Torsional Vibration Measurement Research Articles

Анализ работоспособности силиконовых демпферов крутильных колебаний судовых двигателей внутреннего сгорания на основе результатов испытательного центра Marine Technology Service

The article presents the analysis results of changes in the operability of silicone dampers of torsional vibrations of marine diesel engines on the basis of practical measurements carried out by the Testing Center Marine Technology Service under the Astrakhan State Technical University (TC MTS). TC MTS is accredited by the Russian classification society - the Russian Maritime Register of Shipping (RMRS) in the field of calculation and measurement of torsional vibrations. During its functioning (2001 – to date) the TC MTS has conducted torsiographing procedures of the machine-propulsion systems (MPS) of more than 200 vessels. The large amount of data obtained makes it possible to assess the dynamics of changes in the parameters of torsional vibrations, including amplitude and frequency, according to the results of periodic torsiographing the ship MPS. A change in the technical condition of the torsional vibration damper (a decrease in the efficiency of its operation) and the lack of its constant monitoring lead to the increasing stresses in the ship shaft line and, as a result, to a growing risk of its breakdown, which confirms the urgency of the study. There are given the images as real examples of ship operation failure: Aratere ship shaft fracture, damper mass wedging due to silicone fluid leakage, silicone fluid viscosity increasing to suspension state due to wear products, wear of silicone damper flyweight surfaces, silicone damper body wear. The Hasse & Wrede damper cap fastening with bolts is illustrated.

Bearing inner race fault detection and size estimation using the variable reluctance sensor

The variable reluctance sensor (VRS) has been widely used in the speed measurement system in the fields of automobile, helicopter, and ship, because of its high robustness. In recent years, most studies have verified the effectiveness of the application in rotor torsional vibration measurement and blade monitoring by the VRS. However, there is less research devoted to the VRS in bearing fault diagnosis, and its influencing mechanism between bearing faults and signal characteristics is not clear. In this paper, the raw signal of the VRS is used for bearing diagnosis. The mechanism of bearing partial fault signal response is analyzed by establishing the bearing inner ring fault model and the sensor signal response model. The characteristics of the VRS signal are given and verified by experiments. The results show that the gearwheel tooth-pass frequency is modulated by the bearing fault characteristic frequency, and there is an obvious double peak phenomenon in the high-frequency part. Moreover, the fault data with widths of 1 mm and 2 mm are analyzed by using the interval time of double peak. It is found that the fault sizes estimated are close to the actual defect size, and have small standard deviations. The original signal of the VRS has great potential in bearing diagnosis.

Phase Demodulation of Rotor Torsional Vibration Measurement under Time-Varying Speed

When torsional vibration is measured with the zebra-tape method, the modulation signals can be contaminated by electrical noise, environmental noise, step noise, sensor nonlinearities, and so on. Although the amplitudes of these types of noise are very weak relative to the amplitude of the ideal pulse test signal, they may introduce large-scale random broad-spectrum noise to the signal phases. Such noise is difficult to remove using frequency domain, time-frequency-domain, or threshold sampling methods and seriously affects the accuracy of torsional vibration measurements. This paper presents a phase demodulation algorithm based on downsampling and local resampling (DSLR) to improve the accuracy of torsional vibration measurements. To verify the proposed DSLR algorithm, torsional vibration simulations and experiments are conducted under a time-varying rotation speed. The results show that the angular displacement signal obtained from the torsional vibration test using zebra tapes is the superposition of the dynamic and static angular displacements, with the latter generated because of the varying rotation speed with respect to time. The DSLR algorithm effectively reduces the phase noise and demodulates the pulse signal phases. The work in this paper provides a method for obtaining reference torsional vibration measurements of rotors based on the zebra-tape method under time-varying speeds.

Torsional vibrations in a shaft train of an air compressor: modification, calculation and measurement

PurposeDue to the installation of the new, more powerful gearbox and the dismantling of the exciter machine, the vibration characteristics of the shaft train will be changed. Therefore, it is necessary to reassess the shaft train. It is to be investigated if the shaft train of the compressor meets the general requirements for bending and torsional vibrations and can be safely operated within the electrical network. The purpose of this paper is to show the necessary alignment of modification, calculation and measurement in such a project..Design/methodology/approachAfter some modification work on the shaft train of an air compressor, it was necessary to do some engineering calculations regarding the bending natural and torsional natural frequencies and their mode shapes. The correctness of the calculated values was proven by vibration measurements performed at the shaft train in operation.FindingsIt can be concluded that the change and replacement of rotating equipment in a shaft train never should be done without any engineering calculations in advance and measurements after the component modification. Most important is that the calculation results have to be compared with the measurement results for verifying the calculation assumptions. In the case described above, one can see that theory and practice match well. In addition to this, the very low damping of torsional vibrations is proved again, which can be a significant problem in some situations.Originality/valueAlso, today one can find torsional vibration measurements of rotating machines, including frequency, magnitude and damping factor, very seldom. Especially for smaller machines, there are no real comparisons between calculation and measurement are usual. This paper shows that an alignment between theoretical and practical approaches is necessary to avoid operational problems for rotating machines.

Low excitation spur gears with variable tip diameter

One important source of noise in drive trains are transmissions. In numerous applications, it is necessary to use helical instead of spur gear stages due to increased noise requirements. Besides a superior excitation behaviour, helical gears also show additional disadvantageous effects (e.g. axial forces and tilting moments), which have to be taken into account in the design process. Thus, a low noise spur gear stage could simplify design and meet the requirements of modern mechanical drive trains. The authors explore the possibility of combining the low noise properties of helical gears with the advantageous mechanical properties of spur gears by using spur gears with variable tip diameter along the tooth width. This allows the adjustment of the total length of active lines of action at the beginning and end of contact and acts as a mesh stiffness modification. For this reason, several spur gear designs are experimentally investigated and compared with regard to their excitation behaviour. The experiments are performed on a back-to-back test rig and include quasi-static transmission error measurements under load as well as dynamic torsional vibration measurements. The results show a significant improvement of the excitation behaviour for spur gears with variable tip diameter.

Development and implementation on torsional vibration measurement of rotational machinery’s shaft

The measurement and analysis on torsional vibration is an important aspect to research the performance state of rotating machinery’s shaft. This paper introduces the basic procedure of torsional vibration measurement, deduces the manifestation of torsional vibration signal, focuses on the hardware design and software implementation of torsional vibration measurement system, and applies the measurement system to a certain type of ship and steam turbine generator shaft in actual testing. The measurement results verify the practicability and accuracy of the system.

Torsional vibration test and analysis of an internal combustion engine power assembly by RLV-5500

The vibration characteristics of marine power plant and propulsion system shafting directly affect the navigation safety of the ship. Shafting torsional vibration is an important parameter to evaluate the stability and reliability of shafting. The demand of ship shafting torsional vibration measurement is gradually developing towards high resolution and high accuracy. According to the characteristics of ship shafting installation and operation, this paper selects an internal combustion engine powertrain as the test object, and uses rlv-5500 rotary laser vibration measurement system to test the shafting torsional vibration. The time-frequency analysis of the test results is carried out to calculate the comprehensive angular displacement and the angular displacement amplitude of each harmonic order. The maximum comprehensive amplitude of crankshaft free end torsional vibration is 0.33 °. The crankshaft will not be damaged by torsional vibration.

Theoretical and experimental study of wind turbine drivetrain fault diagnosis by using torsional vibrations and modal estimation

This paper provides an analytical proof and the theoretical development of the idea of using the torsional vibration measurements for a system-level condition monitoring of the drivetrain system. The method relies on modal parameter estimation of the drivetrain system by using the torsional measurements and subsequent monitoring of the variations in the system eigenfrequencies and normal modes. Angular velocity error function extracted from encoder outputs at both input and output of drivetrain is used to estimate modal parameters including natural frequencies and damping coefficients. In the proposed condition monitoring approach, it is shown that any abnormal deviation from the reference values of the drivetrain system dynamic properties can be translated into the progression of a specific fault in the system. In order to extract the condition monitoring features, local sensitivity analysis is engaged to establish a relationship between different categories of drivetrain faults with the system dynamic properties and the amplitude of torsional response, which helps with both to identify the state of the progressive faults and to localize them. Local sensitive analysis shows that abnormal deviations in stiffness and moment of inertia due to the presence of faults result in considerable changes in natural frequencies and modal responses which can be measured and used as fault detecting features by using the proposed analytical approach. Sensitivity analysis is also employed along with the estimated modal frequency for estimation of modal damping from the amplitude of response at the natural frequencies and their subsequent use for estimation of undamped natural frequencies which are later used in the proposed condition monitoring approach. The proposed approach is computationally inexpensive and can be implemented without additional instrumentation. Two test cases, using 10 MW simulated and 1.75 MW operational drivetrains have been demonstrated.

Study on torsional vibration of a harmonic driver based on time-varying stiffness caused by manufacturing error

The torsional vibration of Harmonic reducer is concerned with the positioning accuracy and trajectory accuracy of industrial robots. A study on the parametric torsional vibration based on time-varying stiffness will improve the mechanical performance of Harmonic reducer. In this paper, the phenomenon of time-varying stiffness caused by manufacturing error is investigated on a Harmonic driver through mechanism analysis and experimental investigation. Meanwhile, a model of forced parametric vibration is set up for the Harmonic driver transmission system with an inertia load. The parametric vibration response is simulated by the Runge-Kutta method, and the issue of bi-spectra, combined harmonic group, and the envelope of system sweeping frequency response are analyzed in detail. The influence of double periodic time-varying stiffness on vibration is emphasized with simulation data. To observe the characteristic of parametric vibration in Harmonic driver, a test device has been developed for the measurement of torsional vibration. The dynamic characteristics can be confirmed through signal processing on torsional vibration. An engineering example is given to illustrate that the manufacturing defect can be on-line diagnosed in Harmonic driver by using the characteristic of bi-spectra. As a result, the magnitude of torsional vibration is eliminated to one half of the original case through the reassembly process, and one of the mechanical performances, i.e., the property of torsional vibration-speed, is improved obviously. The dynamic characteristics caused by time-varying stiffness, i.e., bi-spectra, can be used as a new clue of manufacturing quality assurance for Harmonic driver.

A Torsional Vibration Measurement Method for Rotating Blades Based on Blade Tip Timing

During the working process of the turbine, some types of faults can cause changes in the vibration characteristics of the blades. The real‐time vibration monitoring of the blades is of great significance to the stable operation and state‐based maintenance. Torsional vibration is a kind of blade vibration modes and results in failures such as cracks easily. Thus, it is important to measure it due to the harmfulness of torsional vibration. Firstly, the principle of blade tip timing (BTT) is introduced, and the models of the blade are built to analyze the characteristics of torsional vibration. Then, the compressed sensing theory is introduced, and its related parameters are determined according to the measurement requirements. Next, based on the condition that the blade rigidity axis is not bent and bent, respectively, the layout method of sensors is proposed and the numerical simulation of the measurement process is performed. The results of the above two types of numerical simulation verify the proposed measurement method. Finally, by analyzing the influencing factors of measurement uncertainty, the optimization method of sensors’ layout is further proposed. This study can provide important theoretical guidance for the measurement of blade torsional vibration.

Natural frequency estimation by using torsional response, and applications for wind turbine drivetrain fault diagnosis

A method based on torsional vibration measurements for a system-level condition monitoring of the drivetrain system is developed in this paper. The latter is tested by using a 10MW wind turbine drivetrain simulation model, and experimentally validated by the drivetrain operational data obtained from a 1.75MW turbine. The method relies on the estimation of the drivetrain torsional natural frequencies by using the torsional responses residual function and subsequent monitoring of the variations in the eigenfrequencies and normal modes. In other words, an abnormal deviation from the reference values of these dynamic parameters can be translated into a meaningful interpretation on the propagation of a specific fault in the driveline. Local sensitivity analysis is employed to establish a relationship between different types of drivetrain faults and the system dynamic properties.

Experimental study to evaluate the effect of particle size on the small strain shear modulus of coarse-grained soils

Abstract Coarse-grained soils are found commonly in nature and are extensively used for a wide range of engineering applications, such as slopes, earth dams, and railway foundations. This study presents an experimental investigation on the effect of mean particle size D50 on the small strain shear modulus Gmax of coarse-grained poorly-graded and well-graded soils. Combined with particle morphology analysis, a series of shear wave velocity tests were performed on pure sand, pure gravel and sand-gravel mixture specimens by taking advantage of a torsional vibration measurement device in a large scale triaxial apparatus. The results demonstrate that Gmax is insensitive to D50 for uniform sand and gravel specimens. On the other hand, Gmax increases gradually with D50 for well-graded sand-gravel mixture specimens. The discrepancy in the relationship between Gmax and D50 for poorly- and well-graded soils is related to the degree of size polydispersity in the specimens.

Diagnostics of Shaft Trains of Large Turbine Sets for Integrity Using Torsional Vibration Measurements

A promising solution to the problem of early detection for the growth of fatigue cracks in shaft trains of large turbine units at nuclear and thermal power stations based on the results of torsional vibration monitoring by the method of time intervals is considered. It has been demonstrated in the laboratory that this method enables us to detect the growth of fatigue cracks in the shafts of rotor systems from a decrease in the value on natural frequencies of torsional oscillations. However, attempts to use it in the industry were not so successful due to a slight influence of fatigue cracks on the values of the natural frequencies of torsional oscillations as compared with the effect of other factors. Nevertheless, the data obtained in the study of torsional oscillations of the shaft train in a turbine installation of an operating 300-MW power unit using a high-precision optoelectronic monitoring system enabled the establishment and consideration of the effect that the turbine operating conditions has on the natural frequencies of torsional oscillations for the first time. A modal finite-element analysis of the turbine installation shaft train’s most dangerous annular fatigue crack, which cannot be detected at an early stage of development using standard or special vibration-monitoring systems during steady state operation of the turbine installation, has been performed. The analysis yielded the dependence of the torsional natural frequencies on the cross-sectional area and location of the fatigue crack. Monitoring of fatigue crack development has been demonstrated to be performed by measuring the natural frequencies of torsional oscillations (or vibrations) during steady state operation of the turbine set considering the effect of its operating conditions.

Diagnostics of the Internal Combustion Engines Operation by Measurement of Crankshaft Instantaneous Angular Speed

Abstract Diagnostics based on measuring of crankshaft instantaneous rotational speed allows precise location of damage to the injection system and detection of external disturbances. Active measurement of instantaneous rotational speed requires use of equipment with high sensitivity, permanent assembly at the ends of the crankshaft and the analysis of a very large amount of data. Presented method can be used for measurement of torsional vibration of crankshaft, indirectly through simultaneous measurement of the width of the pulses generated by the encoder disks. Momentary, relative displacement of both disks determines the angle of temporary crankshaft twisting. This paper presents first results of pulse width measurement, obtained by using described system.

A Fiber Bragg Grating Based Torsional Vibration Sensor for Rotating Machinery.

This paper proposes a new type of torsional vibration sensor based on fiber Bragg grating (FBG). The sensor has two mass ball optical fiber systems. The optical fiber is directly treated as an elastomer and a mass ball is fixed in the middle of the fiber in each mass ball fiber system, which is advantageously small, lightweight, and has anti-electromagnetic interference properties. The torsional vibration signal can be calculated by the four FBGs’ wavelength shifts, which are caused by mass balls. The difference in the two sets of mass ball optical fiber systems achieves anti-horizontal vibration and anti-temperature interference. The principle and model of the sensor, as well as numerical analysis and structural parameter design, are introduced. The experimental conclusions show that the minimum torsional natural frequency of the sensor is 27.35 Hz and the torsional vibration measurement sensitivity is 0.3603 pm/(rad/s2).

Experimental Study of the Shaft Penetration Factor on the Torsional Dynamic Response of a Drive Train

Typical rotating machinery drive trains are prone to torsional vibrations. Especially those drive trains that comprise one or more couplings which connect the multiple shafts. Since these vibrations rarely produce noise or vibration of the stationary frame, their presence is hardly noticeable. Moreover, unless an expensive torsional-related problem has become obvious, such drive trains are not instrumented with torsional vibration measurement equipment. Excessive levels can easily cause damage or even complete failure of the machine. So, when designing or retrofitting a machine, a comprehensive and detailed numerical torsional vibration analysis is crucial to avoid such problems. However, to accurately calculate the torsional modes, one has to account for the penetration effect of the shaft in the coupling hub, indicated by the shaft penetration factor, on the torsional stiffness calculation. Many guidelines and assumptions have been published for the stiffness calculation, however, its effect on the damping and the dynamic amplification factor are less known. In this paper, the effect of the shaft penetration factor, and hence coupling hub-to-shaft connection, on the dynamic torsional response of the system is determined by an experimental study. More specifically, the damping is of major interest. Accordingly, a novel academic test setup is developed in which several configurations, with each a different shaft penetration factor, are considered. Besides, different amplitude levels, along with both a sweep up and down excitation, are used to identify their effect on the torsional response. The measurement results show a significant influence of the shaft penetration factor on the system’s first torsional mode. By increasing the shaft penetration factor, and thus decreasing the hub-to-shaft interference, a clear eigenfrequency drop along with an equally noticeable damping increase, is witnessed. On the contrary, the influence of the sweep up versus down excitation is less pronounced.

운전금지 구역 통과 시 선박용 중간축의 피로강도와 수명

Recent innovations on low-speed two-stroke ship propulsion engines include higher power rating with lower nominal engine speed for increased propeller efficiency and reduced fuel consumption. Additionally, 5~6 cylinder engines are preferred for having reduced dimension freeing up cargo spaces and lower repair and maintenance costs as well. Likewise, the barred speed range (BSR) protects the shafting system from increased torsional vibration stresses by passing in a shortest possible time at this critical speed. Considering above-mentioned engine specifications, shaft breakage accidents can occur from the accumulated fatigue stress due to the prolonged barred speed range passing and shafting design. This paper evaluates the propulsion shafting system fatigue strength and lifecycle of a 6G70ME model engine through theoretical analysis and torsional vibration measurement data.

Magnetostrictive patch sensor system for battery-less real-time measurement of torsional vibrations of rotating shafts

Real-time uninterrupted measurement for torsional vibrations of rotating shafts is crucial for permanent health monitoring. So far, strain gauge systems with telemetry units have been used for real-time monitoring. However, they have a critical disadvantage in that shaft operations must be stopped intermittently to replace telemetry unit batteries. To find an alternative method to carry out battery-less real-time measurement for torsional vibrations of rotating shafts, a magnetostrictive patch sensor system was proposed in the present study. Since the proposed sensor does not use any powered telemetry system, no battery is needed and thus there is no need to stop rotating shafts for battery replacement. The proposed sensor consists of magnetostrictive patches and small magnets tightly bonded onto a shaft. A solenoid coil is placed around the shaft to convert magnetostrictive patch deformation by shaft torsional vibration into electric voltage output. For sensor design and characterization, investigations were performed in a laboratory on relatively small-sized stationary solid shaft. A magnetostrictive patch sensor system was then designed and installed on a large rotating propulsion shaft of an LPG carrier ship in operation. Vibration signals were measured using the proposed sensor system and compared to those measured with a telemetry unit-equipped strain gauge system.

A 3-axis torsion quasi-zero-stiffness-based sensor system for angular vibration measurement

In this paper, a novel 3-axis torsion quasi-zero-stiffness (TQZS)-based sensor system is proposed for absolute rotation measurement in vibration systems. Analysis on the applied torque and structural parameters shows that the proposed mechanism with two concentric spheres connected by six symmetry distributed springs could approximately achieve TQZS features in three rotational degrees of freedom simultaneously, thus a remarkable torsional vibration measurement performance can be guaranteed. Although due to high stiffness, the mechanism also has high anti-interference ability about force or vibration in translational directions. Mathematical modeling and numerical simulations are carried out to show the effectiveness of the proposed 3-axis sensor system in different base vibrations. In consideration of its feasibility and high performance, it can be foreseen that the proposed TQZS-based sensor will get more and more implementations in various engineering practices with torsional vibration measurements.

Measurement and modelling of torsional warping free vibrations of beams with rectangular hollow cross-sections

This contribution contains the results of experimental measurements and modelling of torsional warping free vibrations of beams with rectangular hollow cross-sections. The experimental results are compared with results from a semi-analytical method, proposed by the authors, and from Finite Element (FE) computations by means of a standard commercial code. In these calculations, beam, solid, and shell elements are used. The semi-analytical calculations are based on the analogy between second-order beam theory, including consideration of the shear force deformation effect, and non-uniform torsion, considering the Secondary Torsion Moment Deformation Effect (STMDE). The influence of warping and of the STMDE on the torsional eigenfrequencies and eigenforms is evaluated. The difference between the measured and calculated eigenfrequencies is investigated and quantified.