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This study aims to study the dynamic characteristics of a helical geared rotor-bearing system with composite material rotating shafts.

A finite element model of a helical geared rotor-bearing system with composite material rotating shafts is developed, in which the rotating shafts of the system are composed of composite material and modeled as Timoshenko beam; a rigid mass is used to represent the gear and their gyroscopic effect is taken into account; bearings are modeled as linear spring-damper; and the equations of motion are obtained by applying Lagrange’s equation. Natural frequencies, mode description, lateral responses, axial responses, lamination angles, lamination numbers, gear mesh stiffness and bearing damping coefficients are investigated.

The desired mechanical properties could be constructed using different lamination numbers and fiber included angles by composite rotating shafts. The frequency of the lateral module decreases as the included angle of the fibers and the principal shaft of the composite material rotating shaft increase. Because of the gear mesh stiffness increase, the resonance frequency of the coupling module of the system decreases, the lateral module is not influenced and the steady-state response decreases. The amplitude of the steady-state lateral and axial responses gradually decreases as the bearing damping coefficient increases.

The model of a helical geared rotor-bearing system with composite material rotating shafts is established in this paper. The dynamic characteristics of a helical geared rotor-bearing system with composite rotating shafts are investigated. The numerical results of this study can be used as a reference for subsequent personnel research.

The dynamic characteristics of the geared rotor-bearing system had been reported in some literature. However, the dynamic analysis of a helical geared rotor-bearing system with composite material rotating shafts is still rarely investigated. This paper shows some novel results of lateral and axial response results obtained by different lamination angles and different lamination numbers. In the future, it makes valuable contributions for further development of dynamic analysis of a helical geared rotor-bearing system with composite material rotating shafts.

The purpose of this paper is to validate mathematically the feasibility of extracting the rotating blades vibration condition from the shaft torsional vibration measurement.

A mathematical model is developed and simulated for extracting rotating blades vibration signatures from the shaft torsional vibration signals. The model simulates n‐blades attached to a rigid disk at setting angles and the shaft drives the disk is flexible in torsion. The model is developed using the multi‐body dynamics approach in conjunction with the Lagrangian dynamics. A three‐blade rotor system example is simulated for blades free and forced vibration under stationary and rotating conditions. Frequency spectrums for the shaft torsional and blades bending vibration are represented and studied for analysis verification purposes.

The torsional vibration frequency spectrums showed blades free and forced vibration signatures. The blade setting angle is shown to reduce the sensitivity of torsional vibration signal to blades vibration signatures as it increases. The torsional vibration signals captured the variation in blades properties and produced broadband frequency components for mistuned system. The shaft torsional rigidity is shown to reduce the sensitivity of torsional vibration signal to blades vibration if increased to extremely high values (approaching rigid shaft). The rotor inertia is shown to have less effect on the torsional vibration signals sensitivity. The method of torsional vibration as a tool for rotating blades vibration measurement, based on the proposed mathematical model and its simulation, is feasible.

There is a growing need for reliable predictive maintenance programs that in turn requires continuous development in methods for machinery health monitoring through vibration data collection and analysis. Turbo machinery and bladed assemblies like fans, marine propellers and wind turbine systems usually suffer from the problem of blades high vibration that is difficult to measure. The proposed new method for blades vibration measurement depends on the shaft torsional vibration signals and can be used also for verifying the signals from other types of bearings sensors for possible blades vibration condition monitoring.

This paper presents a unique mathematical model and simulation results for the rotating blades vibration monitoring. The developed model can be simulated for studying coupled blades vibration problems in the design stage as well as for condition monitoring in maintenance applications.

While the petroleum industry remains to be the main source of energy in the world, it is responsible for a large amount of resource consumption, environmental emission and safety issues. In this industry, most of the refinery equipment are running out of their designed life cycle, leading to many challenges regarding equipment reliability, products quality, organizations’ profitability, human resources safety and job satisfaction, and environmental pollution, which affects not only the human resources of the refinery but also the people who live in the vicinity. This study aims to model and simulate the maintenance system of an oil refinery to reduce the rotating equipment’s downtime while simultaneously considering the three pillars of sustainability.

Considering the complexity of the system and its inherent dynamism, System Dynamics (SD) approach is applied to model and simulate the maintenance system of an oil refinery, aiming at reducing equipment’s downtime considering the three pillars of sustainability simultaneously. As a case study, the maintenance system of rotating equipment in the Abadan oil refinery of Iran is investigated.

Individual policies are investigated and categorized into three main groups: economic, social and environmental. The dynamic nature of the system demonstrates that applying combinations of the policies would be more effective than performing individual ones or even a combination of all policies at the same time. The findings show that to manage the maintenance and reliability issues in complex industries, only operational level maintenance strategies would not be helpful; rather, a holistic strategic solution counting different suppliers or even the government policies supporting the operational level maintenance decisions would be effective.

This study is the first which brings the perspective of sustainable policy-making in the SD modeling of a complex maintenance system like that of the petroleum industry. The developed model considers economic, environmental and social objectives simultaneously. Besides, it reflects the role of different stakeholders in the system. Furthermore, the policy-making attempt is not limited to the operational level corrective and maintenance solutions; instead, a comprehensive, holistic view is applied.

A 3‐dimensional formalism adapted to critical speed and stability analysis of rotating machinery is presented. Gyroscopic effects are properly taken into account in the expression of the kinetic energy through a proper kinematic description which takes account of the local changes of angular velocity induced by the deformation. Two approaches are suggested according to the respective stiffness and geometric properties of the rotating and fixed parts: the rotating frame approach and the inertial frame approach. In both cases, an axisymmetric finite element modelling of the rotor is proposed which takes into account the 3‐dimensional nature of the system while keeping the number of degrees of freedom to a reasonable level. In order to perform the stability analysis, a preliminary reduction of the system is achieved using the component mode method. Critical speeds are calculated next either by the classical sweeping procedure or by a direct method when the restrictive conditions of its applicability are met. The concepts proposed are then applied to an example in order to demonstrate their adequacy.

A laser‐based system has been developed to automatically measure complete inner profiles of various structures. The system uses a pointed laser source passing through a rotating optical device to obtain a series of distance measurements. To enhance the portability of the system, a hand‐held computer is selected to control the laser source and the rotating optical device. In addition to system control, the software associated with the handheld computer has also been developed to use the series distance measurements to construct a complete profile of the measured structure as well as to estimate the crosssectional area of the profile. The system can provide critical information for the construction industry and a variety of other commercial applications. The evaluation and analysis of measurement indicated that on accuracy within 4 per cent, for typical window designs and floor patterns, could be achieved. Recommendations for improvement of the system have also been included.

Describes the use of welding robots for making bridge panels. The system uses a total of 14 sets of High Speed Rotating Arc welding robots and newly‐developed arc sensor techniques are used with both joint end and bead end sensors. A teaching‐less direct CADCAM system was developed to control the robots. The welding robot system is now in commercial operation with welding efficiencies that are twice those possible with conventional processes.

Presents three non‐isothermal, time dependent, three dimensional examples having cylindrical geometries to show the significant effort of numerical precision and dissipation on rotating flow predictions. The examples are relevant to turbomachinery design and geophysical studies. Discusses the relationship between numerical precision, numerical dissipation and co‐ordinate system angular velocity. Compares predictions made in stationary and rotating co‐ordinate systems, using contour plots of dimensionless stream function and temperature. Shows that wrong, axisymmetric solutions are predicted if the co‐ordinate system is not selected to minimize relative tangential velocities/Peclet numbers, thereby increasing numerical precision and reducing dissipation.

Asymmetric rotating machinery supported by oil film bearings is relatively common in practical applications. The purpose of this study is to propose a method for estimating the oil film parameters of the bearings in an asymmetric rotor-bearing system.

The proposed method requires the finite element model and translational displacement responses at the center of mass and bearings locations to form a regression equation to estimate the unknown parameters. Due to the transverse stiffness of the asymmetric rotor is not symmetrical, the analysis and parameter estimation procedures are performed in a rotating coordinate. Numerical simulations were carried out to illustrate the vibration characteristics of the asymmetric rotor system. The proposed method is applied to the simulated responses to estimate the assumed oil film parameters. The influence of the estimated parameter deviations on the rotor dynamic characteristics is discussed.

The vibration characteristics of asymmetric rotors are different from those of symmetrical rotors. The bearing parameters estimated by the proposed method are close to the assumed values, within a maximum error of 9%. The deviations of the estimated parameters have little effect on the vibration characteristic of the rotor system.

The proposed method does not require changing the rotational speed or applying additional excitation force to the rotor, which is suitable for the field test.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2023-0111/

Discusses the 27 papers in ISEF 1999 Proceedings on the subject of electromagnetisms. States the groups of papers cover such subjects within the discipline as: induction machines; reluctance motors; PM motors; transformers and reactors; and special problems and applications. Debates all of these in great detail and itemizes each with greater in‐depth discussion of the various technical applications and areas. Concludes that the recommendations made should be adhered to.

Efficient calculations of the transient behaviour after disturbances of large-scale power systems are complex because of, among other things, the non-linearity and the stiffness of the overall state equation system (SES). Because of the rising amount of flexible transmission system elements, there is an increasing need for reduced order models with a negligible loss of accuracy. With the Extended Nodal Approach and the application of the singular perturbation method, it is possible to reduce the order of the SES adapted to the respective setting of the desired tasks and accuracy requirements.

Based on a differential-algebraic equation for the electric power system which is formulated with the Extended Nodal Approach, the automatic decomposition into reduced order models is shown in this paper. The paper investigates the effects of different coordinate systems for an automatic order reduction with the singular perturbation method, as well as a comparison of results calculated with the full and reduced order models.

The eigenvalues of the full system are approximated sufficiently by the three subsystems. A simulation example demonstrates the good agreement between the reduced order models and the full model independent of the choice of the coordinate system. The decomposed subsystems in rotating coordinates have benefits as compared to those in static coordinates.

The paper presents a systematic decomposition based only on a differential-algebraic equation system of the electric power system into three subsystems.