Effects Of Vibration Parameters Research Articles

Insight into the effect of vibration parameters on deformation mechanism during scratching of nanograin iron alloy by molecular dynamics

Molecular dynamics simulations were employed to study the deformation behavior and microstructure evolution of nanocrystalline iron alloy during vibration-assisted scratching. The mechanical properties of the plastic deformation layer after scratching were tested by uniaxial tension. The results show that dislocation multiplication and twinning occur sequentially during loading, while dislocation rebound and detwinning occur during unloading. High stress induces dislocation multiplication. High strain rate facilitates the formation of deformation twins. Under the inhibitory effect of deformation twins on dislocation activity and the elastic recovery of the surface, dislocation density decreases with increasing frequency but initially increases and decreases with increasing amplitude. The plastic deformation layer at 10 GHz frequency and 1 nm amplitude exhibits optimal yield strength due to dislocation and nanotwin strengthening.

Prediction and optimization of screening performance of three-deck vibrating screen based on surrogate model

ABSTRACT The three-deck vibrating screen can separate the material into various particle sizes. There are a few types of researchers on the screening efficiency and processing capacity of multideck vibrating screens. In this work, the discrete element method was used to simulate the screening process of the three-deck vibrating screen under different vibration parameters (frequency, amplitude, and inclination angle) and a prototype experiment was carried out. The effects of vibration parameters on the screening performance were analyzed based on the orthogonal design of experiments. An approximate model, the Kriging model, was used to replace the simulation process for further optimization. Then, an optimization algorithm conducted multiobjective optimization, and three sets of optimization solutions were obtained via a traversal approach. In addition, the three optimized vibration parameters were verified by simulation. There is a guideline for the design of vibration parameters of the multideck vibrating screen.

Effect of vibration parameters and wall friction on the mixing characteristics of binary particles in a vertical vibrating container subject to cohesive forces

The effect of particle cohesion, vibration parameters, and wall-particle friction conditions on the mixing process of binary spherical particles in a vertical vibrating container were studied by the discrete element method. The phenomena in the simulation can be explained by three mechanisms: void filling, convection, and self-organization. The results show that the mixing rate decreases with the increase of particle cohesion. Increasing the amplitude can increase the mixing rate, but the effect of improvement is no longer obvious when the amplitude exceeds a threshold. There is an optimal vibration frequency, and a higher or lower frequency will lead to the reduction of the mixing rate. The macro convection caused by the strong wall friction can promote the flow and disaggregation of particles, but also cause the segregation that large particles gather in the center of the convection unit and thus reduce the mixing index. The degree of segregation is approximately linearly related to the shear force difference from the sidewall to the center of the container. Cohesion changes the segregation by influencing this difference. Under proper conditions, the segregation increases first and then decreases with the increase of cohesion. The expected mixing degree can be obtained by selecting appropriate wall friction conditions and particle cohesion. • Mixing of binary particles depends on vibration parameters, wall friction and particle cohesion. • The strong wall friction effect leads to the convective segregation of particles. • The shear force difference has a linear negative correlation with the segregation. • There is an upper limit to the effect of promoting mixing by increasing amplitude. • There is an optimal value by changing frequency to promote mixing.

Effect of vibration parameters on the material removal characteristics of high-entropy alloy in scratching

Although vibration-assisted scratching achieves higher machining efficiency than conventional scratching, its microstructural behavior is still unclear. In the present work, the deformation behavior and microstructural growth of monocrystalline CoCrFeNiCu high-entropy alloy during the vibration-assisted scratching through molecular dynamics simulation are investigated. The expected result shows that the vibration-assisted scratching effectively decreases the total force compared to the conventional scratching. The increase in the vibration amplitude and frequency leads to the reduction in the total force, which is advantageous in scratching. The shear strain concentration region in vibration-assisted scratching is larger than that of conventional scratching due to the expansion of the scratched area. Besides, the increase in vibration amplitude and frequency leads to a corresponding increase in shear strain and residual stress. The vibration-assisted scratching produces a larger high-temperature zone than the conventional scratching, and the increase of vibration frequency also results in an increase in the scratched zone temperature, which has a positive effect on easier machining. The microstructure evolution shows that Shockley partial dislocations account for the majority of the total dislocations. Moreover, the scratching with a large vibration amplitude and frequency removes more material. Therefore, insights into scratching behavior at the atomic level can aid in the optimization of the vibration-assisted machining process.

Design of conveyor separation device for potato harvester and analysis of its vibration characteristics

In view of the influence of vibration factors on the vibration characteristics of potato harvester, to study the effect of vibration parameters on the dynamic characteristics of the system and harvested potato quality, in this paper an indoor conveyor separation device for potato harvester with adjustable two-way synchronous conveying vibration parameters was designed. The device, with double-side chain drive to improve conveying efficiency and replaceable eccentric parts to change vibration parameters, allows the system to harvest potatoes under optimal working conditions. A simulation analysis of a dynamics model of the system, which was first established, was carried out. A potato soil separation test was conducted using the vibration testing system and acceleration sensor, and its data was compared with the simulation data to verify the correctness of the model. The results showed that the eccentricity, rotation speed, and inclination had an impact on the potato-soil separation rate and the vibration of the system. The analysis showed that the system had a higher potato-soil separation rate and slighter vibration under optimal working conditions, that is, eccentricity of 0.023 m, rotation speed of 130 r/min, and inclination of 26∘.

Effects of whole-body vibration on driver drowsiness: A review

Introduction: Whole-body vibration has direct impacts on driver vigilance by increasing physical and cognitive stress on the driver, which leads to drowsiness, fatigue and road traffic accidents. Although sleep deprivation, sleep apnoea and alcohol consumption can also lead to driver drowsiness, exposure to steady vibration is the factor most readily controlled by changes to vehicle design, yet it has received comparatively less attention. Methods: This review investigated interrelationships between the various components of whole-body vibration and the physiological and cognitive parameters that lead to driver drowsiness, as well as the effects of vibration parameters (frequency, amplitude, waveform and duration). Vibrations transmitted to the driver body from the vehicle floor and/or seat have been considered for this review, whereas hand-arm vibration, shocks, acute or transient vibration were excluded from consideration. Results: Drowsiness is affected by interactions between the frequency, amplitude, waveform and duration of the vibration. Under optimal conditions, whole-body vibration can induce significant drowsiness within 30 min. Low frequency whole-body vibrations, particularly vibrations of 4–10 Hz, are most effective at inducing drowsiness. This review notes some limitations of current studies and suggests directions for future research. Conclusions: This review demonstrated a strong causal link exists between whole-body vibration and driver drowsiness. Since driver drowsiness has been established to be a significant contributor to motor vehicle accidents, research is needed to identify ways to minimise the components of whole-body vibration that contribute to drowsiness, as well as devising more effective ways to counteract drowsiness. Practical Applications: By raising awareness of the vibrational factors that contribute to drowsiness, manufacturers will be prompted to design vehicles that reduce the influence of these factors.

Experimental Study on Uniaxial Compression Behavior of Fissured Loess Before and After Vibration

Fissured loess is one of the sources of geological hazards such as landslides and collapse under dynamic load. In this study, acrylic pipes with an inner diameter of 62 mm were processed into molds with different inclination angles (α = 0°, 15°, 30°, 45°, 60°, and 90°), and soil samples with preset fissure angles were prepared in two parts, i.e., loess block and weak interlayer. The sample was first vibrated by a test bench with sinusoidal waveform output, followed by uniaxial compression tests to investigate the mechanical properties of fissured loess before and after vibration. Results indicate that the failure mode of fissured loess is independent of the vibration disturbance; four types of failure modes were found after vibration, i.e., compressive fracture failure at α = 0° and 15°, slip failure at α = 60°, slip-fracture coupled failure at α = 45°, and compressive shear failure at α = 30° and 90°. The effect of vibration parameters on the stress–strain curve of fissured loess is mainly reflected in the decrease of both peak strength and initial elastic modulus. U-shaped changes of uniaxial compressive strength were observed in the ranges of 0°–45° and 45°–90°, respectively.

Effects of vibration parameters on the interfacial adhesion system between soil and metal surface

In actual preparation of arable lands, the soil easily adheres to soil-engaging components of tillage machinery and affects the plowing efficiency and quality, thus leading to low traction efficiency and high power consumption. It has been proposed that vibration can effectively reduce the adhesion of soils to the soil-engaging components in field operation. Here, in order to explore the vibration response characteristics of soils and the mechanism for soil detachment under sine wave vibration, a vibration detachment measurement system of soils was assembled with an acceleration sensor, an electric vibration generator, a power amplifier and a data acquisition system. The measurement system was then used to study the effects of three vibration characteristic parameters (amplitude, frequency and time) on the interfacial adhesion system between soil and metal surface (ASSM) in both tangential and normal directions. Taking the soil detachment rate as a representative characteristic of ASSM, the effect of each factor was analyzed through single-factor experiments. The optimal interval of each vibration parameter was determined based on the experiment results. According to the orthogonal experimental design and analysis, we established a mathematical model for the relationship between the vibration soil detachment rate and the vibration parameters, as well as identified their primary and secondary order and interaction effect on the soil detachment rate. As determined by response surface analysis, the optimal combination of parameters for soil detachment rate in the tangential direction is vibration amplitude of 7.99 g, vibration frequency of 42.87 Hz and vibration time of 26.03 s, and that in the normal direction is vibration amplitude of 9.00 g, vibration frequency of 59.76 Hz and vibration time of 88.20 s. The relative errors of the optimization results are 1.05% and 2.65%, respectively, which are generally consistent with the prediction results of regression equation. These results indicate that the mathematical model can be used to predict and evaluate soil adhesion under vibration. Therefore, the soil detachment performance of ASSM can be enhanced by a reasonable setting of vibration parameters, which may be of great significance for improving the working quality and efficiency of tillage machinery.

Simulation of particles screening in pulsating negative pressure shale shaker by coupling CFD and DEM

PurposeThe purpose of this paper is to obtain the combination of working parameters suitable for pulsating negative pressure shale shaker through simulation, which is conducive to efficient recovery of clean drilling fluid and relatively dry cuttings.Design/methodology/approachShale shaker is still one of the main equipment in solid–solid and solid–liquid separation processes in drilling industry. This research is based on a new drilling fluids circulation treatment device, namely pulsating negative pressure shale shaker. In this work, a numerical study of particle flow and separation in the pulsating negative pressure shale shaker is carried out by coupling computational fluid dynamics/discrete element method (CFD-DEM). The effect of vibration parameters and negative pressure parameters are studied in terms of conveyance velocity and percent through screen.FindingsThe results show that, conveyance velocity of particle is mainly affected by vibration parameters, negative pressure in pulsating form can effectively prevent cuttings from sticking to the screen. Vibration parameters and pulsating airflow velocity peak have great influence on percent through screen, while vibration frequency and screen slope have influence on the time when the percent through screen reaches stability.Originality/valueIn this paper, the authors put forward a new kind of drilling waste fluid treatment equipment, and focused on the study of particle movement law. The results have important guiding significance for the selection of structural design parameters and rational use of equipment. In addition, the new device provides a new idea for solid–liquid separation method, which is one of the hot topics in current research.

Structural relaxation and avalanche dynamics of particle piles under vertical vibration

Granular matter can exhibit solid or liquid behavior, which contains complex physical mechanisms. In this work, we experimentally investigated the structural relaxation and avalanche dynamics of particle piles under vertical vibration. The influence of vibration parameters on the avalanche process was studied. The morphological features of avalanches were recorded and classified using high-speed camera. The effects of vibration parameters and particle properties on the relaxation mode are obtained. It is found that the evolution of particle pile height with time can be described by an exponential decay function. The relaxation rate and avalanche characteristics of four types of particles with different sizes are discussed. At the same acceleration level, for two larger particles, a smaller amplitude (A = 0.025 mm) leads to a faster relaxation rate, while for two smaller particles, a large amplitude (A = 0.500 mm) leads to a faster relaxation rate. The analogy powder surface tension is introduced to address the cohesion and flowability evolution of particles under vibration.

DEM simulation of particle segregation in filling of vibratory dies

The homogeneity of the metal powder in the dies is a primary factor affecting the quality of the product obtained by powder metallurgy manufacturing routes. Hence, a desirable goal during die filling is to achieve a homogeneous distribution of particles. However, the presence of particles of different shapes and sizes in metallic powders may give rise to inhomogeneous distribution leading to the segregation of particles. In addition to segregation, the presence of cavities or gaps in the dies with sharp features can affect the quality of final products. In this work, discrete element simulations are carried out to study the die filling of an axisymmetric die with internal stepped features which led to the formation of gaps in the die as it is filled with particles. The die is subjected to vertical vibratory motion and the effect of vibration parameters on the size segregation of particles and the compaction characteristics of the metallic powder are studied. At higher amplitudes, a cluster of coarse particles was observed at the center near the base of the die. At higher vibrational frequencies out of phase, flows were observed in the stepped regions of the die which led to the formation of surface waves.

Numerical simulation of droplet impact on vibrating low-adhesion surfaces

The impact of droplets on low-adhesion solid surfaces vibrating in the vertical direction was numerically investigated. An axisymmetric multiphase lattice Boltzmann model capable of handling high density and viscosity ratios was implemented to simulate the impact. The effects of vibration parameters on the spreading, contact time, and droplet rebound velocity were addressed. According to the results, the phase angle of the surface vibration is the most dominant factor in determining the dynamics of the droplet upon impact. The contact time generally increases when the surface is vibrated. However, for a certain range of phase angles, the contact time can decrease, as compared to the stationary surface. The rebound velocity also shows a strong dependence on the vibration frequency and phase angle. For droplets with higher impact velocities, the surface vibration becomes a less important factor, whereas on surfaces with lower contact angles, the impact dynamics are much more heavily affected by the surface vibration. The rebound velocity is also heavily affected by surface vibration and varies depending on the frequency and phase angle. This study offers insights into the physics of droplet impact upon vibrating surfaces, which can be utilized to improve surface wettability control in applications where vibration is present.

Tool wear rate prediction in ultrasonic vibration-assisted milling

In the current study, a predictive model on tool flank wear rate during ultrasonic vibration-assisted milling is proposed. One benefit of ultrasonic vibration is the frequent separation between tool and workpiece as the cutting time is reduced. In order to account for this effect, three types of tool–workpiece separation criteria are checked based on the tool center instantaneous position and velocity. Type I criterion examines the instantaneous velocity of tool center under feed movement and vibration. If the tool is moving away from workpiece, there is no contact. Type II criterion examines the position of tool center. If the tool center is far from the uncut workpiece surface, there is no contact even though the tool is getting closer. Type III criterion describes the smaller chip size due to the overlaps between current and previous tool paths as a result of vibration. If any criterion is satisfied, the tool flank wear rate is zero. Otherwise, the flank wear rate is predicted considering abrasion, adhesion and diffusion. The proposed predictive tool flank wear rate model is validated through comparison to experimental measurements on SKD 61 steel with uncoated carbide tool. The proposed predictive model is able to match the measured tool flank wear rate with high accuracy of 10.9% average percentage error. In addition, based on the sensitivity analysis, smaller axial depth of milling, larger feed per tooth or higher cutting speed will result in higher flank wear rate. And the effect of vibration parameters is less significant.

DEM study of size segregation of wet particles under vertical vibration

DEM study of the size segregation of spherical and cubical wet particles was conducted with a linear cohesion contact model. The effects of cohesion force on segregation pattern and speed were examined. A hill-shaped segregation mode was observed and analysed in terms of total normal force between small-sized particles, tangential force along the Z-axis by container wall and torque acting on the particles. Then, the effect of vibration parameters on the segregation process was investigated. The results show that the cohesion force has a greater influence on the segregation pattern and speed of spherical particles than on cubical ones. The cubical particles can segregate more easily than spherical particles when the cohesion force is relatively high. With the increase of the cohesion force, both the normal force between small-sized particles, the tangential force along the Z-axis and the torque acting on the particles increase. The average forces and torque of the spherical particles are generally larger than that of the cubical particles under the same conditions. The segregation speed and the volume concentration of large particles are generally increasing with the increase of vibration frequency or amplitude. Moreover, the vibration parameter combination with a relatively low vibration frequency and a relatively high vibration amplitude is good for the segregation of wet particles for a given vibration intensity.

Characterization of fluid mixing in a closed container under horizontal vibrations

The mixing characteristics of two initially stratified miscible fluids in a closed container vibrated horizontally are studied numerically by a validated computational fluid dynamics model. The flow characteristics and interfacial dynamics in the closed vibrating container are analyzed, and the effects of vibration parameters and gravity on mixing efficiency are evaluated both quantitatively and qualitatively. The results show that interfacial instability occurs in the closed container, which leads to interfacial deformation and breakup and quickens mixing. Two distinct stages of the mixing process can be observed in the closed vibrating container. During the macro‐mixing, an increasingly sharp gradient of the concentration field is generated. During the micro‐mixing, the mixing process is dominated by the diffusion of the concentration field and ends up with a nearly homogeneous mixture. The intensification of mixing process by vibration is most pronounced in the absence of static gravity. The gravity can suppress the interfacial instability and retard the mixing process. Over the range of conditions investigated in this paper, vibration is an efficient approach for mixing miscible liquids in a closed container.

Vibration parameters optimum of 316L steel laser welding under high frequency micro-vibration condition

High frequency micro vibration combined with laser was applied in the test. Effect of vibration parameters on the mechanical and micro-structure of High Frequency Micro-vibration laser welded 316L steel were investigated. The best laser welding process parameters were chosen by comparison of weld geometry. In detail, laser power (P) is 2.5 kW, welding speed (V) is 1.2 m min−1, defocusing amount (DA) is −5 mm. Three parameters including frequency (F), vibration acceleration (A) and angle (θ) were changed according to the orthogonal test scheme. The microstructure and the tensile properties of the welded joint were compared and analyzed. The morphology of weld tail was analyzed to describe hole stability. It was found that micro-structure and mechanical of joint was significantly influenced by A and F. In the case of vibration resonance, the higher the F, the better the ultimate tensile strength (UTS), and the higher the hardness. When F was 1360 Hz, UTS was 602 MPa. When A was increased from 10 to 60 m s−2, the UTS was improved by 10 MPa. HW and HL were even disappeared in a higher resonance state. Response surface analysis results showed that factors of F and A have significant effects on the width of weld. Width was increased by 3 mm. The effect of θ on width was little. It was obtained that optimum process parameters were F = 1360 Hz, A = 60 m s−2 and θ = 90°. UTS was 602 MPa, hardness was 214.5 Hv, and elongation was 40%. This is mainly due to the grain refinement strengthening.

Effect of vibration parameters on the bubble absorption characteristics of working fluids R134a–DMAC in a vertical tube

Two-phase flow pattern evolvement characteristic of working pair R134a–DMAC as well as the relationship between the bubble absorption height and vibration parameters (amplitude and frequency) were studied experimentally. Results showed that the bubble behavior and two-phase flow patterns became more complicated and disturbed under the vibration state, besides the bubble jolting and disintegration phenomena were observed. Stability of bubble absorption was also influenced by the vibration parameters. The most significant enhancement effectiveness of system vibration to the bubble absorption of R134a–DMAC occurred when amplitude was 0.4 mm and frequency was 25 Hz within the testing conditions. Finally, absorption pressure and temperature, solution flow rate and solution concentration were testified to influence the bubble absorption height and flow patterns under the vibration conditions.

Research on cavitation involved in ultrasonic-assisted abrasive waterjet machining

The cavitation characteristics involved in ultrasonic-assisted abrasive waterjet were analyzed in the present study. The fluid field corresponding to ultrasonic-assisted AWJ was investigated through utilizing computational fluid dynamics. A cavitation model was adopted to simulate the mass transfer between water liquid and vapor phases. The evolution of cavitation during the impacting process and the effects of vibration parameters on cavitating characteristics were investigated. Moreover, a set of experiments were performed to evaluate the effects of ultrasonic-induced cavitation on erosion and material removal of ceramics. The results indicated that the evolution of cavitation had dependency on the fluid pressure and turbulence at impacted zone, and the synergetic erosion of microjets and accelerated particles induced by collapsing cavitation bubbles can evidently enhance the material removal. The material removal rate was improved by 82% at most under ultrasonic vibration.

Research of Polymer Melt Stability by Vibrating Based on Synergetics

A self-developed experimental facility by the national engineering research center of novel equipment for polymer processing, named as a coaxial barrel dynamic rheometer, is used to test the Weissenberg number and the first and the second normal stress difference coefficient for polymer melt and the effect of vibration parameters on them in vibration shear field. At the same time, it can be used the synergetics analysis method into explain the effects of elasticity stability of polymer melts. The testing principle of the rheometer is to transform the shear power of a motor and extrusion pressure in shear field to melt viscosity. The shear field can simulate orthogonal superposed vibratory flow, boundary vibrating pressure flow, and their combined flow. By comparing equation predictions with experimental results, a satisfied-qualitatively and reasonable-quantitatively predictive ability is shown, which verifies the work of mathematical derivations.

Development of vibration-assisted micro-milling device and effect of vibration parameters on surface quality and exit-burr

Vibration-assisted cutting is an important technology with better performance in manufacturing micro-scaled components, compared with conventional cutting technology. This article first illustrates the development of vibration-assisted micro-milling device which is made based on piezoelectric plates and shows different vibration types with vibration principle of this device. It is then tested stable to output vibration with a frequency accuracy of 100 Hz and an amplitude accuracy of 100 nm. Two groups of experiments in micro-milling 6061 aluminum alloy are carried out. Compared with conventional micro-milling, using vibration assist is verified more effective in improving surface integrity and quality. Furthermore, with a proposed method of characterizing exit-burr size, the influences of vibration frequency and amplitude on surface roughness and exit-burr size are discussed. As a result, the mean surface roughness is found positive related to vibration frequency and negative related to vibration amplitude in most of the study range. To make guidance on optimizing vibration machining parameters, cubic polynomial fitting with 95% prediction interval is of enough accuracy.