scholarly journals A Study on Fluid Self-Excited Flutter and Forced Response of Turbomachinery Rotor Blade

2014 ◽  
Vol 2014 ◽  
pp. 1-20 ◽  
Author(s):  
Chih-Neng Hsu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Power Plants ◽  
Single Mode ◽  
Element Model ◽  
Forced Response ◽  
Structural Dynamic ◽  
Turbine Engine ◽  
Forcing Function ◽  
Structural Dynamic Characteristics

Complex mode and single mode approach analyses are individually developed to predict blade flutter and forced response. These analyses provide a system approach for predicting potential aeroelastic problems of blades. The flow field properties of a blade are analyzed as aero input and combined with a finite element model to calculate the unsteady aero damping of the blade surface. Forcing function generators, including inlet and distortions, are provided to calculate the forced response of turbomachinery blading. The structural dynamic characteristics are obtained based on the blade mode shape obtained by using the finite element model. These approaches can provide turbine engine manufacturers, cogenerators, gas turbine generators, microturbine generators, and engine manufacturers with an analysis system to remedy existing flutter and forced response methods. The findings of this study can be widely applied to fans, compressors, energy turbine power plants, electricity, and cost saving analyses.

Updating of Finite Element Model in Considering Mode Errors with Fuzzy Theory

2009 ◽  
Vol 413-414 ◽  
pp. 785-792 ◽  
Author(s):  
Yang Liu ◽  
Zhong Dong Duan ◽  
Hui Li
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Model Updating ◽  
Fuzzy Theory ◽  
Dynamic Properties ◽  
Fuzzy Model ◽  
Element Model ◽  
Structural Dynamic ◽  
Fuzzy Variables ◽  
Design Variables

Finite element model updating aims at reconciling the analytical model with the test one, to acquire a refined model with high-fidelity in structural dynamic properties. However, testing data are inevitable polluted by noises. In this study, the mode parameters and design variables are modeled as fuzzy variables, and a fuzzy model updating method is developed. Instead of a single optimal model, a set of satisfactory models is obtained. The most physically compatible solution is sorted by insights to the structures. The proposed method is applied to a real concrete bridge, for which a physically meaningful model is identified.

scholarly journals Bridge Damping Extraction Method from Vehicle–Bridge Interaction System Using Double-Beam Model

2021 ◽  
Vol 11 (21) ◽  
pp. 10304
Author(s):  
Fengzong Gong ◽  
Fei Han ◽  
Yingjie Wang ◽  
Ye Xia
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Traffic Flow ◽  
Dynamic Stiffness ◽  
Damping Ratio ◽  
Element Model ◽  
Beam Model ◽  
Modal Shape ◽  
Structural Dynamic ◽  
Double Beam

When vehicles interact with a bridge, a vehicle–bridge interaction (VBI) system is created. The frequency and modal shape of VBI systems have been widely studied, but the damping of VBI systems has not been adequately investigated. In recent years, several incidents of abnormal bridge vibration due to changes in bridge damping have occurred and aroused widespread concern in society. Damping is an important evaluation index of structural dynamic performance. Knowing the damping ratio of a VBI system is useful for analyzing the damping changes while a bridge is in service. This paper presents a method to extract bridge damping values from a VBI system, which can serve as a guide for bridge damping evaluation. First, a double-beam theoretical model was used to simplify the VBI system for cases involving uniform traffic flow. The damping ratio equation for the simplified VBI system was obtained using the extended dynamic stiffness method (EDSM). A double-beam finite element model and a VBI finite element model were established. The damping ratios of the two models were separately calculated and then compared with the simplified VBI model results. The results verified the accuracy of the simplified method. This paper then explains that bridge damping values can be extracted by estimating the equivalent traffic flow parameters and using the damping formula for the simplified VBI system. The bridge damping ratios extracted using this method in an engineering case ranged from 0.75% to 0.78%, which is smaller than the range that was directly identified using monitoring data (0.83–1.19%). The results show that the method can effectively extract bridge damping ratios and improve damping ratio identification.

Ground Vibration Test Planning of a Fighter Aircraft by Using a Rough Finite Element Model

2013 ◽  
Author(s):  
Sertac Koksal ◽  
Erdinc Nuri Yildiz ◽  
Yigit Yazicioglu ◽  
Gokhan Osman Ozgen
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Ground Vibration ◽  
Aircraft Design ◽  
Element Model ◽  
Fighter Aircraft ◽  
Structural Dynamic ◽  
Planning Stage ◽  
Certification Process ◽  
Flutter Testing

Certification process is one of the crucial procedures for safety in the design of a new aerial platform. Flight flutter testing is the most critical component for the certification process. Usually a flutter analysis is performed beforehand for the planning of flight flutter testing of an aircraft which mostly requires the Finite Element Model (FEM) together with Ground Vibration Testing (GVT) to construct the structural dynamic model of the complete aircraft for the flutter analyses. GVT is not only required for new aircraft design but also when considerable changes are made to an existing aircraft or when new external load configurations are introduced. Experimental methods require high effort, high budget, long time, and much repetition. Therefore, the computational and theoretical studies seem more applicable in the early phase. However, GVT of an available fighter aircraft in defense projects becomes an issue for the designers if a detailed FEM of the aircraft is not available prior to test. Hence, planning of the GVT in early stage is vital for project leaders. In this study, a rough FEM of a fighter aircraft is developed and correlated to available GVT data for planning purpose. The representative mode shapes are evaluated by estimation of the several sections of the aircraft. It is also shown that a rough FEM of the aircraft can be utilized for determination of the measurement and excitation points on the aircraft in planning stage. The geometrical properties, physical limitations and basic requirements of GVT are also taken into account for an efficient planning.

Assessing Prestress Losses in a Nuclear Containment Structure for License Renewal

2019 ◽  
Author(s):  
Eric Kjolsing ◽  
Randy James ◽  
Keith Kubischta ◽  
Dan Parker
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Nuclear Power ◽  
Power Plants ◽  
Element Model ◽  
Paper Analysis ◽  
Design Parameters ◽  
Original Design ◽  
Structural Capacity ◽  
Post Tensioning

Abstract Nuclear power plants around the world are nearing the end of their designed service life. Sufficient structural capacity must be demonstrated to extend each plant’s operating license when accounting for concrete creep, shrinkage, and tendon relaxation past the original design life. This may take the form of in-situ values which meet the design allowable or, as outlined in this paper, analysis models which demonstrate capacity. This paper presents an analysis methodology for a concrete containment structure utilizing grouted post-tensioned tendons representative of a non-US design. The methodology is intended to demonstrate that a structure can still meet established design requirements while accounting for creep, shrinkage, and tendon relaxation. The analysis effort is performed in multiple stages. First, design parameters feeding into post-tensioning loss calculations are identified and assigned statistical distributions. Probabilistic estimates of the post-tensioning losses are developed using both a variational and Monte Carlo approach. Second, a finite element model of a representative containment structure is developed with tendons and reinforcement explicitly modeled. Lastly, the finite element model is used in example analyses to demonstrate future performance and pressure capacity accounting for projected tendon losses.

Multi-Stage Modeling of Turbine Engine Rotor Vibration

2005 ◽  
Author(s):  
Sang Heon Song ◽  
Matthew P. Castanier ◽  
Christophe Pierre
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Forced Response ◽  
Interface Motion ◽  
Turbine Engine ◽  
Reduced Order ◽  
Common Basis ◽  
Multi Stage ◽  
Small Set ◽  
Engine Rotor

In this study, an efficient approach for modeling the vibration of multi-stage rotors is proposed in order to allow more realistic predictions of the free and forced response of bladed disks. The reduced-order modeling approach is based on component mode synthesis, with each stage (bladed disk) treated as a separate component. Thus, each component retains cyclic symmetry, and single-sector models may be used for calculating the component modes. Because adjacent stages typically have different numbers of blades, the single-stage models are synthesized by projecting the stage-to-stage interface motion onto a common basis of circumferentially harmonic shapes. In this manner, any mismatch between sector sizes and finite element meshes at the interface can be handled systematically and automatically, without requiring additional multi-point constraints. For further size reduction, secondary modal analysis is performed on the entire synthesized model. Therefore, only a small set of multi-stage modes are retained in the final reduced-order model, yielding an extremely compact model that retains high accuracy relative to the parent finite element model.

Finite Element Simulation and Dynamic Test of the Bridge Structure

2011 ◽  
Vol 52-54 ◽  
pp. 2191-2196
Author(s):  
Yu Qing Liu ◽  
Yan Xiang Wu ◽  
Hai Bo Huo
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Three Dimensional ◽  
Dynamic Test ◽  
Element Model ◽  
Scientific Basis ◽  
Element Analysis ◽  
Structural Dynamic ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

In this paper, we established a bridge three-dimensional finite element model for the structural dynamic analysis according to the geometry and material properties of a bridge Li Gong Yi Qiao at Wuhan University of Technology. On the other hand, we tested the dynamic characteristics of the bridge under environmental excitation by means of bridge sensors arranged at different points. The modal parameters of the bridge were identified through fitting the admittance circle. The comparison between the measured results and the theoretical studies has shown that the low-order vibration frequency and mode obtained from finite element analysis generally consistent with those from test. The finite element model provides a scientific basis for condition monitoring of the bridge in actual operations.

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