Eccentric Weights Research Articles

Analytical Overview of the Methods of Controlling the Parameters of Vibratory Compaction of the Concrete Mixes

Introduction. A historical (retrospective) overview of the evolution and application of the methods of concrete mixture compaction by vibration, as well as an overview of the breakthrough scientific+ advancements in the studied field have been presented. The use of the dry concrete mixes that reduce cement consumption, accelerate the strength gain of concrete, reduce the shrinkage strain and heat emission and increase the strength and durability of products has been proposed. The theoretical and practical issues of vibratory compaction of the concrete mixes, the research on the effect reached by the various vibration modes of the vibrating tables, the issues of choosing an efficient mode of vibration impact during compacting the concrete mixes and optimisation of their parameters have been studied. The vibrating table design, the installation layout of the vibrator’s eccentric weights to obtain a given value of the exciting force and the layout of a vibration module with the directed vibrations have been studied in detail. The criteria of duration of the concrete mixture compaction have been defined, changes of the impact parameters during compacting the concrete mixes have been characterised and technical specifications of the vibrating tables have been defined. In the article considerable attention has been paid to the main parameters of the vibrocompacting machines: frequency, amplitude and acceleration of the working member. Most often, the parameter of intensity is used to assess the efficiency of the vibration impact received by the mixture during the compaction process.Materials and Methods. A mixture that turns into concrete after compaction, setting and hardening was selected for the research. The various methods and parameters of concrete mixture compaction to obtain the high-quality concrete were studied. The impact of the various vibration modes on the process of compaction of concrete mixes was investigated, the criteria for the efficient selection and optimisation of the vibration impact parameters were revealed. The paper presents the criteria for assessing duration of the concrete mixture compaction and describes the changes in the parameters during compaction of the concrete mixes. The technical specifications of the vibrating tables of different types and sizes were also presented. The choice of the vibration compaction mode for the concrete mixture is a complicated task, which includes many parameters.Results. Upon the research, the data on the process of concrete mixture compaction under the impact of vibration forces has been obtained. The process results in the destruction of the structural bonds and weakening the bonds between the particles, which leads to the emergence of a variable stress-strain condition. It has also been found that under such settings, the mineral particles get transferred and a denser packing is formed.Discussion and Conclusion. The resulting denser packing of the concrete mixture particles ensures the undoubted economic advantage due to reduced consumption of a binder without loss of the strength properties of concrete.

Periodic magnetic finishing machine

The present invention is related to finishing mechanical, electronic, and jewelry workpieces. The system comprises a container -including an abrasive medium-, a control unit, a measurement unit, and a display. Adjusting the rotational and vibration motion is conducted using magnetic coils and eccentric weights in the control unit. Moreover, the control system can tune the container's tilt angle. The magnetic coils enclose the container producing a magnetic field, thereby pulling the abrasive particles against the target surfaces. The container is held by two motors located at its top and bottom, which provide the rotational movement of the container around its axis. Besides, the rotary motors that hold the container are bound by the structure related to the vibration motors, which are paid by the vibration motors of the container assembly and the materials inside it due to the resulting vibration. Finally, these motors are placed on the device's frame with the help of a vibration damping system (springs), which allows the device to be adjusted at different tilt angles and create a rocking motion with the help of an angular movement mechanism. The printing circuit companies, ornamental jewelry companies, and factories producing mechanical parts are potential customers of this equipment that can use this machine for surface finishing aiming to increase the surface smoothness on a micro scale for a large number of parts.

Coupled actuators with a mechanically synchronized phase during MR elastography: A phantom feasibility study

AbstractIntroductionMagnetic resonance elastography (MRE) is an MR imaging method for the quantification of spatial stiffness of soft tissues using mechanically induced dynamic shear waves. In some applications, the penetration of shear waves can be limited through attenuation and shadowing of the waves. In order to increase the actuator performance, we present a dual driver approach to compensate for shear wave attenuation and to achieve better coverage over the entire region of interest.Materials and Methods(a) We designed pneumatic turbines that created a sinusoidal centrifugal force due to an eccentric weight. Two turbines were connected in‐phase with each eccentric weight having the same angular position relative to its pivot point. (b) We developed a tissue elasticity mimicking abdominal phantom. (c) The phantom served as a test object to investigate the feasibility to generate shear waves at two surface origins with the dual actuator system and to compare it against a single actuation setup.Results and DiscussionA stable phase relationship of the shear waves generated by the turbines was achieved as the positions of the eccentric weights were mechanically fixed. The abdominal phantom yielded sufficient MR signal. Liver and rib cage were clearly visible in MR imaging. The shear waves generated by the dual turbine propagated through the region of interest. Our turbine design is reproducible through 3D printing and can be integrated into existing clinical equipment for 1.5 T and 3 T scanners.

Development and Evaluation of a Device for Inducing Kinesthetic Illusion of Dual Joint Movements

If kinesthetic sensation can be generated using artificial means, we can experience dynamic sensations in the virtual reality space. Subsequently, it can be used as an instruction tool for rehabilitation. By means of kinesthetic illusion, it is possible to create kinesthetic sensation. In this study, we developed an interface device that creates kinesthetic illusions by inducing vibrations in muscle tendons that coordinate dual joint movements. First, we produced a vibrating device using four vibrators. The rotation of motors moving eccentric weights generated the vibrations. Each motor was independently controlled using specially developed software. Second, we produced vibrator fixation structures, which firmly attached the vibrators to the muscle tendons. Using these structures, the vibrators were maintained in position and allowed to transmit forces to the muscle tendons. Furthermore, we conducted an experiment to evaluate the performance of the kinesthetic illusion device. Accordingly, we created the kinesthetic illusion of drawing figures on a horizontal surface by inducing vibrations in muscle tendons that contribute to dual joint movements. The results demonstrated that, by using this device, it was possible to induce kinesthetic illusions of dual joint movements.

Experimental and Analytical Research on Resonance Phenomena of Vibrating Head with MRE Regulating Element

A vibratory pile hammer (VPH) is a mechanical device used to drive steel piles as well as tube piles into soil to provide foundation support for buildings or other structures. In order to increase the stability and the efficiency of the VPH work in the over-resonance frequency, a new VPH construction was developed at the Military University of Technology. The new VPH contains a system of counter-rotating eccentric weights, powered by hydraulic motors, and designed in such a way that horizontal vibrations cancel out, while vertical vibrations are transmitted into the pile. This system is suspended in the static parts by the adaptive variable stiffness pillows based on a smart material, magnetorheological elastomer (MRE), whose rheological and mechanical properties can be reversibly and rapidly controlled by an external magnetic field. The work presented in the paper is a part of the modified VPH construction design process. It concerns the experimental research on the vibrations during the piling process and the analytical analyses of the gained signal. The results will be applied in the VPH control system.

2A1-N04 偏心重錘機構を用いた自己励振型跳躍ロボットの開発(アクチュエータの機構と制御(1))

2A1-N04 偏心重錘機構を用いた自己励振型跳躍ロボットの開発(アクチュエータの機構と制御(1))

Golf players exhibit changes to grip speed parameters during club release in response to changes in club stiffness

The influence of golf club stiffness on driving performance is currently unclear, and it is possible that this ambiguity is due in part to golfer adaptation to equipment. The purpose of the current study was to elucidate mechanisms of adaptation to club stiffness, during the golf swing, by employing tendon vibration to distort proprioceptive feedback. Vibration (∼50Hz, ∼1mm amplitude) was applied to the upper extremities of 24 golfers using DC motors with eccentric weights. Golfers hit golf balls in a laboratory setting using three clubs of varying shaft stiffness, and club kinematics were recorded using high speed (180Hz) digital cameras. The results demonstrated significant slowing of the club grip during club release for a high-stiffness shaft with vibration. This suggests that, when proprioceptive feedback is available, players adapt to changes in club stiffness by modifying the release dynamics of the club late in the downswing.

Evaluation of a simple fruit tree structural model

A simple three element tree structure model of Lang, 2006 was tested in plum orchard using two different inertia fruit tree shakers. The first was a slider crank type one; the second had rotating eccentric weights. The parameters of both were chosen to give similar frequency and amplitude output in average orchard conditions. Orchard experiments were carried out shaking the trees with both machines at several frequencies and shaking heights. The measured acceleration and amplitude values were plotted on diagrams together with the calculated acceleration and amplitude curves of the fruit tree-shaker machine model. Choosing the right fruit tree parameters, such as apparent spring constant, damping coefficient, reduced trunk mass and coefficient of elasticity of the trunk the measured and calculated values coincided well. This proves the ability of the fruit tree model for optimising the shaker parameters to any given orchard.

Dynamic Modelling Structure of a Fruit Tree for Inertial Shaker System Design

Idling and working power equations for a shaker with rotating eccentric weights and for a slider crank type were established and compared. The tree structure model comprised both trunk and main roots. Using static equations, the location of virtual turning centre versus shaking height function was defined. Based on this function, a simple three-element model composed of reduced mass, spring constant and kinetic damping coefficient was transferred from a trunk cross-section to all others. Replacing these reduced parameters into the power equation of the two types of shaker and into the equation of trunk amplitude, the power consumption and amplitude versus shaking height curves were drawn. These functions, with the free combination of eccentricity, shaking frequency and mass parameters of the shakers help to optimise machine design. Calculating the relationship between power consumption and trunk amplitude for all trunk cross-sections, the most efficient clamping heights of the shakers were found.

Electromechanical coupling model and analysis of transient behavior for inertial reciprocation machines

The dynamical equations for a inertial reciprocating machine excited by two rotating eccentric weights were built by the matrix methodology for establishing dynamical equations of discrete systems. A mathematical model of electromechanical coupling system for the machine was formed by combining the dynamical equations with the state equations of the two motors. The computer simulation to the model was performed for several values of the damping coefficient or the motor power, respectively. The substance of transient behavior of the machine is unveiled by analyzing the results of the computer simulation, and new methods are presented for diminishing the transient amplitude of the vibrating machine and improving the transient behavior. The reliable mathematical model is provided for intelligent control of the transient behavior and engineering design of the equipment.

Study of a Brush-Type Micro-Robot Using Micro Coreless Motor

This paper deals with a new brush-Type micro-robot using micro coreless motor. Though many mobile microrobots using PZT elements generally require some highvoltage amplifiers with electric cable lines, making it little difficult for the mobile microrobot to move about on long, thin pipes. The present micro-robot consists of many brush fibers, two coreless motors and an electric cell. The coreless motors with eccentric weights can generate centrifugal forces transmitted to the elastic brush fibers driving the microrobot. A basic mathematical model of the micro mobile robot using centrifugal forces is derived. Simple prototypes are developed, and high velocity is examined by experiments. The validity of the proposed mathematical mode was examined by way of the comparision of simulated and experimental results.

遠心力を利用した走行マイクロロボットの研究

This paper deals with a new mobile micro-robot using centrifugal force. Many mobile micro-robots using PZT elements have been developed, though their PZT elements generally require some high voltage amplifiers with electric cable lines. Therefore, it is a little difficult for the mobile micro-robot to move about in long and thin pipes. My proposed micro-robot consists of many brush fibers, two coreless motors and a button electric cell. These coreless motors with eccentric weights generate centrifugal forces which transmit to the brush fibers with elastictity, and consequently occur driving forces of the micro-robot. First, I derive a basic mathematical model of the mobile micro-robot using centrifugal forces. Next, some simple prototypes of this robot are developed, and the characteristics of high velocity is examined by experiment. Finally, I verify the validity of the proposed mathematical model by comparing simulation results with experimental results .

The Effect of Bending on the Normalized Stress at Roots of Threaded Connectors

Abstract Three-dimensional photoelasticity was used to analyze the effect of bending on the normalized stress at the roots of threaded connectors. Loading was effected by steel cages and a combination of eccentric weights (to provide the bending load) and concentric weights (to provide the axial load). The ratio of the bending stress to the axial stress was determined and various levels of this stress ratio, Rσ, were tested. The connections were analyzed by taking thin slices in the plane of bending and perpendicular to it. The position of the maximum fringe order at the roots was determined using Mesnager’s theorem and the maximum fringe order found by Tardy compensation. The fringe orders were normalized using the nominal axial stress and the total nominal stress (bending plus axial stress), which were calculated from the loads applied. The results, when normalized using the nominal axial stress and compared to those in connections without bending, exhibit a lower and broader peak of normalized stress values plotted against the helix length. The normalized stress values are also periodic in relation to the bending plane due to the variation in stress around the longitudinal axis of the bolt. It was found that bending in connectors will affect the normalized stress and that it is possible to determine this effect in a similar way to the method used for axially loaded connections.

Motion analysis of a vibrating bristled vehicle for small pipes.

In this study, a novel, vibrating bristled vehicle for small pipes is proposed. Its drive mechanism with two rotating eccentric weights and bristles is simulated and analyzed. The moving mechanism is examined and clarified by motion simulations and experiments conducted using a vehicle with numerous bristles. The fabricated vehicle moves smoothly in a pipe with an internal diameter of 80 mm at a velocity of 0.18 m/sec.

A study of a vibrating bristled vehicle for small pipes. Moving characteristics of the vehicle.

This paper proposes a new vehicle that runs in small pipes with an inner diameter of less than 100 mm in order to maintain and inspect them. Many bristles are attached at an angle to the surface of the vehicle. Eccentric weights at both ends of the vehicle are rotated by a motor inside the vehicle. Since this structure does not require wheels or reduction gears, it has good potential for miniaturization. First, the sliding velocity of each bristle and its friction are discussed. Then, running simulations and experiments are conducted using a vehicle with 16 bristles in order to clarify the relationship between the running velocity of the vehicle and the angular velocity of the eccentric weights. It is shown that the vehicle runs smoothly inside a small pipe and that the calculated running velocity agrees with the experimental results.

A study of a vibrating bristled vehicle for small pipes. (2nd report. Moving characteristics of the vehicle).

This paper proposes a new vehicle that moves inside small pipes with inner diameters of less than 100 mm in order to maintain and inspect them. The vehicle is surrounded by bristles vibrated by centrifugal force provided by rotating eccentric weights. Since this method does not require wheels or reduction gears, there is a good potential for miniaturization. First, the sliding velocity of each bristle and its friction are discussed. Then, moving simulations and experiments are conducted using a vehicle with 16 bristles in order to clarify the relationship between the moving velocity of the vehicle and the angular velocity of the rotating eccentric weights. It is shown that the vehicle moves smoothly inside a small pipe. The calculated moving velocity agrees with the experimental results.

Vibrating screen apparatus having dual function eccentric weights

A vibrating screen apparatus having plural unbalanced shaft assemblies to impart vibratory movement to a screen. Each screen assembly has a gear hub to which a pair of eccentric weights are secured in flanking relationship. The shaft assemblies are drivingly connected to one another by an arrangement including an annular gear mounted on the gear hub. The annular gear has such a special relationship to the weights and gear hub, that the act of clamping the weights in place on the gear hub simultaneously clamps the annular gear in place.

Dynamics of a torsional type inertia shaker

An equation of motion for a torsional type inertia shaker is formed which describes the separate angular motions of the eccentric masses and the driven unit in terms of the geometry of their component parts. In the absence of a satisfactory theoretical relationship between the respective angular motions of the two components performance data from an existing mechanism were analysed to establish an empirical relationship. An expression of the form ▪ in which f is dependent upon both the moment of inertia of the total assembly and that of the eccentric weights, was established and tested. Use of the mathematical model in the design of inertia shakers is discussed. Attention is drawn to the need to confirm the validity of the empirical relationship in applications where the critical dimensions of the inertia shaker and in particular their ratios differ significantly from those on which the relationship was based. Finally a simplified expression defining peak displacement is formulated and tested.

Rubber in Vibration

A machine is described which has been used for determining the vibration properties of various types of rubber mountings used for the isolation of mechanical vibrations. The vibrations are excited by oppositely rotating eccentric weights and are recorded on a tape. It was found that resonance curves for various types of rubber vibrations such as shear, torsion, and compression are, except for some minor deviations, adequately accounted for by the equation which contains a damping term proportional to the velocity and inversely proportional to the frequency. The apparent static modulus of rubber in compression depends upon the shape of the piece, more explicitly, on the ratio of load area to the free area. The same is true for the dynamic modulus. It was found that pieces of similar shape have identical values for the dynamic modulus and also for the internal friction. Some curves are given showing the dependence of dynamic modulus and internal friction on the shape factor. The dynamic stiffness shows the largest deviation from the static values at high shape factors. The internal friction has a linear relationship to the dynamic modulus when the shape factor is varied. This results in damping which is practically independent of the shape. The effect of temperature on the vibration properties of mounting stocks for a range −10°F to 160°F was studied and curves are included showing the temperature dependence in this range.