Rotating Shafts Affected by Transverse Cracks: A Sensitivity Analysis

2008 ◽  
Author(s):  
Nicolo` Bachschmid ◽  
Ezio Tanzi ◽  
Paolo Pennacchi
Keyword(s):  
Sensitivity Analysis ◽  
Element Model ◽  
Dynamical Behaviour ◽  
Crack Model ◽  
Transverse Cracks ◽  
Rotating Shaft ◽  
Shaft Line ◽  
Linear Approach ◽  
Turbo Generator ◽  
Rotating Shafts

The dynamic behaviour of heavy, horizontal axis, rotating shaft-lines affected by transverse cracks can be analysed in the frequency domain by a quasi linear approach, using a simplified breathing crack model applied to a traditional finite element model of the shaft-line. This allows to perform a series of analyses with affordable efforts. The analysis of the modelling procedure allows to define an approximated approach for simulating the dynamical behaviour, which allows to predict the severity of the crack excited vibrations, combined to modal analysis. this answers to the old-age question on how deep a crack must be to be detected by means of vibration measurements. The model of a 320 MW turbo-generator group has been used to perform a numerical sensitivity analysis, in which the vibrations of the shaft-line, and more in detail the vibrations of the shafts in correspondence to the bearings, have been calculated for all possible positions of the crack along the shaftline and for two different values of the depth of the crack. The calculated results confirm the predicted behaviour.

Active Vibration Control of Periodic Rotating Shafts

Aerospace ◽  
2004 ◽  
Author(s):  
M. Toso ◽  
A. Baz ◽  
D. Pines
Keyword(s):  
Transfer Matrix ◽  
Control Strategies ◽  
Spectral Characteristics ◽  
Active Vibration Control ◽  
Element Model ◽  
Rotating Shaft ◽  
Transverse Waves ◽  
Frequency Bands ◽  
Specific Frequency ◽  
Rotating Shafts

The propagation of transverse waves in periodic rotating shafts is controlled actively by using piezoelectric inserts which are placed periodically along these shafts. The control strategies aim at tuning the unique filtering characteristis of the periodic shafts in such manner that prevent the propagation of the waves within specific frequency bands called “stop bands.” The spectral characteristics of these “stop bands” are controlled in response to the shaft vibration. A finite element model is developed for this class of actively controlled periodic shafts which is then used to generate the “transfer matrix” for the unit cell of these shafts. The eigenvalues of the resulting transfer matrix are utilized to predict the characteristics of the stop and the pass bands of the rotating shaft as function of the shaft geometry, rotation speed, and control gains of the active inserts. The obtained characteristics are validated experimentally using shafts driven via gearbox assembly which subject the shafts to broadband excitations. The obtained results are also compared with the characteristics of passive shafts with stepped periodic geometries. Such a comparison aims at demonstrating the effectiveness of the active periodic shafts in redistributing the energy spectrum by confining the propagation to specific frequency bands. Particular emphasis is placed on studying the effect of the active control strategies on the vibration damping characteristics of the shafts. The proposed class of active periodic shafts can be useful in numerous critical applications such as the drive shafts of helicopters where transmitted vibrations can have detrimental effect on the performance of the tail rotor. Other applications are only limited by our imagination.

Bisynchronous Torsional Vibrations in Rotating Shafts

1987 ◽  
Vol 54 (4) ◽  
pp. 893-897 ◽  
Author(s):  
O. Bernasconi
Keyword(s):  
Angular Momentum ◽  
Nonlinear Term ◽  
Rotation Frequency ◽  
Longitudinal Component ◽  
Torsional Vibrations ◽  
Rotating Shaft ◽  
Rotating Shafts

In this study, the intrinsic behavior of rotating shafts with residual unbalance is considered. The longitudinal component of the angular momentum caused by synchronous precession (whirling) induces torsional vibrations with a frequency of twice the rotation frequency (bisynchronous). The nonlinear term which represents this coupling is characteristic of the asymmetrical aspect of rotating shaft kinematics. This result has been obtained analytically and confirmed experimentally.

scholarly journals Sensitivity Analysis of the Influence of Structural Parameters on Dynamic Behaviour of Highly Redundant Cable-Stayed Bridges

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
B. Asgari ◽  
S. A. Osman ◽  
A. Adnan
Keyword(s):  
Sensitivity Analysis ◽  
Finite Element ◽  
Finite Element Model ◽  
Model Updating ◽  
Structural Parameters ◽  
Element Model ◽  
Structural Behavior ◽  
Model Tuning ◽  
The Finite Element Model ◽  
Cable Stayed Bridges

The model tuning through sensitivity analysis is a prominent procedure to assess the structural behavior and dynamic characteristics of cable-stayed bridges. Most of the previous sensitivity-based model tuning methods are automatic iterative processes; however, the results of recent studies show that the most reasonable results are achievable by applying the manual methods to update the analytical model of cable-stayed bridges. This paper presents a model updating algorithm for highly redundant cable-stayed bridges that can be used as an iterative manual procedure. The updating parameters are selected through the sensitivity analysis which helps to better understand the structural behavior of the bridge. The finite element model of Tatara Bridge is considered for the numerical studies. The results of the simulations indicate the efficiency and applicability of the presented manual tuning method for updating the finite element model of cable-stayed bridges. The new aspects regarding effective material and structural parameters and model tuning procedure presented in this paper will be useful for analyzing and model updating of cable-stayed bridges.

On the Nonlinear Behavior of Rotating Shafts

1991 ◽  
Author(s):  
Tatu Leinonen
Keyword(s):  
Theoretical Model ◽  
General Theory ◽  
Nonlinear Model ◽  
Nonlinear Behavior ◽  
Rotating Shaft ◽  
Rotating Shafts ◽  
Bending Behaviour

Abstract This paper presents a nonlinear model to describe the bending behaviour of a rotating shaft, based on the general theory of a bending bar. Justification for this theoretical model has been provided by tests, the resulting curves more closely fitting observed results than those of other models.

A Simplified Method Study of Aluminium Alloy Fatigue Crack Tip Parameters Computed by Elastic-Plastic Finite Element Model

2010 ◽  
Vol 97-101 ◽  
pp. 2748-2751
Author(s):  
Xin Song ◽  
Jing Zhong Xiang ◽  
Jia Zhen Zhang
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Aluminium Alloy ◽  
Crack Tip ◽  
Element Model ◽  
Crack Model ◽  
Dynamic Crack ◽  
Elastic Plastic ◽  
Static Crack ◽  
Element Computation

Fatigue crack propagation of aluminium alloy 7049-OA has been studied by non-linear finite element business-oriented software ABAQUS, and elastic-plastic finite element models of static fatigue crack and dynamic fatigue crack of center crack panel (CCP) specimens are also built. Based on the finite element computation results, the differences of stress and crack opening displacement around crack tip of static crack model have been compared with those of dynamic crack model. The compared results showed that the finite element computation results of dynamic crack model can be replaced by the results calculated by the static crack model. Fatigue crack tip parameters of aluminium alloy CCP specimens can be calculated by elastic-plastic finite element model of static crack. This is an effective method to cut down the computation expense and promote the computational efficiency.

scholarly journals A Multi-Fidelity Model for Simulations and Sensitivity Analysis of Piezoelectric Inkjet Printheads

Micromachines ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1038
Author(s):  
Vinh-Tan Nguyen ◽  
Jason Yu Chuan Leong ◽  
Satoshi Watanabe ◽  
Toshimitsu Morooka ◽  
Takayuki Shimizu
Keyword(s):  
Sensitivity Analysis ◽  
Three Dimensional ◽  
Element Model ◽  
Geometrical Parameters ◽  
Generation Process ◽  
Mechanical Coupling ◽  
Design Variables ◽  
Computational Structural Mechanics ◽  
Lumped Element Model ◽  
Inkjet Printhead

The ink drop generation process in piezoelectric droplet-on-demand devices is a complex multiphysics process. A fully resolved simulation of such a system involves a coupled fluid–structure interaction approach employing both computational fluid dynamics (CFD) and computational structural mechanics (CSM) models; thus, it is computationally expensive for engineering design and analysis. In this work, a simplified lumped element model (LEM) is proposed for the simulation of piezoelectric inkjet printheads using the analogy of equivalent electrical circuits. The model’s parameters are computed from three-dimensional fluid and structural simulations, taking into account the detailed geometrical features of the inkjet printhead. Inherently, this multifidelity LEM approach is much faster in simulations of the whole inkjet printhead, while it ably captures fundamental electro-mechanical coupling effects. The approach is validated with experimental data for an existing commercial inkjet printhead with good agreement in droplet speed prediction and frequency responses. The sensitivity analysis of droplet generation conducted for the variation of ink channel geometrical parameters shows the importance of different design variables on the performance of inkjet printheads. It further illustrates the effectiveness of the proposed approach in practical engineering usage.

Vibration Localization in Rotating Shafts: Part II — Experiment

1995 ◽  
Author(s):  
A. Galip Ulsoy ◽  
Christophe Pierre ◽  
Suhyun Choi
Keyword(s):  
Cross Section ◽  
Circular Cross Section ◽  
Companion Paper ◽  
Rotating Shaft ◽  
Vibration Localization ◽  
State Response ◽  
Mass Unbalance ◽  
Rotating Shafts ◽  
Principal Directions ◽  
Gyroscopic Coupling

Abstract This paper presents an experimental study of vibration localization in single-span, flexible, rotating shafts. It was shown in a companion paper (Part I) that a non-circular cross-section of the rotating shaft, leading to dissimilar lateral moments of inertia, can introduce disorder. Internal coupling between the principal directions of vibration is provided by the rotational speed through the gyroscopic moments. It is experimentally demonstrated here that directional vibration localization can occur for certain appropriate combinations of disorder and coupling. The steady state response, due to mass unbalance, of a simply supported rotating shaft is considered. It is shown that disorder and gyroscopic coupling lead to directional vibration localization; i.e., larger vibration amplitudes in one of the two orthogonal principal directions of the shaft cross section.

A Finite Rotating Shaft Element Using Timoshenko Beam Theory

1980 ◽  
Vol 102 (4) ◽  
pp. 793-803 ◽  
Author(s):  
H. D. Nelson
Keyword(s):  
Timoshenko Beam ◽  
Beam Theory ◽  
Timoshenko Beam Theory ◽  
Internal Damping ◽  
Theory Analysis ◽  
Rotating Shaft ◽  
Element Analysis ◽  
Rotor Systems ◽  
The Finite Element Analysis ◽  
Rotating Shafts

The use of finite elements for simulation of rotor systems has received considerable attention within the last few years. The published works have included the study of the effects of rotatory inertia, gyroscopic moments, axial load, and internal damping; but have not included shear deformation or axial torque effects. This paper generalizes the previous works by utilizing Timoshenko beam theory for establishing the shape functions and, thereby including transverse shear effects. Internal damping is not included but the extension is straight forward. Comparison is made of the finite element analysis with classical dosed form Timoshenko beam theory analysis for nonrotating and rotating shafts.

Torsional Robustness of the Combined Cycle Power Train Arrangement: Application of Statistical Methods to Accelerate Shaft-Line Design Cycles

2016 ◽  
Author(s):  
Mateusz Golebiowski ◽  
John P. C. W. Ling ◽  
Eric Knopf ◽  
Andreas Niedermeyer
Keyword(s):  
Statistical Methods ◽  
Design Space ◽  
Short Circuit ◽  
Probabilistic Approach ◽  
Combined Cycle ◽  
Power Train ◽  
Shaft Line ◽  
Main Challenge ◽  
Turbo Generator ◽  
Line Design

This article presents the application of statistical methods to guide the rotordynamic design of a turbo-generator shaft-line. One of the basic requirements is all shaft components must survive the event of a short circuit at the terminals of the generator. This is typically assessed via a transient response simulation of the complete machine train (including generator’s electrical model) to check the calculated response torque against the allowable value. With an increasing demand of a shorter design cycle and competition in performance, cost, footprint and safety, the probabilistic approach is starting to play an important role in the power train design process. The main challenge arises with the size of the design space and complexity of its mapping onto multiple objective functions and criteria which are defined for different machines. In the presented paper, the authors give an example demonstrating the use of statistical methods to explore (Design of Experiment) and understand (Surface Response Methods) the design space of the Combined Cycle Power Train with respect to the typically most severe constraint (fault torque torsional response), which leads to a quicker definition of a turbo-generator’s arrangement. Further statistical analyses are carried out to understand the robustness of the chosen design against future modifications as well as parameters’ uncertainties.

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