High Frequency Ultrasonic Vibration Research Articles

Simulation Analysis of the Influence of Amplitude on Deformation and Fracture Characteristics of Hard Rock under Ultrasonic Vibration Load

The utilization of auxiliary tools employing ultrasonic high-frequency vibration to enhance rock breaking efficiency holds significant potential for application in underground hard rock excavation engineering. To investigate the failure mechanism of rocks under high frequency ultrasonic vibration load, this study employs particle flow software PFC2D for numerical simulation. By incorporating boundary conditions from actual ultrasonic vibration rock breaking experiments and utilizing a parallel bond model to construct the rock, we analyze the deformation, damage, fracture, and energy evolution process of hard rocks subjected to vibrational loads. The results demonstrate that the maximum displacement in hard rocks increases nearly linearly with vibrations until reaching 5.0199 × 10−3 m, after which it plateaus. Additionally, macroscopic fissures formed during rock failure exhibit an X-shaped pattern. Furthermore, based on our model, we examine the impact of amplitude variation on hard rocks with an equal number of cycles (5,000,000 cycles). Under ultrasonic vibration loads, amplitude influences the total input energy within the rock system. While increasing amplitude does not alter maximum deformation in rocks, it enhances fragmentation degree, fracture degree and energy dissipation coefficient—thereby improving rock breaking efficiency.

The Morphology of al Droplet in an Ultrasonic Oscillation Field: Kinetic and Equilibrium Thermodynamic Analysis

Wetting of metal droplet on the solid substrate is a fundamental phenomenon which is applicable to the surface chemistry. When an oscillation field is included in the wetting condition, the wetting process shows significant advancing and receding behaviors. Also, the use of ultrasonic oscillation field is promising in welding. However, some odd morphologies led by the ultrasonic-treatment have shown wetting kinetics which have not been fully investigated. The high frequency ultrasonic vibration brings hysteresis to the contact angle, whose extra energy is attributed by the oscillation field. The ultrasonic wetting process is excited by the 20 kHz frequency periodic oscillation, during which droplet is swaying cyclically. However, after capturing the transformation of droplet morphologies, it is found that the frequency of each swaying cycle is identified to be 180 ms. Theoretical investigations have also quantitively proved that the energy for the contact angle decrease origins from the ultrasonic field, and the wettability is in a great enhancement. Thermal and kinetic effects of ultrasonic are investigated by making theoretical calculations, the 20 kHz ultrasonic field lasting for 5 seconds. Thermodynamics, vibrational mechanics, and interfacial phenomena affect the sonochemistry of wetting.

Effect of ultrasonic field parameters on interfacial characteristics and mechanical properties of Mg alloy welding joint

In this research, high frequency ultrasonic vibration (UV) was firstly developed for the arc welding of MB3 Mg alloy in order to improve Mg alloy welding prone to porosity defects, coarse weld microstructure, and low joining strength problems. Authors investigated the influences of ultrasonic treatment on weld microstructures and mechanical properties of Mg alloy joints by introducing high frequency ultrasonic vibration into weld pool. Experimental results revealed that ultrasonic treatment encouraged equiaxed grain to form in the weld zone owing to the acoustic streaming effect and cavitation effect induced by ultrasonic treatment. Ultrasonic assisted Mg alloy joints with favorable mechanical properties were obtained through optimization of multiple experimental parameters. With the characteristic of plastic fracture, the tensile strength of the optimized butt joint reached to 239 MPa, which is equivalent to 93% of the tensile strength of the Mg alloy base metal. However, excessive ultrasonic power will destroy the stable solidification process of weld pool, resulting in the degradation of tensile strength.

Effects of ultrasonic vibration on resistance spot welding of transformation induced plasticity steel 780 to aluminum alloy AA6061

A newly developed joining technique, ultrasonic resistance spot welding (URW), where high frequency ultrasonic vibration is effectively integrated into resistance spot welding (RSW) process, has been applied for joining transformation induced plasticity (TRIP) steel 780 to aluminum alloy Al 6061. Comparing URW with traditional RSW, up to 300% increase in strength and more than 150% increase in displacement to failure is achieved. Light optical microscopy (LOM) and scanning electron microscopy (SEM) revealed cracks and wide interfacial debonded regions in conventional RSW AlFe welds. With the assistance of ultrasonic vibrations, these interfacial cracks are effectively removed and a thin AlFe intermetallic layer (IMC) of around 3 um thickness is formed. SEM images of the fractured surface revealed that ultrasonic waves eliminated the eggcrate morphology generally observed in RSW welds fractured surface, which is a typical representative of solidification cracking. In situ high speed videos showed that ultrasonic vibration can help break off surface contamination and oxides as well as improving wetting of melted aluminum over the AlFe interface.

Energy efficient piezoelectrically actuated transducer for direct-contact ultrasonic drying of fabrics

Current clothes drying technology is an energy-intensive process that involves blowing hot air across tumbling wet fabrics to evaporate water. To address the relatively low energy efficiency of this drying technique, a new cloth drying technology was proposed in our prior study. This technology utilizes high frequency ultrasonic vibrations to extract water from a fabric in the liquid phase, resulting in a dramatical reduction in energy consumption and drying time. A piezoelectrically actuated transducer was designed and fabricated. The transducer design was based on a piezoelectric actuator that excites axisymmetric resonant modes in a thin circular metal mesh. The device was constructed by bonding a piezoelectric ring to a thin metal mesh with a hole diameter of 120 µm. Test results demonstrated that the new ultrasonic transducer efficiently dried clothes at an order of magnitude lower resonant frequency compared with the previous commercial devices, 23 kHz versus 135 kHz. Also, the power consumption per area of the new transducer was an order of magnitude less than the commercial devices. Depending on operating conditions, the device was 3–24 times more efficient compared to the commercial ultrasonic transducers utilized in our prior ultrasonic clothes drying studies.

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.

Thawing of Frozen Tissue by Utilizing High-frequency Ultrasonic Vibration

Thawing of Frozen Tissue by Utilizing High-frequency Ultrasonic Vibration

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.

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.

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.

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.

Influence of ultrasonic vibrations on thermal diffuse scattering in X-ray dynamical diffraction conditions

A theory of thermal diffuse scattering (TDS) in a crystal disturbed by high frequency ultrasonic vibrations is considered. In this case additional X-ray reflexes (satellites) are formed which can be used for obtaining information about vibrational excitations in a crystal. By varying the incident angle one can excite all the satellites one after another and detect the variation in the TDS yield. The possibilities of the experimental observation of these phenomena will also be discussed.

Ultrasonic welding of metallic alloy glass to copper

Metallic glasses (MGs) with amorphous structures and tunable compositions have been considered excellent structural and functional materials, especially in the frontier fields of microelectromechanical systems (MEMS), biomedical engineering, energy conversion, etc. Making these materials into desired structures for different applications has always been one of the research focuses in the past decades. Due to high strength and poor plasticity at ambient temperature, MGs are difficult to be formed and manufactured by conventional approaches. Thermoplastic forming, utilizing the superplasticity property of MGs in supercooled liquid region, has been developed to fabricate micro-/nanofeatures. However, the thermal effect inevitably increases the risks of crystallization and oxidation of MGs during forming, leading to material performance degradation and limiting the process feasibility to specific composition systems of MGs. In view of this, a novel strategy proposed recently is to promote plastic deformation and forming of MGs by high frequency ultrasonic vibration at room temperature, which promises to avoid the shortcomings in thermal forming and extend the forming processes of MGs. In this review article, we would like to first discuss the forming mechanisms of supercooled MGs liquid, the joining of MGs and a variety of fabricated structures based on thermoplastic forming. After that, a concept of ultrasonic-assisted forming of MGs is introduced focusing on plastic behavior under high frequency vibration and the latest process advances including shear punching and manufacturing. Finally, the existing problems and the development prospects will be discussed to facilitate the further researches on MGs forming.