Torsional Torque Research Articles

Study on tribo-chemical and fatigue behavior of 316L austenitic stainless steel in torsional fretting fatigue

Fretting fatigue is a complex tribological phenomenon that can cause premature failure of connected components. Combining with the effects of tribological and fatigue, the components have premature fracture, which ultimately leads to disastrous consequences. In this work, the fretting fatigue tests of 316L austenitic stainless steel have been carried out with same normal load and varied torsional torques. The results indicate that the fretting fatigue life significantly depends on the torque amplitude, wear degree of the fretting damage zone, hysteresis loops and energy dissipation. A physical model for fretting crack initiation and propagation is created to explain the failure process of torsional fretting fatigue. The results from X-ray photoelectron spectroscopy analysis show that the extent of oxidation in the fretting damage zone is affected by the amplitude of relative displacement. The tribo-chemical reaction in the slip regime is more activated than that in partial slip regime. It can lead to more severe wear in the slip regime. The wear debris of the fretting damage zone is composed of metallic Fe, Fe2+ and Fe3+.

Phase transitions in copper–silver alloys under high pressure torsion

AbstractThe influence of high pressure torsion (HPT) on the formation and decomposition of solid solutions in the copper–silver system has been studied. The investigated Cu-8 wt.% Ag alloy was annealed at two different temperatures, 500 and 650°C, and quenched. The samples consisted of (Cu) solid solution in the matrix with (Ag) precipitates. During HPT a steady-state value of torsion torque was reached after about 1.5 anvil rotations. After HPT (5 anvil rotations) the composition of the (Cu) solid solution in both samples had become equal. In other words, the concentration of silver in the (Cu) matrix annealed at 650°C decreased and in the sample annealed at 500°C increased. Moreover, a similar process took place in (Ag) precipitates as well. The concentration of copper in (Ag) particles in the sample annealed at 650°C decreased and in the sample annealed at 500°C increased. Thus, the composition of (Cu) and (Ag) solid solutions reached at steady-state during HPT does not depend on that before HPT. The composition of the (Cu) and (Ag) solid solutions after HPT is as high as if the samples were annealed at a certain intermediate temperature about 600 ± 20°C.

Power-Efficient Control of an Induction Motor: Methods of Increasing Its Dynamics

To improve the efficiency of an electric drive system under low speed conditions, a control strategy optimized for maximal torque per ampere (MTPA) is used in the vector control system of an induction motor. MTPA is a control method of motor excitation that significantly reduces the torsion torque dynamics due to the influence of the rotor time constant. Traditionally, for such a control strategy, steady-state motor conditions are considered, but transient modes are not. MTPA control strategies for an induction motor with and without use of a rotor flux controller are compared. New approaches to improving the dynamics of MTPA control are proposed. The transient modes are described and compared.

Subsynchronous resonance oscillations mitigation via fuzzy controlled novel braking resistor model

Subsynchronous resonance (SSR) torsional torque oscillations is a problem of a great concern in the power engineering community. SSR causes torsional torque oscillations with ever-increasing magnitudes occurring in the machine shaft sections causing a premature fatigue life expenditure of the shaft metal. In this paper, dynamic braking switching strategy designed through fuzzy logic control theory and implemented via novel braking resistor model, namely chopper rectifier controlled braking resistor for tempering SSR torsional torque oscillations of a large turbo-generator. The proposed mitigation scheme has been tested on the IEEE second benchmark model for SSR studies. Comparative simulation study via MATLAB/Simulink-based modeling and simulation environment of the test model with and without the suggested mitigation regime should demonstrate its effectuality for mitigation of SSR torsional torque oscillations.

Engine Misfire Diagnosis Based on the Torsional Vibration of the Flexible Coupling in a Diesel Generator Set: Simulation and Experiment

Flexible couplings are widely used for accommodating various imprecisions such as misalignments and torque fluctuations in a diesel generator set. However, excessive vibration due to common engine misfires can cause premature failures in both the couplings and the whole generator set. Moreover, the coupling also affects detection performance and the occurrences of early misfires due to such faults in fuel injections and cylinder seals. In this paper, the torsional vibration along with the dynamic torque of the flexible coupling connecting a 6-cylinder diesel engine to a dynamometer is studied theoretically and experimentally. This system represents a common diesel generator set which is modeled into a torsional dynamic system with 10-degree of freedom (DOF) by the Lagrange equation method. After a verification of the model by the measurement of vibration responses at the free end and the coupling with a magnetic speed sensor and a wireless torque sensor, it is then used to predict the influences of different misfire conditions on the dynamic torque on the coupling, which helps in determining reliable diagnostic features for misfire detection and diagnosis. Results show that the misfires of the diesel engine have significant influences (more than 5 times higher) on the torsional vibration and load of the flexible coupling than on the dynamic torque. Nevertheless, both the torsional vibration and torque of the flexible coupling can be used to detect the occurrence of the diesel engine misfires and the vibration provides slight better results in terms of localizing the misfired cylinders.

Relationship Between Small Crack Propagation Properties and Manson-Coffin's Rule in Low Cycle Torsional Fatigue

A low cycle torsional fatigue test of carbon steel S10C for machine structural use was performed with strain control. Using a mechanism that applied Martens's mirror device, the scale was read, and the torsional torque was increased or decreased to achieve a predetermined torsional angle, and experiments were performed with total strain widths γ = 1.0%, 1.5%, and 2.0%. As a result, the propagation behavior of cracks in low cycle torsional fatigue was connected and propagated by innumerable microcracks. The fatigue life calculated by the small crack propagation law, focusing on the main crack that caused the fracture, was equivalent to the fatigue life of the Manson-Coffin’s law.

Система управления взаимосвязанными электроприводами с электромеханическим распором и распределением нагрузки

The article presents the results from the development of a double-motor electromechanical system, in which the automatic control of interconnected electric drives ensures the formation of electromechanical torsion to maintain the closed state of backlash in the kinematic transmission within the specified load torque variation range. When the load torque escapes from the preset range, it is automatically distributed equally among the electric drives. The aims of this technical solution are to form a torsion when it is needed in accordance with the peculiarities of the load acting on the mechanism, and to prevent the installed capacity of electric drives from being exceeded in comparison with the power required for moving the mechanism. The application of the development results for controlling the motion of the antenna installation lifting axis is illustrated. The peculiarity of this system is that the load torque of this mechanism is active, sign- variable and depends on the lifting angle. When crossing the vertical position, it changes direction, which facilitates the opening of backlash in the kinematic transmission and the occurrence of self-oscillations. At lifting angles close to the horizontal position, the load torque has its maximum value, and the backlash is closed under its action. In addition, when the mechanism is near the vertical position, the wind load facilitates opening of the backlash. The system for controlling the electromechanical systems coordinates includes torque control loops, which are individual for each of the electric drives, and a loop that is common for control of their position. Recommendations for synthesizing these loops are given. The specified torsion torque is calculated by a nonlinear element with a trapezoidal I/O characteristic depending on the mismatch between the specified and actual angular position of the driving mechanism axis processed by the position controller, which makes it possible to indirectly estimate the load torque value. The control system software and hardware have been developed. In developing the microprocessor control system software, model-oriented development tools were used. A prototype replicating the antenna installation lifting mechanism design has been made. The proposed control system made it possible to reduce the influence of backlash at lifting angles close to the vertical position and to distribute the load torque between the electric drives at lifting angles close to the horizontal position, when torsion is not required, as well as when exposed to wind load. Experimental oscillograms of electromechanical system coordinates are presented, confirming the declared results.

Pseudorandom Noise Impulsive Response Analysis and Aerodynamic Forces of Unmanned Aerial Vehicle Structure

This paper concentrated about the effect of both the pseudorandom or random vibration (wind waves) and aerodynamic forces on the wing of unmanned aerial vehicle, which brought the attention of specialists in this field during last years, the performance of wing is improved on a definitive solution for the vibration problems which cause failure in the wings of UAV. The distribution of stresses and distortions with aerodynamic loads is studied. Factors such as tension, pressure and shear stress showed on wing of UAVs due to vibration which caused the structure of wing to break down and then failure. The experimental study was carried out by using wing made of composite material (foam and cover by lamination plate), where airfoil type (NACA Clark y) installed inside wind tunnel of low velocity. It is found that the vibration acceleration at constant wind velocity with variation of attack angle of the wing, it is obtained the relationship between the acceleration and the frequency using the LABVEIW program which analyzed and identified the distribution of forces on the wing. The stress concentration areas is created and found under failure occurs, the aerodynamic force, torsion torque and magnitude of deformation is calculated. It is concluded that the close areas from the root wing (fixed end) is most likely to collapse or break.

Characterization of the torsional structural properties of feline femurs and surrogate bone models for mechanical testing of orthopedic implants.

To characterize the torsional structural properties of the feline femur and design a bone model surrogate for mechanical testing of feline orthopedic implants. Experimental. Paired feline femurs (n = 30) and bone models (8 materials, n = 4/group). Femurs were cyclically tested nondestructively in torsion and then loaded to failure. A generic femoral model was then designed from native femur dimensions and tested similarly by using 1 of 8 materials that were 3-dimensionally printed or machined. Outcome measures consisting of torsional compliance, angular deformation (AD), and torque to failure were compared by using Student's t test (P < .05). Failure modes are reported as descriptive statistics. Torsional compliance (1.6 ± 0.3°/Nm, 2.0 ± 0.1°/Nm), AD (3.1 ± 0.6°, 3.8 ± 0.2°) and torque to failure (7.8 ±1.2 Nm, 8.1 ± 1.3 Nm) did not differ between feline femurs and short-fiber epoxy (SFE) models. Conversely, most printed materials displayed excessive TC and failed by plastic deformation (AD > 15-fold that of native femurs) rather than by fracture. Feline bone and SFE both failed by spiral fractures. None of the outcome measures differed between the 4th generation SFE model and cadaveric femurs, but differences were identified between feline bone and printed materials. Machined SFE can be used to create a surrogate bone model with torsional structural properties similar to those of feline femurs. In contrast, common printable materials appear unsuitable to produce a realistic feline bone surrogate.

Method of calculating variable section shafts shear deformations

This article considered method to measure low-frequency angular oscillations of rotors of electric machines and solved the problem of assess shear deformations of rotating shafts in transient conditions. Method of calculating torsional torques is considered by the example of electric generator shaft of diesel generator unit. This method allows taking into account the angular deformations of the rotating shafts, and reducing vibration overloads, and increasing in both resource and reliability.

Robust control of a wind conversion system based on a hybrid excitation synchronous generator: A comparison between [formula omitted] and CRONE controllers

This paper deals with a Wind Conversion System (WCS) based on a Hybrid Excitation Synchronous Generator (HESG) connected to an isolated load. The set is modeled under Matlab–Simulink. To ensure an efficient and reliable use of the system, a tight control remains vital. In fact, the dynamic equations of a turbine are strongly nonlinear as are the ones of a HESG; most of the system parameters are highly uncertain, and, at last, a WCS is always affected by disturbance sources such as load variances, harmonics, mechanical vibrations…To address these problems, robust control methods must be adopted. In this paper, two strategies for the control of variable speed wind turbine are investigated. First, an H∞ controller is implemented. Then, a second-generation CRONE controller is designed. The performance of the two regulators is compared with respect to the tracking of the optimal rotation speed, the attenuation of the mechanical vibration and the robustness to the uncertainty of the parameters, using time-domain simulations. It has been found that the CRONE controller is more robust to parameters uncertainty and minimizes the fluctuations of the torsional torque and the generator’s angular velocity. Finally, an experimental validation of the velocity controllers is presented to complete the simulation results and fully validate the chosen approach.

Subsynchronous resonance assessment for a large system with multiple series compensated transmission circuits

Generators connecting to a series compensated transmission system can be exposed to subsynchronous resonance (SSR) and require a comprehensive vulnerability assessment. This study presents an SSR assessment framework and tools to more efficiently assess all types of generation in a large system with multiple generators and meshed series capacitors. The developed framework covers torsional interaction, torque amplification, and induction generator effect/control interaction and includes three assessment stages: topology screening, frequency scan, and detailed electromagnetic transient study. Topology screening based on max-flow min-cut theorem is applied to identify the set of transmission outages forming radial connections between generators and series capacitors. Frequency scan analysis is then conducted to further analyse the SSR vulnerability with all the possible combinations of transmission outages identified in the topology screening results. Nearby generators are modelled by frequency-dependent impedance tables, which consider the equivalent impedance looking into the generators over the range of 1-120 Hz. An electromagnetic transient simulation will be required to confirm the SSR vulnerability identified in the frequency scan analysis. The developed framework and tools have successfully been applied to a large power system with multiple series compensated circuits to ensure reliable generation interconnection and operation.

Hierarchical distributed model predictive control of hybrid wind and solar generation system

Distributed networked generation (DNG), which incorporates renewable energy and clean energy into information networks, has become increasingly important for modern power systems. In DNG, wind power and solar power generation are considered as intermittent systems with multiple constraints. The coordinated optimization of the wind power and solar power generation can effectively meet the load demand while guaranteeing the safety of power grids by reducing the wear and tear of generating units and prolonging the lifetime of grids. This study aims to construct a hierarchical distributed model predictive control (HDMPC) for large-scale, geographically dispersed wind-solar power generation systems. In HDMPC, the upper layer utilizes an iterative distributed control strategy to coordinate the power dispatch. Thus, it attains economic objectives, including the reduction in the torsional shaft torque transmitted to the gearbox in the wind turbine system and the generation cost. The lower layer utilizes the supervisory predictive control to realize economic and tracking properties. HDMPC enables the plug-and-play of distributed energy through the coordinated optimization of subsystems. Simulation experiments validated the advantages of the proposed method, which can meet the demands of safe, reliable, highly efficient, flexible, and interactive microgrid controlling.

A strategy to reduce the twist defect in roll-formed asymmetrical-channel sections

The most important step in designing the roll-forming processes is to design of a flower pattern. Currently, this is mostly done based on trial and error and the designer's experience. Using an optimized flower pattern, products with the intended dimensional- and geometrical-tolerance limits could be produced by a minimal number of forming stands. Twisting, which is a common defect in roll-formed asymmetrical-channel sections, affects the appearance and functionality of the product. In this research, the twist defect was studied by finite-element analysis for asymmetrical channels with different flange lengths. Some experiments were also performed on an industrial roll-forming machine to verify the accuracy of the finite-element model. The twist defect was observed to result from a torsional torque produced due to different forming forces applied to long and short flanges. Furthermore, in the roll-forming process of asymmetrical-channel sections, the strip is not deformed symmetrically and the long flange edge touches the roll before the short one. Therefore, the long flange is subjected to a forming force before the short flange. Since predicting the twist angle without costly trial and error in a workshop, or time-consuming finite-element simulations is desirable for the roll-forming industries, a simple relation was introduced considering the geometrical properties of asymmetrical-channel sections. Thereby, asymmetrical forming rolls were presented to form both flanges more symmetrically; a smaller twist defect is achieved.

Dynamic Loading of Cogwheels at the Time of Start-Up

Loading of cogwheels of the high-loaded transfers to the start-up moment is considered. It is shown that at torque transfer on a surface of a nave of a cogwheel are generated and extend in material in the radial direction of a wave of tension of torsion. The equations for definition of distribution of tension of torsion on the radius of a cogwheel and for definition of a torsion torque on an outer surface of a cogwheel at the time of the beginning of its rotational motion are received. It is shown that thus overloads have more considerable sizes, than used at modern calculations. Results of calculations for specific input data allow us to draw a conclusion that the dynamic torsion torque at start-up is more, than a rated torsion torque more than twice.

부하 속도/토크 추정 및 비틀림 토크 보상을 통한 2관성 시스템의 부하 속도제어

We consider the speed control problem for a two-inertia system that consists of two inertias connected by a shaft. In this system, the shaft’s flexibility produces torsional vibrations that usually result in limited tracking performance when employing a conventional control strategy such as PI control. Moreover, the control problem becomes far more challenging if the load-side speed and torsion torque developed in the shaft are not measurable. This paper presents a disturbance observer-based controller that suppresses vibrations due to torsion torque and external disturbance so that the load speed tracks the desired reference. This is done by constructing an observer that estimates the torsion torque, load speed, and load torque at the same time and a controller that can adjust the torsion torque as desired. The proposed idea is validated through numerical simulations.

Microstructural evolution, textural evolution and thermal stabilities of W and W – 1 wt% La2O3 subjected to high-pressure torsion

Ultra-fine grained W and nanocrystalline W – 1 wt% La2O3 (WL10) were successfully fabricated by unconstrained high-pressure torsion at 400 °C. Torsion torque, microstructural evolution, and textural evolution of W and WL10 along torsion revolution were systematically evaluated for the first time. Their deformation mechanisms during high-pressure torsion were proposed. Results show that both materials exhibited work-hardening and geometric dynamic recrystallization during high-pressure torsion. The existence of La2O3 particles caused discontinuous dynamic recrystallization in WL10 and formed γ-fiber texture. The evolution of γ-fiber texture in WL10 along with torsion strain was analyzed as well. The existence of La2O3 particles leaded to dispersion-hardening in WL10 at large strain levels when those particles were sufficiently refined. Deformation inhomogeneity occurred in W at ultrahigh strain levels accompanied by coarsening microstructure. In addition, the as-deformed ultra-fine grained W and nanocrystalline WL10 exhibited marked thermal stability at 1000 °C up to 6 h.

Three-dimensional stress analysis in torsion of laminated composite bar with general layer stacking

Abstract A general laminated composite bar with rectangular cross-section which is subjected to torsional torque is studied and the three dimensional stress state, specially the out of plane stresses is investigated. A reduced displacement field is obtained for the long laminated bar in which the global and local deformation response of the laminate are separated. This reduced displacement field is obtained from integration of the strain components. In order to obtain the three dimensional stress state and free edge effect, the displacement based layer-wise method is employed for formulation of the problem and the governing equations are solved analytically. The numerical results are compared with the predictions of multi-term extended Kantorovich method and mixed-field multi-term extended Kantorovich method which is available in the open literature and with an analytical series solution, and very good agreements are achieved. The twisting, extension, and bending of laminate due to torsion torque, and the out of plane and in-plane stresses are studied for various layers stacking. In order to increase the accuracy, the out of plane stresses are obtained by integrating the equilibrium equations.

A STUDY OF TRIBOLOGICAL LOAD CAPACITY OF VARIOUS FRICTION PAIRS

The paper presents and experimentally verifies a testing method of friction pairs between various materials: steel-cast iron, cast iron-cast iron, and cast iron-ferodo. The applied methodology for the evaluation of tribological mating of a friction part allows for determining the time series of friction torque and mechanical power transmitted by a friction pair at slippage. Time series of parameters variability in the investigated friction process after the loss of contact are presented. In addition, relationships are presented that allow for determining the basic friction pair parameters: friction torque, friction coefficient, and mechanical power. This is a basis for determining the tribological load capacity of a friction pair whose measure has been assumed as the maximum value of torsional torque and mechanical power transmitted by the tested specimens.

The influence of the DNA torque on the dynamics of transcription bubbles in plasmid PTTQ18

In this work, we study numerically the influence of the DNA torque on the movement of transcription bubbles in the potential field formed by the sequence of plasmid PTTQ18. To imitate the movement, we apply a modified sine-Gordon equation with the two additional terms that describe the effects of dissipation and the action of the DNA torsion torque, and with the coefficients that depend on the sequence of bases. We obtain the trajectories of the transcription bubbles and investigate the dependence of the trajectories on the initial bubble velocity and the DNA torsion torque. It is shown that not the initial bubble velocity but the DNA torsion torque governs the trajectories of the transcription bubbles.