Ultrasonic Vibration Frequency Research Articles

Effects of Ultrasonic Vibration on the Welding Process of Friction Stir Welding

Based on the understanding of Friction Stir Welding (FSW) and the effect of ultrasound, the purpose of the paper is trying to find the effective access to reduce the welding resistance and improve the quality of weld during FSW. The best vibration point was first determined through the vibration test system. Then, the thermal cycling, three-force and torque were tested by using paperless recorder and mechanical sensor in heat-power test bench for 4mm thick AZ31 magnesium alloy. The results showed that the periodic vibration took place at the weld under the excitation of ultrasonic vibration, and the frequency of this vibration was as same as the frequency of ultrasonic vibration. The best tracking distance of ultrasonic vibration was 40 mm, and its optimal incident angle was 45°. By applying ultrasonic vibration to FSW, the forward resistance, the axial force and the torque of the tool can be significantly reduced. In addition, the distribution of temperature field was basically consistent with the two conditions, presenting “asymmetrical, non-linear” distribution characteristic. The heating effect of ultrasonic vibration was not obvious, but it was able to make the temperature field of the welding seam become more uniform.

Experimental Study on the Effect of Humidification on the Pollution Characteristics of Particulate Matter in the Office

Indoor air quality has a direct impact on human health. Indoor air quality has aroused great concern. This experimental study compares the effects of different water humidification on the indoor particulate pollution characteristics, and analyzes the mass concentration and the particulate number concentration distribution of different sizes of particulates with time under each condition of the purified water humidification, the tap water humidification and the cold boiled water humidification in the office. The results show that under the three kinds of wetting conditions, the concentration of the fine particulates is higher. More minerals are contained in the tap water and the cold boiled water, so the two kinds of humidification have more significant impact on indoor particulate matter. But the purified water humidification has nearly no significant effect on it. The calcium and magnesium ionic compounds are partly removed after the water boiled, so the cold boiled water humidification has less impact on the indoor particulate matter than the tap water humidification. The mass concentration and particulate number concentration of the particle may also be affected due to the frequency of ultrasonic vibration.

Impact of melt convection induced by ultrasonic wave on dendrite growth in Sn–Bi alloys

The effects of an ultrasonic wave (20kHz) on the dendritic microstructure of Sn–13at%Bi alloys were studied using time-resolved in situ X-ray imaging. Sequential images clearly showed the secondary effects such as the ultrasonic streaming and the oscillation with much lower frequency comparing to the ultrasonic vibration frequency. The ultrasonic wave caused a circulating convection, whose domain size was almost the same as the specimen size, and simultaneously periodic convection (40Hz), which was identified from the longitudinal oscillation of the dendrites. The fragmentation of the primary and secondary dendrite arms in the columnar zone was significantly enhanced under the ultrasonic wave. The secondary effects of the ultrasonic wave play a significant role for modifying the solidification structure.

Diamond Tool Wear Reduction by Combining Ultrasonic Elliptical Vibration with Graphite Particle Atmosphere

For reducing diamond tool wear in ultra-precision cutting of ferrous metals, a process of combining ultrasonic elliptical vibration with graphite particle atmosphere was put forward. An experimental setup was built integrating an ultrasonic elliptical vibration mechanism with a jet lubrication device on a 4-axis ultra-precision lathe. The frequency of ultrasonic elliptical vibration is 38.36 kHz with a trajectory of 8.5×3.5μm. Graphite particles with sizes of 1.3~2μm were selected. Conventional cutting and the combined method were conducted on die steel. Compared with conventional cutting with a wear land width of about 300μm, diamond tool wear in the combined method was decreased to about 20 to 30μm. The combined method is feasible to further reduce the diamond tool wear when cutting die steel.

Analysis of temperature in conventional and ultrasonically-assisted drilling of cortical bone with infrared thermography

Bone drilling is widely used in orthopaedics, dental and neurosurgeries for repair and fixation purposes. One of the major concerns in drilling of bone is thermal necrosis that may seriously affect healing at interfaces with fixtures and implants. Ultrasonically-assisted drilling (UAD) is recently introduced as alternative to conventional drilling (CD) to minimize invasiveness of the procedure. This paper studies temperature rise in bovine cortical bone drilled with CD and UAD techniques and their comparison using infrared thermography. A parametric investigation was carried out to evaluate effects of drilling conditions (drilling speed and feed rate) and parameters of ultrasonic vibration (frequency and amplitude) on the temperature elevation in bone. Higher levels of the drilling speed and feed rate were found responsible for generating temperatures above a thermal threshold level in both types of drilling. UAD with frequency below 20 kHz resulted in lower temperature compared to CD with the same drilling parameters. The temperatures generated in cases with vibration frequency exceeding 20 kHz were significantly higher than those in CD for the range of drilling speeds and feed rates. The amplitude of vibration was found to have no significant effect on bone temperature. UAD may be investigated further to explore its benefits over the existing CD techniques.

An Experimental Study on Real Time Measurement of Ultrasonic Vibration Amplitude and Frequency Using Laser Displacement Sensor

An ultra-high-speed and high-accuracy charge-coupled device (CCD) laser displacement sensor is used to track and measure the ultrasonic vibration in real time. A series of Matlab programs are developed to filter noise from original data. The ultrasonic vibration frequency and period are evaluated and the ultrasonic amplitude is measured within accuracy ±0.1 μm. Effect of the ultrasonic power on the ultrasonic amplitude is also studied.

Experimental study on instantaneously shedding frozen water droplets from cold vertical surface by ultrasonic vibration

The ultrasonic vibration is introduced to remove adherent frozen water droplets from cold surface, which provides the possibilities for effective defrosting. The shedding processes of various frozen water droplets adhered to 70mm×70mm cold vertical surface by 20kHz and 60W ultrasonic vibration were experimentally studied. It was found that the frozen water droplets instantaneously crack and shed off from the vertical surface due to the combined effects of interface transverse shear force generated by ultrasonic mechanical vibration and impact force induced by ultrasonic acoustic pressure. However, the heating effect triggered by ultrasonic vibration has limited effect on the frozen water droplets removal. Moreover, the frozen water droplets in different diameters within 2–30mm can be successfully removed and all the frozen water droplets in different positions of 70mm×70mm cold surface can be completely shed off by 20kHz high frequency ultrasonic vibration. The results showed that the ultrasonic vibration has a very strong ability to remove the frozen water droplets, which are the parasitic substrates for frosting, from cold flat surface and thus it is a highly potential defrosting method for practical application.

Microstructure and Defects Evaluation of Varistors by Ultrasonic Waves in Low Frequency Range

Each material contains defects and in-homogeneities in a structure volume. It has influence on the properties of material (conductivity, mass density, mechanical properties). Interaction of the ultrasonic waves with defects or in-homogeneities in the solid state is not clear. Electro-ultrasonic spectroscopy can help to clarify this phenomenon. The electro-ultrasonic spectroscopy describes defects and un-homogeneities inside the sample structure. This method is quite different from electro-acoustic effect. Ultrasonic signal is in range from 20 kHz to 150 kHz. Ultrasonic signal changes geometry of the sample in elastic range only. The sizes of cracks are changing also in the sample volume. Conductivity near the area of cracks is strongly changing due to ultrasonic vibrations. It has influence on resistance of the sample which is changing along with a frequency of ultrasonic vibrations. The amplitude of the resistance change depends on the material, number of cracks, size of cracks and Eigen frequencies of the sample excited by ultrasonic wave. We applied the electro-ultrasonic spectroscopy on two types of varistors. It can be useful for understanding the relation between microstructure and mechanical properties of these types of varistors.

Effects of Ultrasonic Frequencies on Grinding Force of Nano-Composite Ceramics Based on Nonlocal Theory

Based on nonlocal theory, The effects of ultrasonic frequencies on the grinding force and nonlocal decay rate are obtained through the experimental study of material properties under ultrasonic vibration grinding test. The results of experiments showed that grinding force is attenuated in the ultrasonic vibration frequency ranges and this attenuation phenomenon becomes more and more evident by the increase of the ultrasonic frequencies. Through analysis of the grinding surface morphology and phase structure, it showed that ultrasonic vibration greatly reduces the average grinding force, and the surface quality are improved, and that it is much easier to achieve ductile-mode machining under ultrasonic vibration. The results of experiments are in accordance with the analysis of nonlocal theory.

Research on Surface Roughness of Nano-Composite Ceramics under Multi-Frequency Ultrasonic Grinding and Dressing

The surface roughness of nano-composite ceramics machined by means of multi-frequency ultrasonic vibration grinding was investigated with the diamond grinding wheel dressed by elliptical vibration. The results indicate that the surface roughness is influenced by ultrasonic vibration frequency, feeding speed, grinding depth. The ultrasonic vibration frequency and the grinding depth are not the higher the better and there are suitable values. The surface roughness gets worse with the increase of feeding speed.

Research on Surface Residual Stress of Nano-Composite Ceramics under Multi-Frequency Ultrasonic Grinding and Dressing

The surface residual stress of nano-composite ceramics prepared by mixed coherence system and machined both in ordinary grinding(OG) and ultrasonic vibration grinding(TDUVG) respectively were described. Researches showed that the characteristics of residual stress on ceramic surface is affected by grinding load, ultrasonic vibration frequency and released stress induced by generation of cracks whose magnitude is affected by material removal mechanism. Whether in ordinary grinding or ultrasonic grinding, tangential residual stress (TRS) in X direction is tensile stress, and in Y direction is compressive stress. The surface residual tensile stress in ordinary grinding is larger than that in ultrasonic grinding with the same grinding conditions. The influences of multi-frequency on the residual stress are studied.

Experimental study on frosting suppression for a finned-tube evaporator using ultrasonic vibration

An experimental study was conducted to investigate the possibility and the effect of frost release from a finned-tube evaporator by using ultrasonic vibrations in natural convection. A compressor was adopted as cold source, and a finned-tube evaporator was placed horizontal on the frames inside a chamber. The aluminum fins surface was covered with hydrophilic coatings whose contact angle of the water drop of the surface is 37.7°, and the fins had wing-cases to enlarge the heat-exchange area. The thickness of a fin was approximately 0.1 mm, and the gap distance between any two fins of the evaporator was about 1.55 mm in average. An ultrasonic transducer with resonance 28.2 kHz and rating power 60 W was adopted as a vibrator to excite the evaporator. A microscopic image system was used to observe and record the whole frosting process with/without ultrasonic vibrations, a method of frost thickness measurement on the double sides of a fin was present and realized through digital image processing technology. From microscopic view, the deposited frost nearly block the fins gaps when the compressor worked for 32 min without ultrasonic vibration, while almost 2/3 of the gaps between two neighbor fins were unblocked when the compressor worked for 92 min with ultrasonic vibration, which shows that the frost deposited on the fins surfaces could be suppressed with high frequency ultrasonic vibrations. From macroscopic view, the frost growing on the fins are being vibrated to fall off and accumulated under the evaporator to form frost piles. Although the fins above the braze tubes were deposited with frost, the fins between any two neighboring tubes were unblocked. Experiments show that the basic ice layer on the fins cannot be removed with ultrasonic vibrations, but frost crystals and frost branches on the ice layer can be fractured and removed effectively, the frost growing on the evaporator can be suppressed by using ultrasonic vibrations. The main mechanism of ultrasonic frost suppression maybe mainly attributed to the high frequency ultrasonic mechanical vibrations that can break up frost crystals and frost layers, then frost will fall off with the gravity, not to ultrasonic cavitation effect or heat effect.

Finite element modeling of a micro-drill and experiments on high speed ultrasonically assisted micro-drilling

Modal characteristics of a generic micro-drill and experiments on the micro-drilling with superimposing of longitudinal ultrasonic vibration are presented. Finite element (FE) analysis is used for identification of eigenfrequencies and modes of the drill. Dynamic influence of the drill shank is discussed and a hybrid model is proposed to account for it. The model is proven to be efficient for complicated drill models and advanced analysis. A high speed ultrasonically assisted micro-drilling (UAMD) system is established with air bearings and longitudinally vibrating workpiece. During the experiments the thrust force reduction is studied as well as effects of ultrasonic vibration frequency and rotational speed. A correlation study was conducted between the thrust force measurements and simulations from a nonlinear force model. It can be seen that the current one-dimensional model is not sufficient to describe the complete behavior of the drill. The FE model and force experimental results can be utilized for a full dynamic model of the UAMD system to study vibration and the cutting mechanism in the future.

Parameter Optimization of Ultrasonic Machining Process Using Nontraditional Optimization Algorithms

The optimum selection of process parameters is essential for advanced machining processes, as these processes incur high initial investment, tooling cost, and operating and maintenance costs. This article presents optimization aspects of an important advanced machining process known as ultrasonic machining (USM). The objective considered is maximization of material removal rate (MRR) subjected to the constraint of surface roughness. The process variables considered for optimization are amplitude of ultrasonic vibration, frequency of ultrasonic vibration, mean diameter of abrasive particles, volumetric concentration of abrasive particles, and static feed force. The optimization is carried out using three nontraditional optimization algorithms, namely, artificial bee colony (ABC), harmony search (HS), and particle swarm optimization (PSO). An application example is presented and solved to illustrate the effectiveness of the presented algorithms. The results of the presented algorithms are compared with the previously published results obtained by using genetic algorithm (GA).

Research on the Performance of Ultrasonic Vibration Assisted Electrical Discharge Surface Modification Layer

Ultrasonic vibration assisted electrical discharge surface modification was studied in the paper. The influence of ultrasonic vibration amplitude and frequency on the modification layer performance, such as surface roughness, sectional morphology, micro hardness and wear resistance was investigated. Experimental results show that ultrasonic vibration assisted electrical discharge surface modification can improve surface roughness and make the melting material well-distributed. The surfaces have higher micro hardness and wear resistance when the tool electrode is assisted with ultrasonic vibration.

Rapid patterning of spin-on-glass using ultrasonic nanoimprint

The authors succeeded in room-temperature patterning on a spin-on-glass (SOG) coated Si substrate by an ultrasonic nanoimprinting in a short duration of 1 min. Typically, at a room-temperature it takes a large press pressure and a long contact time to nanoimprint without a thermal pretreatment. In our ultrasonic nanoimprinting, a mold is attached directly to an ultrasonic generator, and mold patterns are set in motion at a high-speed in a direction aligned with the direction of the contact force applied. By this movement of mold patterns, plastic deformation and thermal deformation caused by the initial pressure and frictional heat generated by the ultrasonic vibration are combined to achieve precise structures. The authors had already confirmed the assisting effect of ultrasonic vibration at room-temperature nanoimprinting on various engineering plastics and baked SOG without any heating of mold. They then experimented to apply the ultrasonic nanoimprint method on nonbaked SOG coated substrates. They prepared an organic SOG and an inorganic SOG as molding materials, and executed ultrasonic nanoimprinting under various experimental conditions based on the optimized conditions for polyethylene terephthalate (frequency of ultrasonic vibration=10 kHz, contact force=500 N, and contact time=60 s). Moreover, the relationship between the amplitude of ultrasonic vibration and the imprinted depth was investigated, and the influence that the ultrasonic vibration exerted on the transfer accuracy of mold patterns was also determined.

Study on Grinding Force in Two-Dimensional Ultrasonic Grinding Nano-Ceramics

In this paper, the characteristic of grinding force in two-dimensional ultrasonic vibration assisted grinding nano-ceramic was studied by experiment based on indentation fracture mechanics, and mathematical model of grinding force was established. The study shows that grinding force mainly result from the impact of the grains on the workpiece in ultrasonic grinding, and the pulse power is much larger than normal grinding force. The ultrasonic vibration frequency is so high and the contact time of grains with the workpiece is so short that the pulse force will be balanced by reaction force from workpiece. In grinding workpiece was loaded by the periodical stress field, which accelerates the fatigue fracture.

Analysis of Ultrasonic Honing Chatter Vibration Trajectory

Grinding chatter belongs to non-linear vibration, whose generation mechanism is complex. The eliminating and reducing of vibration are very difficult, which have been one of the hot and difficult problems at home and abroad. Power ultrasonic vibration honing is a special processing that adds secondary ultrasonic into traditional honing. Adding ultrasound not only superimposes high-frequency vibration components on the trajectories, which makes trajectories become very complex, but also makes high frequency ultrasonic vibration elements greatly influence the vibration trajectory of chatter, which makes the stability analysis of ultrasonic honing become more complex, so it is necessary to specially study in vibration trajectories of honing process. Taking axial ultrasonic vibration honing as an example, the paper respectively takes single wear debris, two adjacent wear debris, oilstone as study object to discuss on the variation rules of honing chatter vibration trajectory after adding ultrasonic, and obtains the following conclusions: adding ultrasonic can larger vibration trajectory for single wear debris or two adjacent wear debris on microscopic scales, on the view of macroscopic which is performed as honing depth of oilstone increasing; the effects of adding ultrasonic to chatter depend on the t value; through appropriately adjusting or selecting process parameters and structural ones, chatter can be completely avoided.

Ultrasonic Nanoimprinting in Organic Spin-on-Glass-Coated Si Substrates

We have already reported on our success in molding engineering plastics by an ultrasonic nanoimprinting technology. In this paper, we report on our experimental results of ultrasonic nanoimprinting in organic spin-on-glass (SOG)-coated Si substrates. A 753-nm-thick layer of Accuglass 512B, an SOG also known as methyl siloxane, was spin-coated on a sputter-deposited 10-nm-thick Ti layer on a Si substrate. Typically, SOG needs to be baked in a two-step thermal treatment by annealing at a low temperature and then at a high temperature. Therefore, a group of substrates previously heated at 150 °C for 1 min using a hot plate, and another group of substrates previously soft baked at 150 °C followed by hard baking at 450 °C for 1 h in a rapid thermal processor were prepared for tests. Nanoimprinting was carried out under conditions similar to those used in earlier experiments on engineering plastics. In the tests, the frequency and amplitude of ultrasonic vibration were set at 10 kHz and 3 µm, while the contact force and contact time were set to 500 N and 60 s, respectively. In the experiment, we succeeded in transferring mold patterns with linewidths of 500 nm, 700 nm, and 1 µm onto the substrates. The maximum depths of imprinting in the SOG-coated substrates without and with hard baking were 294 and 214 nm, respectively, as measured using a confocal microscope. In addition, the effect of a Ti interlayer and those of the frequency and amplitude of ultrasonic vibration on the depth of imprinting were investigated. The results of these experiments demonstrated the potential wide application of ultrasonic nanoimprinting technology for SOGs as well as for engineering plastics.

Frequency and amplitude dependences of molding accuracy in ultrasonic nanoimprint technology

We use neither a heater nor ultraviolet lights, and are researching and developing an ultrasonic nanoimprint as a new nano-patterning technology. In our ultrasonic nanoimprint technology, ultrasonic vibration is not used as a heat generator instead of the heater. A mold is connected with an ultrasonic generator, and mold patterns are pushed down and pulled up at a high speed into a thermoplastic. Frictional heat is generated by ultrasonic vibration between mold patterns and thermoplastic patterns formed by an initial contact force. However, because frictional heat occurs locally, the whole mold is not heated. Therefore, a molding material can be comprehensively processed at room temperature. A magnetostriction actuator was built into our ultrasonic nanoimprint system as an ultrasonic generator, and the frequency and amplitude can be changed between dc–10 kHz and 0–4 µm, respectively. First, the ultrasonic nanoimprint was experimented by using this system on polyethylene terephthalate (PET, Tg = 69 °C), whose the glass transition temperature (Tg) is comparatively low in engineering plastics, and it was ascertained that the most suitable elastic material for this technique was an ethyl urethane rubber. In addition, we used a changeable frequency of the magnetostriction actuator, and nano-patterns in an electroformed-Ni mold were transferred to a 0.5 mm thick sheet of PET, polymethylmethacrylate (PMMA) and polycarbonate (PC), which are typical engineering plastics, under variable molding conditions. The frequency and amplitude dependence of ultrasonic vibration to the molding accuracy were investigated by measuring depth and width of imprinted patterns. As a result, regardless of the molding material, the imprinted depth was changed drastically when the frequency exceeded 5 kHz. On the other hand, when the amplitude of ultrasonic vibration grew, the imprinted depth gradually deepened. Influence of the frequency and amplitude of ultrasonic vibration was not observed on the width of imprinted patterns. Moreover, the imprinted depth deepened as the Tg of the molding material lowered, and a progressive change according to conditions of ultrasonic vibration also became remarkable. Therefore, it seems that impressing ultrasonic vibration with a high frequency and large amplitude promotes thermal deformation and improves the molding accuracy in the ultrasonic nanoimprint technology.