Torsional Oscillations Research Articles

Technological Capabilities of Impulse Rotators

In the article “Technological capabilities of impulse rotators” the results of use of impulse rotators in some technological processes, differential adjustment of their motion with kinematic and dynamic vibration exciter are considered. Equation of kinetic energy of impulse rotator allows to determine mutual influence of design elements on rational use of supplied pulse energy for useful work. Positive qualities of kinematic torsional vibration exciters are noted, the main of which is organization of force pulse regularity and its considerable force possibilities of pulse creation. A generalized graph of the change of productivity and wear of the working element of the pulse converter compared to the static one is given.Features of impulse rotators with kinematic excitation of torsional oscillations make it possible to change the mode of work performance, to apply low-energy processes of individual operations. Transportation way of destruction products by the screw with use of an impulse rotator on breeds above average fortress excludes use of the compressor. Machines with rolling and spring impact tools do not correspond to the screw method of destruction products discharge and require compressor use. In this case, the energy intensity of production unit increases more than twice.

A Simple Experimental Setup for Simultaneous Superfluid-Response and Heat-Capacity Measurements for Helium in Confined Geometries

Torsional oscillator (TO) is an experimental technique which is widely used to investigate superfluid responses in helium systems confined in porous materials or adsorbed on substrates. In these systems, heat capacity (HC) is also an important quantity to study the local thermodynamic properties. We have developed a simple method to incorporate the capability of HC measurement into an existing TO without modifying the TO itself. By inserting a rigid thermal isolation support made of alumina and a weak thermal link made of fine copper wires between a standard TO and the mixing chamber of a dilution refrigerator in parallel, we were able to carry out simultaneous TO and HC measurements on exactly the same helium sample, i.e., four atomic layers of $^4$He adsorbed on graphite, with good accuracies down to 30 mK. The data reproduced very well the previous workers' results obtained independently using setups optimized for individual measurements. This method is conveniently applicable to a variety of experiments where careful comparisons between results of TO and HC measurements are crucial. We describe how to design the thermal isolation support and the weak thermal link to manage conflicting requirements in the two techniques.

Robust Power Designing of Supplementary Damping Controller in VSC HVDC System to Improve Energy Conversion Efficiency of Wind Turbine and Power System Stability

Because of low losses and voltage drop, fast control of power, limitless connection distance, and isolation issues, using high-voltage direct-current (HVDC) transmission system is recommended to transfer power in the power systems, including wind farms. This paper aims to propose a supplementary damping controller (SDC) based on the HVDC to improve not only power system dynamic stability but also energy conversion efficiency and torsional vibration damping in the wind power plants (WPPs). When the WPPs are working in power control mode, the active power is set to its reference value, which is extracted from power-speed curve. This paper shows that torsional oscillations associated with the poorly torsional modes can be affected by different operating regions of the power-speed curve of WPP. Therefore, it is essential to employ an SDC to have the optimum energy conversion efficiency in the wind turbine and the most dynamic stability margin in the power system. The SDC is designed using a fractional-order PID controller (FOPID) based on the multiobjective bat-genetic algorithm (MOBGA). The simulation results show that the proposed control strategy effectively works in minimizing the torsional and electromechanical oscillations in power system and optimizing the energy conversion efficiency in the wind turbine.

Gear Rattle during a start-up transient in a driveline equipped with a tuneable torsional Vibration Damper with Magneto-Rheological Elastomers

The paper reports a numerical investigation on the dynamic behaviour of a vehicle driveline, equipped with a Torsional Vibration Damper (TVD) based on Magneto-Rheological Elastomeric (MRE) spring elements, during the start-up transient considering an abrupt manoeuvre of clutch engagement. The TVD device consists of a flywheel and a damper disk, with interposed some elastomeric samples which react for relative angular displacements of the two disks. The dynamical parameters of the TVD can be properly tuned by varying the magnetic field surrounding the MRE springs to mitigate the torsional oscillations of the flywheel, causes of many undesired inconveniences as critical speeds or vibro-acoustic issues. The present study promotes the use of the MRE torsional vibration damper to reduce the annoying vibroacoustic phenomenon of “gear rattle” arising in the unloaded gear pairs of the gear box, during and after the rapid clutch engagement transients in the vehicle start-up phase and is conducted on a simplified automotive driveline equipped with a dry clutch. The possibility of quickly tuning the mechanical properties of the MRE-TVD, makes this device particularly eligible for suppressing the above disturbance, adapting to the various operative conditions of the automotive driveline. Results of the analysis, by the help of a Gear Rattle Index (GRI), demonstrate the effectiveness of the proposed device in reducing the vibroacoustic phenomenon during the transient phases of the vehicle start-up, until the vehicles speed conditions are reached.

Measurement-Driven Source Tracing of Torsional Subsynchronous Oscillations Caused by Open-Loop Modal Resonance

Open-loop modal resonance is the mechanism that a grid-connected wind farm (WF) excites dangerous torsional subsynchronous oscillations (SSOs) of a synchronous generator. However, the open-loop modal resonance analysis (OMA) has to rely on the parametric model, while, in practice, it is often difficult to gain the parametric information of wind farms so as to establish the parametric model for the OMA. Hence, this article proposes a method of the OMA based on the measurement data, rather than parametric model. The proposed method is particularly for the application to trace the source of torsional SSOs, which is the trouble-making wind farm taking part in the open-loop modal resonance. The proposed method of the OMA is developed by the machine learning to train a model of convolutional neural network (CNN). In order to solve the problem of lack of sufficient and labeled training data, it is proposed to build a simplified simulation system. Then, the CNN model is trained by deep transfer learning algorithm using the training data generated by the simulation system to trace the source of torsional SSOs in a practical power system from limited measurement data. In this article, the proposed method is demonstrated and evaluated by a test example.

Enhancement of plastic flow in lateral direction by torsional oscillation in upsetting and lateral extrusion

Plastic flow of hollow cylinders under combining axial compression with torsion was examined in upsetting and in lateral extrusion. The hollow cylinders with initial height/outer diameter of 0.5–2.5 and initial inner/outer diameter of 0.3–0.9 were compressed/extruded and simultaneously twisted with respect to the axisymmetric forging axis in one-way or cyclic alternating. Due to superposition of torsional shear stress, the lateral metal flow was found to be assisted. Barreling of the workpiece was reduced by approximately 10 % in upsetting with torsion/compression speed of 6 °/mm. The enhancement of the plastic flow in upsetting was applied to fill up tooth cavity in lateral extrusion. The extruded tooth depth of the workpiece was approximately 5–7% larger in lateral extrusion with torsion/extrusion speed of 30°/mm. In addition, cyclic alternating torsion was effective to extrude evenly in the tooth thickness direction due to the periodic reversal of die rotation in peripheral direction.

On the external and internal resonance phenomena of the elastic bodies with the complex oscillations

Complex nonlinear oscillations in the elastic bodies are studied using a priori information about the oscillations form and taking into account a refined mathematical model of the second (other) form of oscillations. Application of existing methods or development of the new ones for the analysis of received non-autonomous boundary value problems is proposed. The effectiveness of the practical implementation of the discussed methodology significantly increases in cases where the magnitude of the elastic body displacements due to the one form of oscillations is much higher than the other one. To analyze the problem one can use the well-known tested analytical methods for the systems with the small nonlinearity. Torsional and bending oscillations of the elastic body are shown as the example. It is also demonstrated that especially dangerous resonant processes can be caused not only by the external perturbations but also by the internal influence between some forms of oscillations. The obtained results allow to choose the basic technological and operational parameters of the machine oscillating elements in order to avoid the resonance phenomena.

Impulse Moments Influence on Single-Frequency Torsional Oscillations of Nonlinear Flexible Bodies

A method of analytical study of the influence of impulse moments on nonlinear torsional oscillations of a homogeneous constant cross-section of a body under classical boundary conditions of the first, second, and third types have been developed. When the flexible material properties meet the body close to the power law of flexibility, mathematical models of the process have been obtained. They are the boundary value problems for an equation of hyperbolic type with a small parameter at the discrete right-hand side. The latter expresses the effect of pulse momentum on the oscillatory process. Under the effect of periodic pulse momentum on a flexible body, resonant and non-resonant processes are possible, and resonant processes occur when the amplitude of natural oscillations approaches a fixed value. The peculiarities of resonant oscillations are established. Relative torsional oscillations of a nonlinear flexible body that rotates around the axis with a constant portable angular velocity are considered, taking into account the periodic action of pulse momentum acting in a fixed cross-section. It is shown that: the amplitude of passing through the main resonance is more significant for larger values of the nonlinearity parameter; the case of the action of pulse momentum closer to the middle of the body. If the initial perturbation amplitude is less than the amplitude at which the resonance occurs in the presence of only internal forces of viscous friction, the external periodic impulse moments of resonance processes have occurred. The reliability of the calculation formulas is confirmed by the fact that in the extreme case known from the literature, resources are obtained related to the dynamics of the respective objects under the continuous action of autonomous perturbation.

Stability of a suspension bridge with a localized structural damping

<p style='text-indent:20px;'>Strong vibrations can cause lots of damage to structures and break materials apart. The main reason for the Tacoma Narrows Bridge collapse was the sudden transition from longitudinal to torsional oscillations caused by a resonance phenomenon. There exist evidences that several other bridges collapsed for the same reason. To overcome unwanted vibrations and prevent structures from resonating during earthquakes, winds, ..., features and modifications such as dampers are used to stabilize these bridges. In this work, we use a minimum amount of dissipation to establish exponential decay- rate estimates to the following nonlocal evolution equation</p><p style='text-indent:20px;'><disp-formula> <label/> <tex-math id="FE1"> \begin{document}$ u_{tt}(x,y,t)+\Delta^2 u(x,y,t) - \phi(u) u_{xx}- \left(\alpha(x, y) u_{xt}(x,y,t)\right)_x = 0, $\end{document} </tex-math></disp-formula></p><p style='text-indent:20px;'>which models the deformation of the deck of either a footbridge or a suspension bridge.</p>

Динаміка відносних крутильних коливань при формуванні регулярного мікрорельєфу на внутрішніх циліндричних поверхнях

An analysis of modern literature sources to search for mathematical models describing the dynamics of the process of forming a regular microrelief on the inner cylindrical surface of parts, gas transmission equipment operating in severe operating conditions, in order to increase their life. It is established that there are no mathematical models describing this process and the peculiarities of its implementation under the point action of the deforming element on the workpiece surface. The molding movements accompanying the process of forming a regular microrelief on the inner cylindrical surface of the workpiece are considered and the driving forces that accompany this process are analyzed. On the basis of the conducted analysis the mathematical model of dynamic process of formation of a regular microrelief on an internal cylindrical surface of a detail is developed. The peculiarity of this process is that the process of microrelief formation occurs by a concentrated force, the point of application of which in relation to the part is constantly changing in radial and axial directions, and then the mathematical model describing this process will be with a discrete right. It is proposed to model such an action using Dirac delta functions with linear and temporal variables, using the method of regularization of these features, in particular, existing methods of integrating the corresponding nonlinear mathematical models of torsional oscillations of a part. Analytical dependences are obtained, which describe these oscillations in the process of formation of a regular microrelief. Using Maple software, 3D changes in the torsion angle depending on different output values are constructed. The conducted researches will allow to consider torsional fluctuations that is especially actual for long cylindrical details, such as sleeves of hydraulic cylinders, details of drilling mechanisms and others.

Aerodynamic and dynamic loading in a blade cascade designed for flutter research

Flow-induced vibration of turbine and compressor blades, so called blade flutter, represents a serious problem for designers and operators of large turbomachines. The research of mechanisms leading to this dangerous aeroelastic instability, which can occur especially in modern long and slender blades, is hindered by lack of experimental data. A new experimental setup for controlled flutter testing has been designed in cooperation of the Institute of Thermomechanics of the Czech Academy of Sciences and Faculty of Mechatronics of the Technical University of Liberec. The test section consists of five planar blades placed in a transonic wind tunnel, with high-frequency torsional oscillation of the middle blade driven by an electric motor. The contribution presents the results of first measurements, namely the static pressure distribution for various inlet Mach numbers, aerodynamic moments and deformation of the middle blade due to inertial loads during high-frequency oscillation.

ДИНАМІЧНИЙ СИНТЕЗ МОБІЛЬНОЇ ЗЕМЛЕРИЙНОЇ МАШИНИ БЕЗПЕРЕРВНОЇ ДІЇ З ЛАНЦЮГОВО-БАЛКОВИМ РОБОЧИМ ОРГАНОМ

This article depics the mobile continuous earth-moving machine dynamic model with a chain-type trenching equipment in order to determine the effect of changes in the elastic-inertial system parameters on its own resonant frequencies. The object of the research: natural resonant transmission frequencies of the soil-working working equipment drive in the mobile earth-moving continuous action machine with a chain-beam working body. The purpose of the work: to determine the system elements, in which the elastic-inertial parameters affect the lower natural resonant frequencies. To give practical recommendations on the parameter choice of such elements in order to deviate from the resonant frequency. Creation of strong, reliable and durable machines depends on the dynamic load accuracy and ways to reduce it. Modern earthmoving machine structure formation can be realized using the modular principle, but always with taking into account the full picture of possible machine loads and their drives in the process, these load magnitude and their dynamic characteristics. In accordance with the dynamic synthesis conditions, the dynamic system machine parameters should be selected so that the external load machine change frequency in its maximum productivity mode doesn’t coincide with the dynamic system natural frequency. According to the theoretical and strain gauge research results, it is established that the frequency of the first form of earth-moving machine drive torsional oscillations is close to 9 Hz. The first frequency oscillation shape has a node between the gearbox masses, which can lead to fatigue shaft destruction, joints or gears of the base tractor transmission part destruction. The frequency of the natural oscillation system is close to the traction chain link engagement frequency with the sprocket teeth in the earth-moving machine maximum productivity mode.

Effect of wing rigidity on behavior and aerodynamic characteristics of wing

In general, flexible plastic wings are the primary components of small lightweight aircrafts such as unmanned aerial vehicles (UAVs). One of the authors has shown that the torsional oscillation of a plastic wing occurs in a certain range of its attack angle, which causes a rise in lift of the wing. However, the conditions under which the wing exhibits the high-lift characteristics remain unclear. To find out the conditions, the aerodynamics characteristics of the wing are experimentally investigated by changing its rigidity and aspect ratio under various flow speeds in the wind tunnel. The experimental results reveal that the aerodynamic characteristics of flexible wing are dominated by the two dimensionless parameters which are derived from the equation governing the torsional oscillation of the wing.

CONTINUOUS TUNING OF SHIP PROPULSION SYSTEM BY MEANS OF PNEUMATIC TUNER OF TORSIONAL OSCILLATION

Mechanical system drives consist of driving machines and gearing mechanisms interconnected by shafts and couplings. In terms of dynamics it is possible to say that every driving mechanism is able to oscillate. Especially piston devices can create excessive torsional oscillation, vibrations, as well as noise. Important task of a designer is to reduce torsional oscillation in mechanical systems. Presently this problem is mainly solved by the flexible shaft couplings that are selected with regard to the dynamic properties of the given system. It means that every torsional oscillating mechanical system needs to be suitably tuned. The aim of this paper is to present the possibilities of controlling of dangerous torsional oscillations of the mechanical systems by the means of new method, i.e. its optimal tuning by means of the pneumatic coupling with self-regulation, which were developed by us.

Vibration Energy Harvester Based on Torsionally Oscillating Magnet.

Most of the miniaturized electromagnetic vibrational energy harvesters (EVEHs) are based on oscillating proof mass suspended by several springs or a cantilever structure. Such structural feature limits the miniaturization of the device’s footprint. This paper presents an EVEH device based on a torsional vibrating magnet over a stack of flexible planar coils. The torsional movement of the magnet is enabled by microfabricated silicon torsional springs, which effectively reduce the footprint of the device. With a size of 1 cm × 1 cm × 1.08 cm, the proposed EVEH is capable of generating an open-circuit peak-to-peak voltage of 169 mV and a power of 6.9 μW, under a sinusoidal excitation of ±0.5 g (g = 9.8 m/s2) and frequency of 96 Hz. At elevated acceleration levels, the maximum peak-to-peak output voltage is 222 mV under the acceleration of 7 g (±3.5 g).

Technology Focus: Bits and Bottomhole Assemblies (December 2021)

Well construction must always be executed safely at reduced operational costs, while ensuring appropriate wellbore quality and placement, per asset team requirements. Consequently, analysis of drilling efficiency, a critical performance indicator, has moved from maximizing rate of penetration (ROP) to improving cycle time. This recognition establishes the need for holistic solutions that address drilling challenges and promote efficient improvement strategies. This endeavor achieves well construction objectives, with associated reductions in cycle time and operations costs. Holistic solutions must start with project analysis and comparisons to offsets to identify application differences and similarities. These evaluations establish project risks, which ultimately have positive or negative effects on well construction. Consequently, implications from these risks (limiters and potential dysfunctions) must be addressed in the planning phase, or preparations must be made for their remediation during project execution. It is not enough to know what worked or failed. Rather, it is essential to understand why and how specific trends, events, results, or relationships come about. Effective and permanent remediations for all drilling dysfunctions must focus on identification and analysis of their initiating risks. Additionally, holistic solutions require detailed analysis of drilling systems, which include bits and reamers, bottomhole assemblies (BHAs), drive systems, hydraulics considerations, and drilling-parameter ranges and roadmaps. In addition to establishing component relevance, this effort must ensure their functional compatibility and effectiveness at addressing project risks. Drilling-parameter roadmaps must focus on well construction objectives and cycle time reduction, not ROP maximization. In this regard, cycle time is defined as the cumulative time associated with the following operations: pick up the BHA, drill out, drill ahead, trip out of hole, and run casing. Bits and BHAs have a major role in this discussion. The industry’s fast-developing capabilities with modeling and deeper under-standing of downhole tools and systems, coupled with applications based on big data analytics, are leading these efforts. The door has been kicked open. Let’s walk through. Recommended additional reading at OnePetro: www.onepetro.org. SPE 205965 - Oil and Gas Drilling Optimization Technologies Applied Successfully to Unconventional Geothermal Well Drilling by Junichi Sugiura, Sanvean Technologies, et al. SPE 205993 - Using Downhole Sampled High-Frequency Torsional Oscillation Measurements for Identifying Stringers and Minimizing Operational Invisible Lost Time by Andreas Hohl, Baker Hughes, et al. SPE 206064 - Mud Motor PDM Dynamics: An Analytical Model by Robello Samuel, Halliburton, et al.

Spatio-temporal bands of coronal bright points and their relation to solar torsional oscillations

ABSTRACT Using automatic processing of daily fits files from SOHO_EIT, we studied the temporal evolution of the latitudinal distribution of bright coronal points from 1995 to 2020. The study revealed homogeneous and inhomogeneous components of the latitudinal distribution. The homogeneous component has cyclical variations with a significant phase shift compared to the number of sunspots. The residual inhomogeneous component manifests itself as migration of the centre of increased density from high to low latitudes. The bands of the residual density of coronal bright points (CBP) reflect solar torsional oscillations. It should be associated with the strengthening of the local alpha-omega dynamo. However, the cyclical nature of the number of CBP is explained by the diffusion of large-scale magnetic fluxes.

Adaptive centrifuge vibration damping module for biofuel production

The present study considers the problem of obtaining promising renewable energy sources, in particular biofuel. Biomass is the main fuel for green energy accounting for two-thirds of renewable energy. Industry further development depends on improvement of used equipment and technologies. Biofuel usually contains significant amounts of harmful impurities that need to be isolated. The paper deals with the problems of centrifuge operation for the biofuel production. In particular, the most significant operation problem is the residual rotor imbalance which causes torsional oscillations that negatively affect the biodiesel production process and centrifuge reliability. A new technology for damping torsional vibrations of centrifugal device rotating system is described as well as adaptive module device for its implementation is developed. The module main feature is vibrations adaptive level of the rotor elements interaction with external environment. Computer simulation of the module operation process in ANSYS Fluent program was carried out. Data on the module efficiency depending on various factors in the dynamics of its work are obtained. The most effective device configuration is determined.

Parametric control of a diffractive axicon beam rider.

A laser beam rider is a large-scale optical structure designed so that it is attracted toward the optical axis, while also affording forward propulsion via radiation pressure along the beam path. Such structures form the basis of laser-driven light sails. Experimental measurements are described whereby a thin diffractive axicon film is shown to exhibit a natural restoring force when its axis is displaced from the optical axis. This effect is attributed to the optical momentum change of diffracted light. Whereas continuous illumination supports harmonic motion, modulated illumination is shown to support both parametric gain and parametric damping. The 12.7µm period photopolymer axicon grating was suspended in a vacuum torsion oscillator and irradiated with a 1.5 W near-infrared laser modulated at a period of 38 s.

Simultaneous Deconvolution of In‐Plane and Out‐of‐Plane Forces of HOPG at the Atomic Scale under Ambient Conditions by Multifrequency Atomic Force Microscopy

AbstractMultifrequency atomic force microscopy (AFM) is shown to be an excellent tool for imaging crystal structures at atomic resolution in different spatial directions. However, determining the forces between single atoms remains challenging, particularly in air under ambient conditions. Developed here is a trimodal AFM approach that simultaneously acquires torsional and flexural frequency‐shift images and spectroscopic data to transfer these observables into in‐plane and out‐of‐plane forces between single bonds of highly oriented pyrolytic graphite (HOPG) at atomic resolution in air under ambient conditions based on the Fourier method. It is found that the cantilever mean deflection is an excellent indicator to understand that strong attractive interactions between the tip and the surface of HOPG in dynamic AFM imply a local lift of the topmost carbon layer when using higher eigenmodes for the topographical feedback. Cross‐talk between torsional and flexural‐oscillation modes is shown to be negligible. Interestingly, significant differences are observed in the in‐plane forces depending on the orientation of the carbon bonds relative to the direction of torsional oscillation.