Modeling Support Effects: Finite Element and Experimental Modal Methods

1996 ◽  
Author(s):  
Jonathan R. Buckles ◽  
Keith E. Rouch ◽  
John R. Baker
Keyword(s):  
Finite Element ◽  
High Speed ◽  
Transfer Functions ◽  
Coupling Effects ◽  
Support Effects ◽  
Critical Speeds ◽  
Modal Data ◽  
The Stability ◽  
Direct Use ◽  
Reduced Matrices

The effects of support/foundation dynamics are often significant in high speed turbomachinery, and can affect the stability and response to unbalance. In some cases additional critical speeds are introduced, related to resonances in the foundation or interaction with rotor resonances of foundation resonances. This paper reviews several methods for representing these effects, including (1) reduced matrices from finite element substructures (ANSYS, for example), (2) matrices generated from modal data, and (3) direct use of experimental transfer functions. These methods are implemented in a finite element rotor program in a PC-DOS environment. The application of the methods to two laboratory rotor configurations described and results presented. Situations with a foundation resonance above and near the rotor critical are included. The importance of including coupling effects between supports is shown.

An Evaluation of Stability Indices Using Sensitivity Functions for Active Magnetic Bearing Supported High-Speed Rotor

2006 ◽  
Vol 129 (2) ◽  
pp. 230-238 ◽  
Author(s):  
Naohiko Takahashi ◽  
Hiroyuki Fujiwara ◽  
Osami Matsushita ◽  
Makoto Ito ◽  
Yasuo Fukushima
Keyword(s):  
High Speed ◽  
Transfer Functions ◽  
Mimo System ◽  
Magnetic Bearing ◽  
Singular Value ◽  
Active Magnetic Bearing ◽  
Sensitivity Functions ◽  
Phase Lags ◽  
The Stability ◽  
Stability Indices

In active magnetic bearing (AMB) systems, stability is the most important factor for reliable operation. Rotor positions in radial direction are regulated by four-axis control in AMB, i.e., a radial system is to be treated as a multi-input multioutput (MIMO) system. One of the general indices representing the stability of a MIMO system is “maximum singular value” of a sensitivity function matrix, which needs full matrix elements for calculation. On the other hand, ISO 14839-3 employs “maximum gain” of the diagonal elements. In this concept, each control axis is considered as an independent single-input single-output (SISO) system and thus the stability indices can be determined with just four sensitivity functions. This paper discusses the stability indices using sensitivity functions as SISO systems with parallel/conical mode treatment and/or side-by-side treatment, and as a MIMO system with using maximum singular value; the paper also highlights the differences among these approaches. In addition, a conversion from usual x∕y axis form to forward/backward form is proposed, and the stability is evaluated in its converted form. For experimental demonstration, a test rig diverted from a high-speed compressor was used. The transfer functions were measured by exciting the control circuits with swept signals at rotor standstill and at its 30,000 revolutions/min rotational speed. For stability limit evaluation, the control loop gains were increased in one case, and in another case phase lags were inserted in the controller to lead the system close to unstable intentionally. In this experiment, the side-by-side assessment, which conforms to the ISO standard, indicates the least sensitive results, but the difference from the other assessments are not so great as to lead to inadequate evaluations. Converting the transfer functions to the forward/backward form decouples the mixed peaks due to gyroscopic effect in bode plot at rotation and gives much closer assessment to maximum singular value assessment. If large phase lags are inserted into the controller, the second bending mode is destabilized, but the sensitivity functions do not catch this instability. The ISO standard can be used practically in determining the stability of the AMB system, nevertheless it must be borne in mind that the sensitivity functions do not always highlight the instability in bending modes.

Harmonic Analysis of the High Speed Direct Coupled SCO2 Turbo-Generator

2021 ◽  
Author(s):  
Ashutosh Patel ◽  
Vijay Biradar ◽  
Pramod Kumar
Keyword(s):  
Finite Element ◽  
Harmonic Analysis ◽  
High Speed ◽  
Computation Time ◽  
Lumped Mass ◽  
Axisymmetric Model ◽  
Critical Speeds ◽  
Turbo Generator ◽  
Shaft Deflection ◽  
Rotor Assembly

Abstract The rotordynamics and harmonic characteristics of the rotor assembly designed for 40-kW high-speed sCO2 direct-coupled turbo-generator pair have been evaluated numerically using finite element solver “ANSYS Mechanical”. First, the shaft geometry and dimensions have been optimized using lumped mass-inertia-based AxSTREAM RotorDynamics module followed by the bearing selection analysis using SKF SimPro expert to ensure enough separation margin from the nearby critical speeds. Equivalent 2D geometry has been used with an FEA-based ANSYS general axisymmetric model to reduce the computation time. The effect of the damping on the forces transmitting to the bearings and shaft deflection at the critical speeds are analyzed by performing harmonic analysis under various damped and undamped conditions (ζ = 0, 0.005, 0.01, and 0.02).

scholarly journals ANALISA STABILITAS LERENG DAN ALTERNATIF PERKUATAN TANAH PADA JALUR KERETA API CEPAT JAKARTA-BANDUNG MENGGUNAKAN APLIKASI PLAXIS 8.6

BANGUNAN ◽  
2021 ◽  
Vol 26 (1) ◽  
pp. 29
Author(s):  
Ainun Nafis ◽  
Eko Setyawan ◽  
Mohammad Musthofa Al Mohammad Musthofa
Keyword(s):  
Finite Element ◽  
Safety Factor ◽  
High Speed ◽  
Earthquake Dynamics ◽  
High Speed Rail ◽  
Alternative Reinforcement ◽  
Embankment Slope ◽  
Geological Conditions ◽  
Rail Line ◽  
The Stability

Abstrak: Masalah dalam perencanaan struktur jalan kereta seperti tinggi lereng embankment yang lebih dari sama dengan 6 m, tanah asli yang tergolong sedang lunak, dan merupakan daerah rawan terjadinya longsor merupakan alasan dilakukannya penelitian ini. Hal tersebut didukung oleh hasil uji lab tanah, kondisi geografis dan geologis Kabupaten Purwakarta berupa bukit dan lembah yang terbentuk dari endapan batuan sedimen dan aluvium vulkanik dengan kemiringan lahan 8-40%. Oleh karena itu penelitian ini bertujuan untuk mengetahui stabilitas lereng embankment berupa nilai safety factor pada jalur kereta cepat Jakarta-Bandung daerah konstruksi DK70+150.00 sampai DK70+181.88. Adapun analisis numerik yang dilakukan pada penelitian ini menggunakan program Plaxis 8.6 yang dikembangkan berdasarkan metode Finite Element dengan model Mohr-Coulomb. Proses analisis dengan menginput parameter material yang dibutuhkan berdasarkan Mohr-Coulomb. Hasil analisis berupa angka safety factor yang menunjukkan kondisi stabilitas suatu lereng embankment. Penambahan alternatif perkuatan lereng embankment berupa cerucuk (micropile), bronjong (gabion) dan geotextile sebagai upaya pencegahan adanya kelongsoran jangka pendek dan panjang pada lereng embankment yang tidak stabil. Hasil analisis lereng embankment kereta api cepat Jakarta-Bandung DK70+150 sampai DK70+181.88 kondisi eksisting sebesar ΣMSF 1,1565 (cek global) dan ΣMSF 1,0515 (cek dinamik gempa) yang artinya lereng dalam kondisi tidak stabil dan perlu penambahan alternatif perkuatan. Berdasarkan simulasi kombinasi alternatif perkuatan. Menunjukkan kombinasi alternatif perkuatan geotextile dengan micropile menghasilkan angka safety factor ΣMSF 1,8151 (cek stabilitas global) dan ΣMSF 1,6262 (cek stabilitas akibat beban dinamik gempa).Kata-kata kunci: stabilitas lereng embankment, Plaxis 8.6, safety factor, kereta cepat Jakarta-BandungAbstract: Problems in the design of the railway structure such as the embankment slope height of 6 m, the original soil which is classified as moderately soft, and is an area prone to landslides is the reason for conducting this research. This is supported by the results of soil lab tests, geographical and geological conditions of Purwakarta Regency in the form of hills and valleys formed from sedimentary rock deposits and volcanic alluvium with a slope of 8-40%. Therefore, this study aims to determine the stability of the embankment slope in the form of the safety factor value on the Jakarta-Bandung high-speed rail line in the construction area DK70+150.00 to DK70+181.88. The numerical analysis carried out in this study used the Plaxis 8.6 program which was developed based on the Finite Element method with the Mohr-Coulomb model. The analysis process by inputting the required material parameters based on Mohr-Coulomb. The results of the analysis are in the form of safety factor numbers which indicate the stability condition of an embankment slope. The addition of alternative reinforcement for embankment slopes in the form of micropile, gabion (gabion) and geotextile as an effort to prevent short and long term landslides on unstable embankment slopes. The results of the slope analysis of the Jakarta-Bandung high-speed rail embankment DK70+150 to DK70+181.88 existing conditions of MSF: 1.1565 (global check) and MSF: 1.0515 (earthquake dynamics check) which means the slope is in an unstable condition and needs additional alternative reinforcement. Based on the simulation of alternative reinforcement combinations. Showing the alternative combination of geotextile reinforcement with micropile produces a safety factor number MSF: 1.8151 (check global stability) and MSF: 1.6262 (check stability due to dynamic earthquake loads)..Keywords: embankment slope stability, Plaxis 8.6, safety factor, Jakarta-Bandung high-speed train

scholarly journals On the Importance of Sleeve Flexibility in Passive Control of Critical Speeds of a Rotating Shaft Using Eccentric Sleeves

Machines ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 56
Author(s):  
Antony Kirk ◽  
Jonathan Griffiths
Keyword(s):  
Finite Element ◽  
Experimental Test ◽  
High Speed ◽  
Passive Control ◽  
Finite Element Simulations ◽  
Test Facility ◽  
Rotating Shaft ◽  
Critical Speeds ◽  
Dynamic Finite Element

In this paper, the critical speeds of a rotating shaft fitted with eccentric balance sleeves are identified from a scaled, high speed experimental test facility. The results are compared with the results of dynamic finite element simulations. It is shown that the stiffness of the sleeves must be accommodated when considering passive control characteristics critical speeds of a rotating shaft using eccentric sleeves.

A Statistical Study of Process Variables to Optimize a High Speed Curtain Coater: Part I

TAPPI Journal ◽  
2009 ◽  
Vol 8 (1) ◽  
pp. 20-26 ◽  
Author(s):  
PEEYUSH TRIPATHI ◽  
MARGARET JOYCE ◽  
PAUL D. FLEMING ◽  
MASAHIRO SUGIHARA
Keyword(s):  
Boundary Layer ◽  
Experimental Design ◽  
High Speed ◽  
Statistical Study ◽  
Process Variables ◽  
High Speeds ◽  
The Stability ◽  
Air Removal ◽  
Removal System

Using an experimental design approach, researchers altered process parameters and material prop-erties to stabilize the curtain of a pilot curtain coater at high speeds. Part I of this paper identifies the four significant variables that influence curtain stability. The boundary layer air removal system was critical to the stability of the curtain and base sheet roughness was found to be very important. A shear thinning coating rheology and higher curtain heights improved the curtain stability at high speeds. The sizing of the base sheet affected coverage and cur-tain stability because of its effect on base sheet wettability. The role of surfactant was inconclusive. Part II of this paper will report on further optimization of curtain stability with these four variables using a D-optimal partial-facto-rial design.

Formation of Standing Waves in Radial Tires

1984 ◽  
Vol 12 (1) ◽  
pp. 44-63 ◽  
Author(s):  
Y. D. Kwon ◽  
D. C. Prevorsek
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Unit Length ◽  
Standing Waves ◽  
Rolling Resistance ◽  
Damping Coefficient ◽  
Circular Membrane ◽  
Critical Speeds ◽  
Steel Cord ◽  
The Individual

Abstract Radial tires for automobiles were subjected to high speed rolling under load on a testing wheel to determine the critical speeds at which standing waves started to form. Tires of different makes had significantly different critical speeds. The damping coefficient and mass per unit length of the tire wall were measured and a correlation between these properties and the observed critical speed of standing wave formation was sought through use of a circular membrane model. As expected from the model, desirably high critical speed calls for a high damping coefficient and a low mass per unit length of the tire wall. The damping coefficient is particularly important. Surprisingly, those tire walls that were reinforced with steel cord had higher damping coefficients than did those reinforced with polymeric cord. Although the individual steel filaments are elastic, the interfilament friction is higher in the steel cords than in the polymeric cords. A steel-reinforced tire wall also has a higher density per unit length. The damping coefficient is directly related to the mechanical loss in cyclic deformation and, hence, to the rolling resistance of a tire. The study shows that, in principle, it is more difficult to design a tire that is both fuel-efficient and free from standing waves when steel cord is used than when polymeric cords are used.

LANDSLIDE RISK MANAGEMENT IN THE COASTAL ZONE OF THE KUIBYSHEV RESERVOIR DUE THE DESIGN OF HIGH-SPEED LINE "MOSCOW-KAZAN"

2017 ◽  
Author(s):  
Nikolai Petrov ◽  
Nikolai Petrov ◽  
Inna Nikonorova ◽  
Inna Nikonorova ◽  
Vladimir Mashin ◽  
...  
Keyword(s):  
High Speed ◽  
Computational Models ◽  
Stable State ◽  
Landslide Risk ◽  
Kuibyshev Reservoir ◽  
Stepped Surface ◽  
The Stability ◽  
Landslide Slope ◽  
The Village

High-speed railway "Moscow-Kazan" by the draft crosses the Volga (Kuibyshev reservoir) in Chuvashia region 500 m below the village of New Kushnikovo. The crossing plot is a right-bank landslide slope with a stepped surface. Its height is 80 m; the slope steepness -15-16o. The authors should assess the risk of landslides and recommend anti-landslide measures to ensure the safety of the future bridge. For this landslide factors have been analyzed, slope stability assessment has been performed and recommendations have been suggested. The role of the following factors have been analyzed: 1) hydrologic - erosion and abrasion reservoir and runoff role; 2) lithologyc (the presence of Urzhum and Northern Dvina horizons of plastically deformable rocks, displacement areas); 3) hydrogeological (the role of perched, ground and interstratal water); 4) geomorphological (presence of the elemental composition of sliding systems and their structure in the relief); 5) exogeodynamic (cycles and stages of landslide systems development, mechanisms and relationship between landslide tiers of different generations and blocks contained in tiers). As a result 6-7 computational models at each of the three engineering-geological sections were made. The stability was evaluated by the method “of the leaning slope”. It is proved that the slope is in a very stable state and requires the following measures: 1) unloading (truncation) of active heads blocks of landslide tiers) and the edge of the plateau, 2) regulation of the surface and groundwater flow, 3) concrete dam, if necessary.

Dynamic Performance of High-Speed Electric Multiple Unit within Multi-Body System Simulation

2019 ◽  
Vol 12 (4) ◽  
pp. 339-349
Author(s):  
Junguo Wang ◽  
Daoping Gong ◽  
Rui Sun ◽  
Yongxiang Zhao
Keyword(s):  
High Speed ◽  
Rapid Development ◽  
Dynamic Performance ◽  
Body System ◽  
High Speed Railway ◽  
Evaluation Indexes ◽  
Actual Operation ◽  
Multiple Unit ◽  
The Stability ◽  
Multi Body

Background: With the rapid development of the high-speed railway, the dynamic performance such as running stability and safety of the high-speed train is increasingly important. This paper focuses on the dynamic performance of high-speed Electric Multiple Unit (EMU), especially the dynamic characteristics of the bogie frame and car body. Various patents have been discussed in this article. Objective: To develop the Multi-Body System (MBS) model of EMU, verify whether the dynamic performance meets the actual operation requirements, and provide some useful information for dynamics and structural design of the proposed EMU. Methods: According to the technical characteristics of a typical EMU, a MBS model is established via SIMPACK, and the measured data of China high-speed railway is taken as the excitation of track random irregularity. To test the dynamic performance of the EMU, including the stability and safety, some evaluation indexes such as wheel-axle lateral forces, wheel-axle lateral vertical forces, derailment coefficients and wheel unloading rates are also calculated and analyzed in detail. Results: The MBS model of EMU has better dynamic performance especially curving performance, and some evaluation indexes of the stability and safety have also reached China’s high-speed railway standards. Conclusion: The effectiveness of the proposed MBS model is verified, and the dynamic performance of the MBS model can meet the design requirements of high-speed EMU.

Calculating the response of waveguides to base excitation using the wave and finite element method

2021 ◽  
pp. 107754632098131
Author(s):  
Jamil Renno ◽  
Sadok Sassi ◽  
Wael I Alnahhal
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Transfer Functions ◽  
Travelling Waves ◽  
Model Free ◽  
Time Harmonic ◽  
Element Approach ◽  
Response Transfer ◽  
Free Wave Propagation ◽  
Element Method

The prediction of the response of waveguides to time-harmonic base excitations has many applications in mechanical, aerospace and civil engineering. The response to base excitations can be obtained analytically for simple waveguides only. For general waveguides, the response to time-harmonic base excitations can be obtained using the finite element method. In this study, we present a wave and finite element approach to calculate the response of waveguides to time-harmonic base excitations. The wave and finite element method is used to model free wave propagation in the waveguide, and these characteristics are then used to find the amplitude of excited waves in the waveguide. Reflection matrices at the boundaries of the waveguide are then used to find the amplitude of the travelling waves in the waveguide and subsequently the response of the waveguide. This includes the displacement and stress frequency response transfer functions. Numerical examples are presented to demonstrate the approach and to discuss the numerical efficiency of the proposed method.

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