Effect Of Vibration Frequency Research Articles

MATHEMATICAL MODEL OF VIBRATION PROCESSING OF METAL DURING WELDING OF BILLETS

This article discusses methods for numerical measurement of the effect of vibration frequency on the physical properties of the metal. A literature review of known studies on the effect of vibration on the physical properties of metal. According to the wave theory of vibration, by determining the natural frequency of oscillations of the plastic flow, it is possible to intensify the process of metal processing by pressure and to achieve a reduction in the magnitude of the deformation force. The mathematical model of pipe welded connection in the conditions of vibration influence taking into account the assumptions necessary for approximation of calculations is offered. Particular attention was paid to the specific potential energy of a single layer, which consists of the potential energies of interaction of individual particles. The dependences presented in the work allow to make positive conclusions about the application of mathematical modeling in order to predict the level of residual stresses in welds.

Effects of mechanical vibration on melting behaviour of phase change material during charging process

Mechanical vibration exists in many thermal energy storage systems and thermal management systems. It is well-known that mechanical vibration can enhance heat transfer of thermal systems. However, the open studies on the effects of mechanical vibration on the performance of thermal energy storage and/or thermal management systems are quite sparse. To bridge the knowledge gap, the effects of vibration frequency and orientation of vibration axis on melting processes are investigated numerically. Three findings are reported for the first time: (1) for low frequency mechanical vibration ( ω ≤ 10 ), the enhanced mixing of molten phase change materials (PCMs) will accelerate the melting processes critically; (2) a higher vibration frequency ( ω ≥ 100 ) can cause an obviously faster charging speed, but the acceleration effect will become weak against the increasing of vibration frequency; (3) when the vibration axis is parallel to the gravity, the thermal response rate is the fastest. Especially, the present study answers a very interesting question: how does low frequency vibration ( ω ≤ 10 ) accelerate the charging processes? It is observed that the time averaged heat transfer rate under the low frequency vibration condition is lower than its counterpart without mechanical vibration. The knowledge learnt from this work can provide guides for many practical applications. • Effect of vibration frequency on melting process is revealed for the first time. • Effect of orientation of vibration axis on melting process is revealed for the first time. • The contributions of low frequency vibration to melting process are analysed from a new viewpoint.

Correction to: Effect of Vibration Frequency on Microstructure and Properties of Laser-Welded Inconel 718 Nickel-Base Superalloy

The name of coauthor Peilei Zhang was misspelled as “Peilie Zhang” in this article as originally published.

Effect of vibration frequency on the vibration-assisted densification for alfalfa

Densifying alfalfa into briquettes is one of the effective ways to increase its density and reduce the cost of storage and transportation. To explore the influence of vibration frequency on alfalfa briquetting, vibration-assisted compression tests with six vibration frequencies of 0, 9.52, 15.56, 21.24, 27.50, and 33.44 Hz were carried out. The results showed that the compression with vibration could reduce the maximum forming pressure and the energy consumption. The quality of alfalfa briquettes was improved compared with the compression without vibration. Within the range of test, when the vibration frequency was 21.24 Hz, the maximum pressure was the minimum, which was 5.83 MPa. In addition, the specific energy consumption was the lowest, which was 1374 J/g/cm3. The experimental results provided a basis for determining the optimum vibration parameters of alfalfa compression.

Vibration induced active rheology control for 3D concrete printing

3D concrete printing, an emerging automation technology for construction, requires the concrete to be flowable during pumping and extrusion but firm immediately after layer deposition. This study investigated an active rheology control using vibration to achieve these opposing requirements. The effects of vibration frequency and acceleration on rheological parameters of concrete were studied with different levels of nanoparticles in the mix. It was found that extrusion pressure and yield stress show less sensitivity to the peak velocity of the vibration up to a certain level and then they both decrease beyond this level. Also, certain level of nanoparticles inclusion found to double the reduction in extrusion pressure and yield stress. Buildability studies using 3D printers were conducted to demonstrate the active rheology control using vibration. The mechanical properties of the printed structures were also found to have improved when vibration rheology control was used.

Effect of vibration frequency on frictional resistance of brain tissue during vibration-assisted needle insertion

Deep brain stimulation (DBS) is an effective treatment for Parkinson's disease. The cannula insertion process plays an important role in DBS. The friction force during needle insertion influences the precision of the insertion and the degree of damage to the brain tissue. This paper proposes a method of longitudinal vibration assisted insertion to reduce the friction during insertion and improve the effects of the insertion. Cannulas were inserted into twenty eight pig brains at multiple frequencies and fixed amplitudes, and the resulting friction force was measured. On this basis, the LuGre model was used to analyze the friction force trend under vibration-assisted conditions. The frictional forces of vibration-assisted insertion with frequencies ranging from 200–1200 Hz and an amplitude of 1 μm were measured. The results show that the friction between the needle shaft and the tissue is smaller with vibration than without vibration. In this experiment, the friction is reduced by up to 24.43%. The friction force trend of vibration-assisted insertion conforms to the simulation results of the LuGre model.

Droplet Generation in a Flow-Focusing Microfluidic Device with External Mechanical Vibration.

The demand for highly controllable droplet generation methods is very urgent in the medical, materials, and food industries. The droplet generation in a flow-focusing microfluidic device with external mechanical vibration, as a controllable droplet generation method, is experimentally studied. The effects of vibration frequency and acceleration amplitude on the droplet generation are characterized. The linear correlation between the droplet generation frequency and the external vibration frequency and the critical vibration amplitude corresponding to the imposing vibration frequency are observed. The droplet generation frequency with external mechanical vibration is affected by the natural generation frequency, vibration frequency, and vibration amplitude. The droplet generation frequency in a certain microfluidic device with external vibration is able to vary from the natural generation frequency to the imposed vibration frequency at different vibration conditions. The evolution of dispersed phase thread with vibration is remarkably different with the process without vibration. Distinct stages of expansion, shrinkage, and collapse are observed in the droplet formation with vibration, and the occurrence number of expansion–shrinkage process is relevant with the linear correlation coefficient.

Magnetic resonance elastography of the supraspinatus muscle: A preliminary study on test-retest repeatability and wave quality with different frequencies and image filtering

The purpose of this study was to determine an optimal condition (vibration frequency and image filtering) for stiffness estimation with high accuracy and stiffness measurement with high repeatability in magnetic resonance elastography (MRE) of the supraspinatus muscle. Nine healthy volunteers underwent two MRE exams separated by at least a 30 min break, on the same day. MRE acquisitions were performed with a gradient-echo type multi-echo MR sequence at 75, 100, and 125 Hz pneumatic vibration. Wave images were processed by a bandpass filter or filter combining bandpass and directional filters (bandpass-directional filter). An observer specified the region of interest (ROI) on clear wave propagation in the supraspinatus muscle, within which the observer measured the stiffness. This study assessed wave image quality according to two indices, as a substitute for the assessment of the accuracy of the stiffness estimation. One is the size of the clear wave propagation area (ROI size used to measure the stiffness) and the other is the qualitative stiffness resolution score in that area. These measurements made by the observer were repeated twice at least one month apart after each MRE exam.This study assessed the intra-examiner and observer repeatability of the stiffness value, ROI size and resolution score in each combination of vibration frequency and image filter. Repeatability of the data was analyzed using the intraclass correlation coefficient (ICC) and 95% limits-of-agreement (LOA) in Bland-Altman analysis. The analyses on intra-examiner and observer repeatability of stiffness indicated that the ICC and 95% LOA were not varied greatly depending on vibration frequency and image filter (intra-examiner repeatability, ICC range, 0.79 to 0.88; 95% LOA range, ±23.95 to ±32.42%, intra-observer repeatability, ICC range, 0.98 to 1.00; 95% LOA range, ±5.10 to ±10.99%). In the analyses on intra-examiner repeatability of ROI size, ICCs were rather low (ranging from: 0.03 to 0.69) while 95% LOA was large in all the combinations of vibration frequency and image filter (ranging from: ±62.66 to ±83.33%). In the analyses on intra-observer repeatability of ROI size, ICCs were sufficiently high in the total combination of vibration frequency and image filter (ranging from 0.80 to 0.87) while the 95% LOAs were better (lower) in the bandpass-directional filter than the bandpass filter (bandpass directional filter vs. bandpass filter, ±28.81 vs. ±54.83% at 75 Hz; ±25.63 vs. ±37.83% at 100 Hz; ±34.51 vs. ±43.36% at 125 Hz). In the analyses on intra-examiner and observer repeatability of resolution score, the mean difference (bias) between the two exams (or observations) was significantly low and there was almost no difference across all the combinations of vibration frequency and image filter (range of bias: −0.11–0.11 and −0.17–0.00, respectively).Additionally, effects of vibration frequency and image filter on wave image quality (ROI size and resolution score) were assessed separately in each exam. Both mean ROI size and resolution score in the bandpass-directional filter were larger than those in the bandpass filter. Among the data in the bandpass-directional filter, mean ROI size was larger at 75 and 100 Hz, and mean resolution score was larger at 100 and 125 Hz. Taking into consideration with the results of repeatability and wave image quality, the present results suggest that optimal vibration frequency and image filter for MRE of the supraspinatus muscles is 100 Hz and bandpass-directional filter, respectively.

Reduction Method of the Residual Stress using Ultrasonic Vibration (Effect of Vibration Frequency on Fill Welding using SUS304 Stainless Steel)

Reduction Method of the Residual Stress using Ultrasonic Vibration (Effect of Vibration Frequency on Fill Welding using SUS304 Stainless Steel)

Development of AZ91/SiC surface composite by FSP: effect of vibration and process parameters on microstructure and mechanical characteristics

A surface composite layer enhances the mechanical characteristics of a surface while retaining the properties of the base material. Friction stir processing (FSP) is a method for forming surface metal matrix composites (SMMCs) that reinforce a surface with particles. In the current study, a new method entitled friction stir vibration processing (FSVP) was applied to form SMMCs on the surface of AZ91 magnesium alloy with SiC particles as the reinforcing particles. Contrary to FSP, in FSVP, the workpiece was vibrated normal to the processing line while the tool rotated and traversed. The microstructure and mechanical properties of friction stir (FS) and friction stir vibration (FSV) processed specimens were evaluated. Additionally, the effects of vibration frequency and process parameters on different characteristics of FS and FSV processed specimens were studied. The results showed that the stir zone grains for FSV processed specimens were finer than those for FS processed specimens, and the second phase particles (SiC particles) had a more homogenous distribution in the former specimens than in the latter specimens. This was related to the effect of workpiece vibration during FSVP, which increased the material deformation and led to enhanced dynamic recrystallization and the breakdown of agglomerated SiC particles. The results indicated that the stir zone grain size decreased, and the distribution homogeneity of the SiC particles increased as vibration frequency increased. It was also observed that the stir zone grain size increased, and the mechanical properties of the processed specimens decreased as tool rotation speed increased.

Effect of vibration frequency on primary phase and properties of grey cast iron fabricated by lost foam casting

The properties of gray cast iron (GCI) are affected by density of matrix, size of flake graphite and primary austenite. In this paper, the Y-type specimen of GCI was prepared by lost foam casting (LFC) with and without vibration, and the influence of vibration frequency on the density of matrix, size of primary phase, and properties of the GCI was studied. The results show that the length of the flake graphite and the size of the primary austenite in GCI firstly decrease and then increase with the increase of the vibration frequency. With a vibration frequency of 35 Hz, the length of the flake graphite is the shortest, the primary austenite is the finest and the density of the matrix is the highest. In addition, the tensile strength, elongation and hardness of the GCI firstly increase and then decrease with the increase of the vibration frequency, due to the refinement of the primary phase and the increase of the matrix density. In order to analyze the refinement mechanism of the primary phase of the GCI fabricated by the LFC with vibration, the solidification temperature fields of the GCI fabricated by the LFC with the vibration frequency of 0 and 35 Hz were measured. The results show that the vibration reduces the eutectic point of the GCI and increases the supercooling degree during the eutectic transformation. As a result, the length of the flake graphite and the size of the primary austenite in GCI fabricated by LFC with the vibration frequency of 35 Hz decrease.

Effect of Vibration Frequency on Laser Filler Wire Welded Joints

The effects of different vibration frequencies on the microstructure, residual stress, and fatigue life of welded joints are investigated using laser filler wire welding combined with mechanical vibration. The results show that the vibration frequency of 1055 Hz has a significant effect on the melting width of the laser welding with filler wire joint. The welds have three morphological features of columnar crystals, dendrites, and equiaxed crystals. In addition, the welds with 1055 Hz vibration frequency have the most equiaxed crystals and the highest hardness. The vibration frequency of 524 Hz increases the residual stress of the welded joint by 16%, whereas the vibration frequency of 1055 Hz reduces its residual stress by 8%. It can be shown by tensile experiments that the laser filler wire–welded joints have a higher tensile strength and greater elongation with increase in the vibration frequency. The fracture observation shows that the cleavage step appears in the crack propagation zone. Compared with the vibration frequency of 524 Hz, fatigue fracture at the 1055 Hz vibration has narrower fatigue striation spacing, lower crack growth rate, and higher fatigue life.

Effect of vibration frequency on settlement characteristic of reinforced embankment by geogrid with strengthened nodes using DEM simulation

Geogrid with strengthened nodes (GSN) is a new reinforcement system that is formed by attaching blocks of a certain thickness to the joints of the longitudinal and transverse ribs of an ordinary biaxial geogrid to form strengthened nodes. A series of discrete element method (DEM) simulations were performed to investigate the dynamic response of GSN-reinforced embankment at various vibration frequencies and compare the reinforcing effect of GSN with that of the ordinary geogrid. It was concluded that the settlement ratio of the loading platen at the top of the unreinforced and reinforced embankment decreases with the increase of the vibration frequency. As the frequency increases, the difference between the settlement ratios decreases, which is especially evident in the reinforced embankment. At the same frequency, GSN performs better in restricting the settlement ratio than the ordinary geogrid, and as the frequency increases, the reinforcing effects of both the ordinary geogrid and GSN decrease. The displacement fields of the simulated embankments were analyzed. It was found that the movement of soil particles below the loading platen is restricted due to the presence of the geogrid, resulting in less settlement of the loading platen and smaller lateral deformation of the embankment slope, compared with the unreinforced embankment. As for the GSN-reinforced embankment, the strengthened nodes provide resistance to soil particles, leading to a more effective reinforcing effect, so that the displacement vectors are even smaller.

Steady and unsteady aerodynamic forces on a long-span membrane structure

This paper reports the steady and unsteady (motion-induced) aerodynamic forces on long-span roofs based on computational fluid dynamics (CFD) analysis with a large eddy simulation (LES). Three types of roofs, i.e., flat, cylindrical, and suspended roofs, are tested. First, the wind pressures on a rigid flat roof in a smooth uniform flow and a turbulent boundary layer are computed. The computational model and method are verified by comparing the obtained wind pressure distributions on the roofs with previous experimental results. Next, a forced vibration test is performed to understand not only the wind pressures on and the flow around the vibrating roof but also the unsteady aerodynamic forces, which are represented by the aerodynamic stiffness and damping. In the test, the roof is forced to vibrate in the first antisymmetric mode. The effects of vibration frequency on the pressure distribution and unsteady aerodynamic forces are investigated. On the basis of the results, the stability of the roofs is discussed. Furthermore, the dynamic response of a flat roof is analyzed considering the fluid–structure interaction (FSI) to investigate the vibration mechanism of the roof in more detail.

Extraction process of charged droplets in ultrasonic electric propulsion system: An experimental study

As a novel propulsion technology, ultrasonic electric propulsion is mainly applied to micro-satellite platforms (<10 kg). In this work, effects of vibration frequency and typical operating conditions on extraction process of charged droplets in ultrasonic electric propulsion are investigated by an ultra-high speed imaging technique. A long-distance microscope coupled with an ultra-high speed camera (NAC HX-6) is also used. A solution of formamide and lithium chloride is employed as propellant. Experimental results show that mean diameters of charged droplets are 43.3 ± 4.2 µm (120 kHz), 76.2 ± 5.8 µm (60 kHz), and 101.4 ± 7.1 µm (25 kHz), respectively. Besides, the theoretical diameter values are calculated, which are close to experimental ones and both values decrease with the increase of vibration frequency. Meanwhile, experimental results indicate that the diameter of charged droplets increases as the propellant flow rate rises, and such effect is obvious when the flow rate is ranging from 3 to 10 ml/h. It is also found that charged droplets are not uniformly accelerated and their motion directions are also divergent.

Experimental Analysis on the Influence and Optimization of μ-RUM Parameters in Machining Alumina Bioceramic.

Fabrication of precise micro-features in bioceramic materials is still a challenging task. This is because of the inherent properties of bioceramics, such as low fracture toughness, high hardness, and brittleness. This paper places an emphasis on investigating the multi-objective optimization of fabrication of microchannels in alumina (Al2O3) bioceramics by using rotary ultrasonic machining (RUM). The influence of five major input parameters, namely vibration frequency, vibration amplitude, spindle speed, depth of cut, and feed rate on the surface quality, edge chipping, and dimensional accuracy of the milled microchannels was analyzed. Surface morphology and microstructure of the machined microchannels were also evaluated and analyzed. Unlike in previous studies, the effect of vibration frequency on the surface morphology and roughness is discussed in detail. A set of designed experiments based on central composite design (CCD) method was carried out. Main effect plots and surface plots were analyzed to detect the significance of RUM input parameters on the outputs. Later, a multi-objective genetic algorithm (MOGA) was employed to determine the optimal parametric conditions for minimizing the surface roughness, edge chipping, and dimensional errors of the machined microchannels. The optimized values of the surface roughness (Ra and Rt), side edge chipping (SEC), bed edge chipping (BEC), depth error (DE), and width error (WE) achieved through the multi-objective optimization were 0.27 μm, 2.7 μm, 8.7 μm, 8 μm, 5%, and 5.2%, respectively.

Effect of Road Vibrations on the Mechanical Properties of Olive Fruit During Transport

Post-harvest processes, such as transportation and packaging, should be carried out in such a way that less damage is made to the product. Inappropriate transport of fruits causes mechanical damage. Transport vibrations have a great effect on the extent of damage to agricultural products. In this research, the effects of road vibration on the mechanical properties of olive fruit, including fracture force, fracture energy and elasticity modulus were measured through pressure testing by the instrument before and after Vibration and results were checked. The effect of different parameters of vibrations caused by road transport (frequency, acceleration and time) on the mechanical properties of olive was investigated. Experiments were carried out at two levels of 7.5 Hz and 13 Hz, two acceleration levels of 0.3g and 0.7g and two levels of 30 and 60 minutes. The results of the data analysis showed that the effects of vibration frequency, vibration acceleration, vibration duration were significant on the amount of damage during vibration at the 1% level. The factors caused reduction in mechanical properties.

The Effects of Vibration Frequency and Amplitude on Serratus Anterior Muscle Activation During Knee Push-up Plus Exercise in Individuals with Scapular Winging

The Effects of Vibration Frequency and Amplitude on Serratus Anterior Muscle Activation During Knee Push-up Plus Exercise in Individuals with Scapular Winging

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.

Application of low frequency vibration to degassing of highly viscous shear-thinning fluids

The removal of unwanted gas bubbles is an important operation in many processes. In this paper, the mechanism of the degassing of highly viscous fluids by low-frequency vibration is studied numerically using the computational fluid dynamics (CFD). The effects of vibration frequency and amplitude on the degassing rate are investigated. The results show that the superimposed mechanical vibration largely affects the degassing rate of shear-thinning fluids but exerts no effect on that of Newtonian fluids. The de-gassing rate of shear-thinning fluids depends on the vibration frequency and amplitude. What’s more, low-frequency and small-amplitude vibration is particularly useful in re-moving gas bubbles from viscous shear-thinning fluids, however, high-frequency or large-amplitude vibration may intensify air entrapment and brings new gas bubbles into fluids.