Increase Of Vibration Amplitude Research Articles

The influence of ultrasonic elliptical vibration amplitude on cutting tool flank wear

In this article, the effect of vibration amplitude during ultrasonic elliptical vibration–assisted turning on cutting tool flank wear ( VBmax) and tool diffusion wear mechanism has been experimentally studied in machining of AISI 4140 hardened steel. To achieve this goal, an ultrasonic elliptical vibration–assisted turning setup was designed and manufactured. This device was then used in both ultrasonic-assisted tuning and ultrasonic elliptical vibration–assisted turning tests (i.e. one-dimensional and two-dimensional ultrasonic-assisted machining). According to the achieved results, ultrasonic elliptical vibration–assisted turning is more effective than ultrasonic-assisted tuning in reducing tool flank wear; at an amplitude of 13 μm, work velocity of 180 mm/s and feed of 0.09 mm/rev, VBmax were decreased 30.3% and 54.3%, respectively, in case of ultrasonic-assisted tuning and ultrasonic elliptical vibration–assisted turning. It was also observed that increasing the amplitude of ultrasonic vibrations reduces VBmax; at work velocity of 180 mm/s and feed of 0.09 mm/rev, the reduction of VBmax in ultrasonic elliptical vibration–assisted turning with amplitudes of 5 and 13 μm is, respectively, 39.3% and 54.3%, compared with that of conventional machining. The results also show that the application of ultrasonic vibrations weakens the cutting tool diffusion wear mechanism. This attenuation is much higher for ultrasonic elliptical vibration–assisted turning in comparison to ultrasonic-assisted tuning. Besides, the amount of attenuation in cutting tool diffusion wear mechanism decreases with increasing vibration amplitude.

Impacts of panel vibration on shock train structures and performance of two-dimensional isolators

As one of the most critical components in scramjet engines, isolators are designed to prevent the hypersonic inlets from pressure disturbances raised from combustors. Shock trains dominate the internal flow field of isolators, the characteristics of which is crucial to the performance of isolator. However, recent studies have primarily focused on rigid isolators without structural deformation. The impact of structural vibration on the flow structures and performance of isolators receives little attention. The current study focuses on this problem by investigating the effect of vibration panel at the foot of shock train on the flow and performance of isolator which is quantified by 11 parameters regarding separation zone, shock structures, flow asymmetry, and isolator performance. Results examine the difference due to vibration amplitude, frequency and wavelength. Analyses indicate that the panel vibration will cause the upstream movement and length increase of shock train and separation zones, the increase of flow asymmetry and decrease of isolator performance. With increasing vibration amplitude, the shock train and separation zone travel upstream with the increase of shock train length, the flow asymmetry increases with large transient side loads, and the influence on the performance of isolator isminor. With increasing vibration frequency, the shock train and separation slightly travel downstream with the decrease in length, the change of flow asymmetry is minor with large transient side loads and the change of performance is minor. With increasing mode number (decreasing wavelength), the shock train and separation zones move downstream with the increase of shock train length, the flow asymmetry increases with significant transient side load at 2nd structural mode, and the change of performance is minor.

On size-dependent nonlinear free vibration of carbon nanotube-reinforced beams based on the nonlocal elasticity theory: Perturbation technique

Based on the first-order shear deformation (FSD) model and nonlocal elasticity theory, the simultaneous effects of shear and small scale on the nonlinear vibration behavior of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) beams are investigated for the first time. To this end, the governing equations of bending and stretching with von Kármán geometric nonlinearity are decoupled into one fourth-order partial differential equation in terms of transverse deflection. A closed-form solution of the nonlinear natural frequency, which can be used in conceptual design and optimization algorithms of FG- CNTRC beams with different boundary conditions, is developed using a hybrid method of Galerkin and perturbation technique. First, the decoupled equation is reduced to a nonlinear ordinary one with respect to time by implementing the Galerkin method. Next, multiple scales perturbation technique is used to replace this nonlinear ordinary differential equation with a series of linear equations which can be solved analytically. Finally, numerical results are presented to compare with the existing ones in the literature as well as to study the effects of CNTs distribution, boundary conditions and nonlocal parameter on the frequency ratio. It is seen that the influence of CNTs distribution becomes more significant when the nonlocal parameter increases. Also, the difference between results obtained from the classical and nonlocal elasticity theories increases as the amplitude of vibration increases. Therefore, it is concluded that the classical elasticity theory is inadequate to predict the nonlinear vibration behavior of FG-CNTRC beams with large deformation.

Theoretical and Computational Analysis on the Melt Flow Behavior of Polylactic Acid in Material Extrusion Additive Manufacturing under Vibration Field

Material extrusion (ME), an extrusion-based rapid prototyping technique, has been extensively studied to manufacture final functional products, whose forming quality is significantly influenced by the melt flow behavior (MFB) inside the extrusion liquefier. Applied vibration has a great potential to improve the MFB, and thereby promote the forming quality of the built product. To reveal the mechanism, a dynamic model of the melt flow behavior (DMMFB) is established based on fluid dynamics, Tanner nonlinear constitutive equation and Newton’s power law equation. The MFB, i.e., pressure drop, shear stress and apparent viscosity, is investigated without and with different vibration applied. The corresponding finite element analysis (FEA) is then carried out. From the comparison between DMMFB and FEA results, it is concluded that the proposed model is reliable. When vibration is applied onto the extrusion liquefier, the time-domain MFB will change periodically. Its effective value decreases significantly, and further decreases with the increase of vibration frequency or amplitude. This paper provides the theoretical basis to improve the MFB by applied vibration, and thereby to enhance the forming quality of ME products.

Investigation of mechanical vibration effect on proton exchange membrane fuel cell cold start

A three-axis vibration platform is first constructed and utilized in the investigation of the effects of mechanical vibration on the cold start performance of a proton exchange membrane (PEM) fuel cell. In addition, an intermittent pattern of purging is adopted to improve the purging efficiency. The applied vibrations are found to promote water dispersion, but ultimately do not enhance water removal. Under subzero conditions (−13 °C), the vibration of the fuel cell improves cold start performance via delayed freezing, especially when vibrating at the fuel cell natural frequency (10 Hz). With an increase in vibration amplitude, the freezing rate is found to be slow and eventually plateau. Finally, the vibration in the vertical axis is found to play a positive role in improving cold start performance; the effects of other orientations depend on the startup temperature. The result of cold start under vibration might indirectly prove the existence of super-cooled water.

Nonlocal nonlinear vibration of an embedded carbon nanotube conveying viscous fluid by introducing a modified variational iteration method

In this study, the large amplitude vibration and the stability of embedded carbon nanotubes (CNTs) conveying viscous fluid are analyzed. The effects of small-scale are presented into the model based on the nonlocal elasticity theory by changes in the fluid properties. Moreover, the viscosity effect is modeled by Rayleigh’s dissipation function. After separating the time part of the governing equation, a modified method based on He’s variational iteration method is proposed, the time response, and the complex nonlinear frequencies are obtained. Then, the effects of the geometric parameters, the velocity and the viscosity of the flowing fluid and small-scale effects are investigated on the nonlinear vibration behavior of CNTs. Results reveal that small-scale effects reduce the critical flow velocity. The viscosity effect appears as the nonlinearity due to large vibration amplitude increases, which cause reduction in both nonlinear frequencies and critical flow velocities.

Determination of the kinetics of the process of pumpkin seeds vibrational convective drying

Experimental studies of the drying process of high-moisture pumpkin seeds in a vibrating dryer are carried out. The research is caused by the need to solve the problem of fast and high-quality post-harvest treatment with minimal cost. Existing technologies and equipment do not ensure high performance of the drying process in the post-harvest period or carry it out with significant expenses of time and resources. The main objective of the study is to determine the rational parameters of the process and equipment for drying pumpkin seeds. As a result of the experimental studies of the kinetics of pumpkin seeds vibrational convective drying, rational process parameters were obtained, i. e. the maximum allowable temperature of the drying agent is t da =50 °С, which corresponds to the maximum allowable heating temperature of seeds t h2 =46.7 °С. At this temperature, the grain retains conditional values of germination ability and energy. The maximum allowable temperature is 0.3 °C lower than the maximum allowable heating temperature for pumpkin seeds. The results of the study of the intensification of vibration exposure indicate a direct relationship between the vibration frequency of the drying chamber and drying duration: the higher the frequency, the greater the intensity of vibration-convection drying, as well as a reduction in drying duration with increasing vibration amplitude. The obtained results confirm the feasibility of using a filtration-convective vibrating dryer, which ensures compliance with rational drying parameters, i. e. temperature and speed of the drying agent, amplitude, frequency, and filling of the working chamber. The combination of these parameters allows drying the seed material with minimal cost and maintaining its high quality

Feedback control of flow-induced vibration of a sphere

The flow-induced vibration of a sphere elastically mounted in the cross-flow direction with imposed feedback rotation was investigated experimentally. The application of rotation provides a means to exercise control over the vibration response of axisymmetric three-dimensional objects. Both the rotational amplitude, which was imposed in proportion to sphere transverse displacement, and the phase of the control signal were varied over a broad parameter space comprising: a non-dimensionalised proportional gain ( ); rotation phase ( ), which is the phase between the applied sphere rotation and the transverse displacement; and reduced velocity ( ). The corresponding Reynolds number range was ( ). The structural vibration, fluid forces and wake structure were examined to characterise the effect of the imposed rotation. It was found that the rotation not only altered the magnitude of the vibration response, either amplifying or attenuating the response depending on operating conditions, but it also altered the reduced velocity at which vibrations commenced, the vibration frequency and periodicity and significantly altered the phase between the transverse fluid force and displacement. It was possible to almost completely suppress the vibration in the mode I, mode II and mode III transition regimes for imposed rotation over the ranges , and , respectively. In particular, this could be achieved at effective rotation rates well below those required by using open-loop control (Sareen et al., J. Fluid Mech., vol. 837, 2018, pp. 258–292). Past the peak of mode II, a ‘galloping-like’ response, similar to that reported by Vicente-Ludlam et al. (J. Fluid Mech., vol. 847, 2018, pp. 93–118) for the circular cylinder, was observed with an increase in vibration amplitude of up to 368 % at the highest reduced velocity tested ( ). Particle image velocimetry measurements revealed a change in the timing and spatial position of the streamwise vortex structures with imposed rotation. Contrary to what has been observed for the circular cylinder, however, no de-synchronisation between vortex shedding and sphere motion was observed.

Investigation on the effect of cavitation in ultrasonic-assisted AWJ

In order to provide some insight into the complex fluid behavior involved in ultrasonic vibration-assisted abrasive waterjet machining, a three-dimensional CFD model is established to investigate the cavitating characteristics. Governing equations of the impacting jet flow field are solved accompanied with the mass transfer equation which is based on Schnerr-Sauer cavitation model. Vibrating motion of the target surface is performed through adopting a moving wall boundary with dynamic mesh method. The evolution of cavitating bubbles and fluid pressure at the impact zone is analyzed. The results imply that the variation of vapor phase fraction has a close correspondence with the pressure fluctuation. Moreover, an increase of vibration amplitude can effectively enhance on the intensity of cavitation. The maximum volume fraction is increased by 78% with a 20 μm increase of amplitude. The experimental results indicate that irregular craters induced by cavitation are formed on the eroded surface when applying ultrasonic vibration to the workpiece.

A hybrid approach of NSGA-II and TOPSIS for minimising vibration and surface roughness in machining process

Increasing vibration amplitude during end milling process can seriously affect the life of end mills and reduces surface finish. Spindle and worktable vibration has a significant influence on surface quality of machined components. This paper confronts and investigates the effect of machining and geometrical parameters (spindle speed, feed rate, axial depth of cut, radial depth of cut and radial rake angle) on spindle and worktable vibration in terms of acceleration amplitude and surface roughness. Experiments were conducted on aluminium alloy 6061-T6 with high-speed steel (HSS) end mill cutter based on the central composite design (CCD). Response surface methodology (RSM) was used to develop the predictive models and the adequacy of the models were verified using analysis of variance (ANOVA). Non-dominated sorting of genetic algorithm (NSGA-II) was adopted to solve the multi objective optimisation problem and the optimised results were resulted with a set of Pareto-optimal solutions. The multi criteria decision making method (MCDM) such as technique for order preference by similarity to ideal solution (TOPSIS) and analytical hierarchy process (AHP) were designed to rank the Pareto optimal solutions based on response of closeness coefficient values.

Effect of the impact of rigid rods on coffee fruit detachment efficiency by mechanical vibrations

The mechanization of field activities has been the response of coffee producers to the labor shortage, especially for fruit harvesting. The use of mechanical harvesters allows greater harvesting efficiency and ensures the economic viability of coffee plantations, which currently depend mainly on the reduction in production costs. The principle used for mechanized coffee harvesting is based on the principle of mechanical vibration. The objective of this studywas to analyze the dynamic behavior of the coffee fruit-peduncle-branch system under mechanical vibration and the impact of the vibrating rods on the fruit detachment process in association with this behavior. Fragments of coffee branches containing fruits in the unripe and ripe stages were used in this experiment. These samples were subjected to different frequencies (20, 30, 40, and 50 Hz) and amplitudes (0.002, 0.003, and 0.004 m). Another variableanalyzed was the form of vibration transmission to the fruits, with the vibrations being transmitted to the samples with or without the impact of the fiberglass rods. The fruit detachment efficiency increased as the ripening stage progressed from unripe to ripe. A higher detachment efficiency occurred with the increase in vibration frequency and amplitude because of the higher vibrational energy imposed on the fruit. The detachment efficiency was low when the vibration was transmitted without the impact of the rods. Conversely, the vibration in combination with impact achieved a mean detachment efficiency of approximately 90%.Key words: Coffee crop; dynamic behavior; harvester machine; mechanical harvesting.

A Hybrid Approach of NSGA-II and TOPSIS for Minimizing Vibration and Surface Roughness in Machining process

Increasing vibration amplitude during end milling process can seriously affect the life of end mills and reduces surface finish. Spindle and worktable vibration has a significant influence on surface quality of machined components. This paper confronts and investigates the effect of machining and geometrical parameters (spindle speed, feed rate, axial depth of cut, radial depth of cut and radial rake angle) on spindle and worktable vibration in terms of acceleration amplitude and surface roughness. Experiments were conducted on aluminium alloy 6061-T6 with high-speed steel (HSS) end mill cutter based on the central composite design (CCD). Response surface methodology (RSM) was used to develop the predictive models and the adequacy of the models were verified using analysis of variance (ANOVA). Non-dominated sorting of genetic algorithm (NSGA-II) was adopted to solve the multi objective optimisation problem and the optimised results were resulted with a set of Pareto-optimal solutions. The multi criteria decision making method (MCDM) such as technique for order preference by similarity to ideal solution (TOPSIS) and analytical hierarchy process (AHP) were designed to rank the Pareto optimal solutions based on response of closeness coefficient values.

Dynamic behaviors of droplets impacting on ultrasonically vibrating surfaces

Ultrasonic vibration has a wide application prospect in the fields of droplet atomization and aircraft anti/de-icing. The present work experimentally investigates the dynamic behaviors and anti-icing characteristics of droplets, with a wide range of velocities, impacting on ultrasonically vibrating surfaces. Two kinds of splash mode are observed, including edge splash and surface splash, and a novel rebound mode, named sub-droplet rebound, is found in our experiments. The surface splash is mainly induced by the Faraday instability of surface capillary waves, and the appearance of a large number of bubbles proves that cavitation is also one of the influence factors. By analyzing the interaction of aerodynamic force and surface tension, the critical curve of the edge splash is obtained. The convergence of capillary waves at the apex contributes to the sub-droplet rebound. In addition, the influences of impact velocities and ultrasonic vibration amplitudes on the droplet spreading and the size distribution of secondary droplets are elucidated and discussed. A higher excitation amplitude results in a wider secondary droplet size distribution and a larger average size. We also investigate the dynamic process of supercooled water droplets impacting on ultrasonically vibrating surfaces with and without preformed frozen ice, respectively. The ultrasonic vibration could effectively promote the droplet splash and prevent the ice accumulation even in the state that the surface has been frozen. The anti-icing efficiency of the ultrasonic vibration increases with the increase of the ultrasonic vibration amplitude. The results of this work could provide insights for controlling droplet spreading, atomization, and anti-icing by using ultrasonic vibration.

Influence of vibration on mechanical polishing micro-structured surface using discrete element method

A model using discrete element method (DEM) was conducted to simulate vibration assisted mechanical polishing micro-structured surface process by particle flow code in three dimensions (PFC3D). The effect laws of vibration frequency and amplitude on abrasive grains and polishing force were researched in detail according to the simulation results. The effects of vibration on the particles average motion velocity in one fluid cell were researched, and the simulation results show that average velocity increases with increase of vibration frequency and amplitude on the whole. The effects of vibration on the unbalanced force acting on the workpiece surface were quantified at first. The changes of average unbalanced force obviously increase for low feed rate with increase of frequency and increase approximately linearly with increase of amplitude. It is concluded that vibration with high frequency and great amplitude can significantly increase machining efficiency and improve surface quality in micro-structured surface polishing.

The Effect of Overlap Ratio and Silicon Carbide Wheel Grinder on Vibration Amplitude and Surface Roughness for Material OCR12VM.

This research aims to find out how big the effect of the overlap ratio and grit size silicon carbide wheel grinder to the vibration amplitude and surface roughness when grinding process and the corelation between the vibration amplitude and surface roughness. This research used the material hardened tool steel OCR12VM. This research using the surface grinding machine KGS818AH model and this research using a variation of process parameters namely 5 variations on the overlap ratio, 4 variations on grit size silicon carbide wheel grinder, 2 variations in the depth of the cut and this research using constant parameters namely constant spindle speed and constant longitudinal feed. The selection the type of abrasive and the selection process parameters (overlap ratio and grit size silicon carbide wheel grinder) can give a great impact on the increased vibration amplitude and surface roughness on material OCR12VM. The conclusion of this study is with increasing overlap ratio, the vibration amplitude and surface roughness will decrease and the finer the grit size silicon carbide wheel grinder, the vibration amplitude and surface roughness will be lower.

Thermal-Fluid Coupling Numerical Simulation of Axial Ultrasonic Vibration Friction Stir Welding

In this study, a mathematical model of axial ultrasonic vibration enhanced friction stir welding is developed to predict the effect of ultrasonic vibration during friction stir welding of aluminum alloys 6061. The research focuses on the effect of with/without axial ultrasonic vibration in friction stir welding by the temperature distribution and material flow characteristics. Results indicate that the addition of axial ultrasonic vibration can reduce the heat generation rate and the temperature of contact surface between the rotating tool tip and the workpiece during the welding process, and improve the flow rate of the plastic metal material near the rotating tool tip. Under the same process parameters, when the vibration frequency is constant, as the vibration amplitude increases, the peak temperature of the welding decreases gradually, and the flow rate of the plastic metal material gradually increases

A total Lagrangian elasticity formulation for the nonlinear free vibration of anisotropic beams

The large amplitude free vibration response of isotropic and anisotropic beams is considered using a total Lagrangian description of the motion along with Ritz-based approximations to the dynamic statement of virtual work. Results are presented for both axial and bending modes and are compared with existing results in the literature using various formulations along with a finite element solution of the Euler–Bernoulli beam with Föppl–von Karman nonlinearity. Results from the present formulation include all nonlinear strain terms and give frequency ratios that are in excellent agreement with both Euler–Bernoulli and higher order beam theories for slender beams under small amplitudes but grow noticeably higher than those of other beam models as the beam becomes thick and the amplitude of vibration increases.

Failure mechanism of rigid polyurethane foam under high temperature vibration condition by experimental and finite element method

ABSTRACTThe failure mechanism of rigid polyurethane foam (RPUF) under room temperature (RT) and high temperature vibration conditions was investigated by experiment and finite element stimulation. Damaged RPUF specimens were prepared at different vibration amplitudes ranging from 0 to 19.879 mm at RT and 150 °C for different vibration times. The tensile test was utilized to evaluate the vibration damage degree of RPUFs, and the results exhibited that tensile strength decreased gradually with the increase of vibration amplitude and time at both RT and 150 °C. Thermogravimetric analysis and Fourier transform infrared spectroscopy illustrated that thermal degradation of RPUF is attributed to the decomposition of carbonyl urethane groups at 150 °C. The scanning electron microscopy analysis of the tensile fracture surfaces revealed that the vibration failure of RPUF mainly resulted from the existence of microcracks in cell structure. A finite element simulation was established by ABAQUS to study stress distribution of RPUF under different vibration loads, which then demonstrated that the microcracks are most likely to exist on the junction of two microcell units, which is due to convergence of stress in the process of vibration. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48343.

Feasibility Studies and Advantages of Using Dual Fiber Array in Laser Ultrasonic Inspection of Electronic Chip Packages

Fabrication and inspection techniques of electronic packages are two key factors influencing a chip’s success in post-Moore’s law era. As the electronic packaging industry rapidly evolves to cope with modern demands, a versatile inspection method for present and future packages is required. One approach is the development of a fiber array laser ultrasonic inspection system as presented in this paper. The new system uses two laser excitation points, allowing higher total energies to be delivered to the chip’s surface without exceeding the thermoelastic regime and causing damage. These beams induce strong ultrasonic waves, which can penetrate deeper and farther into and across a package. As a result, larger and thicker packages can be nondestructively inspected than was previously possible. Flip-chip ball grid array packages of size 52.5 mm $\times52.5$ mm from Cisco were evaluated using this system and compared against a single-beam system. Benefits of the new system include an increase in vibration amplitude due to high laser power, improved signal-to-noise ratio (SNR), an increase in resolution/sensitivity to measure microcracks, and high speed. The new dual-fiber-array system can administer 400-mW power safely, and as a result, the peak-to-peak amplitude of the generated ultrasound is three times that of ultrasound generated from a single laser beam. The SNR of 8:1 is achieved on the current Cisco package with double excitation point sources compared to the SNR of 1:1 that was obtained with a single excitation point source.

Vibration Signature of Normal and Notched Tooth Gear Pump

Gear pumps are critical devices in many industrial applications. An unexpected failure of the gear pump may cause significant effect on its performance. Consequently, there will be economic losses. As a result of that, fault diagnosis in gears has been the subject of intensive research. Vibration analysis has been used as an effective tool in machines diagnosis and in machinery maintenance decisions. As a rule, an increased vibration level is a warning form before failure or breakdown. By measuring and analyzing the gear pump vibration, it is possible to determine both the nature and severity of the defect, and hence predict the machine’s failure. The vibration signal of a gear pump carries the signature of the fault in the gears, and early fault detection of the gear pump is possible by analyzing the vibration signal using different signal processing techniques. This paper presents, experimentally, the external gear pump signature for normal and faulty gear pumps at different rotational speeds (1080, 1200, and 1439rpm). The considered faults herein are two different notches on one of the pump teeth— small notch and large notch. The paper concludes that features of the vibration are different with the notch shape and the rotational speed. The amplitude of vibration increases by increasing both rotational speed and notch size.