Vibration Direction Research Articles

Analysis of Vibration Frequency and Direction for Facilitating Upper-Limb Muscle Activity.

We aimed to determine the effect of vibration frequency and direction on upper-limb muscle activation using a handheld vibrator. We recruited 19 healthy participants who were instructed to hold a handheld vibrator in their dominant hand and maintain the elbow at 90° flexion, while vertical and horizontal vibrations were applied with frequencies of 15, 30, 45, and 60 Hz for 60 s each. Surface electromyography (EMG) measured the activities of the flexor digitorum superficialis (FDS), flexor carpi radialis (FCR), extensor carpi ulnaris (ECU), extensor carpi radialis (ECR), biceps, triceps, and deltoid anterior muscles. EMG changes were evaluated as the difference in muscle activity between vibration and no-vibration (0 Hz) conditions. Muscle activity was induced under vibration conditions in both vertical and horizontal (p < 0.05) directions. At 45 Hz, FDS and FCR activities increased during horizontal vibrations, compared with those during vertical vibrations. ECU activity significantly increased under 15-Hz vertical vibrations compared with that during horizontal vibrations. Vibrations from the handheld vibrator significantly induced upper-limb muscle activity. The maximum muscle activations for FDS, ECR, ECU, biceps, and triceps were induced by 45-Hz horizontal vibration. The 60-Hz vertical and 30-Hz horizontal vibrations facilitated maximum muscle activations for the FCR and deltoid anterior, respectively.

Quantification of the Effect of Simultaneous Tri-Axis over Sequential Single-Axis Vibration Testing

The launch mechanical environment presents a multi-axis random vibration excitation to the launch vehicles and spacecraft payloads. However, ground vibration testing of these systems abides by sequential, single-axis inputs, enveloping flight vibration levels along individual axes. The actual vibration direction depends on the excited mode shapes, and in general it is not precisely aligned with any given reference axis of the article. The response acceleration could be in any direction, with strong local variations expected, depending on both the properties of the structure of interest and the applied loads. In this paper, it is first shown that matching all response acceleration components due to a realistic environment by single-axis testing is, in general, impossible. Subsequently, minimum amplification factors for single axis to match realistic reference environments are quantified, such that both acceleration responses and elemental stresses were covered for the whole spacecraft in at least one of the uniaxial tests. This procedure was repeated for five different realistic spacecraft models. It was found that a consistent amplification factor and, respectively, overtesting, were necessary for the single-axis excitation sequence to properly validate the articles’ survivability against the true mechanical launch loads.

Acoustic analysis of jet atomization for uniform dispersion of nano- and micro-droplets

In this study, the mechanisms of jet atomization were analyzed based on a frequency analysis of atomization sounds in the audible range (∼20 kHz). Jet atomization is a two-dimensional, high-speed atomization using a diaphragm, and interesting acoustic signals and atomization phenomena were detected on hydrophobic and hydrophilic diaphragms. The hydrophilic diaphragm strongly interacted and resonated with the surface wave, resulting in symmetrical jet atomization relative to the diaphragm. The resonance between the diaphragm and the surface wave was supported by a calculation of the eigenfrequency of the diaphragm and the coincidence of the droplet diameters as calculated from Lang's equation. Notably, the diaphragm excited by the ultrasonic transducer acted as a new transducer vibrating perpendicular to the transducer. As a result, when the diaphragm and the surface wave were in resonance at 2.4 MHz, a symmetrical two-dimensional high-speed jet atomization was generated in the direction perpendicular to the transducer’s vibration direction. This study also revealed that the atomization state can be determined based on the acoustic analysis. This acoustic analysis of atomization sounds can be applied in more advanced atomization control, such as for providing uniform dispersions of droplets containing DNA, drugs, or microplastics.

Study on Migration Law of Solid Particles on Sieve Surface of Solid-liquid Separator

Based on the discrete element method and the three-dimensional discrete element analysis software EDEM, simplify the tube net type solid liquid separator model, to explore the net type solid liquid separator inside the cylindrical screen opaque screen the migration law of solid phase particles and different vibration frequency, vibration amplitude, vibration direction Angle, diameter of sieve sieve speed and sieve cylinder is opaque screen the influence of solid phase particles migration rule, In order to provide reference for the selection of structural parameters and vibration parameters of solid-liquid separator in field application. The results show that the motion trajectory of solid particles on the screen is a three-dimensional spiral curve. The larger the vibration frequency and amplitude of the screen box, the higher the particle migration speed. The larger the vibration direction Angle, diameter and speed of sieve box, the smaller the particle migration speed. The research results can be used for reference in the selection of structural parameters and motor vibration parameters that affect the comprehensive performance of the cylinder net solid-liquid separator.

Capillary-Wave Sieve: Continuous Particle Separation Using Millimeter-Scale Capillary Waves

Size-dependent continuous microparticle separation is important for various applications in sensing and drug delivery to particle manufacturing. Several invasive, noninvasive, active, and passive methods have been developed, spanning operation across a wide range of system scales, from bulk-macroscale devices to precise-microscale systems. However, devices in these wide system scales have contradictory benefits. Bulk methods have limitations with the size of particles that can be manipulated, while microscale methods have limitations with processing volumes. Here, we present a method to continuously separate micron- and submicron-sized particles using low-frequency vibrations (of the order of 10 Hz). We generate capillary waves in an open channel with a continuous particle-laden flow perpendicular to the vibration direction. The size-based response of the ensuing flow field aligns particles above a critical size along the center of the channel, while the remaining particles remain in the bulk and undergo downstream separation. A key feature of this mechanism is that the separated particle sizes can be controlled by changing the vibration amplitude. The proposed mechanism and design provides a semibulk method to distinguish submicron-sized particles with robust in situ control using a simple millimeter-scale setup and operation.

Effects of the whole-body vibration direction on the cognitive response of standing subjects

This study aims to investigate the effect of whole-body vibration along different axes on the response time (RT) of standing subjects during a customised psychomotor vigilance task (PVT). Twenty-five subjects were exposed to harmonic vibration with amplitude of 0.7 m/s2 RMS and frequencies between 1.5 Hz and 12.5 Hz. ANOVA was used to assess if the difference of RT with and without vibration had a statistical relevance. Results showed that the RT was statistically affected by the vibration only at frequencies below 2 Hz. The vibration at higher frequencies had a minor effect on the RT. The RTs during the vibration exposure was, on average, 15% higher than the RT post exposure. Practitioner summary: This study investigates the effects of whole-body vibration (WBV) along different axes on the response time (RT). We measured the RTs to a psychomotor vigilance task of 25 standing subject exposed to WBV. The cognitive response was statistically affected by the WBV and, on average RT have increased of 15%.

Test Study on Vortex-Induced Vibration of Deep-Sea Riser under Bidirectional Shear Flow

A model test was carried out to reveal the vortex-induced vibration characteristics of a deep-sea riser under bidirectional shear flow. Bandpass filtering and modal analysis were used to process the test strain data, and the amplitude and frequency response characteristics of the vortex-induced vibration of the riser in the bidirectional shear flow field were obtained. The results of the test data analysis show that the dominant frequency of the vortex-induced vibration of the riser model under bidirectional shear flow is locked in the natural frequency of the riser and does not increase with the increase in flow velocity, that the average resistance coefficient of the riser model has little change under different flow velocities because of the distribution characteristics of the “bidirectional shear” flow field, that there is an extreme value of the shear force in the middle of the riser model, and that the Strouhal number in the transverse direction of the vortex-induced vibration under bidirectional shear flow is less than the recommended value of the current vortex-induced vibration prediction software. The obtained results provide basic data for the prediction of vortex-induced vibration and research into the fatigue analysis method of a riser under an internal wave flow field.

Parameter optimization and mechanism research of double-layer variable screen surface vibrating screen

In the vibrating screening operation, each area of the screen surface has a different screening environment, and the material layer thickness, target particle proportion and other parameters of each area are different, which limits the screening efficiency of a vibrating screen with a traditional screen surface. In this paper, a double-deck variable screen surface screening method is proposed to optimize the design of the double-deck screen surface. The relationship between the elements of the screening process, screening parameters and screening efficiency of a double-deck variable screen surface vibrating screen is investigated through DEM numerical simulation. Using the particle swarm algorithm to support the vector regression model for global optimization, the parameters of the double-deck variable screen surface vibrating screen further optimized to obtain screening parameters: screen area A screen hole edge length of 4.7 mm, screen area D screen hole edge length of 2.7 mm, screen area D screen surface inclination angle of 6.3°, amplitude 2.6 mm, vibration frequency of 22.2 Hz, vibration direction angle of 35°, and through the experimental prototype for physical experimental verification.

Photodeformable Azo Polymer Janus Particles Obtained upon Nonsolvent-Induced Phase Separation and Asynchronous Aggregation.

Photodeformable submicron Janus particles (JPs), containing an epoxy-based azo polymer (BP-AZ-CN) and poly(methyl methacrylate) (PMMA), were fabricated upon nonsolvent-induced phase separation. The formation of the JPs was induced by gradually adding deionized water into a tetrahydrofuran (THF) solution of both polymers. The results show that the two polymers start to precipitate from the solution at almost the same water content and immediately separate into two phases in each particle due to the strong incompatibility between the two components. After the nucleation, the sizes of the aggregates increase with increasing water content in the following growth stage. The amount of BP-AZ-CN molecules assembling into the aggregates is controlled by the water content in the medium, while the aggregation of PMMA molecules is a slow diffusion-controlled process due to the much higher molecular weight of this polymer. With a further increase in the water content in the dispersion medium, the swollen aggregates collapse to form JPs. Interestingly, when a dispersion with a water content of 50 vol % is diluted with a THF/H2O mixture with the same water content, the shapes of the JPs are significantly modified and vitrified after removal of THF through evaporation. By increasing the dilution multiples adopted to dilute the intermediate dispersions, JPs with more asymmetric shapes are obtained due to the enhanced asynchronous aggregation. Ternary phase diagrams calculated according to the Flory-Huggins theory provide a semi-quantitative description and rationalization of the phase separation behavior related to the thermodynamic factors. The differences in the transport behavior and aggregation dynamics of the two polymers are also proven to be critical for the formation of the asymmetric structures. Upon irradiation, the BP-AZ-CN compartments of JPs exhibit remarkable elongation along the electric vibrational direction of a linearly polarized laser beam at a wavelength of 488 nm.

Advances in Marine Self-Powered Vibration Sensor Based on Triboelectric Nanogenerator

With the rapid development of advanced electronics/materials and manufacturing, marine vibration sensors have made great progress in the field of ship and ocean engineering, which could cater to the development trend of marine Internet of Things (IoT) and smart shipping. However, the use of conventional power supply models requires periodic recharging or replacement of batteries due to limited battery life, which greatly causes too much inconvenience and maintenance consumption, and may also pose a potential risk to the marine environment. By using the coupling effect of contact electrification and electrostatic induction, triboelectric nanogenerators (TENGs) were demonstrated to efficiently convert mechanical vibration movements into electrical signals for sensing the vibration amplitude, direction, frequency, velocity, and acceleration. In this article, according to the two working modes of harmonic vibration and non-harmonic vibration, the latest representative achievements of TENG-based vibration sensors for sensing mechanical vibration signals are comprehensively reviewed. This review not only covers the fundamental working mechanism, rational structural design, and analysis of practical application scenarios, but also investigates the characteristics of harmonic vibration and non-harmonic vibration. Finally, perspectives and challenges regarding TENG-based marine self-powered vibration sensors at present are discussed.

Influence of the Directions of Vibrations and Gravity on the Formation of Vortex Structures of a Nonuniformly Heated Fluid in a Square Cavity

Influence of the Directions of Vibrations and Gravity on the Formation of Vortex Structures of a Nonuniformly Heated Fluid in a Square Cavity

Scaling-up ultrasonic vibration assisted additive manufacturing to build 316 L 3 m3 waste container flange

Directed-energy deposition is a 3D printing method that uses a focused energy source, such as a plasma arc, laser, or electron beam to melt a material that is simultaneously deposited by a nozzle. As with other additive manufacturing processes, this technology is used to add material to existing components, for repairs, or to build new parts. Direct-energy deposition additive manufacturing techniques have gained much attention from the industry to build/repair in-service components. However, this process undergoes complex dynamics of melting and solidification raising challenges to the effective control of grain structure causing potential structural failure. This research study was conducted to investigate the potential of using high-intensity ultrasonic to control the solidification process and scaling up the system to manufacture large components. From the feasibility study, it was noted that ultrasonic can assist in the refinement of the grain structure and also reduce anomalies such as porosities. Under the feasibility study, a range of frequencies and power configurations were considered to ease the scale-up of the system. Based on the studied ultrasonic configurations, the 40 kHz 60 W configuration was finalized to use in the scale-up. It was also noted the reduction of hot cracks in the ultrasonic-assisted additive manufacturing due to the constitutional supercooling during solidification by lowering the temperature gradient in the bulk of the melt pool. Furthermore, it was also noted that the grain orientation is perpendicular to the direction of vibration which potentially can be used to control the orientation of the grains as required. This new finding provides new applications to exploit the ultrasonic-assisted additive manufacturing process.

Metastructure with integrated internal oscillators of constant, linearly and nonlinearly varying natural frequency

This research focuses on the analysis of the model and performance of lightweight metastructures encompassing a distributed array of internal homogenous oscillators, integrated into the host structure to create a single-piece element. This metastructure performs longitudinal vibrations, whose axis is colinear with the direction of the transverse vibration of the internal oscillators. First, the mechanical models of the separate elements of the metastructure and the metastructure as a whole are created and considered. The first modal frequencies of longitudinal vibrations of the metastructure with blocked and free internal oscillators are tuned to the first modal frequency of transverse vibration of one internal oscillator, yielding the optimal number of internal oscillators for this to be achieved, which is a new result for the proposed design. This theoretical result is then checked experimentally with the metastructures produced by 3D printing technology, comprising a different number of internal oscillators, all of which have the same natural frequency. Besides validating the theoretical results, experimental investigations with blocked and freely vibrating internal oscillators of the constant natural frequency are used to explore other performance characteristics, such as the width of the regions where the reduced amplitude is achieved. Finally, based on the theoretical and additional numerical results, the internal oscillators are modified in two ways, which is an original approach: their natural frequency is increased linearly and nonlinearly along the metastructure in accordance with the previous new theoretical results. The benefits of such new redesigns for the multi-modal performance characteristics of the metastructure are discussed.

Failure Mode Detection and Validation of a Shaft-Bearing System with Common Sensors.

Failure mode detection is essential for bearing life prediction to protect the shafts on the machinery. This work demonstrates the rolling bearing vibration measurement, signals converting and analysis, feature extraction, and machine learning with neural networks to achieve failure mode detection for a shaft bearing. Two self-designed bearing test platforms with two types of sensors conduct the bearing vibration collection in normal and abnormal states. The time-domain signals convert to the frequency domain for analysis to observe the dominant frequency between these two types of sensors. In feature extraction, principal components analysis (PCA) combines with wavelet packet decomposition (WPD) to form the two feature extraction methods: PCA-WPD and WPD-PCA for optimization. The features extracted by these two methods serve as input to the long short-term memory (LSTM) networks for classification and training to distinguish bearing states in normal, misaligned, unbalanced, and impact loads. The evaluation arguments include sensor types, vibration directions, failure modes, feature extraction methods, and neural networks. In conclusion, the developed methods with the typical lower-cost sensor can achieve 97% accuracy in bearing failure mode detection.

The Nonlinear Dynamic Behavior of a Particle on a Vibrating Screen Based on the Elastoplastic Contact Model

The dynamic response of particles is closely related to screening efficiency. To study the dynamic response of particles, the dynamic equations of a particle on a screening surface are established based on the elastoplastic contact model of spherical particles and are solved for the coal particle. Then, the trajectories of the particles are given with different falling heights and particle radii. The completely different trajectories with slight changes in the falling height and particle radius indicate strong nonlinearity. Second, the nonlinear dynamic behavior under different amplitudes and frequencies is discussed, and the route of transition from quasiperiodic motion to chaotic motion is revealed. Finally, we discuss the average speed along the screening surface considering the frequency, amplitude, friction coefficient, inclination angle, and vibration direction angle. In addition, the convergence conditions of particle motion are proposed, and they are only affected by the inclination angle and friction angle. The results show that in the normal direction of the vibrating screen, the particle motion is quasiperiodic at low frequencies. With increasing frequency, the motion of the particle becomes chaotic, and its Poincaré map becomes petal-shaped. In addition, the number of petals increases at the mutation of the bifurcation diagram. The increase in frequency, amplitude and inclination angle and the decrease in friction coefficient lead to an increase in particle speed along the screen surface. In addition, the particle speed reaches a maximum when the vibration direction angle is 65°. This work provides a theoretical basis for controlling the thickness of granular material flow on a vibrating screen and selecting screening process parameters.

Transfer matrix modeling and experimental verification of forked piezoelectric actuators

Piezoelectric actuators with forked substructures are popular in practical applications. However, there is still a lack of effective modeling methods for forked piezoelectric actuators whose essential substructures converge on the same interface. The critical problem is establishing the transfer conditions between the state vectors distributed on the interface for the forked piezoelectric actuators. To ease these issues, the transfer matrix method is adopted to create forked transfer conditions and to achieve the modeling of the forked piezoelectric actuators in this paper. The forked transfer conditions, including the velocity and force relationships at the interface, are first created. The velocity relationships between state vectors are built by the method of relative velocity, and the force components acting on the interface are equilibrant. Then, a piezoelectric actuator with forked substructures is designed, and its electromechanical coupling model is developed as a case study to confirm the created forked transfer condition. Finally, an actuator prototype is manufactured to verify the proposed forked transfer conditions and the correctness of the developed transfer matrix model of the whole system. The computational and measured vibration characteristics, including resonant frequencies and vibration shapes, agree with each other. Results powerfully demonstrate that the forked connection can transform the vibration direction and realize the amplitude amplification. This modeling method can analyze the vibration characteristics of other similar piezoelectric actuators with the forked substructures.

Structural displacement estimation using accelerometer and FMCW millimeter wave radar

Structural displacement plays a crucial role in structural health monitoring. However, its measurement remains challenging for many civil infrastructure applications. This study proposes a structural displacement estimation technique that fuses measurements from a collocated accelerometer and frequency-modulated continuous-wave millimeter wave radar at displacement estimation location on a structure. Automated initial calibration was first performed using short-period (less than 1 min) radar and acceleration measurements. The best target is automatically selected from the surroundings, and a conversion factor to convert the line-of-sight displacement to the structural displacement in the actual vibration direction is automatically estimated for the target. After calibration, the displacement is estimated in real time from radar measurements using the selected best target and its estimated conversion factor. Note that an accelerometer-aided phase-unwrapping algorithm is proposed and applied to address the phase-wrapping issue when the structural displacement is larger than the radar wavelength. The radar-based displacement is further fused with the acceleration measurement using a finite impulse response filter to estimate the displacement with improved accuracy at the cost of a short time delay. Laboratory tests on a four-story building model and a field test on a pedestrian bridge were conducted to validate the proposed displacement estimation technique. The displacements estimated by the proposed technique had an error of less than 1 mm in both tests compared to the ground-truth displacements measured by laser-based displacement sensors.

Research on mechanism of ultrasonic-assisted nano-cutting of sapphire based on molecular dynamics

Ultrasonic vibration grinding improves the surface quality and processing efficiency of sapphire machining compared with conventional grinding, but its nano-scale deformation mechanism is still unclear. In this study, the molecular dynamics method was used to simulate the ultrasonic vibration cutting of a single abrasive grain along the [010] direction on the sapphire (0001) surface to study the effects of different vibration directions, amplitudes and frequencies on the cutting force, stress, temperature, number of amorphous atoms, surface morphology and subsurface damage layer. The results show that the tangential and radial vibration cutting reduces the tangential force, normal force and total force compared with conventional cutting. At the same time, it is also found that different vibration directions have different effects on material removal efficiency and subsurface damage depth. In the material removal efficiency, the radial vibration cutting has the highest removal efficiency, and the tangential vibration cutting and conventional cutting have the same removal efficiency. In the subsurface damage depth, the subsurface damage depth in tangential vibration cutting is the smallest, the subsurface damage depth in conventional cutting is the second, and the subsurface damage depth in radial vibration cutting is the largest.

Attitude Magnetic Measurement Compensation Method of Fiber-Optic Submarine Seismometer

When the optical fiber submarine seismometer is applied to the seabed, the direction of vibration should be compensated by heading angle. In order to meet the stringent requirements of small size and low power consumption, geomagnetic sensors are used to measure the heading angle. Due to the complexity of magnetic field interference in the seismometer, the heading angle calculated by electronic compass based on the geomagnetic sensors is not accurate. In order to improve the accuracy of heading angle, we propose a geomagnetic compensation method based on unscented Kalman algorithm, which can solve the problems of difficult calibration operation and long-term accuracy in existing magnetic compensation methods. Meanwhile, according to the environmental conditions of underwater applications, we further optimize the method to reduce the calculation amount and avoid the non-positive definite problem of some Cholesky decomposition. The experiment is carried out to validate the effectiveness of the proposed method. The results show that the heading angle errors compensated by proposed method are all within 0.5°, which meets the application requirements of fiber optic submarine seismometer. In addition, the experimental operation is simple when using the proposed method.

Evaluation of hand-arm vibration(HAV) exposure levels among grounds maintenance workers: An observational human exposure measurement study.

Evaluation of hand-arm vibration(HAV) exposure levels among grounds maintenance workers: An observational human exposure measurement study.