Rotor-Blade Coupled Torsional Vibration Analysis Using Modal Parameters Based on FEM Analyses and Experiments

2010 ◽  
Author(s):  
Akira Okabe ◽  
Koki Shiohata ◽  
Takeshi Kudo ◽  
Hideo Yoda ◽  
Shigeo Sakurai ◽  
...  
Keyword(s):  
Torsional Vibration ◽  
Vibration Analysis ◽  
Rotor Blade ◽  
Fem Analysis ◽  
Design Tool ◽  
Modal Parameters ◽  
Disk System ◽  
Fem Method ◽  
Standard Product ◽  
Model Rotor

The quasi-modal technique is used for rotor-blade coupled torsional vibration analysis due to its unique characteristics in providing a visually reduced model. Given the rapid advances in computation technology in recent years, the FEM method is now widely used as a standard product design tool in many industries, because it can reflect a more detailed structure quickly in the design process. In this paper we proposed the use of a commercially available FEM method program (ANSYS®) to calculate quasi-modal parameters of the bladed disk system. This program was applied to the model rotor of two disks with continuously coupled blades. Rotor-blade coupled torsional frequencies of the model rotor based on the FEM based quasi-modal technique were compared with a complete FEM analysis of the model rotor. Both methods gave results in good agreement. We also compared the frequencies measured through rotation testing of the model rotor to calculations. Finally, we presented the procedure for calibrating modal parameters based on the measured blade-disk frequencies. Quasi-modal modeling was judged practicable for feeding back test results to achieve higher accuracy.

A validated robust and automatic procedure for vibration analysis of bridge structures using MEMS accelerometers

2020 ◽  
Vol 14 (3) ◽  
pp. 327-354
Author(s):  
Mohammad Omidalizarandi ◽  
Ralf Herrmann ◽  
Boris Kargoll ◽  
Steffen Marx ◽  
Jens-André Paffenholz ◽  
...  
Keyword(s):  
Vibration Analysis ◽  
Damping Ratio ◽  
Fem Analysis ◽  
Cost Effective ◽  
Analysis Procedure ◽  
Modal Parameters ◽  
Bridge Structure ◽  
Modal Damping ◽  
Mems Accelerometers ◽  
Better Than

AbstractToday, short- and long-term structural health monitoring (SHM) of bridge infrastructures and their safe, reliable and cost-effective maintenance has received considerable attention. From a surveying or civil engineer’s point of view, vibration-based SHM can be conducted by inspecting the changes in the global dynamic behaviour of a structure, such as natural frequencies (i. e. eigenfrequencies), mode shapes (i. e. eigenforms) and modal damping, which are known as modal parameters. This research work aims to propose a robust and automatic vibration analysis procedure that is so-called robust time domain modal parameter identification (RT-MPI) technique. It is novel in the sense of automatic and reliable identification of initial eigenfrequencies even closely spaced ones as well as robustly and accurately estimating the modal parameters of a bridge structure using low numbers of cost-effective micro-electro-mechanical systems (MEMS) accelerometers. To estimate amplitude, frequency, phase shift and damping ratio coefficients, an observation model consisting of: (1) a damped harmonic oscillation model, (2) an autoregressive model of coloured measurement noise and (3) a stochastic model in the form of the heavy-tailed family of scaled t-distributions is employed and jointly adjusted by means of a generalised expectation maximisation algorithm. Multiple MEMS as part of a geo-sensor network were mounted at different positions of a bridge structure which is precalculated by means of a finite element model (FEM) analysis. At the end, the estimated eigenfrequencies and eigenforms are compared and validated by the estimated parameters obtained from acceleration measurements of high-end accelerometers of type PCB ICP quartz, velocity measurements from a geophone and the FEM analysis. Additionally, the estimated eigenfrequencies and modal damping are compared with a well-known covariance driven stochastic subspace identification approach, which reveals the superiority of our proposed approach. We performed an experiment in two case studies with simulated data and real applications of a footbridge structure and a synthetic bridge. The results show that MEMS accelerometers are suitable for detecting all occurring eigenfrequencies depending on a sampling frequency specified. Moreover, the vibration analysis procedure demonstrates that amplitudes can be estimated in submillimetre range accuracy, frequencies with an accuracy better than 0.1 Hz and damping ratio coefficients with an accuracy better than 0.1 and 0.2 % for modal and system damping, respectively.

435 Rotor-Blade Coupled Vibration Analysis by Measuring Modal Parameters of Actual Rotor

2010 ◽  
Vol 2010 (0) ◽  
pp. _435-1_-_435-6_
Author(s):  
Takeshi KUDO ◽  
Akira Okabe ◽  
Koki Shiohata ◽  
Shigeo SAKURAI ◽  
Hideo YODA ◽  
...  
Keyword(s):  
Vibration Analysis ◽  
Rotor Blade ◽  
Modal Parameters ◽  
Coupled Vibration

scholarly journals Rotor-Blade Coupled Vibration Analysis by Measuring Modal Parameters of Actual Rotor(Mechanical Systems)

2009 ◽  
Vol 75 (751) ◽  
pp. 566-573 ◽  
Author(s):  
Akira OKABE ◽  
Takeshi KUDO ◽  
Hideo YODA ◽  
Shigeo SAKURAI ◽  
Osami MATSUSHITA ◽  
...  
Keyword(s):  
Vibration Analysis ◽  
Rotor Blade ◽  
Mechanical Systems ◽  
Modal Parameters ◽  
Coupled Vibration

CHIMERA volume grid generation within the EROS code

2000 ◽  
Vol 214 (3) ◽  
pp. 125-141 ◽  
Author(s):  
C B Allen
Keyword(s):  
Computational Fluid Dynamic ◽  
Rotor Blade ◽  
Fluid Dynamic ◽  
Grid Generation ◽  
Design Tool ◽  
Software Project ◽  
Blade Design ◽  
Collaborative Project ◽  
Structured Grid ◽  
Research Institutes

The EROS (European ROtorcraft Software) project was a three-year, European Commission funded, collaborative project between research institutes, universities and industry, with the goal of producing a practical computational fluid dynamic (CFD)-based design tool for rotor blade design. The overlapping mesh, or CHIMERA, approach was adopted for structured grid generation within the project. The specifics of volume grid generation in GEROS, the EROS grid generator, are presented here. The capabilities and effectiveness of GEROS are demonstrated, and sample grids are shown for fixed-wing hovering rotor and forward-flight rotor cases.

Torsional Vibration Analysis of Shafts With Sections of Tapered Diameter

1993 ◽  
Author(s):  
John R. Baker ◽  
Keith E. Rouch
Keyword(s):  
Torsional Vibration ◽  
Vibration Analysis ◽  
Natural Frequencies ◽  
Displacement Function ◽  
The Other ◽  
Mode Shapes ◽  
Axial Distance ◽  
Rotational Degree ◽  
Rotor Systems ◽  
Constant Diameter

Abstract This paper presents the development of two tapered finite elements for use in torsional vibration analysis of rotor systems. These elements are particularly useful in analysis of systems that have shaft sections with linearly varying diameters. Both elements are defined by two end nodes, and inertia matrices are derived based on a consistent mass formulation. One element assumes a cubic displacement function and has two degrees of freedom at each node: rotation about the shaft’s axis and change in angle of rotation with respect to the axial distance along the shaft. The other element assumes a linear displacement function and has one rotational degree of freedom at each node. The elements are implemented in a computer program. Calculated natural frequencies and mode shapes are compared for both tapered shaft sections and constant diameter sections. These results are compared with results from an available constant diameter element. It is shown that the element derived assuming a cubic displacement function offers much better convergence characteristics in terms of calculated natural frequencies, both for tapered sections and constant diameter sections, than either of the other two elements. The finite element code that was developed for implementation of these elements is specifically designed for torsional vibration analysis of rotor systems. Lumped inertia, lumped stiffness, and gear connection elements necessary for rotor system analysis are also discussed, as well as calculation of natural frequencies, mode shapes, and amplitudes of response due to a harmonic torque input.

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