Torsional Shaft Research Articles

712 軸方向き裂を有するスプライン軸の応力解析

As the spline shafts have been used for various machines to transmit big power for the power-driven machine. Recently, data on the strength and the fracture is necessary. In the past, some studies on the spline shafts has been reported, but there is a few study torsional loading spline shafts having three-dimensional crack. In this study, we produce the spline shafts for epoxy resin and make various cracks. We used stress frozen method for the spline shafts under the state of torsional load. Photoelasticity and method of caustics are used to determine the deformation pattern of the tip of a cracks and to calculate stress intensity factor for fracture mechanics.

Speed Control of 2-Inertia System with Gear Backlash based on Gear Torque Compensation

In this paper, we propose a novel speed control method for 2-inertia system with gear backlash based on the gear torque compensator. The compensator consists of two elements: the gear torque observer and a feedback gain to be adjusted. The ideal gear torque compensation makes the characteristic from motor torque to motor speed to that of 1-inertia system. However, such a direct usage of the compensator causes harmful vibration due to the torsional shaft. To make a compromise, we introduce a feedback gain and adjust it. By combining this method with a usual PID controller, we realized superior performances in vibration suppression and disturbance rejection. Its effectiveness is shown by simulations and experiments.

Speed control of two-inertia system with gear backlash based on gear torque compensation

In this paper, we propose a novel speed control method for a two-inertia system with gear backlash based on the gear torque compensator. The compensator consists of two elements: the gear torque observer and a feedback gain to be adjusted. The ideal gear torque compensation makes the characteristic from motor torque to motor speed to that of one-inertia system. However, such a direct usage of the compensator causes harmful vibration due to the torsional shaft. To compromise, we introduce a feedback gain and adjust it. Combining this method with a typical PID controller, we realized superior performances in vibration suppression and disturbance rejection. Its effectiveness is shown by simulations and experiments. © 2000 Scripta Technica, Electr Eng Jpn, 134(2): 36–43, 2001

Description of the creep and failure of beams in bending and shafts in torsion by equations with a scalar damage parameter

Results of the theoretical and experimental investigations of beam bending by a constant moment and torsion of continuous shafts with a constant rate of the torsion angle are given. It is shown that the kinetic equations of creep and damage with a scalar parameter can be applied to the description of deformation in the presence of nonuniform stresses.

Calculation and Measurement of Torsional Vibrations in Large Steam Turbosets – New Technique

ABB has been carrying out torsional vibration test on steam turbine sets for many years, with sizes ranging from 350MW coal fired steam turbines to 1000MW nuclear steam turbines. Rated speeds have been 1,800 rpm and 3600 rpm. Torsional shaft vibrations are excited in large steam turbine generators sets by electrical disturbance torques occurring in the active part of the generators. Due to the low torsional damping of the shaft trains, resonance can cause high torsional vibration amplitudes. Some thermal power plant operators require experimental verification of the natural torsional shaft frequencies. ABB has developed a new measurement technique which allows torsional vibration to be measured in a selected measurement plane along the shaft. With today's highly sensitive sensors and modern measurement and data analysis equipment, the excitation due to normal random disturbances in the electrical grid provides sufficiently good results. All natural torsional frequencies in the range of interest are obtained with an accuracy of ± 0.2 Hz and identified using the calculated natural frequencies. The new measurement technique, places no restrictions on normal power plant operation.

A comparison of two cocured damped composite torsion shafts

Cocuring layers of viscoelastic damping materials with composite material systems offers the possibility of manufacturing light-weight, stiff, highly damped structural components. The objective of this work was to design two cocured damped composite torsion shafts and compare their respective performances. The first shaft uses the extension-twist coupling mechanism of off-angle composite materials to enhance the performance of a damping material. The second shaft uses a constraining layer embedded inside the shaft that floats between two layers of damping material. Finite element analysis was used to determine optimal damping material shear modulus and ply orientation to maximize shaft imaginary stiffness. Four shafts in total (two of each type) were built and modal tests were performed. Torsion damping increased by factors of 5.8 to 20.0 and 6.1 to 10.9 over the undamped case for the extension-twist and floating constraining layer dampers, respectively. While both damping concepts provide significant levels of damping, the performance of each was hindered due to the increase in shear modulus of the damping material as it was cocured with the composite material.

Elastodyamic analysis of torsion of shaft of revolution by line-loaded integral equation method

The dynamic response of an elastic torsion shaft of revolution is analysed by the Line-Loaded Integral Equation Method (LLIEM). A "Dynamic Point Ring Couple" (DPRC) is used as a fictitious fundamental load and is distributed in an elastic space along the axis of the shaft outside the shaft occupation. According to the boundary condition, our problem is reduced to a 1-D Fredholm integral equation of the first kind, which is simpler for solving than that of a 2-D singular integral equation of the same kind obtanied by Boundary Element Method (BEM), for steady periodically varied loading. Numerical example of a shaft with quadratic generator under sinusoidal type of torque is given. Formulas for stresses and dangerous frequency are mentioned.

バックラッシ軸系の制振制御

バックラッシ軸系の制振制御

REMOVAL OF SPECKLE HARMONICS IN LASER TORSIONAL VIBROMETRY

Torsional vibration measurements on rotating machinery have traditionally been undertaken using techniques such as mechanical torsiographs, strain gauging with slip rings or telemetry systems, and encoders (slotted disks, gears, etc.). These techniques have the common limitation that the test machine has to be stopped in order to attach the transducer. The application of a cross-beam laser vibrometer to torsional vibrometry by Simpson and Lamb [1] and further development by Halliwellet al.[2] provided a non-contact torsional measurement technique, resulting in significant time savins. However, this design was restricted to use on shafts with a circular cross-section and had a very small beam crossing zone (<1 mm in depth), which had to be focussed carefully on the shaft surface. This cross-beam design was also unable to distinguish between torsional and transverse shaft vibrations.The invention of the modern (parallel beam) laser torsional vibrometer (LTV) by researchers at the ISVR in Southampton [3,4] overcame the main limitations of the cross-beam device. Their elegant design responds inherently to torsional vibrations only and may be used with shafts of arbitrary cross-section. In addition, the laser probe may be hand-held and there is a significant tolerance in the allowable distance between the laser source and the target surface (typically between 5 and 45 cm). A recent review paper on the development and application of laser torsional vibrometers has been published by Halliwell [5].

Anisotropic creep modelling of the single crystal superalloy SRR99

The starting point is a uniaxial non-linear rheological model, which performs the essential properties of the uniaxial behaviour under different loadings, such as monotonous and cyclic creep and LCF. A tensorial generalization of the uniaxial differential equations is derived by a projection method, which gives a general three-dimensional model obeying the crystal symmetries. An identification for the single crystal superalloy SRR99 at 760 °C has been made for tensile creep tests in different orientations. The model can be used to determine the creep behaviour of structural elements such as bars, torsional shafts or turbine blades.

Stress concentration factor in collar and shouldered shafts in torsion

In a previous work the stress intensity factors of shouldered and collar shafts are determined by a boundary element method (BEM) analysing the influence of the ratios between shaft and collar diameters, between the rounded fillet radius and shaft diameter, between length and height of the collar. In general the values obtained are lower than experimental values of the literature, hence it seems advisable to compare results with those obtained by another numerical method. In addition to studying other configurations by BEM, stress concentration factors are hence calculated by a finite element method (FEM) and compared with the BEM and literature results. BEM and FEM values are interpolated in order to give useful plots and a formula.

Acoustic-emission testing of torsion shafts

We study some problems connected with the estimation of fatigue damages to torsion shafts on the basis of an analysis of parameters of the signals of acoustic emission recorded in the course of static and cyclic tests. We describe the experimental procedure and present the results of the tests. Hypotheses that can explain the dependences obtained are suggested.

A novel torque sensor based on elastic waves generated and detected by piezoelectric thick films

Abstract Screen-printed and fired PZT-based films have been used as the source and detectors of elastic waves near the surface of a torsional shaft. The change in wave propagation velocity due to applied torques has been taken as the operating principle of a torque sensor. The new opportunities opened by piezoelectric thick-film materials in the implementation of this novel sensor are demonstrated.

DIGITAL COMPUTER STUDY OF THE CONTROL OF TORSIONAL INTERACTIONS IN HVDC TURBINE-GENERATORS

ABSTRACT This paper presents the results of a digital computer study of the control of torsional interaction in a monopolar, two-terminal HVDC system with detailed representation of rectifier, inverter, and their associated controls. The generator and its associated torsional shaft dynamics are also represented in detail. The study includes the examination of the effects of an auxiliary subsynchronous damping controller (SSDC), with signal derived from the generator rotor speed. The system is subjected to a disturbance involving a change in the DC current reference. Plots of shaft torques are given to illustrate the effect of SSDC in reducing the torsional stress.

A coupled tortional vibration of a rotating blade and shaft system of axial-flow-type machinery. (Continued report. Application of the equivalent reduced modeling method).

An analytical and experimental study on the coupled torsional vibration was carried out in the previous paper in order to determine the influencing factors in the coupled effect. In this paper, an equivalent reduced modeling method, which has been recently proposed as a new numerical analysis procedure, is applied for the previous torsional blade and shaft system. The results obtained are in good agreement with the experimental data of the previous paper, and the method seems to be effective for numerical estimation of the coupled torsional phenomena.

On the effect of key edge shape on keyway edge stresses in shafts in torsion

Two-dimensional, photoelastic tests of cross-sections of two keyed shafts with 13 different shapes of keys showed that rounded edges of keys give lower stress concentrations in the shaft than chamfered edges. Stress concentrations are reduced by making both rounding radii and chamfers larger than the key way fillet radius. Making the key a sliding fit in the keyway allows significant relative movement and produces lower stress concentrations than the usual interference fits. Boussinesq's theoretical solution for stresses near a concentrated edge load has been successfully used for direct calibration of small photoelastic models.

Dynamic investigations of single gear transmission taking into account microcracks

The paper concerns dynamic investigations of the model of gear transmission consisting of four rigid bodies and two torsion shafts. The shafts are assumed to contain microcracks which are taken into account by means of the equivalent shear modulus in accordance with the results of the papers [2, 3]. The influence of microcracks on the behaviour of the gear transmission in dynamic conditions is investigated for the first two frequencies of free vibrations and suitable amplitude-frequency curves. The investigations are carried out by means of two methods: the wave method which takes into account all the reflections of waves and the multibody system approach.

Stabilizing SSR oscillations with a shunt reactor controller for uncertain levels of series compensation

The authors demonstrate how frequency-domain techniques based on I. Horowitz et al.'s (1986) quantitative feedback theory can be applied to the design of fixed-parameter controllers in power systems where the plant parameters have large uncertainties. They present the design of a controller for a shunt reactor to eliminate torsional shaft oscillations in a turbogenerator susceptible to subsynchronous resonance (SSR). The considered parameter uncertainty is the series capacitor compensation level, which has been assumed to vary between 12% and 76%. Simulated transients results of the uncontrolled/controlled system are depicted.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Damping of Torsional Shaft Oscillations in Two Interacting Neighbouring Turbogenerators

This paper investigates the damping of torsional oscillations in a power station with two identical 1072 MVA generating units connected to an infinite bus through a series capacitor compensated transmission line. It considers a single common controlled shunt reactor to damp torsional oscillations of both turbogenerator shafts. To overcome the mathematical difficulties arising from having to use a high order model of the power system, together with powerful techniques for controller design, the order of the system model is firstly reduced by considering an 'equivalent' single generator and then applying a known model reduction method to this 'equivalent' generator's model. The transient response of the complete unreduced system is then evaluated when the two generator units are equipped with this single common controlled shunt reactor (1SR) and compared against the case when each generator unit has its own separate controlled shunt reactor (2SR). The results show that torsional oscillations in the turbogenerator shafts of such a multimachine system can be damped by the action of a single common controlled shunt reactor; nevertheless, a system where each turbogenerator is equipped with its own individual shunt reactor shows better overall system behavior.

Damping of Torsional Shaft Oscillations in Two Interacting Neighboring Turbogenerators

Damping of Torsional Shaft Oscillations in Two Interacting Neighboring Turbogenerators