrolyte concentration, electrolyte pressure, inter electrode gap, pulse on time of ultrasonic vibrations and other physical properties related to ultrasonic vibrations such as speed of ultrasonic waves in the electrolyte, amplitude and frequency of ultrasonic vibrations. Electrochemical properties of work piece material namely chemical equivalent of copper and Faraday's constant were also taken into considerations. The use of regression analysis has been done to model the process responses. From the resultant π terms contained in the developed models, insignificant terms based on their percentage contributions were reduced and the models for both MRR and hole taper were modified. The formulated models for MRR and hole taper were validated with the statistical models obtained from experimental results.

Model and Mechanism of Stabilization of Carbon Nanotubes with Placticizer on the Basis of Sulfonated Naphthalene Formaldehyde Resins

The entry presents studies of the effect of dispersion temperature on the deposition rate of CNTs in the presence of a plasticizer based on sulfonated naphthalene formaldehyde resins, on the dispersed composition of CNTs in aqueous and aqueous-polymer dispersion media and on the strength characteristics of samples with stabilized CNTs. It was established that the ultrasonic dispersion of aqueous suspensions of CNTs in the presence of a plasticizer based on sulfonated naphthalene formaldehyde resins at an ultrasonic vibration frequency of 44 kHz; dispersion temperature - 25 ± 2 °C; dispersion time - 10 - 30 minutes is capable of ensuring the stability of CNTs suspensions for 7 days or more. The mechanism of stabilization of aqueous suspension of CNTs by a plasticizer based on sulfonated naphthalene formaldehyde resins is presented. It has been established that the stabilization of CNTs is achieved by fixing the functional groups of the plasticizer on the surface of the nanoparticle, the nonpolar component of which ensures the formation of a high-viscosity interlayer between the CNTs particles and the dispersion medium, and the polar component is the formation of a double electric layer (DEL) that promotes the micellization of CNTs. As a result, the CNTs stabilized with sulfonaphthalene formaldehyde are evenly distributed in the volume of the cement system, causing the production of cement stone with enhanced performance properties.

Effect of vibration frequency and displacement on melt expulsion characteristics and geometric parameters for ultrasonic vibration-assisted laser drilling of steel

Recently, the applications of ultrasonic vibration assistance to laser-based manufacturing processes are rapidly proliferating. Ultrasonic vibration-assisted laser drilling (UVLD) process involves simultaneous application of high frequency vertical vibrations to the workpiece while being irradiated with a continuous wave laser beam. In UVLD, the ultrasonic vibration assistance causes expulsion of droplets from the laser melted surface, resulting in the formation of deep holes. In this paper, systematic analysis of the effects of ultrasonic vibration frequency (20–40 kHz) and displacement (16–32 µm) on melt expulsion characteristics in early stages of drilling and geometric/quality features of the holes for UVLD of AISI 316 is presented. Based on the analysis of initiation of droplet ejection from the melt pool and particle size of the ejected droplets, mechanisms of droplet ejection based on capillary wave theory are proposed. It was observed that while increasing both ultrasonic vibration frequency and displacement resulted in reduction in droplet ejection initiation time and the formation of deeper holes for the given laser irradiation time (100 ms), the effect of vibration displacement was much more pronounced than the frequency on the variation.

Amplitude-Frequency Characteristics of the Oscillations of Methane Gas Bubbles in Oil

The author presents an analytical solution to the problem of acoustic-wave-induced oscillations of methane gas bubbles in an oil reservoir at bottom-hole conditions. The amplitude-frequency characteristics are computed for realistic reservoir temperature, pressure, and dissolved gas parameters that make the oil compressibility, density, and viscosity quite different from those of the degassed oil at surface conditions. The author compares the damping decrement of these ultrasonic oscillations to those at normal atmospheric-pressure surface conditions. The solution allowed the author to estimate the ultrasonic vibration frequency range that is optimal and most effective for improving the flow characteristics in a producing reservoir in the near-well zone at a realistic bottom-hole regime.

A nonuniform moving heat source model for temperature simulation in ultrasonic-assisted cutting of titanium alloys

The ultrasonic-assisted machining (UAM) technique has been widely used in machining of difficult-to-cut materials for its well comprehensive performance, especially in the mechanical and thermal aspects. In this paper, a nonuniform moving heat source model is proposed to analyze the heat transfer problem during ultrasonic vibration-assisted machining of Ti6Al4V. The influences of ultrasonic vibration amplitude and frequency on temperature distribution are discussed in detail. Two main characteristics are observed according to the temperature contours caused by the ultrasonic-assisted machining: one is that the equivalent heat source center tends to move backward the tool rake face, and the other is that the temperature gradients in cutting direction and depth direction are inconsistent. For further study, the temperature variation with respect to vibration parameters near the shear plane and machined surface is calculated. Results show that the increase of vibration amplitude and frequency can reduce the temperature near the shear plane due to a large temperature gradient. Besides, a large vibration amplitude can obtain a low temperature on the machined surface while the increased vibration frequency results in a higher surface temperature after machining. The research can be used to provide guidance for improving the quality and efficiency of difficult-to-cut material machining.

The Influence of Ultrasonic Vibration Frequency on the Properties of TiN Coated Biomedical Ti–13Zr–13Nb

Bare biomedical grade titanium alloys are prone to degradation when in a body fluid environment. Surface coatings such as Physical Vapor Deposition (PVD) can serve as one of the options to minimize this issue. Past reports showed that the PVD coated layer consists of pores, pinholes, and columnar growths which act as channels through which the aggressive medium attacks the substrate. Duplex and multilayer coatings seem able to address this issue to varying extents but at the expense of manufacturing time and cost. In this paper, the effect of an ultrasonic vibration frequency on PVD TiN coated Ti–13Zr–13Nb biomedical alloy was studied. Disk type samples were prepared and coated with TiN at fixed conditions: bias voltage (−125 V), substrate temperature (300 °C), and nitrogen gas flow rate (300 standard cubic centimeters per minute (SCCM)). An ultrasonic vibration was then subsequently applied to the TiN coated samples at frequencies of 8 kHz and 16 kHz for 5 min. All TiN coated samples treated with ultrasonic vibrations exhibited a higher corrosion resistance than the untreated ones. Microstructure analysis under Field Emission Scanning Electron Microscopy (FESEM) confirmed that the coated sample at frequencies of 16 kHz produced the most compact coating. It is believed that the hammering effect of the ultrasonic vibration reduced the micro channels’ size in the coating and thus decelerated the corrosion’s attack.

Ultrasonically Assisted Single Point Diamond Turning of Optical Mold of Tungsten Carbide.

To realize high efficiency, low/no damage and high precision machining of tungsten carbide used for lens mold, a high frequency ultrasonic vibration cutting system was developed at first. Then, tungsten carbide was precisely machined with a polycrystalline diamond (PCD) tool assisted by the self-developed high frequency ultrasonic vibration cutting system. Tool wear mechanism was investigated in ductile regime machining of tungsten carbide. The cutter back-off phenomenon in the process was analyzed. The subsequent experimental results of ultra-precision machining with a single crystal diamond tool showed that: under the condition of high frequency ultrasonic vibration cutting, nano-scale surface roughness can be obtained by the diamond tool with smaller tip radius and no defects like those of ground surface were found on the machined surface. Tool wear mechanisms of the single crystal diamond tool are mainly abrasive wear and micro-chipping. To solve the problem, a method of inclined ultrasonic vibration cutting with negative rake angle was put forward according to force analysis, which can further reduce tool wear and roughness of the machined surface. The investigation was important to high efficiency and quality ultra-precision machining of tungsten carbide.

Material removal mechanism of two-dimensional ultrasonic vibration assisted polishing Inconel718 nickel-based alloy

In this paper, a two-dimensional ultrasonic-assisted polishing Inconel718 nickel-based alloy has been investigated. This polishing technique combines the functions of ultrasonic machining and conventional mechanical polishing, which improves the material removal rate (MRR) of the Inconel718 nickel-based alloy by nearly two times (from 220 nm/min to 415 nm/min), and the surface roughness and average standard deviation of the roughness values are significantly reduced. The MRR model of two-dimensional ultrasonic-assisted polishing Inconel718 nickel-based alloy was established by analyzing the mechanism of material removal and the movement of abrasive grains, including the polishing pad material and properties, abrasive particle size and ultrasonic vibration frequency and amplitude and other related polishing process parameters. The experimental results show that the MRR prediction model of ultrasonic-assisted polishing material has a good consistency with the experimental results. The model can be used to predict and guide the two-dimensional ultrasonic-assisted polishing process of Inconel718.

Fabrication of Micro Structures by Ultrashort Voltage Pulse Electrical Discharge Machining

The machining of small holes and array holes has been a difficult problem in machining field. Tiny hole is widely used in mechanical field, for instance, fuel injection nozzles, spinneret holes for synthetic fibers and wire drawing dies. This paper investigated the application of EDM (electrical discharge machining) to the fabrication of micro structures. There are obvious limitations in the process of micro-electrical discharge machining, such as electrode wear, unstable discharge condition and low machining efficiency. The effects of EDM parameters were investigated, such as voltage, pulse frequency, and frequency of ultrasonic vibration applied to electrode. Micro holes were machined with Pt electrode made by focused-ion-beam chemical vapor deposition (FIB-CVD) and Cu electrode made by wire-electrode cutting. The comparison experiments between EDM and ECM (electrochemical machining) indicated that the processing of ECM has serious stray current corrosion and poor machining precision. Moreover, the workpiece vibration was firstly proposed to be utilized in the micro-electrical discharge machining. It can be concluded that maximum machine could be obtained under the amplitude ratio of 76%, which was an appropriate parameter.

Modeling and simulation of surface roughness in ultrasonic assisted magnetic abrasive finishing process

An ultrasonic assisted magnetic abrasive finishing (UAMAF) is a hybrid finishing process. In UAMAF, ultrasonic vibrations are introduced into the finishing zone of magnetic abrasive finishing (MAF) process to finish the workpiece surface more efficiently as compared to MAF in the nanometer range. In the present work, a model of surface roughness during UAMAF process has been presented. The model assumes that the instantaneous rate of change of surface roughness is proportional to the material removal rate (MRR) and the amount of irregularities present on the surface. A model of MRR was presented, considering it to be attributed to two simultaneous and independent phenomena—a steady state material removal and a transient material removal. The MRR model has further been used to model the instantaneous surface roughness during finishing. The surface roughness model not only incorporates the effect of initial surface roughness value but also assimilates a critical surface roughness value below which no reduction in roughness is possible. The constants included in the modeling are predicted by using an inverse method. A simulation of 3-D surface roughness profile has also been presented to visualize the effect of finishing numerically. The developed model predicted the surface roughness in UAMAF as a function of supply voltage, working gap, rpm of the electromagnet, amplitude and frequency of ultrasonic vibration, hardness and initial surface roughness of the workpiece. The predicted value shows a good agreement with the experimental observation with a maximum deviation of ±7.35%. The model affirms that an exponential correlation exists between instantaneous surface roughness value and finishing time during finishing.

Modeling of material removal in ultrasonic assisted magnetic abrasive finishing process

Ultrasonic assisted magnetic abrasive finishing (UAMAF) integrates ultrasonic vibrations with magnetic abrasive finishing (MAF) process to finish the workpiece surface more efficiently as compared to MAF. In this work, mechanism of material removal has been discussed. A kinematic analysis of an abrasive particle and an analysis of material removal during UAMAF is presented. The total material removal during finishing is attributed to two simultaneous and independent phenomena — a steady state material removal and a transient material removal. The steady state removal mainly depends on the finishing condition and remains constant throughout the finishing time, while transient removal is primarily associated with the surface roughness of the workpiece. A finite‒element analysis of electromagnet was performed to calculate magnetic‒flux density in the finishing region to evaluate the normal force acting on the active abrasive particles. The steady state material removal was modeled as a function of velocity and normal force using the process physics. The transient material removal was modeled as a function of the volume of instantaneous irregularities available on the workpiece surface. The developed model predicted the material removal rate (MRR) in UAMAF as a function of supply voltage, working gap, angular speed of the electromagnet, amplitude and frequency of ultrasonic vibration, hardness and initial surface roughness of the workpiece. The model brought out that there was an exponential relationship between MRR and finishing time.

Finite element analysis of ultrasonic vibration-assisted microstructure hot glass embossing process

Hot glass embossing is a novel technology to manufacture microtips for Field Emission Displays with high quality and low cost. This technology recently has been assisted by ultrasonic vibration. Previous studies showed that high energy of ultrasonic vibration would lead to the temperature rise inside the glass so that micro-formability of glass material has been especially improved efficiently. However, these findings were experimental only. Therefore, this work is aimed to utilise the proposed model in the previous study to analyse the shape of pyramid structures on K-PSK100 optical glass substrate during ultrasonic vibration-assisted hot glass embossing process. Microstructure hot embossing experiments were first conducted without and with the assistance of ultrasonic vibration (frequency of 35 kHz and amplitude of 3 μm). Three-dimensional simulations were then performed to predict the height of pyramids after hot embossing process. The consistency between simulations and experiments not only proved that ultrasonic vibration could increase the filling ability of glass material into microcavities up to 17% but also indicated the value of the proposed model in predicting the final shape of microstructures after ultrasonic vibration-assisted hot glass embossing process.

Study on the Law of Ultrasonic Vibration-Assisted Adhesive Bonding of CFRP-to-Aluminum Joints

A novel ultrasonic vibration-assisted adhesion method for CFRP-to-aluminum joints is proposed. Extra force caused by ultrasonic vibration is introduced to reinforce the process of CFRP adhesion, which can overcome shortcomings in passive adhesion enhancement methods. The relationship between each ultrasonic vibration factor is explored, and the optimal ultrasonic vibration frequency, 15 KHz, is found. Through orthogonal experiment optimizing adhesive bonding process, it is found that the order of the influence of the factors on the adhesion strength is: Vibration time > Vibration amplitude > Vibration pressure > Vibration position, and the optimal ultrasonic vibration-assisted adhesive bonding of CFRP-to-aluminum joints (vibration time is 8s, vibration pressure is 0.40MPa, vibration position is 30mm and vibration amplitude is 56 μm) can improve adhesion strength by 40.14% and improve consistency of adhesion strength by 58.29%. This study provides a feasible and effective method for CFRP component adhesion.

Influence of the parameters of a high-frequency acoustic wave on the structure, properties, and plastic flow of metal in the zone of a joint of materials welded by ultrasound-assisted explosive welding

The results of an investigation of the influence of the parameters of high-frequency acoustic wave on the structure and properties of the zone of joint of homogeneous metals bonded by explosive welding under the action of ultrasound have been presented. The influence of the frequency and amplitude of ultrasonic vibrations on the structure and properties of the explosively welded joints compared with the samples welded without the application of ultrasound has been established. The action of high-frequency acoustic waves on the metal leads to a reduction in the dynamic yield stress, which changes the properties of the surface layers of the metal and the conditions of the formation of the joint of the colliding plates upon the explosive welding. It has been shown that the changes in the length and amplitude of waves that arise in the weld joint upon the explosive welding with the simultaneous action of ultrasonic vibrations are connected with a decrease in the magnitude of the deforming pulse and time of action of the compressive stresses that exceed the dynamic yield stress beyond the point of contact.

Construction of mathematical model of dissolution process of solids under action of ultrasound

An influence of the ultrasound beam on the process, dissolution of solids in liquid solvents is considered: influence of frequency, intensity, velocity of acoustic vibrations, cavitation and acoustic flows on mass transfer process. Experimental researches show that the intensification of dissolution process of solids in liquid solvents under action of ultrasound is influenced by acoustic flows, microflows and under influence of cavitation bubbles. Development of new efficient equipment for solution requires the development of calculation methods of dissolution processes of solids in liquid solvents under conditions of ultrasonic irradiation. Such methods should take into account the characteristics of ultrasonic generators, irradiation frequency of ultrasonic vibrations, power and intensity of ultrasonic vibrations. Mathematical model of dissolution process of the granule is constructed. It identifies the change of size of the granule over time under influence of the source of ultrasonic irradiation. Mathematical model consists of three differential equations used to calculate depending on the ratio of the granule size and the maximum turbulence scale of acoustic flows and for cavitation. The mathematical model will enable use in conducting numerous studies as a basis of equipment calculation methods for dissolution process of granular material.

Characterization of Piezoelectric Accelerometers Beyond the Nominal Frequency Range

Abstract Ultrasonic testing is preferred widely for the evaluation of material properties. However, ultrasonic signals are highly affected by the characteristics of the piezoelectric transducers employed for the measurements. Since ultrasonic transducers are mostly used to measure the travel time of waves only, their non-flat frequency response does not affect the results. On the other hand, the analyses based on the full-waveform provide more reliable results, as thousands of additional data points in the measured signals are taken into account to determine the material properties (e.g., material damping). To perform such analyses, however, the transfer function of the transducer is required in order to normalize the recorded signals. In this paper, a new calibration approach was proposed to determine the transfer function of the piezo-electric accelerometers that are used beyond their nominal frequency range. A nano-laser vibrometer was utilized to measure the high frequency ultrasonic vibrations generated by the piezoelectric transmitter employed as the excitation source for the accelerometers. The transfer functions of two accelerometers with different nominal frequency ranges were determined for frequencies between 20 and 70 kHz, which were then used to capture the ultrasonic waves on a lightly cemented-sand medium. The original signals and the ones corrected by eliminating the effect of the transfer functions were processed to determine the material damping of the medium. Improvement in the accuracy of the material damping is achieved with the corrected signals compared to the uncorrected ones.

Feed-direction ultrasonic vibration−assisted milling surface texture formation

ABSTRACTThe formation mechanism of surface texture for feed-direction ultrasonic vibration−assisted milling (UVAM) was investigated in this study by establishing a kinematic model and a pressing model of UVAM. The kinematic model showed that the cutter tip, which was supposed to be totally sharp, produced closed scratches by crossed trajectories. The variation trends of the interval for closed textures were of sine function. A comparative experiment was carried out by UVAM and conventional milling. A dividing line close to the X coordinate divides the surface feature into two parts. The pressing model showed that the tool minor cutting edge left clear traces with certain width because of the tool minor cutting edge angle. Scratches by tool minor cutting edge were intermittent and regularly varied when feed-direction vibration was introduced. All the surface feature changes are in the radial direction and the trajectory intersections shall always be the scratch grooves or ridges. The ratio between ultrasonic vibration frequency and spindle speed, tool radius, and the located cutter rotation angle affected the changing rule of scratches by tool minor cutting edge. The analytical models and the experimental results proved to each other reasonable.

Investigation on feed direction cutting force in ultrasonic vibration-assisted grinding of dental ceramics

The feasibility of ultrasonic vibration-assisted grinding in dental restoration has been preliminarily proved. Improving the machining quality of zirconia ceramics by controlling cutting force is the focus of the researchers. However, the existing feed direction cutting force model for ultrasonic vibration-assisted grinding does not take the ultrasonic vibration amplitude and frequency into account. This paper presents a mathematical model for feed direction cutting force in ultrasonic vibration-assisted grinding of zirconia under the consideration of amplitude and frequency, and assuming that brittle fracture is the primary mechanism of material removal in ultrasonic vibration-assisted grinding of zirconia. The effects of amplitude and frequency on the motion, effective cutting distance, and theoretical removal of an abrasive particle have been analyzed. Besides, the number of active abrasive particles is calculated with analyzing the influences of lateral cracks and ultrasonic vibration. The variation laws of cutting force and penetration depth of an abrasive particle during ultrasonic vibration-assisted grinding have also been analyzed. Therefore, the relationship between feed direction cutting force and input variables is predicted through the developed model. Finally, pilot experiments are conducted for the mathematical model verification. Experimental results show that the trends of input variables for feed direction cutting force agree well with the trends of the developed cutting force model. Hence, the mathematical model can be applied to evaluate the feed direction cutting force in ultrasonic vibration-assisted grinding of zirconia ceramics.

Theoretical study on brittle–ductile transition behavior in elliptical ultrasonic assisted grinding of hard brittle materials

The elliptical ultrasonic assisted vibration can lead to a higher comprehensive performance with better machined quality and lower grinding force during brittle materials machining. The undeformed chip thickness in grinding can be defined as the distance between two consecutive grinding surfaces formed by the adjacent abrasive grain trajectories. The ductile–brittle transition point of chip formation in brittle materials machining is believed to be represented by the threshold value of undeformed chip thickness (critical undeformed chip thickness). In this paper, an energy based method is proposed to predict the critical undeformed chip thickness in elliptical ultrasonic assisted grinding (EUAG). The effects of vibration parameters on grinding force and specific grinding energy are analyzed in detail. Results show that the axial vibration amplitude leads to a slight reduction in grinding force, whereas the vertical vibration amplitude results in a significant reduction of grinding force. The increase of wheel speed and ultrasonic vibration frequency can reduce the grinding force as well. Nevertheless, the grinding force ratio remains relatively steady fluctuating from 1.37 to 1.56. Additionally, the critical undeformed chip thickness increases with the increasing grinding speed, axial vibration amplitude and ultrasonic vibration frequency, while firstly increases and then decreases with the increasing vertical vibration amplitude. Especially, a ductile-mode grinding in micron-level can be achieved when the axial vibration amplitude is above 3μm and a totally brittle fracture occurs when the axial vibration does not exist. Thus, a reasonable selection of vibration parameters in EUAG process is required. The above theoretical evaluations coincide well with the variable experimental results.