Suspensions Of Rods Research Articles

Development of fiber Bragg grating vibration sensor for bidirectional monitoring of thin rod cantilever beam

Monitoring of vibration frequencies and forces in cables and suspension rods of bridges is crucial. In order to achieve high-precision and bidirectional low-frequency monitoring of cable force and suspension rod, in this work, a thin rod cantilever beam type FBG vibration sensor was developed for bidirectional monitoring based on theory, experiment, and finite element simulation. Firstly, elastic structure of the thin rod was analyzed, and the structural parameters of the sensor were optimized based on theoretical analysis and finite element simulation. Then, the frequency and sensitivity of the sensor were tested. The obtained test results showed that the resonant frequency of the sensor in the x/y direction was 48 Hz, sensitivity was 90.5/102.3 pm/g, and error in frequency was less than 2 %. Furthermore, the force in the cable measured by the sensor was verified through indoor tension tests. The test results showed that the maximum error in the force measured in the cable was 0.86 % relative to the actual tension in the cable, indicating high measuring accuracy of the developed sensor. Finally, the sensor was applied to monitor forces in actual engineering cables, where an error of 4.21 % was noticed, which further validated the accuracy and applicability of the sensor. The research results of the present would provide guidance for improving the ability of the bidirectional low-frequency FBG vibration sensors to measure low-frequency random vibrations.

Viscosity prediction for dense suspensions of non-spherical particles based on CFD-DEM simulations

Reliable estimation of the viscosity and rheology of dense suspensions formed from non-spherical particles is of high importance for studies of many natural and industrial processes. Still, the complexity of underlying physics makes predicting the viscosity of such suspensions a challenging task, resulting in a lack of models capable of doing so for general suspensions. In this work, we present an approach based on a combination of the computational fluid dynamics (CFD) and discrete element method (DEM) developed for arbitrarily shaped particles and use it to predict viscosity of dense suspensions of spheres, rods, and glitters. Simulation results are compared to available experimental data and commonly used engineering correlations. The developed model can reliably predict suspension viscosity in a wide range of solid volume fractions and particle shapes. The simulations with spherical particles also reveal a shear-thickening trend at increased shear rates, which corresponds to the experimentally observed non-Newtonian behavior.

Tension identification of bridge suspension rods based on multiple impedance parameters from self-inductive coils

ABSTRACT This study introduces a method for identifying tension in suspension rods based on impedance from self-inductive coils, grounded in electromagnetic induction and magnetic elasticity principles. The theoretical feasibility of this method was analysed through a high-frequency inductive coil model. Steel strand tensile tests, utilising self-inductive coil sensors at various frequencies, explored the relationship between resistance, inductance, and capacitance with tension. According to the experimental results, the sensitivity coefficient is used to determine the optimal prediction frequency of each impedance parameter. Within the optimal frequency range, a single impedance parameter regression prediction method based on the impedance difference ratio index was proposed. To improve the accuracy and stability of the predictions, a GA-BP neural network prediction model based on the fusion of multiple impedance parameters was proposed. The results indicate that the GA-BP neural network prediction method, which integrates multiple impedance parameters, achieves higher accuracy in identifying cable forces than the single impedance parameter regression prediction method. Specifically, at a frequency of 5 kHz, the relative error of the GA-BP neural network prediction method, which integrates multiple impedance parameters, was only 3.74%. This research offers a novel approach for future in-service tension identification in bridge suspension rods.

Shear flow of non-Brownian rod-sphere mixtures near jamming.

We use the discrete element method, taking particle contact and hydrodynamic lubrication into account, to unveil the shear rheology of suspensions of frictionless non-Brownian rods in the dense packing fraction regime. We find that, analogously to the random close packing volume fraction, the shear-driven jamming point of this system varies in a nonmonotonic fashion as a function of the rod aspect ratio. The latter strongly influences how the addition of rodlike particles affects the rheological response of a suspension of frictionless non-Brownian spheres to an external shear flow. At fixed values of the total (rods plus spheres) packing fraction, the viscosity of the suspension is reduced by the addition of "short"(≤2) rods but is instead increased by the addition of "long"(≥2) rods. A mechanistic interpretation is provided in terms of packing and excluded-volume arguments.

Coupled Vibration Analysis of a Beam-Arch Composite Continuous Rigid Structure with Parallel Traffic Flow

To investigate the structural dynamic characteristics of a beam-arch composite continuous rigid structure bridge under the action of parallel moving loads on a multi-lane highway, a joint simulation analysis program based on Easy Language and ANSYS was developed. This study was conducted using a six-span beam-arch composite continuous rigid structure bridge located in Shaanxi Province as the reference project. The research focused on the most adverse dynamic coupled responses of the main beam midspan, arch crown, and suspension rods caused by double-axle cars, double-axle trucks, and three-axle trucks on a single-direction three-lane road surface.

Vibration loading of self-propelled sprayer booms on ultra-low pressure tires

BACKGROUND: The article presents the results of experimental studies of the vibration loading of the booms of a self-propelled sprayer equipped with ultra-low pressure tires 1020x420-18 model Bel-79 when driving through single artificial bumps. Based on the results of the tests, the dependences of the influence of maximum vertical accelerations on the suspension of rods on the speed of movement at different air pressure in the tires and levels of filling the sprayer tank with process liquid were obtained. It has been established that with a decrease in the filling of the tank with process liquid and an increase in the speed of movement, the level of fluctuations on the sprayer booms proportionally increases relative to the full filling. When moving a self-propelled sprayer through artificial irregularities with the booms opened in the working position, located at a distance of 700 mm from the supporting surface, in the entire range of speeds from 3 m/s to 12 m/s, the oscillation amplitude at the ends of the booms did not exceed 80 mm.
 AIMS experimental evaluation of the impact of operational parameters of a mobile power tool equipped with ultra-low pressure tires on the vibration loading of sprayer booms.
 METHODS: Methods of laboratory and field research on the passage of a mobile power tool equipped with a boom sprayer through artificial bumps are given. The maximum vertical accelerations on the sprayer booms were determined using the ASSISTANT TOTAL instrument complex, which consists of a measuring unit with a vibration analyzer and an AR38R vibration transducer.
 RESULTS: The dependences of the influence of air pressure in ultra-low pressure tires and the speed of movement of the MEV-600 on the level of fluctuations of the sprayer booms when moving along artificial single irregularities are obtained. The minimum level of fluctuations on the rods at different air pressures in tires and different degrees of tank filling reaches at a MES speed of 9 m/s. The most vibration-loaded for sprayer booms is the empty driving mode.
 CONCLUSIONS: 
 The minimum level of fluctuations on the sprayer booms takes place in the speed range of 7.5 - 10.5 m/s. When the air pressure in the tires is reduced from 80 kPa to 20 kPa, the vibration loading of the rods is reduced by 2.8 times. An increase in vibration loading takes place in the range of filling level of the sprayer tank from 50% to empty. When moving along individual irregularities in the speed range from 3 m/s to 12 m/s, the sprayer booms were stably in a horizontal position, no intense vibrations and resonant modes of boom sections were observed.

Dilute suspensions of Janus rods: the role of bond and shape anisotropy.

Nanometer-sized clusters are often targeted due to their potential applications as nanoreactors or storage/delivery devices. One route to assemble and stabilize finite structures consists of imparting directional bonding patterns between the nanoparticles. When only a portion of the particle surface is able to form an inter-particle bond, finite-size aggregates such as micelles and vesicles may form. Building on this approach, we combine particle shape anisotropy with the directionality of the bonding patterns and investigate the combined effect of particle elongation and surface patchiness on the low density assembly scenario. To this aim, we study the assembly of tip-functionalised Janus hard spherocylinders by means of Monte Carlo simulations. By exploring the effects of changing the interaction strength and range at different packing fractions, we highlight the role played by shape and bond anisotropy on the emerging aggregates (micelles, vesicles, elongated micelles, and lamellae). We observe that shape anisotropy plays a crucial role in suppressing phases that are typical to spherical Janus nanoparticles and that a careful tuning of the interaction parameters allows promoting the formation of spherical micelles. These finite-size spherical clusters composed of elongated particles might offer more interstitials and larger surface areas than those offered by micelles of spherical or almost-spherical units, thus enhancing their storage and catalytic properties.

A barrier method for contact avoiding particles in Stokes flow

Rigid particles in a Stokesian fluid experience an increasingly strong lubrication resistance as particle gaps narrow. Numerically, resolving these lubrication forces comes at an intractably large cost, even for moderate system sizes. Hence, it can typically not be guaranteed that artificial particle collisions and overlaps do not occur in a dynamic simulation, independently of the choice of method to solve the Stokes equations. In this work, the potentially large set of non-overlap constraints, in terms of the Euclidean distance between boundary points on disjoint particles, are efficiently represented via a barrier energy. We solve for the minimum magnitudes of repelling contact forces and torques between any particle pair in contact to correct for overlaps by enforcing a zero barrier energy at the next time level, given a contact-free configuration at a previous instance in time. Robustness for the method is illustrated using a multiblob method to solve the mobility problem in Stokes flow, applied to suspensions of spheres, rods and boomerang shaped particles. Collision free configurations are obtained at all instances in time, and considerably larger time-steps can be taken than without the technique. The effect of the contact forces on the collective order of a set of rods in a background flow that naturally promote particle interactions is also illustrated.

Cox–Merz rules from general rigid bead-rod theory

The value of this work is in its macromolecular explanations of both Cox–Merz rules, thus of when to expect them to work. For polymeric liquids and their solutions, the measured values of the steady shear viscosity and the magnitude of the complex viscosity often equate, within experimental error, when compared at common shear rate (in units of t−1) and angular frequency (in units of rad t−1). Called the first Cox–Merz rule, this remarkable empiricism, with one exception, has defied most macromolecular explanations. This one exception is the suspension of multi-bead rods and its special case of rigid dumbbells. The second Cox–Merz rule equates approximately the slope of the first derivative of steady shear viscosity with respect to shear rate with the real part of the complex viscosity when compared at common shear rate (in units of t−1) and angular frequency (in units of rad t−1). In this paper, we explain both Cox–Merz rules for all axisymmetric macromolecules, be they prolate or oblate, of almost any lopsidedness. Furthermore, through the lens of general rigid bead-rod theory, we define under what conditions these rules do not apply. Specifically, the first Cox–Merz rule fails when the macromolecules are too oblate.

Characterizing Phase Transitions of Microfibrillated Cellulose Induced by Anionic and Cationic Surfactants.

Rheological modifiers are used to tune rheology or induce phase transitions of products. Microfibrillated cellulose (MFC), a renewable material, has the potential to be used for rheological modification. However, the lack of studies on the evolution in rheological properties and structure during its phase transitions has prevented MFC from being added to consumer, fabric, and home care products. In this work, we characterize surface-oxidized MFC (OMFC), a negatively charged colloidal rod suspension. We measure the rheological properties and structure of OMFC during sol-gel phase transitions induced by either anionic or cationic surfactant using multiple particle tracking microrheology (MPT). MPT tracks the Brownian motion of fluorescent probe particles embedded in a sample, which is related to the sample's rheological properties. Using MPT, we measure that OMFC gelation evolution is dependent on the charge of the surfactant that induces the phase transition. OMFC gelation is gradual in anionic surfactant. In cationic surfactant, gelation is rapid followed by length scale-dependent colloidal fiber rearrangement. Initial OMFC concentration is directly related to how tightly associated the network is at the phase transition, with an increase in concentration resulting in a more tightly associated network with smaller pores. Bulk rheology measures that OMFC forms a stiffer structure but yields at lower strains in cationic surfactant than in anionic surfactant. This study characterizes the role of surfactant in inducing phase transitions, which can be used as a guide for designing future products.

CALCULATION OF THE MAIN ELEMENTS OF THE ROPE-PULLEY DRIVE OF A DOWNHOLE ROD PUMPING UNIT

The goal of minimizing oil production costs is becoming increasingly crucial in current oil production settings, particularly during the operation of oil fields in the final phases of development and the ever-expanding commissioning of difficult-to-recover hydrocarbon reserves. Oil production practice has shown, lengthening the length of the steel pumping plant's loop needs a lower frequency of rolling, which extends the life of the well equipment and enhances pumping installation performance. The engine's weight and cost increase as the drive lengthens. The necessary characteristics made it impossible to build long-stroke balancing drives. One of the ways to solve this problem is the use of long-stroke unbalanced sucker-rod pump drives as part of pumping units, which will significantly reduce energy consumption for oil production and, accordingly, reduce the cost. The presented article shows the prospects of using unbalanced drives of sucker-rod pumping units in the operation of wells by mechanized method. The kinematic-power diagram of the drive of the downhole rod pumping unit is shown. A method for calculating the acting forces is given. To calculate the strength of the structure being developed, it is important to determine the change in the force acting on the suspension point of the rods. In order to carry out repair work, the goal was set to further improve the unbalanced drive WRPU (well rod pump unit). For this, a scheme was proposed for changing the fixed guide pulley to a movable one, installed on the base with the possibility of its rotation. The proposed design of the rotary pulley makes it possible to free up space above the wellhead. Keywords: unbalanced drive, long stroke, swivel pulley, beamless drive of pumping unit, rod suspension point, crank-pulley converting mechanism.

Modeling and numerical simulations of Brownian rodlike particles with anisotropic translational diffusion

The suspension of Brownian rods in flow has a major effect in many engineering applications. We numerically examine Brownian rod suspensions through a rectangular channel with and without the effect of circular obstacles, taking into consideration the isotropic translational diffusion tensor using the finite element method. We develop a kinetic macro-model that reduces the computational effort of the Brownian rod suspensions and it gives a good approximation with errors less than 5%.

Ground State Configurations and Metastable Phases of Charged Linear Rods.

This computational study investigates the energy minimum, that is, ground state, of suspensions of monodisperse (single-component) charged linear rods at various densities and screening lengths. We find that closed-packed unidirectional configurations have the lowest energies for all studied cases. We further specify the lattice parameters for these crystalline structures. In addition, we identify a few metastable phases, including heliconical structures. These metastable heliconical phases are composed of hexagonal smectic C layers with particle orientations forming a conical helicoid with a short pitch of three layers. We evidence this by zero-temperature Monte Carlo simulations starting from an energy-minimized hexagonal cholesteric configuration, which rapidly transforms to a heliconical phase. Furthermore, this heliconical phase is remarkably stable even at finite temperatures and melts to a disordered phase at high temperatures. Finally, we conduct simulations at room temperature and conditions typical for cellulose nanocrystal suspensions to study the onset of nematic order and compare our results to available experimental data. Our findings suggest that electrostatics play an important role in the isotropic/anisotropic transition for dense suspensions of charged rods.

Effect of sample height and particle elongation in the sedimentation of colloidal rods.

We study theoretically the effect of a gravitational field on the equilibrium behaviour of a colloidal suspension of rods with different length-to-width aspect ratios. The bulk phases of the system are described with analytical equations of state. The gravitational field is then incorporated via sedimentation path theory, which assumes a local equilibrium condition at each altitude of the sample. The bulk phenomenology is significantly enriched by the presence of the gravitational field. In a suspension of elongated rods with five stable phases in bulk, the gravitational field stabilizes up to fifteen different stacking sequences. The sample height has a non-trivial effect on the stable stacking sequence. New layers of distinct bulk phases appear either at the top, at the bottom, or simultaneously at the top and the bottom when increasing the sample height at constant colloidal concentration. We also study sedimentation in a mass-polydisperse suspension in which all rods have the same shape but different buoyant masses.

Rod Suspension of Inertial Mass for Pendulum-Type Sins

Rod Suspension of Inertial Mass for Pendulum-Type Sins

Cause Analysis and Solution of Premature Fracture of Suspension Rod in Metro Gear Box

Through the appearance observation of suspension rod in the metro gearbox, macro and micro observation of the fracture and quantitative analysis of the fracture, combined with the metallographic and hardness examination results of the boom, the finite element model was established and the force analysis of suspension rod was carried out to explore the causes of the fracture of the gearbox boom. The results show that the nature of suspension rod fracture is fatigue. The cause of its fatigue fracture is related to the low fatigue tolerance for booms in metro operation, and the surface shallow decarburization plays a role in promoting the fatigue fracture of suspension rod. The life of fatigue crack growth in the boom is 819 stations (or 1210 km), and the fatigue initiation life is 522,452 km.

Study on the Contamination Characteristics of V-Type Double Suspension Rod Insulators Based on the Influence of Wake Flow

The insulators of the catenary of the Lanzhou-Xinjiang High-speed Railway in windy areas suffer from serious contamination, which has led to frequent flashover accidents. The catenary of the Lanzhou-Xinjiang High-speed Railway has adopted the unique external insulation of V-type double suspension rod insulators. To further determine the contamination characteristics of this type of insulator, a contamination simulation model of insulator is established in this paper based on the principles of fluid mechanics, which is used to analyze the contamination characteristics of the V-type double suspension rod insulators under the influence of wake flow. The research results show that wind speed directly determines the static pressure on the surface of the insulator, the wind speed and particle concentration are proportional to the contamination volumes on the windward and crosswind sides of insulator, while the particle size is inversely proportional to the contamination volume on the leeward side of the insulator. The direction of wake flow is consistent with the direction angle of external incoming flow, and the wake flow generating area affects the contamination characteristics of the insulator. When the incoming flow is at a prevailing wind direction of 0°, focus should be put on the windward and crosswind sides of the two insulators during insulator cleaning, and the contamination distributions on these two insulators are similar; when the incoming flow is at a prevailing wind elevation of 0°∼60°, focus should be put on the entire surface of 1# insulator and the windward and crosswind sides of 2# insulator during insulator cleaning.

ABOUT THE METHOD OF CALCULATION THE PUMJACK`S BALANCING

The consistent performance of a modern oil-well pumping unit depends on many factors. One of them is equalizing the operation of the electric motor. The article considers the equilizing method applicable for double lever pumping units manufactured according to the industry standard of Azerbaijan OST 26-16-08-87. The study is based on the idea that the work done on the crankshaft of the pumping unit per cycle is the sum of the work done during the upward stroke and the work performed during the downward stroke of the rod suspension point (RSP). Formulas for determining the weight of balancing masses are presented. Key words: driver, pumping unit, electric motor, equilizing, equilizer, crank, torque.

Hydrodynamic interaction and complex viscosity of multi-bead rods

One good way to explain the elasticity of a polymeric liquid is to just consider the orientation distribution of the macromolecules. When exploring how macromolecular architecture affects the elasticity of a polymeric liquid, we find the general rigid bead–rod theory to be both versatile and accurate. This theory sculpts macromolecules using beads and rods. Whereas beads represent points of Stokes flow resistances, the rods represent rigid separations. In this way, how the shape of the macromolecule affects its rheological behavior in suspension is determined. Until recently, general rigid bead–rod theory has neglected interferences of the Stokes flow velocity profiles between nearby beads. We call these hydrodynamic interactions, and we here employ our new method for exploring how these interactions affect the complex viscosity of suspensions of multi-bead rods. These multi-bead rods are also called shish-kebabs. We use the center-to-center distance between adjacent beads as the characteristic length. We proceed analytically, beginning with a geometric expression for the shish-kebab bead positions. Our analytical solution for the complex viscosity presents as one for N=3,5,6,7,8,…, one for N=4, and another for the rigid dumbbell, N=2. We find that for shish-kebabs, hydrodynamic interactions (i) increase zero-shear viscosity, (ii) increase zero-shear first normal stress coefficient, (iii) decrease the real part of the dimensionless complex viscosity, and (iv) increase minus the dimensionless imaginary part. We find that the combination of (iii) and (iv) explains crossovers of the parts of the complex viscosity. We further find that for a monodisperse polystyrene solution, the general rigid bead–rod theory with hydrodynamic interaction, for both parts of the complex viscosity, provides stunning improvement over without.

Yield stress and microstructure of composite halloysite-LAPONITE® gels: Effects of mixing ratio, surface chemistry, and ageing time

The dependences of yield stress and microstructure of composite halloysite (Hal)-LAPONITE® (Lap) gels on the Lap/Hal mixing ratio, surface chemistry (pH and ionic strength), and ageing time were investigated in this study. The yield stress was measured using the vane technique and the microstructure was revealed by the cryogenic scanning electron microscopy (cryoSEM) images. At a fixed solid loading, the yield stress of composite Hal-Lap gels first quickly decreased to a lowest point and then kept increasing as Lap/Hal mixing ratio increased. The corresponding microstructure changed from Hal dominated network to Lap dominated network showing strong interactions between Hal and Lap particles through heterogeneous charge attractions. Six stages, each with distinct features, were identified during the transition. The maximum of yield stress displayed at around pH 11 for composite Hal-Lap gels and pure Hal gel. The attractive interactions between pure Hal-Hal and Lap-Lap particles and composite Lap-Hal particles were still present in a significant manner at pH 12 as reflected by the high yield stress. The microstructure of composite Hal-Lap gels and pure Hal gel displayed a high content of fibre end-face interactions even at high pH. However, “phase separation” occurred at low pH 4. Increasing ionic strength resulted in higher bond strength due to the van der Waals attraction and heterogeneous charge attraction, so it produced higher yield stress gels of pure Hal gel and composite Hal-Lap gels with low Lap content. At high ionic strength, small Hal particles formed aggregates with large Hal nanotubes while Lap particles formed large agglomerates. The H18L2 showed microstructure with circular agglomerates dispersed in a suspension of Hal rods. The agglomerates consisted of a mixture of tightly packed Hal rods and Lap particles. The microstructure of composite Hal-Lap gels was also strengthened during ageing due to the particle rearrangement. A water-gel phase separation due to the Hal particles sedimentation was observed for composite gels with low Lap/Hal mixing ratio as increasing ageing time.