The Method of Harmonic Excitation for Determination of the Flexibility of the Support of Machine’s Rotor

2002 ◽  
Author(s):  
Jozef Rybczynski
Keyword(s):  
Rotor Dynamics ◽  
Harmonic Excitation ◽  
Experimental Results ◽  
Experimental Investigations ◽  
Test Rig ◽  
Harmonic Force ◽  
Damping Coefficients ◽  
Stiffness Coefficients ◽  
Made In

A series of experimental investigations were made in order to determine the set of coefficients of flexibility of construction supporting the rotor. The investigations were made on the test rig for the rotor dynamics investigation. A harmonic force of known amplitude was applied to all supports of the system to induce vibration of the system. Then the system’s reaction in the form of displacement in all connections at the same time was measured. On the bases of the experimental results a square 36-element (6×6) matrix of flexibility coefficients for each frequency of excitation was created. The matrices are the initial material to determine the modal masses, stiffness coefficients and damping coefficients in such form so that they could be the data to calculate the dynamics of the experimental rotor by means of computer programs. Moreover the experimental results are interesting information in the to analysis of the behavior of the test rig’s pedestals.

Experimental Investigations on the Contour Generation of a Reconfigurable Stewart Platform

2011 ◽  
Vol 1 (4) ◽  
pp. 87-99
Author(s):  
G. Satheesh Kumar ◽  
T. Nagarajan
Keyword(s):  
Error Analysis ◽  
Vibration Isolation ◽  
Stewart Platform ◽  
Design Tool ◽  
Experimental Investigations ◽  
Variable Geometry ◽  
Test Rig ◽  
Optimum Geometry ◽  
Complete Set

Reconfiguration of Stewart platform for varying tasks accentuates the importance for determination of optimum geometry catering to the specified task. The authors in their earlier work (Satheesh et al., 2008) have indicated the non availability of an efficient holistic methodology for determining the optimum geometry. Further, they have proposed a solution using the variable geometry approach through the formulation of dimensionless parameters in combination with generic parameters like configuration and joint vector. The methodology proposed provides an approach to develop a complete set of design tool for any new reconfigurable Stewart platform for two identified applications viz., contour generation and vibration isolation. This paper details the experimental investigations carried out to validate the analytical results obtained on a developed Stewart platform test rig and error analysis is performed for contour generation. The experimental natural frequency of the developed Stewart platform has also been obtained.

Rotordynamic Instability in Centrifugal Compressors: Are All the Excitations Understood?

1980 ◽  
Author(s):  
J. M. Vance ◽  
F. J. Laudadio
Keyword(s):  
Journal Bearing ◽  
Working Fluid ◽  
Experimental Measurements ◽  
Simple Test ◽  
Test Rig ◽  
Centrifugal Compressors ◽  
Damping Coefficients ◽  
Stiffness Coefficients ◽  
History Of ◽  
Stiffness And Damping

A published history of rotordynamic instability problems with centrifugal compressors is documented from the literature. Established theory for computerized stability anaylysis is reviewed, and the use of cross-coupled stiffness and damping coefficients to represent destabilizing forces is explained. A derivation of cross-coupled stiffness coefficients for torquewhirl is presented. Experimental measurements made on a simple test rig with a radial-vaned impeller are described, which show that a working fluid can exert destabilizing forces on such an impeller. These forces must be considered, in addition to journal bearing and internal hysteresis excitations, if accurate predictions of rotordynamic instability thresholds are to be made. Several classifications of these forces are hypothesized.

Numerical and Experimental Investigations on Flexible Multi-bearing Rotor Dynamics

2004 ◽  
Vol 127 (4) ◽  
pp. 408-415 ◽  
Author(s):  
Q. Ding ◽  
A. Y. T. Leung
Keyword(s):  
Angular Acceleration ◽  
Rotor Dynamics ◽  
Dynamic Responses ◽  
Experimental Investigations ◽  
Test Rig ◽  
Theoretical Simulation ◽  
Speed Up ◽  
Simultaneous Existence ◽  
Stationary Bifurcation ◽  
The Mathematical Model

An experimental test rig is built to verify the dynamics of a multi-bearing rotor. It consists of two flexibly coupled shafts and is connected to a motor at one end via a flexible coupling. Each of the shafts is supported at the ends by two hydrodynamic bearings and is attached with two disks with equal and unequal masses, respectively. The mathematical model of the test rig is developed and is simulated numerically. The non-stationary dynamic responses of the system during speed-up with a constant angular acceleration are shown, respectively, by the non-stationary bifurcation diagrams, the selected time flows, and the spectrum cascades. Experiments are then carried out on the test rig. Generally, the numerical results are verified qualitatively by the experiments. Both results indicate that the non-synchronous whirls of the two shafts influence each other when flexibly coupled together. In particular, a new phenomenon is found for the four-bearing rotor system: the pre-existing non-synchronous whirl/whip resulted from the instability of one shaft can activate the onset of oil instability of another shaft. In the theoretical simulation, this phenomenon represents the rapid increase of the non-synchronous whirl orbit, whereas in the experiment, it represents the simultaneous existence of two whirl/whip frequencies in the spectra.

Rotordynamic Instability in Centrifugal Compressors—Are All the Excitations Understood?

1981 ◽  
Vol 103 (2) ◽  
pp. 288-293
Author(s):  
J. M. Vance ◽  
F. J. Laudadio
Keyword(s):  
Journal Bearing ◽  
Working Fluid ◽  
Experimental Measurements ◽  
Simple Test ◽  
Test Rig ◽  
Centrifugal Compressors ◽  
Damping Coefficients ◽  
Stiffness Coefficients ◽  
History Of ◽  
Stiffness And Damping

A published history of rotordynamic instability problems with centrifugal compressors is documented from the literature. Established theory for computerized stability analysis is reviewed, and the use of cross-coupled stiffness and damping coefficients to represent destabilizing forces is explained. A derivation of cross-coupled stiffness coefficients for torquewhirl is presented. Experimental measurements made on a simple test rig with a radial-vaned impeller are described, which show that a working fluid can exert destabilizing forces on such an impeller. These forces must be considered, in addition to journal bearing and internal hysteresis excitations, if accurate predictions of rotordynamic instability thresholds are to be made. Several classifications of these forces are hypothesized.

DISTRIBUTION OF POTENTIAL IN A TWO-LAYERED MEDIUM DUE TO AN INTERNAL SOURCE AND SINK AND THE DETERMINATION OF THE APPROXIMATE AVERAGE RESISTIVITY OF THE MEDIUM

1950 ◽  
Vol 28a (1) ◽  
pp. 1-28
Author(s):  
Lachlan Gilchrist ◽  
Normon Rostoker ◽  
Ben Bernholtz
Keyword(s):  
Layered Medium ◽  
Experimental Methods ◽  
Experimental Results ◽  
Internal Source ◽  
The Earth ◽  
Drill Holes ◽  
Local Anomalies ◽  
Source And Sink ◽  
Made In

A brief review is presented of simple forms of electrical layout which are used in resistivity investigations on the upper surface of a two-layered medium of which the crust of the earth is assumed to be an example. The associative formulas for resistivity are given.The necessity for equalization in magnitudes of the source and the sink in all experimental methods of resistivity investigation is emphasized in order to be in accord with the basis of development of the formula, and in order to eliminate experimentally pseudo anomalies which may appear in homogeneous media.Formulas are developed for use in conjunction with experimental results obtained by the use of drill holes whereby the source and sink are embedded in a two-layered medium. Distinction is made in the cases where the source and sink are remote from, or are in the neighborhood of, the plane of separation of the layers.Some experimental results on the values of the interbowl résistance, R, are presented in comparison with the values of R that would be obtained from a medium of two homogeneous layers of a suitably chosen resistivity ρ. The local anomalies in these layers appear clearly.

scholarly journals Determination of hydraulic conductivity for granular filters based on constriction size and shape parameters

2021 ◽  
Author(s):  
Nasir Ahmad Rather ◽  
Mohd Akbar Lone ◽  
Abdul Qayoom Dar ◽  
Mir Bintul Huda
Keyword(s):  
Experimental Study ◽  
Hydraulic Conductivity ◽  
Empirical Model ◽  
Filter Material ◽  
Experimental Results ◽  
Experimental Investigations ◽  
Shape Parameters ◽  
Granular Filter ◽  
Granular Filters

Abstract This experimental study is an attempt to apply the constriction size concept for determination of hydraulic conductivity of filter material. Five shapes of granular filter material having varying gradations were used for the experimental investigations. The controlling constriction size of selected shapes having varying gradations were worked out and related to the experimental results of hydraulic conductivity. The empirical model for hydraulic conductivity determination based on controlling constriction size for each selected shape of granular filter material was developed. Finally, a combined empirical model for the determination of hydraulic conductivity of granular filters was developed based on shape parameters and the controlling constriction size.

The quantitative comparison of experimental and simulated diffraction contrast images

1995 ◽  
Vol 53 ◽  
pp. 102-103
Author(s):  
Stuart McKernan
Keyword(s):  
Image Processing ◽  
Personal Computer ◽  
Close Agreement ◽  
Quantitative Comparison ◽  
Image Simulation ◽  
Computing Power ◽  
Diffraction Contrast ◽  
Simulated Images ◽  
Made In

For many years the concept of quantitative diffraction contrast experiments might have consisted of the determination of dislocation Burgers vectors using a g.b = 0 criterion from several different 2-beam images. Since the advent of the personal computer revolution, the available computing power for performing image-processing and image-simulation calculations is enormous and ubiquitous. Several programs now exist to perform simulations of diffraction contrast images using various approximations. The most common approximations are the use of only 2-beams or a single systematic row to calculate the image contrast, or calculating the image using a column approximation. The increasing amount of literature showing comparisons of experimental and simulated images shows that it is possible to obtain very close agreement between the two images; although the choice of parameters used, and the assumptions made, in performing the calculation must be properly dealt with. The simulation of the images of defects in materials has, in many cases, therefore become a tractable problem.

Science of Ahangyol and Its Importance for Modern Scientific Thought

2019 ◽  
Vol 10 (5) ◽  
pp. 473-478
Author(s):  
Ahmad Gashamoglu ◽  
Keyword(s):  
Modern Science ◽  
Scientific Basis ◽  
New Paradigm ◽  
Islamic Philosophy ◽  
Scientific Thought ◽  
Religious Books ◽  
Strategic Approach ◽  
Scientific Potential ◽  
Made In

The Article briefly discusses the need for generation of the Science of Ahangyol, and this science’s scientific basis, object and subject, category system, scientific research methods and application options. Ahangyol is a universal science and may be useful in any sphere. It may assist in problem solving in peacemaking process and in many areas such as ecology, economics, politics, culture, management and etc. This science stipulates that any activity and any decision made in the life may only and solely be successful when they comply with harmony principles more, which are the principles of existence and activity of the world. A right strategic approach of the Eastern Philosophy and the Middle Age Islamic Philosophy and scientific thought has an important potential. This strategic approach creates opportunities to also consider irrational factors in addition to rational ones comprehensively in scientific researches. The modern scientific thought contributes to implementation of these opportunities. Ahangyol is a science of determination of ways to achieve harmony in any sphere and of creation of special methods to make progress in these ways through assistance of the modern science. Methods of the System Theory, Mathematics, IT, Astronomy, Physics, Biology, Sociology, Statistics and etc. are more extensively applied. Information is given on some of these methods. Moreover, the Science of Ahangyol, which is a new philosophical worldview and a new paradigm contributes to clarification of metaphysic views considerably and discovery of the scientific potential of religious books.

Determination of Charge Coefficient of Piezoelectric Films Using a Combined Finite Element Model and Dynamic Loading Technique

2020 ◽  
Vol 835 ◽  
pp. 229-242
Author(s):  
Oboso P. Bernard ◽  
Nagih M. Shaalan ◽  
Mohab Hossam ◽  
Mohsen A. Hassan
Keyword(s):  
Finite Element ◽  
Dynamic Loading ◽  
Material Properties ◽  
Accurate Determination ◽  
Substrate Material ◽  
Experimental Results ◽  
Piezoelectric Composite ◽  
Piezoelectric Film ◽  
Piezoelectric Charge

Accurate determination of piezoelectric properties such as piezoelectric charge coefficients (d33) is an essential step in the design process of sensors and actuators using piezoelectric effect. In this study, a cost-effective and accurate method based on dynamic loading technique was proposed to determine the piezoelectric charge coefficient d33. Finite element analysis (FEA) model was developed in order to estimate d33 and validate the obtained values with experimental results. The experiment was conducted on a piezoelectric disc with a known d33 value. The effect of measuring boundary conditions, substrate material properties and specimen geometry on measured d33 value were conducted. The experimental results reveal that the determined d33 coefficient by this technique is accurate as it falls within the manufactures tolerance specifications of PZT-5A piezoelectric film d33. Further, obtained simulation results on fibre reinforced and particle reinforced piezoelectric composite were found to be similar to those that have been obtained using more advanced techniques. FE-results showed that the measured d33 coefficients depend on measuring boundary condition, piezoelectric film thickness, and substrate material properties. This method was proved to be suitable for determination of d33 coefficient effectively for piezoelectric samples of any arbitrary geometry without compromising on the accuracy of measured d33.

scholarly journals Stiffness Estimation and Equivalence of Boundary Conditions in FEM Models

2021 ◽  
Vol 11 (4) ◽  
pp. 1482
Author(s):  
Róbert Huňady ◽  
Pavol Lengvarský ◽  
Peter Pavelka ◽  
Adam Kaľavský ◽  
Jakub Mlotek
Keyword(s):  
Boundary Condition ◽  
Finite Element ◽  
Boundary Conditions ◽  
Model Updating ◽  
Element Model ◽  
Computational Time ◽  
Stiffness Coefficients ◽  
First Case ◽  
Numerical Approaches

The paper deals with methods of equivalence of boundary conditions in finite element models that are based on finite element model updating technique. The proposed methods are based on the determination of the stiffness parameters in the section plate or region, where the boundary condition or the removed part of the model is replaced by the bushing connector. Two methods for determining its elastic properties are described. In the first case, the stiffness coefficients are determined by a series of static finite element analyses that are used to obtain the response of the removed part to the six basic types of loads. The second method is a combination of experimental and numerical approaches. The natural frequencies obtained by the measurement are used in finite element (FE) optimization, in which the response of the model is tuned by changing the stiffness coefficients of the bushing. Both methods provide a good estimate of the stiffness at the region where the model is replaced by an equivalent boundary condition. This increases the accuracy of the numerical model and also saves computational time and capacity due to element reduction.

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