Influence of Multiphysical Effects on the Dynamics of the High Speed Mini Rotors—Part II: Results

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Emre Dikmen ◽  
Peter J. M. van der Hoogt ◽  
André de Boer ◽  
Ronald G. K. M. Aarts
Keyword(s):  
Modal Analysis ◽  
Dynamic Behavior ◽  
High Speed ◽  
Structural Model ◽  
Natural Frequencies ◽  
Experimental Setup ◽  
Flexible Supports ◽  
The Stability ◽  
Surrounding Fluid ◽  
Theoretical Results

In Part I of this work, a theoretical analysis showed that the surrounding air in the closed confinement between rotor and casing has a significant effect on the dynamic behavior of high speed minirotors. In order to validate the developed theoretical model, an experimental setup is designed and the dynamic behavior of the rotor with medium gap confinement is studied. The experimental setup has flexible supports, which consist of beams with adjustable length. The support stiffness is changed by altering the beam length. Modal analysis of the rotor is done in free-free conditions in order to test the capability of the rotordynamic model without the supports and multiphysical effects. The experimental and simulation results agree well with a difference of 1%. Then modal analysis of the whole structure is done at standstill and during operation in the absence of the casing. In this way, multiphysical effects are eliminated and only support effects on the dynamics of the structure are observed. The supports appear to have significant effect on the natural frequencies of the flexural modes of the system. Different support modeling techniques are studied and adequate equivalent models are obtained. These models are then implemented into the structural model of the rotor. Finally, multiphysical effects are tested at different speeds with different support stiffnesses. Experiments are performed with and without the casing for determining the change in the natural frequencies and onset of instability. The surrounding fluid has a significant effect on the stability of the system while the natural frequencies do not change significantly. The experimental and theoretical results are in fair agreement for predicting the natural frequencies and the onset of instability.

scholarly journals Limitations of a dynamic shear-frame model based in a small-scale experimental steel structure

2018 ◽  
Vol 211 ◽  
pp. 14005
Author(s):  
Augusto de S. Pippi ◽  
Pedro L. Bernardes Júnior ◽  
Suzana M. Avila ◽  
Marcus V. G. de Morais ◽  
Graciela Doz
Keyword(s):  
Dynamic Behavior ◽  
Geometric Modeling ◽  
Structural Model ◽  
Natural Frequencies ◽  
Numerical Models ◽  
Steel Structure ◽  
Small Scale ◽  
The Real ◽  
Frame Model ◽  
Shear Frame

Many engineering problems require geometric modeling and mechanical simulation of structures. Through the structural models, engineers try to simulate the real behavior of these structures. It is important that a model contain all the necessary parameters that describe the structure and its behavior during its useful life. In the field of dynamics, one of the most used models is the shear-frame, in which the stiffness of the structure is given by the stiffness of the columns and the whole mass is concentrated in the floor levels, which are considered with infinite stiffness. In some cases, this simplification offers more conservative results, which can lead to considerable errors, especially in the case of natural frequencies. Knowing that the quality of a structural model depends on the simplifications considered, an experimental 3D steel frame, constructed to typify the dynamic behavior of a tall building, was tested with a data acquisition system and accelerometers, in order to obtain its natural frequencies. In addition, a numerical model was developed in order to ascertain the results. These values of natural frequencies are compared with an idealized shear-frame model obtained from the experimental model. This comparison allows a critical analysis of the numerical models that can be employed to represent the real dynamic behavior of structures. The aim of the investigation is to show the results of the modal analysis for each model, comparing them with the experimental results and commenting their advantages and the limitations.

Influence of Multiphysical Effects on the Dynamics of High Speed Minirotors—Part I: Theory

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Emre Dikmen ◽  
Peter J. M. van der Hoogt ◽  
André de Boer ◽  
Ronald G. K. M. Aarts
Keyword(s):  
Temperature Increase ◽  
High Speed ◽  
Heat Dissipation ◽  
Rotation Speed ◽  
Beam Theory ◽  
Added Mass ◽  
Air Gap ◽  
Finite Element Models ◽  
Surrounding Fluid ◽  
Theoretical Results

In this study, a modeling approach has been developed to take multiphysical effects into account in the prediction of the rotordynamic behavior of high speed minirotating machinery with a moderate flow confinement. The temperature increase in the confinement and the flow induced forces resulting from the surrounding fluid have been studied and these models are combined with the structural finite element models for determining the rotordynamic behavior. The structure has been analyzed via finite elements based on Timoshenko beam theory. Flow induced forces are implemented to the structure as added mass-stiffness-damping at each node representing the structure in the fluid confinement. A thermal model based on thermal networks in steady-state has been developed. This model is used to calculate the heat dissipation resulting from air friction and temperature increase in the air gap as a function of rotation speed. At each rotation speed, the temperature in the air gap between the rotor and stationary casing is calculated and air properties, which are used for the calculation of flow induced forces are updated. In this way, thermal and fluid effects in medium gap confinements are coupled with the rotordynamic model and their effects on stability, critical speeds, and vibration response are investigated. The experimental results are reported and compared with the theoretical results in an accompanying paper (Part II).

INVESTIGATION OF DYNAMIC PROPERTIES OF ELASTOMERIC BEARING COMPONENTS VIA MODAL ANALYSIS

2015 ◽  
Vol 76 (8) ◽  
Author(s):  
A. I. Yusuf ◽  
M. A. Norliyati ◽  
M. A. Yunus ◽  
M. N. Abdul Rani
Keyword(s):  
Modal Analysis ◽  
Dynamic Behavior ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Experimental Modal Analysis ◽  
Mode Shapes ◽  
Seismic Loads ◽  
Ground Structure ◽  
Elastomeric Bearing ◽  
Earthquake Load

Elastomeric bearing is a significant device in structures such as in bridges and buildings. It is used to isolate the ground structure (substructure) and the above ground structure (superstructure) from seismic loads such as earthquake load. Understanding the dynamic behavior of the elastomeric bearing in terms of natural frequencies, mode shapes and damping are increasingly important especially in improving the design and the failure limit of the elastomeric bearing. Modal analysis is one of the methods used to determine the dynamic properties of any materials. Hence, the main objective of this research is to determine the dynamic properties of elastomeric bearing components in terms of natural frequencies, mode shapes, and damping via numerical and experimental modal analysis. This method had been successfully performed in investigating the dynamic behavior of rubber and steel shim plate.

A Flexible Rotor on Flexible Supports: Modeling and Experiments

2009 ◽  
Author(s):  
Emre Dikmen ◽  
Peter van der Hoogt ◽  
Andre´ de Boer ◽  
Ronald Aarts ◽  
Ben Jonker
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Structural Model ◽  
Element Model ◽  
Flexible Rotor ◽  
Static Loads ◽  
Flexible Supports ◽  
Simple Support ◽  
Modeling And Experiments ◽  
Mass Spring

In this study, a flexible rotor with variable support stiffness has been analyzed. Simple support models consisting of mass, spring systems are extracted from modal analysis of the isolated support and by applying static loads to the finite element model of the supports. The derived equivalent models of the supports are then implemented in the finite element based structural model which predicts the dynamic behavior of the rotor. Finally experimental modal analysis of the rotor is performed with different support stiffnesses. The experimental and theoretical results have been compared and different support modeling approaches have been examined.

High-Speed Driving of a Lateral Guided Vehicle With Sensor Steering Mechanism

1999 ◽  
Author(s):  
Yoshihiro Takita
Keyword(s):  
Mobile Robot ◽  
Dynamic Behavior ◽  
High Speed ◽  
Simple Relation ◽  
Front Wheel ◽  
Dual Mode ◽  
Automatic Guided Vehicles ◽  
Steering Mechanism ◽  
The Stability ◽  
Moving Speed

Abstract This paper proposes a simple relation of the lateral guidance mechanism for automatic, guided vehicles and Dual Mode Trucks, and named it SSM (Sensor Steering Mechanism). SSM consists of a guide bar and deceleration gear which reduces the bar angle to one-second. In order to demonstrate the effectiveness of this relation, this paper examines the stability of the dynamic behavior of the front wheel steering of the vehicle. These results show that there is no limitation of the moving speed unless without a slip of the tire. For the test, a self-standing mobile robot, reduced to a scale of one-twentieth of the real car, is developed. Experimental results show that high-speed automatic moving is realized by using this relation.

High-Speed Rotor With Air Bearings Mounted on Flexible Supports: Test Bench and Experimental Results

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
G. Belforte ◽  
F. Colombo ◽  
T. Raparelli ◽  
V. Viktorov
Keyword(s):  
High Speed ◽  
Test Bench ◽  
Dynamic Stiffness ◽  
Experimental Results ◽  
Air Bearings ◽  
Stability Threshold ◽  
Air Turbine ◽  
Flexible Supports ◽  
The Stability ◽  
Rotational Response

A test bench for rotors supported by air bearings floating on O-rings is designed in order to study the whirl phenomenon and characterize the stability threshold with damping elements mounted on bearings. The work includes a description of the test bench and some preliminary experimental results. A rotor of 1kg mass and 37mm diameter is rotated up to 75,000rpm by an air turbine machined on the rotor. Capacitance probes, placed in two radial planes, allow orbit scanning of both the rotor and the bushing at different rotating speeds and suitable load devices permit measurement of the static and dynamic stiffness of the rotor-bearing system. Curves of rotational response using rubber O-rings of three different materials are shown and compared. Also presented are the Fourier spectra of the signals for rotor displacement. The phenomenon of whirl instability is shown in terms of whirl frequency and orbit amplitudes of the rotor and bearings. The effects of both supply pressure and angular velocity on the stability threshold are shown.

Modal Analysis for the Framework of Beam Pumping Unit Based on Solidworks Simulation

2013 ◽  
Vol 318 ◽  
pp. 39-43 ◽  
Author(s):  
Qiang Wang ◽  
Jian Fu Xiao
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Load Bearing ◽  
Key Technology ◽  
Pumping Unit ◽  
The Stability ◽  
Vibration Performance ◽  
Bearing Part

The framework is the main load bearing part of beam pumping unit. Its vibration performance has an important effect on the stability and reliability of beam pumping unit. This article takes the beam pumping unit (API C-228D-173-74) as an example, carries out the modal analysis in the environment of Solidworks Simulation, and obtains the first 6 orders of modal shapes and natural frequencies of the prestressed framework. This article clarifies the key technology of how to build the solid modal and how to apply load and constraints. The analysis result of the modal shows that the lowest frequency of the pumping unit framework (API C-228D-173-74) is 22.39Hz, which may be most likely resonant with the motor. We can adjust the rotate speed of the motor to avoid resonance. At the same time, the stiffness of the front legs is insufficient, suitable strengthen measures should be taken.

Modal Analysis of High-Speed Parallel Manipulator with Flexible Links

2016 ◽  
Vol 826 ◽  
pp. 8-14 ◽  
Author(s):  
Zheng Sheng Chen ◽  
Ming Liu ◽  
Min Xiu Kong ◽  
Chen Ji
Keyword(s):  
Modal Analysis ◽  
Parallel Manipulator ◽  
High Speed ◽  
Structural Model ◽  
Lagrange Equation ◽  
Flexible Link ◽  
Flexible Coupling ◽  
Flexible Links ◽  
Coupling Technique ◽  
Abaqus Model

The modal analysis was carried out to investigate the proposed improved curvature based finite element method (ICFE) for parallel manipulator with flexible links. The flexible link was discretizatied with ICFE first, and with the proposed rigid-flexible coupling technique, the flexible displacement of the moving platform and passive links was obtained, then through Lagrange equation, the structural model was derived. At last, to investigate the accuracy and efficiency of the ICFE and rigid-flexible coupling technique, modal analysis of ICFE model with different nodes and comparison studies with CFE and the ABAQUS model was carried out.

scholarly journals The contribution to the modal analysis using an infrared camera

2018 ◽  
Vol 157 ◽  
pp. 05003 ◽  
Author(s):  
Vladimír Dekys ◽  
Zuzana Stankovicova ◽  
Pavol Novak ◽  
Ondrej Stalmach
Keyword(s):  
Infrared Spectrum ◽  
Modal Analysis ◽  
High Speed ◽  
Natural Frequencies ◽  
Infrared Camera ◽  
Resonant Frequencies ◽  
Frame Sequence ◽  
Lock In ◽  
Test Objects ◽  
Narrowband Noise

The paper deals with modal analysis using an infrared camera. The test objects were excited by the modal exciter with narrowband noise and the response was registered as a frame sequence by the high speed infrared camera FLIR SC7500. The resonant frequencies and the modal shapes were determined from the infrared spectrum recordings. Lock-in technology has also been used. The experimental results were compared with calculated natural frequencies and modal shapes.

scholarly journals EVALUASI PENGUJIAN VIBRASI STRUKTUR (STUDI KASUS : DERMAGA DONGGALA)

2019 ◽  
Vol 3 (1) ◽  
pp. 71
Author(s):  
Devlin Tedy ◽  
Wiryanto Dewobroto
Keyword(s):  
Numerical Analysis ◽  
Numerical Model ◽  
Natural Frequency ◽  
Dynamic Behavior ◽  
Structural Model ◽  
Natural Frequencies ◽  
Vibration Test ◽  
Test Results ◽  
Vibration Testing ◽  
Accelerometer Sensor

Setiap struktur memiliki perilaku dinamik berupa frekuensi alami yang dapat dicari dengan uji vibrasi di lapangan secara empiris dan analisis numerik. Frekuensi alami terdiri dari massa, kekakuan, dan arah (mode shape). Parameter-parameter tersebut menghasilkan banyak variasi model struktur. Model yang paling tepat dengan kondisi lapangan dapat dicari dengan bantuan hasil uji vibrasi yang berfungsi sebagai kalibrator. Dalam mencari frekuensi alami melalui uji vibrasi sangat tergantung pada teknologi seperti tipe sensor dan cara penempatannya yang digunakan untuk merekam getaran yang diberikan. Tipe sensor terdiri dari berbagai macam seperti uniaxial, biaxial, dan triaxial. Pada kasus uji vibrasi struktur dermaga Donggala menggunakan 6 buah sensor accelerometer uniaxial. Sensor dipasang dalam 3 tempat berbeda masing-masing tempat dalam arah lateral dan vertikal. Hasil pengujian dari pihak surveyor didalam mengevaluasi hasilnya hanya rata-rata tanpa memperhitungkan pengaruh arah. Hal ini yang akan dievaluasi pada penelitian ini. Evaluasi yang akan dilakukan adalah membandingkan hasil pengujian vibrasi dengan analisis numerik. Dari berbagai model analisis numerik dapat diketahui bahwa meskipun nilai frekuensi alaminya bervariasi tetapi masih didalam batas nilai tertentu. Dengan melihat apakah arah penempatan sensor dan arah tumbukan kapal, maka dapat diprediksi perilaku dinamik dermaga apakah translasi atau rotasi yang terjadi. Dengan demikian evaluasi yang digunakan oleh surveyor dengan melakukan rata-rata  tanpa melihat arah adalah tidak tepat. Oleh sebab itu akan dilakukan evaluasi ulang mempelajari arah pemberian gaya, arah pemasangan dan penempatan sensor accelerometer serta perlu melakukan pengelompokan hasil pengujian vibrasi berdasarkan arah sensor. Setelah mempelajari model numerik dari dermaga dapat diketahui bahwa model numerik yang bertranslasi mempunyai kesesuaian dengan data tumbukan pada salah satu titik sensor yang dipasang. Pemodelan numerik yang mendekati nilai ini adalah sesuai dengan data perencanaan sebelumnya. Dari penelitian ini dapat diketahui bahwa pemahaman pengujian vibrasi perlu dilakukan pengelompokan sesuai arah penempatan sensor dan tidak dapat dilakukan rata-rata. Each structure has dynamic behavior in the form of natural frequencies that can be searched by vibration testing in the field empirically and numerical analysis. Natural frequency consists of mass, stiffness, and direction (shape mode). These parameters produce many variations of the structural model. The most appropriate model with field conditions can be sought with the help of vibration test results that function as a calibrator. In searching for natural frequencies through vibration testing it is very dependent on technology such as the type of sensor and the way it is used to record the vibrations given. Sensor types consist of various types such as uniaxial, biaxial, and triaxial. In the case of vibration test the Donggala pier structure uses 6 uniaxial accelerometer sensors. Sensors are installed in 3 different places each in lateral and vertical directions. Test results from the surveyor in evaluating the results are only average without taking into account the influence of direction. This will be evaluated in this study. The evaluation will be done is to compare the results of vibration testing with numerical analysis. From various numerical analysis models, it can be seen that although the natural frequency values vary, they are still within certain limits. By looking at the direction of the placement of the sensor and the direction of the collision of the ship, it can be predicted the dynamic behavior of the pier whether translation or rotation is happening. Thus the evaluation used by the surveyors by averaging without looking at directions is incorrect. Therefore a re-evaluation will be conducted to study the direction of the force, the direction of the placement and placement of the accelerometer sensor and the need to group the results of vibration testing based on the sensor direction. After studying the numerical model from the dock, it can be seen that the numerical model that translates has conformity to the collision data at one of the installed sensor points. Numerical modeling which is close to this value is in accordance with previous planning data. From this research it can be seen that the understanding of vibration testing needs to be grouped according to the direction of the sensor placement and cannot be carried out on average.

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