Ultrasonic Vibration Frequency Research Articles

Effect of ultrasonic vibration-assisted laser cladding frequency on the microstructure and properties of Fe-0.5C-15Cr alloy cladding layers

In this paper, Fe-0.5C-15Cr wear and corrosion resistant alloy coating was prepared on 3Cr13 stainless steel surface by ultrasonic vibration assisted laser cladding technology. The effects of ultrasonic vibration frequency on the microstructure, microhardness and corrosion resistance of the coating were studied. The results show that the length of the dendrites of the cladding layer decreased significantly after ultrasonic vibration is applied, the grains size is refined significantly, and the morphology of the grain boundary carbides changed from fishbone-like to short rods, when the vibration frequency is 20.2 kHz, the grain refinement is the most significant, and the orientation of the dendrites is obviously weakened. The hardness of the applied ultrasonic vibration specimens increased by 10–20 HV0.2 relative to the non-ultrasonic specimens, with the increase of vibration frequency, the hardness of the cladding layer firstly increased and then slightly decreased, and the peak appeared at 20.2 kHz. The coefficient of friction of the specimens when the ultrasonic frequency of 20.2 kHz is applied is lower than that of the specimens with non-ultrasonic frequency by 12.8 %, and the abrasive wear rate is reduced by 14.3 %. After ultrasonic vibration, the pitting potential of the cladding layer increases, the dimensional passivation current density decreased, the width of the passivation zone becomes wider, and the intergranular corrosion reactivation rate decreased, When the ultrasonic frequency is 20.2 kHz and 20.4 kHz, the pitting corrosion resistance and intergranular corrosion resistance of the cladding layer are significantly improved. This is because the cavitation effect, resonance effect and acoustic flow effect of ultrasonic vibration promote the non-uniform nucleation, refine the dendrites and intergranular carbides, and promote the redistribution of the corrosion-resistant element Cr in the in-grain martensite and grain boundary carbides, increasing the content of Cr in the matrix, and thus improving the wear resistance and corrosion resistance of the cladding layer.

Ultrasonic tool shank with multiple vibration mode for micro-nano drilling: Design, optimization and experiment

The machining effects of hole drilling is limited by merely changing the amplitude. Adjusting ultrasonic vibration frequency to expand the matching range of machining parameters optimization is necessary to improve hole drilling effects. Therefore, the design, optimization, and experiment evaluation for a novel integrated, fined, low-cost dual-frequency ultrasonic tool shank is proposed, which can work in three vibration modes for micro-nano precision drilling. The principle of the dual-frequency ultrasonic transducer is introduced. The electro-mechanical equivalent circuit model with step horn is applied to study the dual-frequency characteristics. The transducer displacement equation model based on the wave equation theory is deduced to find the shared vibration node of the first and third frequency. Sensitivity analysis by equivalent circuit model and Finite element method (FEM) simulation of the key parameter is both conducted to optimize ultrasonic transducer geometry dimension. The vibration node of mounting flange is specified in an identical position for the dual vibration modes. A prototype of ultrasonic tool shank is fabricated and evaluated in experiments. It demonstrates that the dual working frequency of the ultrasonic transducer is 34.9 kHz and 104.5 kHz in the first and third mode resonant vibration, which is benefit to the low and high frequency drilling. Three working modes of the low, high, and coupling frequency vibration is measured by a self-developed ultrasonic generator. When 40 V voltage is excited, the vibration amplitudes of the low and high frequency are 17.8 µm, and 9.3 µm, respectively, which can meet with the drilling requirement. Moreover, the coupling vibration with the low and high mode are excited simultaneously, and the motion trajectory of the coupling vibration is observed in a “M” shape, which is a novel trajectory for the precision micro-nano drilling. Micro drilling experiments show that the 35 kHz ultrasonic vibration drilling can achieve better machining effect than conventional drilling (CD). The 105 kHz ultrasonic drilling outperforms the CD, 35 kHz and coupling ultrasonic drilling at cutting force reduction. The coupling ultrasonic vibration drilling achieves the lowest chipping diameter. It is to be noted that the 105 kHz-8 µm produce the fined smoothly surface. The 35 kHz, 105 kHz and coupling ultrasonic drilling can produce better surface micro morphology with less quantity and size of craters than that of CD.

Effect of Ultrasonic Vibration on Tensile Mechanical Properties of Mg-Zn-Y Alloy

Ultrasonic vibration assisted (UVA) plastic forming technology has proven to be a highly effective processing method, particularly for materials that are challenging to deform. In this research, UVA tensile tests were carried out on Mg98.5Zn0.5Y1 alloy at different vibration frequencies and amplitudes. The experimental results indicate that, compared with conventional tensile tests, the yield strength and tensile strength of Mg98.5Zn0.5Y1 alloy exhibit a decrease. Furthermore, the application of ultrasonic vibration demonstrates an ability to enhance the material’s elongation and plasticity. In order to further predict the stress-strain relationship in the metal tensile process, a hybrid constitutive model coupling the frequency and amplitude of ultrasonic vibration was developed based on the modified Johnson Cook model. The calculated results of the constitutive equation are in good agreement with the experimental results, indicating that the established constitutive equation can accurately predict the trend of alloy stress change at different amplitudes and frequencies. It establishes a theoretical foundation for scrutinizing the deformation mechanisms of the alloy under ultrasonic vibration. Furthermore, Abaqus finite element analysis software was employed to simulate and analyze the UVA tensile process, elucidating the impact of ultrasonic vibration on stress distribution, strain patterns, and material flow in the tensile behavior of Mg98.5Zn0.5Y1 alloys.

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.

Removal mechanism of NiTi alloy by ultrasonic assisted polishing based on molecular dynamics simulation

NiTi alloy has been widely used in mechanical and electronic, aerospace, energy and transportation, petrochemical industry and various biomedicine fields due to its unique super elasticity and shape memory effect. The traditional polishing method of NiTi alloy has the problems of poor consistency of polishing quality and low efficiency, especially for some NiTi alloy with complex shapes, the traditional mechanical contact method is difficult to polish its inner surface. For some NiTi alloys prepared by additive manufacturing, due to the existence of “step effect” and “spherodizing effect”, there are unmelted powder particles on the surface, and it also needs to be polished. However, it is necessary not to destroy the original structure shape and performance, but also to achieve high efficiency, high quality and consistent polishing, so it is a technical problem. Its polishing process is still unclear, and the polishing effect needs to be improved. Therefore, in this paper, molecular dynamics method was used to study the polishing process of ultrasonic vibration diamond abrasive particles on NiTi alloy. The influences of ultrasonic vibration frequency, ultrasonic amplitude and temperature on polishing force, average friction coefficient, surface morphology, structural evolution and dislocation distribution were studied, and the microscopic material removal mechanism was revealed. The results indicate that as the ultrasonic frequency increases, the number of normal force fluctuations increases, and the elastic and plastic deformation during the scratching process also increases. With the increase of ultrasonic amplitude, the average friction coefficient decreases, and the adoption of larger vibration amplitude is conducive to the scratching process, and the average friction coefficient will increase when the temperature increases, which is not conducive to the polishing process.

On the cooling performance and entropy generation characteristics of a heat sink under ultrasonic vibration: Exploring the impact of porous medium

Ultrasonic vibration and porous medium utilization are both proven to be beneficial techniques to improve cooling performance of heat sinks. Present work aims at exploring the impacts of using porous medium in heat sinks under ultrasonic vibration effect on the cooling performance and entropy generation characteristics, hence, the interrelation of these two techniques is evaluated. Simulations are performed for a constant Reynolds number (Re=2000) and ultrasonic vibration frequency (f = 30 kHz), whereas five different porosities (ε=0.75 to 0.95) along with five different pore diameters (dp=1 to 17 mm) determining the permeability of the porous structure are considered. The results are compared to the non-porous case to determine the effects of porous medium on the ultrasonically vibrated heat sink. It is found that using porous medium increases convective heat transfer coefficient by up to 84.5% attaining a temperature reduction of 10.22 K. Low porosity along with high pore diameter attains an effective cooling, while high porosity with high pore diameter ensures lower pumping power requirement, which is only 1.2-folds of the non-porous case. Frictional entropy generation rises by up to 23% due to porous structure restricting fluid flow depending on its porosity and permeability, while thermal entropy generation can be even decreased below that of non-porous case by 8% with appropriate choice of parameters. Yet, considering the total irreversibility, the frictional entropy generation is significantly dominant compared to the thermal entropy generation. Overall, using ε=0.95 and dp=17 mm along with 30 kHz of ultrasonic vibration is recommended for significantly enhanced heat transfer together with lowest possible pressure drop penalty and low thermal entropy generation.

Study of wetting promotion mechanism of Sn/Cu interface assisted by ultrasonic vibration from molecular dynamics simulation and experiments

In this study, molecular dynamics method was used to simulate ultrasonic vibration by applying periodic displacement to the fixed substrate, and the wetting promotion mechanism of liquid Sn/solid Cu system under ultrasonic vibration was studied. The results indicated that whether wetting with or without ultrasonic vibration, the contact angle decreased and interfacial reaction intensified with the increase of temperature. The contact angle with ultrasonic vibration was smaller than that without ultrasonic vibration, and the difference between contact angles decreased with the increase of temperature. In addition, the frequency of ultrasonic vibration had a significant effect on the wettability. The intermetallic compound (IMC) layer was broken by 250 GHz ultrasonic vibration. However, low-frequency ultrasonic vibration was not enough to break the IMC layer, and the influence on interface was mainly reflected in promoting the spreading of precursor film and the interface reaction. In addition, the experimental results at different temperatures showed that ultrasonic vibration improved the wettability. The wetting promotion mechanism: ultrasonic vibration introduced alternating pressure and tension, which accelerated the diffusion of atoms, promoted the interface reaction. And ultrasonic vibration broke the reaction layer and promoted the dissolution and diffusion between solid-liquid atoms, the wettability of Sn /Cu system was improved.

Physico-Chemical Substantiation of Obtaining an Effective Cement Composite with Ultrafine GGBS Admixture

To solve a number of problems in construction materials science, composites with nano and ultrafine admixtures were analyzed. Their properties were studied, taking into account the variants of homogenization and stabilization of the system. To characterize the processes of the structure formation of a new material, mathematical methods were also applied. According to the literature review, the aim of the work was formulated. The subject of this research is to conduct physico-chemical studies that characterize the processes occurring during the homogenization and stabilization of the cement system with GGBS components and to establish the effect of the admixture on the properties of the composite. To achieve this goal, an ultrafine admixture based on GGBS was obtained, and the possibility of its introduction into the cement system in the form of a stabilized suspension instead of mixing water was considered. To provide increased characteristics of cement stone modified with the ultrafine admixture, a number of tests were carried out to study homogenization and stabilization of fine slag particles in suspension. The ultrasonic processing parameters were defined to provide uniform distribution of fine slag additive in the suspension: the processing time is 15–20 min, the frequency of ultrasonic vibrations is 44 kHz, the temperature of the dispersed medium is 25 ± 2 °C. To define physical and chemical processes appearing during the introduction of fine slag into water and water-polymer dispersed medium, the mechanism of interaction between fine slag and water was studied. In addition, the mechanism of chemisorption on the surface of fine slag particles and the stabilization mechanism of ultrafine slag particles with a plasticizer was studied to form the concept of aggregate and sedimentation stability of slag particles in suspension. It was found that the stabilization of fine slag particles by a plasticizer is significantly influenced by the hardness of water. The higher the water hardness, the more plasticizer required to stabilize the fine slag particles. At the same time, it was established that the concentration of the plasticizer should not exceed the critical micelle concentration value. If it is exceeded, the plasticizer solution transforms into the micellar colloidal system, and the stabilization of fine slag suspension will not occur. The studies of homogenization and stabilization of the slag suspension allowed the authors to substantiate the possibility of uniform distribution of fine particles in the cement matrix, followed by the formation of a denser and stronger cement stone structure. Cement-sand samples based on Portland cement (OPC) and slag-Portland cement (SPC) with GGBFS admixture showed higher compressive and flexural strength characteristics in the initial hardening periods and at 28 days. It was found that modified samples are more stable in an aggressive medium. On the 90th day of exposure, the resistance coefficient was 0.9 for a modified sample based on OPC and 0.98 for a modified sample based on SPC. The increased sulfate attack resistance of the samples is due to the formation of a dense stone with reduced porosity. It is noted that the porosity of modified OPC samples decreases by 14% and by 18% for SPC-based modified samples compared to the control sample at 28 days. Due to the fact that pores in the cement stone are blocked with hydration products, which make the structure of the cement stone denser, the filtration of aggressive solutions deep into its structure is difficult. Thus, the obtained concrete based on a cement composite with ultrafine slag can be applied as a protective layer of steel reinforcement in a reinforced concrete structure.

Effect of ultrasonic vibration on residual stress in plasma cladding of iron-based alloy

To explore the effect of ultrasonic vibration power and frequency on the residual stress of single-channel iron-based alloy plasma cladding, the single-factor ultrasonic vibration plasma cladding test was designed, and ten groups of single-channel iron-based alloy cladding samples under different process parameters were studied. The drilling method was used to measure the residual stress of the substrate at the beginning, middle and tail positions of each sample cladding layer. The residual stress of the substrate was analyzed and the significant characteristics of the effect of ultrasonic vibration power and frequency on the residual stress at different positions were explored using variance analysis. The results show that the residual stress is significantly reduced after applying ultrasonic waves. When the ultrasonic frequency is constant and the ultrasonic power is 240 W, the residual stress of the formed sample is the smallest. Compared with the unapplied ultrasonic assistance, the residual stress in the X direction is reduced by 62.56%, and the residual stress in the Y direction is reduced by 63.23%. When the ultrasonic power is constant and the ultrasonic frequency is 28 kHz, the residual stress of the formed sample is the smallest. Compared with the unapplied ultrasonic assistance, the residual stress in the X direction is reduced by 17.23%, and the residual stress in the Y direction is reduced by 19.79%. The ultrasonic power significantly affects the middle part of the substrate, and the ultrasonic frequency significantly affects each point of the substrate.

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 Vibration Frequency on Ni-Based Alloy Cladding Layer

In order to maximize the performance of the nickel-based cladding layer without adding a reinforcing phase, ultrasonic vibrations of different frequencies are assisted in the laser cladding process. The morphology of the cladding layer was analyzed by a metallographic microscope, the microstructure of the cladding layer was analyzed by SEM, the element segregation of the cladding layer was analyzed by EDS energy spectrum, and the microhardness of the cladding layer was tested by a microhardness tester. Hardness and friction-wear performance of the cladding layer were tested using a friction and wear tester. The test results show that the appropriate ultrasonic frequency can obviously refine the microstructure of the cladding layer, the hardness and wear resistance of the cladding layer have been significantly improved due to the refinement of the structure, and it has a good fine grain for the cladding layer. The strengthening effect maximizes the performance of the cladding layer.

EFFECT OF ULTRASONIC VIBRATION ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF ADC12 ALUMINUM ALLOY BY PERMANENT MOLD CASTING

In this study, the effect of ultrasonic vibration on mold filling ability, microstructure, and mechanical properties of the aluminum alloy during solidification is investigated. Microstructure and mechanical properties were compared with casting without ultrasonic. Grain refinement and an increase in mechanical properties were obtained due to the ultrasonic vibration. The material used for the research was ADC12 aluminum alloy, and the frequency of ultrasonic vibration was 20 kHz. The casting was carried out in SKD11 steel molds. It was found that the ultrasonic mold vibrated casting has less porosity , fine grain and improvement in mechanical properties as compared to the casting without ultrasonic mold vibration. Where the tensile strength increased by about the tensile strength increased by 20% at 660oC and 9% at 700oC while the hardness changed insignificantly.

Identification of self-lubricative mode for the ultrasonic treated AA6061-B4C-CNT hybrid composites

This research investigates the self-lubricative behavior of boron carbide (B4C) and carbon nanotube (CNT) reinforced 6061 aluminium alloy hybrid composites. Hybrid composites were prepared by varying the volume percentages (5–15%) of B4C and CNT. Novel ultrasonic vibration (frequency of 20 kHz and power of 2.5 kW) assisted stir casting process was used for fabricating hybrid composites. A pin-on-disc type tribometer mounted with EN-8 as the counterface material was used to evaluate the friction and wear behavior of hybrid composites under dry sliding conditions. Normal loads ranging from 15–45 N and sliding speeds ranging from 1–2 m/s were applied during the experiments. The self-lubricative properties of different hybrid composites were assessed through the examination of the worn surface of pins using surface characterization techniques such as Scanning electron microscopy, Electron dispersive spectroscopy and Raman spectroscopy. The experimental results indicated that the addition of CNT particles increased the hardness of hybrid composites. The matrix strengthening efficiency of CNT was found to be greater at 10 vol.% of B4C, indicating a maximum hardness ranging from 102 to 109 VHN. In comparison, 10 vol.% of CNT hybrid composites showed superior tribological performance at all wear testing conditions. The mode of wear of hybrid composites suggested by the analysis on the worn pin surface was as follows: Scarce (5 vol.% CNT), Tribolayer (10 vol.% CNT) and Fracture (15 vol.% CNT).

Designing and Calculating the Nonlinear Elastic Characteristic of Longitudinal-Transverse Transducers of an Ultrasonic Medical Instrument Based on the Method of Successive Loadings.

This paper presents a numerical method for studying the stress–strain state and obtaining the nonlinear elastic characteristics of longitudinal–transverse transducers. The authors propose a mathematical model that uses a direct numerical solution of the boundary value problem based on the plain curved rod equations in Matlab. The system’s stress–strain state and nonlinear elastic characteristic are obtained using the method of successive loadings based on the curved rod’s linearized equations. For most ultrasonic instruments, the operating frequency of ultrasonic vibrations is close to 20 kHz. On the other hand, the received own oscillation frequencies are close to the working range. Using the method of successive loadings in the mathematical complex Matlab, a numerical calculation of the stress–strain state of a flat, curved rod at large displacements has been carried out. The proposed model can be considered an initial approximation to the solution of the spatial problem of the longitudinal–torsional transducer.

Analysis of the high-efficiency and low-damage abrasive processing mechanism for SiC based on the SPH simulation of single-grain indentation and scratching

During the wafer fabrication procedure, abrasive machining occupies a large proportion in time and economic cost, mainly including grinding, lapping, and polishing. The third-generation semiconductor materials, represented by SiC, have the properties of high hardness, large brittleness, and strong chemical inertness, which make abrasive machining more challenging. To improve the machining efficiency and quality, this paper applied the smoothed particle hydrodynamics (SPH) method to simulate the machining behavior of single abrasive grain for SiC wafer. The micro-mechanical mechanisms of the main influencing parameters, such as velocity, depth, and angle, were studied in abrasive machining for SiC wafer. First, it is proved that using SPH coupled with a finite element to study the mechanical effects of abrasive machining for SiC wafer is a feasible and useful method. Then, the explanations for the beneficial effects of ultrasonic vibration-assisted machining, high-speed machining, and other abrasive machining are provided through the analysis of the simulated results. In addition, the optimization basis for parameters such as scratching velocity, scratching depth, and ultrasonic vibration frequency is obtained. This research provides a good insight into implying the micro-mechanical mechanisms of abrasive machining and achieving the optimization for the abrasive machining of hard-brittle wafer materials, which help avoid the shortcomings of experimental research and produce economic benefits.

The first micro thrust measurement of the ultrasonic electric propulsion system

The Ultrasonic Electric Propulsion system is mainly used in space missions within the limits of 50 kg, and employs capillary standing waves as emitters to extract charged droplets in electric field. Due to multi-physics field such as ultrasonic vibration, liquid mechanics and electrostatic field in the Ultrasonic Electric Propulsion system, its thrust prediction always faces a big challenge. In this work, the thrust of Ultrasonic Electric Propulsion system is first measured by a measurement platform, and the test results are 565.23 μN, 715.65 μN and 842.73 μN with an accuracy in the order of 10% at 5 kV, 7 kV and 9 kV, and a flow rate of 5 ml/h and ultrasonic vibration frequency of 120 kHz. The test results also indicate that the thrust value increases with extraction voltage in the same flow rate with propellant and vibration frequency. Besides, the vacuum emission plume of Ultrasonic Electric Propulsion system is first investigated by a high-speed imaging technique, which reveals different emission conditions at different time such as parabolic emission trajectory and varied plume angles.

Optimal parameters of processing wheat grain in an ultrasonic installation

The article deals with the issues related to the process of grain processing to accelerate the process of wetting during simple grinding into wallpaper flour and decontamination of grain during storage with ultrasonic intensification of the process. A mathematical simulation of the grain processing process was carried out using the Statistica.10 program. The optimal operating parameters of the preparation of wheat grain for simple grinding were selected: water temperature – 300C, processing time – 40 seconds, the frequency of ultrasonic vibrations – 18-18.2 kHz, the intensity of the ultrasonic field – no more than 1 W/cm2.

Experimental study on influence of ultrasonic vibration on forming limit

Applying ultrasonic vibration in sheet metal forming can change its forming mechanism and improve its formability. The uniaxial tensile and bulging forming limit experimental setups were designed to study the ultrasonic vibration and forming limit relationship induced by ultrasonic excitation, and the results under different experimental conditions were analyzed. It was found that ultrasonic vibration has different effects on the left and right sides of forming limit diagram (FLD). Under the same ultrasonic vibration frequency, the maximum increment of left and right major limit strain is about 9.3% and 8.7%, respectively. The former is larger than the latter, and the strain increment increases with the increase of ultrasonic vibration frequency, but the basic shapes of FLD are unchanged.

��������� ������� �������� ������� �������������� ����������

The economic performance of ship power plants is directly dependent on fuel consumption. Consumption is determined by the completeness of fuel combustion, which is influenced by many factors, one of which is the component composition. High molecular weight compounds, resins and asphaltenes contained in marine fuels are poorly flammable. They also form a coarse dispersed phase in the fuel, which complicates the process of hydrocarbon oxidation and leads to a decrease in its efficiency. It is known that ultrasonic influences increase the degree of fuels dispersion. The purpose of the work is to identify the regularities of ultrasound effect on the physicochemical indicators of distillate marine fuel of the DMA brand, which determine its operational properties: flammability, combustibility and pumpability. Experimental studies on the processing of marine fuel are carried out on ultrasonic devices LUK-0.125/50-O and Volna UZTA-0.4/22- 014 at a frequency of 50 and 22 kHz, respectively. For the theoretical substantiation of the observed effects, changes in the dispersed and structural-group composition of marine fuel are studied. The analysis of indicators in accordance with the regulatory documents is carried out. The greatest changes in all studied parameters are noted at an ultrasonic vibration frequency of 50 kHz. It is found that, in comparison with the initial sample, the kinematic viscosity decreases by 15 % after ultrasound exposure. The fuel density decreases by 0.002 kg / m3, the flash point of the fuel drops by 5 °C, and the cetane number shows a tendency to decrease by 2 points. The average particle size of the dispersed phase decreases by 12 %. An explanation for the improvement of the investigated fuel indicators on the basis of an increase in its degree of dispersion and redistribution of structural-group components is proposed. Ultrasonic treatment of marine fuel (50 kHz, 100 W, 43 s), carried out before feeding it to the engine on the fuel line in front of the filter and high-pressure pumps, can be used to improve the operational properties of the fuel and, consequently, reduce its consumption.

Research on ultrasonic-assisted multi-point stretch bending process of aluminum profile

The tensile and bending process of asymmetric L-shaped aluminum alloy profile is studied by the Abaqus software using the finite element numerical simulation method. The geometric parameters of the ultrasonic-assisted vibration multi-point die (UMPD) and the law of influence on the stress-strain and spring-back of the L-section profile after bending are studied. The results show that the UMPD can reduce the forming stress of the profile during plastic deformation, and the stress-strain distribution of the aluminum profile is more uniform. The changes in the ultrasonic vibration frequency and amplitude of the mold are beneficial to reduce the spring-back of aluminum profiles. The ultrasonic process parameters with a vibration frequency of 20 kHz and an amplitude of 0.02 mm have the best effect on suppressing spring-back, which is reduced by 20.6% compared to the case of no ultrasonic application. Finally, it is verified by experiments that the experimental results are basically consistent with the simulation results, and the changing trend of spring-back deformation is consistent.