Science topic

Vibration - Science topic

A continuing periodic change in displacement with respect to a fixed reference. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)
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I want to calculate the angle between C=O and C=C symmetric and asymmetric vibrating mode of phenol. I was trying to calculate by using DFT calculations but could not do it? please help.
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Vibrational modes involve all of the atoms in a molecule, not just a selected few bonds, and while C=O stretching modes tend to be relatively localized, C=C stretching modes tend to be less localized, often involve C-H motion, and will at a minimum involve multiple C=C bonds in the phenol molecule. Perhaps it would help to define more precisely what you mean by "the angle between the vibrating modes" and perhaps what question you are trying to answer with that information?
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During the operation of industrial hoists an external mechanical vibration happened using two synchronous motors (master and follower)?
Is it solve this problem?
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Dear Thaker, to allow making a reasonable answer, you must describe far more precisely the vibration problem you want to solve! (graphics, sketches of the affected plant, on-site pictures, vibration records...) Thanks!
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During commissioning activities a static equipment was subject to sever vibration and high acoustic sound vibration. Although operated within the design normal operating parameters.
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Your information contains too little information.
As a general comment - industry tends to build systems assuming component property specifications suffice. Often, they do not. One has to take into account that components interact.
Very simply stated - if it was super easy to slap components together and get a well functioning system, then there would not exist a difference between, say, a Rolls Royce and a low cost entry level car. Both will take you from A to B, albeit differently when comfort is evaluated.
That said - aeroacoustics is a rather complicated field. Here is an introduction to the very basics
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This is a boundary control problem of a hybrid ODE-PDE system. The system consists of an actuator, a flexible link fixed to the actuator, and a tip mass at the free end of the link. In most literature, two control inputs are used for the simultaneous position and vibration control of the said system: One is the actuator's torque and the other is a force at the tip mass. The application of a control force at the tip mass of a manipulator does not seem to be a practical solution. Can we use only the actuator's torque to simultaneously control the position and vibration of the beam and the tip mass?
I would be grateful to anyone for sharing any theorem or paper addressing this issue (in support or against).
Thank you!
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Dear Umer Hameed Shah,
I suggest you look at the following relevant links:
(If you have further questions please contact me at any time)
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Greetings everyone, I have recently found a contradiction between the two usual ways of calculating energy barriers for a chemical reaction. Usually, following the Gaussian whitepaper, I take the different reactants in separate calculations. (https://gaussian.com/wp-content/uploads/dl/thermo.pdf)
But I have found a free energy value for a reaction which made me suspect that this method might not be correct (I will describe it below). Following this suspicion, I found this other Orca guide, (https://www.orcasoftware.de/tutorials_orca/react/actibar.html) where they do the calculation with the reagents together (although this would really be the vdW complex, which will always be a few kcal/mol lower). Analyzing the output of the vibration calculations, I realized that the reagents separately tend to miss a few kcal/mol compared to the combined calculation, with both reagents at a long distance. The electronic energy matches, but the free energy therefore does not.
The reaction that I am studying is a reduction of a hydroperoxide with phosphine/phosphite, experimentally it is a fast reaction and therefore I expected a low reaction barrier, however, following the Gaussian method, the free energy barrier is 25 kcal /mol. Following Orca's guide with the same calculation, the barrier is 15 kcal/mol, closer to what is expected (with other DFT functionals it is even lower). The calculation method is M062X/aug-cc-pVTZ, which itself should be accurate to within 1-2 kcal/mol.
In these cases, the usual thing is to think that oneself is wrong, but being the contradiction between two guides provided by two of the best known software in this area, it is possible to think that there is something that is not being done well. In addition, it is a detail that is not usually mentioned in the methods of most publications, so it is difficult to know which guide each researcher follows.
Best regards and thanks in advance,
Pablo Ortega
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Your separated reactants have 3 translational (they can move in the x, y and z directions), and 3 rotational (they can rotate around the x, y and z axes) degrees of freedom each (thus, 6 DoF each). This amounts to 12 DoF. When they associate (as the VdW complex, or as the TS), the complex moves and rotates as a whole, so only 6 DoF now. Six DoF were lost during association, which has an entropy cost. The same applies when you calculate your reactants in the same run, separated by an arbitrary distance. This is why your VdW complex will frequently have a positive DG of formation with respect to the free reactants.
Regarding the specific energy values you got, it is really method-dependent. Which protocol did you use with Gaussian? If your method is not dispersion-corrected, very high barriers are commonplace. M06-2X accounts for dispersion, but I am not sure if previous studies with this functional have shown how well it performs with this specific class of reactions.
Now, if you used the exact same protocol with both Gaussian and Orca, there is definitely something suspicious going on. I can gladly give a look at your outputs if there seems to be some unidentified problem.
Finally, some unrequested advice. The cc-pVTZ basis set (and its family) was optimized for correlated wavefunction methods, and using it with DFT, although not wrong at all, tends to be unnecessarily expensive. I would recommend the Ahrlichs basis def2TZVP instead. Or, if you are in the exploratory phase, I would optimize and calculate frequencies with the def2svp basis set, and then a single point on top with the def2tzvp basis set. This can be a huge time-saver that you can easily benchmark against a set of reactions you already calculated with a larger basis.
Good luck!
Mauricio
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Which is the most crack direction is studied in a metal cantilever beam? When the crack is vertical or horizontal? (I mean if the crack propagates vertically or horizontally?)
And how each type of excitation(Bending, Axial,..) is sensitive for each type of crack shape and orientation?
I am asking for test purposes .. So I can use the crack direction that is more sensitive for measurements in my experiment.
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I think it depend on the type of load applied.
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How can I get the second and third natural frequency of a cantilever beam experimentally??
The problem that I am facing is that I got only the first natural frequency.. I can't get other frequencies..
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To expand on the answer provided by Vyacheslav Ryaboy, when performing the increasing-frequency sine sweep test, you would pass through the first resonance frequency of the cantilever beam. This is what is referred to as "hitting" the first resonance frequency. If you continue to increase the frequency, you will eventually reach and pass through the second resonance frequency. If you continue to increase the frequency further, you will eventually reach and pass through the third resonance frequency.
Depending on the equipment at your disposal, you may wish to use an impact hammer to simultaneously excite a number of modes of vibration. The measurement system would likely have the ability to compute the transfer function between the response and the excitation force. The frequency response curve would generally show the first few natural frequencies of vibration of the cantilever beam, dependent somewhat on the bandwidth of the force impulse and also the point of application of the transient excitation force.
The links provided by Om Prakash Chhangani and Mohamed-Mourad Lafifi give the formulas for the first three natural frequencies of a cantilever beam, as well as a graphical representation of the associated mode shapes. There are some suggestions for how to go about experimental testing there too.
What test equipment do you have available to conduct the experiments with?
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I am trying to use vibrotactile feedback to convey information, using LRA-actuators on a glove that operate at a fixed frequency of 205Hz. By adjusting the amplitude I try to convey the information.
Let's assume we have a given range of amplitudes I can use (e.g. 0% to 100%). I wonder how big the steps have to be for a human to notice the difference in a decrease or increase in the perceived intensity. (e.g. if I trigger four actuators in sequence, how huge do the gaps between the amplitudes have to be set, to be perceived as a decrease or increase compared to the previously felt vibration)
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Dear Til, I am afraid there is no answer to your question... For sure the scale will be shorter than the audio one, as our ear+brain system is extremely powerful and well trained compared to touching. You might get better results with a log scale of vibration thresholds as human perception is not linear, but the key issue will be training: untrained people might only detect few thresholds while training could result maybe into a ten level scale - just try! And you don't explain why you choose 205Hz, which is clearly a very high frequency for the muscle-skeleton system (the sensitivity might be elevated if the frequency activates a resonance of the hand/finger structure, which is in the tens of Hertz, not hundreds)
We are probably more sensitive to pressure: would you solve your actuation challenge by a sequence of pressure pulses at few Hz exerted by an inflatable glove cell driven by a servo-valve? You can play both with pressure and pulse length/ rate to build a collection of signals conveying the information to the holder...
Good luck, my only advice is to multiply trials as you try to address an uncharted domain of biodynamics...
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I get a peak at 240 Hz in FFT plot of tool vibration. The accelerometr is placed at 45 mm from tool tip during machining. Turning of nickel steel of dia 60 mm and length 300 mm at spindle speed 256 RPM. PCLNR2020K tool holder. Panther conventional precision lathe it is.
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240 Hz is in the audible range. Do you hear any sound while your spindel is rotating? Perharps, it is friction-induced sound, because, for example, spindel is not well oiled.
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Hello,
I need to extract mode shapes and damping ratios from ambient vibration measurement we have performed on a dam (2 setups with 6 sensors). Would you have any suggestions for an open source code that works well to perform such analysis (a code with similar capabilities than the commercial software Artemis)?
Thanks
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We have developed this software for OMA https://github.com/dagghe/PyOMA
It also has a GUI!
To cite this tool:
Pasca, D. P., Aloisio, A., Rosso, M. M., & Sotiropoulos, S. (2022). PyOMA and PyOMA_GUI: A Python module and software for Operational Modal Analysis. Software X, In press
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Hello,
The model that I am working on is basically a long hollow tube including many small cylinders that initially in contact with the inner surface of this tube. However, these cylinders might disconnect or breakage from the tube surface when it is subjected to an external impact loading or a vibration. So, I am trying to find a contact feature that including a failure criterion between these cylindrical surfaces and the tube surface. I have found a keyword in LS-DYNA so-called “*CONTACT_TIED_SURFACE_TO_SURFACE_FAILURE” that simulate this kind of contact interface problem; however, I have to do this analysis using ABAQUS and thus I am looking for a similar keyword in ABAQUS. Any help in defining this kind of contact interface using ABAQUS, will be highly appreciated.
Thank you
Belal
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Hai
sir, as of my knowledge you can choose the Mechanical submodule of the interaction property module , it contains the damage criteria option in the submodule
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What is lattice mode in RAMAN vibration mode? In general, can you help me about what the lattice mode is in the RAMAN analysis?
I'm working on Sb2S3 thin films. During the Raman analysis, I saw that there are lattice mode vibrational modes. How is it different from symmetric S–Sb–S stretching or symmetric S–Sb–S bending? In General, can you help me about what the lattice mode is in the RAMAN analysis?
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Thank you so much for your reply, and have a nice day. Best regard.
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I understand there will be exact multiple of fundamental frequency based bearing rotation with respect to fundamental, based on gear rotation with respect to fundamental. But what exactly means for multiples of bearing rotations, multiples of blade passes like 1x, 2x, 3x etc.,
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Honestly, it depends...
It depends on the specific machinery and source mechanism.
It can be nonlinearities in the system (e.g., nonlinearities in linear drives like speakers), it can be (periodic) elements in the system (e.g. number of teeth in gears), it can be wear in components (which needs to be periodic on rotating parts, e.g. higher harmonics on railcar wheels - polygonalization), it can be impulsive behaviour triggered periodically by a rotating part (e.g. combustion impulses in internal combustion engines), it can be linearly moving parts that are not rotating (e.g. pistons), it can be some additional higher order torque components from inbalances, ...
The key point is that for all of these processes (except of some non-linearities that might generate subharmonics), you can only get integer multiples of the base period.
Nevertheless, it is important to mind the base period. For a 4-stroke engine, for example, this is 2 rotations, which is why you might also find "half orders" at internal combustion engines (and only full and half orders, no third or something...).
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i need some helping material regarding hilbert transform and empirical mode decomposition. i want to apply on my vibration signal to evaluate the frequency at different phases of the signal. i am using EMD in matlab. if there is some kind of code regarding this kindly share. i want to ask some question related to EMD and hilbert transform
i will be thankful
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I tried EMD and its modifications. Also Hilbert transform and Teager kaiser Energy operator for the estimation of parameters. If you find any difficulties in these methods, please let me know, I can help.
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There are a lot of software for modeling vibrational spectra, but what is the best one? There are two major branch of software: firs principal (ab initio) and semi empirical. I'm interesting the both. The "best" means is the software gives the relevant result comparing with experimental spectra.
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Nowadays several quantum chemical program packages contain not only geometry optimization but also force field calculation. I have personal experience with ChemBio3DUltra 13.0. The reliability of the result depends on the level of approximation (from semiempirical to ab initio), an can be used for medium sized molecules. I remember when I was young and wrote my PhD you needed a considerable size computer to perform such calculations. Nowadays such programs run on PCs. It does not replace careful interpretation of experiments, but it can be helpful, especially in comparative studies.
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I‘m doing some research about time-varying cable forces. I need some data about cable vibration. Where can I find the data about cable vibration ?
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Kindly for datasets check these resources:
Kaggle
Google Dataset Search
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Dear researchers,
I am just trying to vibrate a plate with a horn (see attached figure) in one direction with ultrasonic vibrations in Abaqus. I am new to Abaqus, how can I apply an external vibration/vibrational load to surface of a plate? Harmonic analysis needs a force but can I manipulate it as a vibration? I am open to any suggestions.
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The cycle load module can completely solve this problem
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as i had done this in ansys so how can i verify my result as my project head said to verify whether it is correct or not please help
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as i had not found any paper in which ansys simulation is done for the underwater pipe if you find can you please refer me
as i had to submit my project@claudio Pedrazzi
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The stress strain curve of rubber is not linear and follows a curved line both as the strain increases and as it decreases again. Does this hysteresis lead to formation of harmonics or other non lienar phenomena in eg a vibration insulated system?
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My experience with elastomeric vibration isolators is limited by vibration control of precision instruments, that is, small vibrations (micron and sub-micron range). Hysteresis leads to dissipation of mechanical energy (damping) that can be described in terms of complex stiffness incorporating a (rather large) loss factor. In frame of this model, the dynamic reaction includes a phase shift but stays linear, described by complex transfer functions. See more in Vibration Control for Optomechanical Systems, by V.M. Ryaboy, World Scientific, 2021, ISBN 9789811237331, pages 132-137. https://www.amazon.com/Vibration-Control-Optomechanical-Systems-Vyacheslav/dp/9811237336/ ;
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Hi everyone,
I want to extract the global mass and stiffness matrices of an Abaqus modal analysis, so as to post-processing it with Matlab.
I have already read many comments on RG regarding this question and added the following lines at the end of my Input file to get the mass and stiffness matrix.
*STEP
*MATRIX GENERATE, STIFFNESS, MASS
*MATRIX OUTPUT, STIFFNESS,MASS,FORMAT=MATRIX INPUT
*END STEP
So far, everything is fine.
I have also written Matlab code that works perfectly for 3D solids or shell elements, but not when both solid and shell elements are together.
In my model, I had to use both solid and shell elements in Abaqus. Looking at the mass and stiffness matrices, I saw that there are 3DOF per node for solid elements and 6 DOF for shell elements, so I cannot use the attached Matlab code as the model has 3DOF for solid elements and 6DOF for shell elements.
My mass matrix looks like this:
1,1, 1,1, 5.115770202111807e-10
1,2, 1,1, 4.923414202110917e-12
1,3, 1,1, -5.733085750203833e-15
2,1, 1,1, 1.453330463639921e-11
2,2, 1,1, -2.461707101055460e-12
2,3, 1,1, 2.866542875101822e-15
1,4, 1,4, 4.295511112920469e-14
1,5, 1,4, -4.054846090561977e-14
1,6, 1,4, -8.889774326370160e-16
2,4, 1,4, 1.225209356335630e-14
2,5, 1,4, -1.103358818158063e-14
2,6, 1,4, -4.552490123962178e-16
...
131010,1, 131010,1, 6.793914400596321e-08
131010,2, 131010,2, 6.793914400596321e-08
131010,3, 131010,3, 6.793914400596321e-08
131011,1, 131011,1, 7.423556175182037e-08
131011,2, 131011,2, 7.423556175182037e-08
131011,3, 131011,3, 7.423556175182037e-08
As you see here, some parts have 3DOF and some parts have 6DOF. Some parts are like a lumped and some parts are like a consistent mass matrix.
In this case, how can one use Matlab in order to get a global stiffness and mass matrices from this?
I've been struggling with this problem for a long time and still haven't been able to solve it.
Here, I am attaching both the mass.mtx file and the Matlab code.
Any help would be appreciated.
function [matlab_matrix] = import_matrix(mtx_file)
%============== Import Stiffness Matrix ==============%
abaqus_stiffness_matrix = dlmread(mtx_file);
% merge node number info from column 1 and DOF info from column 2 and
% store in the 1st column of a new matrix
%If number of DOF are 2,multiply by 2.
matlab_nodes(:,1) = 2*(abaqus_stiffness_matrix(:,1)-1)+ ...
abaqus_stiffness_matrix(:,2);
% merge node number info from column 3 and DOF info from column 4 and
% store in the 2nd column of a new matrix
matlab_nodes(:,2) = 2*(abaqus_stiffness_matrix(:,3)-1)+ ...
abaqus_stiffness_matrix(:,4);
% extract the stiffness values from the .mtx file, and store in a double
% length vector
stiffness_values = [abaqus_stiffness_matrix(:,5); ...
abaqus_stiffness_matrix(:,5)];
% create a matrix of the new matlab node numbers, and a vector of indices
% of their position in the abaqus stiffness matrix
[matlab_matrix_indices, abaqus_stiffness_value_index] = unique( ...
[matlab_nodes; matlab_nodes(:,2) matlab_nodes(:,1)], 'rows');
% compile the stiffness matrix using the new node numbering convention
matlab_matrix = accumarray( matlab_matrix_indices, ...
stiffness_values(abaqus_stiffness_value_index), [], @max, [], true);
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I wish you all the best I apologize that this is not my specialty
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What Is The Relationship Between Vibration Of The Chest Wall And The Resulting Chest Wall Forces, Chest Wall Circumference, Intrapleural Pressure, And Expiratory Flow Rate?
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Hi Thomas,
You might need to read Dr. Bredge McCarren and the research that is published by this group. You will find answers in these publications.
Group has shown that the expiratory flow rate produced by vibration is approximately equal to the sum of the flow rates due to recoil of the lung and due to the compression and oscillation components of vibration https://pubmed.ncbi.nlm.nih.gov/16515421/ PMID: 16515421
In terms of an intrapleural pressure (IPP), what is proposed is that vibrational forces applied to the chest wall are transmitted to the lungs and airways. Also, that high frequency oscillation component of vibration influences IPP and expiration. An application of vibration during the expiratory phase increases expiratory flow rates PMID: 17132121
These forces increase IPP, which in turn increases expiratory flow rate hence helping to mechanically unload secretions (if you are interested in this).
I am interested how these forces influence hemodynamics. It looks like, they decrease an afterload, if applied during expiration.
Good luck with your studies, hope this helps.
Filip
You can also connect with the group on RG
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I am collecting some data from the machines through sensors (like vibration, temperature, etc.) for predictive maintenance purpose. But there is no any "historical failure data" yet to establish a machine learning algorithm and predict the next failure, etc. So, how can i make PdM or which other methods&algorithms can i use in the beginning for this purpose? 
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what could be the vibration band mode of intense 2440 cm-1
the main substance is phosphate, potassium, magnesium, and water molecule.
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adenine, guanine, cytosine, thymine
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What is its unit of measure?
How can it be calculated?
How can it be used when shaking the tree stem?
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the rate at which the amplitude of a free damped vibration decreases
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Can anyone suggest to me method to design fuzzy inference system (FIS) for MIMO structural damage detection (i.e. data distribution on the membership function, parameters of MF, Generate rules ... etc )
In my system there are 3 inputs and 2 outputs:
Inputs: Relative 1st Natural frequency , Relative 2nd Natural frequency , Relative 3rd Natural frequency
Outputs: Crack depth ratio , Crack Length
Note: I tried to use "genfis" By MATLAB it didn't give me reasonable results.
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Hi Murana Awad
Is it possible for you to share your data with me? I have some idea to solve your problem but I need your data.
I'm in touch by : ahmadi.v.1380@gmail.com
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Hello,
The fist mode shape (Out of plane) of my MEMS chip occurs at 7.7 MHz. there is released cantilever in my chip and I would like to vibrate it to its resonance frequency. What method do you suggest to actuate the MEMS chip? If you have any product in your mind I appreciate that if you send me the link as well.
Best
Masoud
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Hi Masoud,
I'd propose you try the following two solutions:
1. Try to measure the resonance frequency of your cantilever using a laser interferometer without actuation. At 7.7 MHz, I'd expect there to be very little ambient noise and also that your cantilever has a pretty high Q-factor. This means that the cantilever will self-resonate at its resonance frequency, acting as a signal filter, which you will be able to observe.
2. As Vinod suggested, use a piezo element, firmly connected to the base of the cantilever chip. Connect the piezo element to a signal generator that will sweep the frequency in the range of interest.
Good luck with your experiment!
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I think, Both FTIR and Raman Spectroscopy give the information about vibration of molecules/atom and stretching of molecules/atom or lattice vibration then what is the main difference between both Spectra (FTIR and Raman). Is there any difference between them?
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Raman and FTIR spectroscopy differ in some key fundamental ways. Raman spectroscopy depends on a change in polarizability of a molecule, whereas IR spectroscopy depends on a change in the dipole moment. Raman spectroscopy measures relative frequencies at which a sample scatters radiation, unlike IR spectroscopy which measures absolute frequencies at which a sample absorbs radiation. FTIR spectroscopy is sensitive to hetero-nuclear functional group vibrations and polar bonds, especially OH stretching in water. Raman on the other hand is sensitive to homo-nuclear molecular bonds. For example, it can distinguish between C-C, C=C and C≡C bonds.
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Generally, in literature (from what I've read), to monitor conditions of mechanical rotating drivetrains connected to an electric motor are used accelerometers. Or in the case of short drivetrains also the current signals can be significant to detect anomalous torque load oscillations related to a mechanical fault. In the case of nonstationary conditions (not constant speed of the electric motor), the Computed Order Tracking (
Article Analysis of computed order tracking. Mech Syst Sig Proces
) is a technique that is able to extract Orders of the rotor speed in vibration signals even when the speed change over time. In that way, is possible to relate each component that rotates at a known, fixed rate with respect to the motor rotor, and detect unwanted vibrations.
Could I apply the same technique for electric signals? If I have an electric motor with a speed reducer attached with a damaged bearing running at varying speeds, once acquired the one-phase current signal and the rotor speed feedback, if I apply a resampling of that signal with respect to the angle (as in the Computed Order Tracking for vibration signals), would I be able to detect speed Orders that can be related to the defecting bearing? In literature, there are no papers that apply COT to electric signals (or at least I haven't found it), which is the reason? This technique would be ineffective? There are some resolution limits? Or depends on the fact that electric signals are rich in frequency content related to the supply and mechanical oscillations are too weak to be detected?
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Thank you for your suggestion and your kind reply Dayong Zheng .
Certainly, electric signals to detect mechanical malfunction on the transmission contain weaker information. However, I was thinking, as a target of Condition Monitoring, on robotics systems (e.g. robotic arms). In such systems, is not so easy to add extra sensors, like accelerometers, while the current measurements are already available from the controller. Moreover, these systems use a relatively short drive train (each joint has its motor and a speed reducer). Thus, maybe, could be possible to detect mechanical and electrical malfunctions using only electric measurements.
I will continue studying and investigating in this direction.
Thank you also Bhupendra Desai for your information, I will have a look at your work.
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We would like to use Polytech microsystem analyzer (MSA) to characterize the resonance frequency of a fabricated cantilever and compare them with FE. However, the stage of the MSA is passive and we need an actuator to vibrate the cantilever to its resonance frequency. What would people use in such situations? Is there any commercial actuator for this purpose? Or do people design them according to their purpose?
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The MEMs are actuated either electrically by means of electrostatic charge or it can be actuated magnetically if it is made of magnetic material or it can be actuated mechanically by subjecting it to a mechanical knock or subjecting it to a mechanical vibration from a piezo transducer.
Best wishes
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Of course, set the damping ratio of a structure to 5% will simplify the dynamic calculation. However, we all know it is just an assumption and since structures are quite sensitive to their "real" damping ratio, especially when the frequency ratio is near the unit. I wonder how we can achieve an actual damping coefficient numerically?
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First you should find the mass matrix and the stiffness matrix. Afterwards, you should solve the eigenvalue problem associated with the problem at hand and these specific matrices. The structural damping coefficient is equivalent to the fraction of Im(lambda) over Real(lambda), where lambda is the complex eigenvalue and Im and real, respectively denote imaginary part and real part of the eigenvalue. I have attached a triple of screenshots to my comment for your perusal.
For forced vibration (for example in presence of air dynamic pressure), the solution of the eigenvalue problem is a bit harder than to find a solution to an ordinary eigenvalue problem. For concreteness, in this regard, I have attached a PDF of my own original idea to this comment. The PDF is also available in my ResearchGate project:
Linear Aeroelastic Analysis of Laminated Composite Plates with Fully Elastic Boundaries
Under the title:
Eigenvalue problem for aeroelastic vibrations: The solution
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Are there any theoretical methods and/or literature available to carry out flow induced vibration study of orifice in a pipe.
If so can you please share the same?
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Usually, when the restriction orifice plates (ROs), installed in the pipes, vibrate by the pass of flow through them, is because they have cavitation if the fluid is liquid or they have an excessive pressure drop if the fluid is gas or steam.
Another reason, in the case of liquids, could be that the flow is pulsating.
If the cause is the cavitation, change the 1 hole orifice plate by a multi-hole orifice plate.
In the other cases, increase the thickness of the plate, taking into account that values of t/d (t = plate thickness and d = hole diameter) equal or greater than 1, change the RO thin plate to a RO thick plate that have different hydraulic coefficients.
See the book Vibration Problems in Engineering of S. Timoshenko that in the Chapter VI analyzes the vibration of circular plates.
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There are different empirical equations and techniques like Fuzzy, ANN, etc.. for predicting Blast Induced Ground Vibration. In addition to these is there any software for predicting Blast Induced Ground Vibration
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It is appreciated if you recommend a benchmark study with the available dataset for video processing.
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Very interested in the topic
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A flexible beam has vibration, we want to eliminate its vibration using an active arm jointed to free end of the flexible beam.
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If ai understood good, for vibration suppression, you can use a dynamical absorber (flow divider), if the space allows this.
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Hi all
I am simulating a diaphragm structure sensor. I want to give the excitation as sinusoidal displacement whose amplitude will be fixed but frequency will be varied. when I apply the boundary load(N) and run the simulation for frequency domain study it gives expected output. but I want to give a displacement excitation(m )(or we can say sinusoidal vibration) to that boundary. Can anyone please help me to do this task?
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Prescribed displacement is not a excitation. If you apply prescribed displacement of 1m in z direction. then the boundary will be displaced by 1m only. it does not depend on frequency.
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I have been working on 1D and 2D materials; now, I would like to measure the vibrational properties using the Raman spectroscopy of these samples in the liquid state measurement.
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Hi Akash,
Sample preparation for Raman is very simple. Disperse a small amount of sample in a solvent in which the sample is soluble, and place the solution in a sample holder. Ideally, do different tests at various proportions and contrast the result with that of the solvent alone. There are times when the signal is not very strong and you have to increase your concentration a bit.
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I have question regarding to 1d cantilever beam problem which is divided to five elements.
I want to reduce the degree of freedom for each node to 1(just keep uy)instead of 6.
I added fixed support in the first node and applied displacement on each other nodes( make it freely translate in y direction)
But it still gives me results for 6 dof for each node.
My goal is to get only 5×5 MK matrices but it gave me 30*30.
Anyone knows how to fix this problem?
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Not clear what you mean
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Hello Everyone,
We have recently investigated a Semi-Supervised Deep Learning approach for anomaly detection of Wind Turbine generators based on vibration signals in the paper entitled "Anomaly Detection on Wind Turbines based on a Deep Learning Analysis of Vibration Signals" [1]. We found that vibration data enables a promising mechanism to detect abnormal behavior on wind turbines with a careful Machine Learning pipeline design. The paper presents an IoT-ready Machine Learning pipeline that encompasses data gathering, preprocessing, feature extraction, and classification. The approach is based on a Semi-Supervised Deep Learning approach, using Deep Autoencoders combined with a normality threshold selection based on the F1-Score analysis for a labeled data-set. The vibration data is preprocessed with band-pass filters and DC-component removal, rotation speed relation, and FFT. Finally, 11 features are extracted, from minimum, maximum, RMS, and standard deviation, to kurtosis, shape factor, energy, and entropy. The trained detection model achieved accuracy >99%, precision >97%, and recall of 100% for the evaluated data-set.
Moreover, with the IoT integration, the proposed workflow can notify users whenever abnormal behavior is noticed. What do you think about our findings? For more details, check the full paper at . If you have similar experiences with anomaly detection in rotating machinery, or if you have any comments or questions, feel free to leave a comment so we can start a fascinating discussion.
[1] José Luis Conradi Hoffmann, Leonardo Passig Horstmann, Mateus Martínez Lucena, Gustavo Medeiros de Araujo, Antônio Augusto Fröhlich, and Marcos Hisashi Napoli Nishioka, Anomaly Detection on Wind Turbines Based on a Deep Learning Analysis of Vibration Signals, In Applied Artificial Intelligence:9, 2021. DOI: 10.1080/08839514.2021.1966879.
Best Regards,
José Luis Conradi Hoffmann
Software/Hardware Integration Lab
Federal University of Santa Catarina, Florianópolis - SC, Brasil
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Dear Dr Hoffmann,
Thank you for sharing this interesting topic and I would be happy to participate in the future step of this project. the below paper might be interesting to read,
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Dear Researchers.
I am studying the vibration of twisted blade under rotation using scanning head PSV 500 .
We positioned the LDV to be in front of the blade . dispositions is available in the attached picture.
- The case is for the same blade but oriented in different manner.
the (x1) is the direction where the vibration appears in each case of blade disposition.
- I would like to know at each case how the vibrometry work and how it gives the results. is there any need to re-position it.
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I agree with Nitesh Anerao.
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any types of vibration which can be discussed with nonlinear oscillation
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  • Nonlinear vibration energy harvesting system
  • Nonlinear aeroelasticity/vibration of morphing wings
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We are using a horn-type ultrasonic transducer for cavitation and cleaning purposes.
We experimentally found that the cavitation effect and cleaning effectiveness were decreased when input power was higher than a certain value.
The sound pressure measured by the hydrophone showed a periodic wave pattern when we applied proper input power, but it showed an irregular wave pattern when the input power is high (maximum value of sound pressure was high, but RMS value was low).
I have two questions
1. Does cavitation is promoted when the acoustic field shows a uniform and periodic pattern?? (even the maximum sound pressure is lower). Why??
2. Does the tip of the ultrasonic horn irregularly vibrate when high power was applied?? If not, why does the measured sound pressure showed an irregular pattern??
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Please read carefully the discussion https://www.researchgate.net/post/What_is_the_relationship_between_the_acoustic_pressure_and_the_amplitude_of_ultrasound as your question on the loss of cleaning efficiency when you exceed some intensity levels is largely similar...
At high level, the ultrasonic generator becomes largely non-linear meaning widening the frequency spectrum, including low frequency components able to induce unstable horn vibration, but also large fluctuations of pressure in the fluid and unstable cavitation bubbles size.
The only way to remain under control is to stay in the quasi-linear electric power/piezo-electric conversion/fluid coupling domain...
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The vibration sensor (e.g. accelerator) is commonly used to monitor the vibration signal of a bearing for condition monitoring and fault diagnosis. If there any Standard for bearing vibration signal monitoring?
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Dear
J. Rafiee
Thank you very much for sharing, it is really helpful to me!
Regards,
Zhenyu
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Hello everyone,
I'm trying to model the motion of a cylinder in both CF and IL directions, but the UDF code that I have only can move the cylinder in the CF direction. Sadly I have never had the chance to learn to code UDF. Can someone please help me?
I will share the code below.
I really appreciate any help you can provide or at least promote this question to find the best answer to my issue.
FYI, this code is for Vortex-Induced Vibration of cylinders
####################################################
#include "udf.h"
#include "dynamesh_tools.h"
#include "unsteady.h"
FILE *fout;
static real v_prev;
DEFINE_SDOF_PROPERTIES(stage,prop,dt,time,dtime)
{
Thread *t;
Domain *d=Get_Domain(1);
real x_cg[3],force[2],moment[3];
real cg; /*Center of gravity position*/
real vel; /*Cylinder velocity*/
real Fy; /*Lift Force*/
real mass=8.88; /*Cylinder mass*/
real fn=1.06; /*System frequancy*/
real wn=2*M_PI*fn; /*System angular velocity*/
real z=0.002; /*Damping coefficeint*/
real k=mass*wn*wn; /*System stiffness*/
real c=2*mass*wn*z; /*System damping*/
/*Get the thread pointer for this which motion is define*/
t=DT_THREAD(dt);
prop[SDOF_MASS]=8.88; /*System mass of the 6DFOF*/
prop[SDOF_ZERO_TRANS_X]=TRUE;
prop[SDOF_ZERO_TRANS_Z]=TRUE;
prop[SDOF_ZERO_ROT_X]=TRUE;
prop[SDOF_ZERO_ROT_Y]=TRUE;
prop[SDOF_ZERO_ROT_Z]=TRUE;
cg=DT_CG(dt)[1];
vel=DT_VEL_CG(dt)[1];
prop[SDOF_LOAD_F_Y]=-k*cg-vel*c;
fout=fopen("results.txt", "a"); /*Open file*/
/*Wrtie data into file*/
fprintf(fout, "%g %g %g\n",time,DT_CG(dt)[1],DT_VEL_CG(dt)[1]);
fclose(fout);
}
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I'm trying to reduce a 3d printer extruder vibration. When the extruder starts to move, vibrates that decrease printing quality. How can I reduce the vibration? I need a procedure to solve the problem using FEM methods like Abaqus. The procedure should contain an optimization method.
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Reduce the printing speed; examine the Z-axis level; the machine may need a complete calibration; and inspect the mechanical components that hold the extruder.
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I wish to understand whether it is possible to make a phonon mode resonate with an externally applied signal in a lab, and whether a laser can be used for the purpose (if not, is there any other source that will do the job?).
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Dear Sourabh Lahiri , yes, it is indeed possible to couple a phonon mode with an electromagnetic wave, to create a sort of hybrid quasiparticle called polariton.
Rigorously speaking a polariton is a quantum superposition state between a photon and a matter excitation. The matter excitation can be a collective mode (a phonon) in solids or an electron in atoms or molecules.
"Polaritons are hybrid particles made up of a photon strongly coupled to an electric dipole. Examples of such a dipole include an electron–hole pair in a semiconductor, which forms an exciton polariton, and the oscillating electrons at the surface of a metal, which creates a surface-plasmon polariton."
A good description of different polaritons can be found in the following article and review, please have a look to them:
Polaritons are also fairly well described on the book by Le Ru and Etchegoin:
Hope this helps. Good luck with your research work and my best wishes.
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The vibration caused by a bearing is usually used as a key parameter to evaluate the health and operating conditions of the bearing. To achieve this purpose, a threshold value of vibration signal to distinguish the healthy and abnormal bearing is often required. How to set/determine a threshold value of a bearing in a specific application?
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Thank you for your answer!
Regards,
Zhenyu
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Hi everyone,
I'd like to inquire about the best method for monitoring the water level of a borehole with a depth of up to 400 meters. Although the depth of the boundary is unknown, it is assumed to be fractured diorite (upper) and diorite bedrock (lower). I've read about open standpipes and vibrating wire piezometers, but I'm concerned about their long-term reliability. It would be fantastic if you could contribute your practical ideas and opinions. I am open to ideas and eager to learn more from you. Thank you sincerely!
Best regards,
Raymond
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Hi Raymond,
400m is challenging but should work.
a pressure level sensor should work, if they are able to manufacture a 400m gauge wire.
I’ve worked a lot with these devices and they are quite durable. You can set up them for automatic monitoring. If you need a high failure safety, you can setup them in a array of 2 or 3.
if you are looking for manual monitoring devices, a contact gauge is a easy to use tool.
There are some other methods, like pneumatic level monitoring but I have no practical experience in terms of durability.
the diameter of the borehole should be at least 100mm with smooth edges.
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Is there any defined radii ratio with respect to the plate thickness exceeding to which an annular plate may be treated as a ring? Moreover what changes in vibrational behaviour may be observed when we increase the radii ratio of an annular plate and make it a ring?
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Nitish Kumar Guru I have added the example to the PERMAS4EDU project. See the project log at https://www.researchgate.net/project/PERMAS4EDU
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Hi!
I would love it if someone can explain how to read the vibrational frequency data listed in NIST website. For example, there are four vibrational modes (in cm-1) listed for Methane (https://webbook.nist.gov/cgi/cbook.cgi?ID=C74828&Mask=800), 2917 (symmetric stretching), 1534 and 1306 (both degenerate deformation), and 3019 (degenerate stretching) . Methane should have 3N-6 = 9 vibrational frequencies, so how do I know which of the above mentioned degenerate modes are doubly or triply degenerate? This website (https://lweb.cfa.harvard.edu/hitran/vibrational.html) mentions 1534 is doubly degenerate and 3019 and 1306 modes are the triply degenerate modes which makes up the 9 frequencies for methane. But it also mentions the following 12 modes for Ethane (2954, 1388, 995, 289, 2896, 1379, 2969, 1468, 823, 2985, 1469, 822) where the last 3 are stated as doubly degenerate. But that would still give us 15 frequencies instead of 18. NIST mentions almost similar frequencies for ethane (https://webbook.nist.gov/cgi/cbook.cgi?ID=C74840&Mask=800) but lists 2969, 1468, 2985, & 1469 as degenerate modes. Hence, my question is, how do I know which of the NIST listed vibrational modes are doubly or triply degenerate to make up the 3N-5 or 3N-6 frequencies for linear and non-linear molecules?
Thank you so much!
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Yes the NIST data is often a bit confusing.
You are correct there are 9 NORMAL modes of methane there's a nice animation here:
You could predict the number and degeneracy (and the atom movements) using group theory (Td point group).
Problem is when you come to experimentally measure the spectrum:
1. Many of the modes "couple"
2. Many are only Raman active. Raman and IR often show at (slightly) different frequencies.
3. Gas phase and liquid phase will have different frequencies
4. There will also be rotational excitation.
So it is often difficult to find two frequency tabulations that agree (exactly).
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Had tried lubricating and adjusted the position of the foundation, but they still vibrate.
When the motor and gearbox are unconnected with the sprocket, they won't vibrate. The motor and gearbox only vibrate when connected with the sprocket via chain.
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Don't quite understand the problem. Am I correct in assuming that the electric motor is connected to the gearbox using the sprocket and chain? If this is not the case, then how are they connected?
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clc;clear
fs=100; tspan=[1/fs:1/fs:50];
fi=linspace(0,fs/2,2*fs);
Am=10*exp(-linspace(0,20,length(fi)));
for i=1:length(fi);
x(:,i)=Am(i)*sin(2*pi*fi(i).*tspan+2*pi*rand);
end;
noise=sum(x')/length(fi); % noise data
signal=0.1*sin(2*pi*3*tspan).*sin(2*pi*0.5*tspan);
signal_measure=signal+noise;
% Question: how to seperate signal from signal_measure?
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J. Rafiee
Hi, J. Rafiee
thanks for your reply. I'm not trying to generate coloured noise but denoise.
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We have a one meter long copper pipe through which water passes at a certain speed. The outer wall of the tube is covered by the heater where all the energy of the heater is transferred to the tube. Now the outer wall of the tube is vibrated in a vertical direction by a vibrator using different frequencies up to 3000 Hz. We want to examine the rate of heat transfer at each of the vibrational frequencies at the end of the fluid.
Which physics can be used to perform this analysis in COMSOL software?
(outer diameter of tube = 9.52mm / inner diameter of tube = 8.72mm / Speed of Fluid = 0.059m/s)
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Erfan Shamsolketabi if you are trying to simulate this problem in the Laminar flow regime you have to know in laminar flow, wall roughness is neglected and we use this boundary condition just in the turbulent flow.
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I have a nonlinear ODE (second order) and exponential force in right side of equation ( q(t)=p0(1-t/t0)EXP[(-r*t)/t0] ) . p0, t0 and r are constant. I see in Nayfeh and Mook book only harmonic force. but i have a exponential force. How I can use from the Method of multiple scale to solve this problem?
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thank you Mr Anders Buen for your response.
yes, this is a sudden pressure wave that changes exponentially.
if I want to explain completely, I have 3 PDE-coupled equations for a plate. at the first, by use of some method, I changed 3 equations to 1, and then, by use of Galerkin method, I have 1 ODE equation that is a function of T. after use of the Galerkin method, the equation is in the frequency domain, But I do not know how to solve it when I have an exponential force.
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I am measuring the thrust of an electric thruster, but the data obtained is noisy. Because the thrust value is too small (micro N), it is greatly affected by factors such as temperature, vibration, and vacuum pressure. How to denoise the thrust data and eliminate those interference items?
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It is possible to greatly reduce the noise level using moving averages within the equipment you use for measurements.
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I'm attempting to figure out how to organise the nonlinear stiffness matrices and entire solution technique utilising the generalised differential quadrature approach. Many research articles cite open literature, however, none of the researchers reveal how to organise nonlinear stiffness with linear stiffness.
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Ahmed Youssef Dear Sir,
Thank you for suggesting me this article to me. But this article is on the free vibration of nanobeams based on various nonlocal theories with an application of DQM.
On the other hand, I'd want to address the problem of nonlinear free vibration of the beam. So, for this, I'm searching for literature that will provide me with a clear grasp of how to deal with the nonlinear components that arise in the equation of motion, as well as the solution technique.
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This is just like the EAS of NDRRMC. It will strongly vibrate your phone for a bad weather update.
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How they are activated Open your phone's Settings. Next, look for the Notifications section and access it. Access the Advanced Settings. The name may vary in some manufacturers, such as Advanced Settings. Once there, look for the Wireless Emergency Alerts tab.
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my cell line is THP-1 cell
that black dot moves or looks like vibration...
is it contamination??
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I agree with Ashten Stambersky
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Dear all.
I am using a Laser Doppler vibrometry to me measure the vibration of a structure, what I am doing now consist of exporting velocity to signal processing and integrate it to obtain Displacement but due to that an error will be always added to the results where the signal will be fluctuating around different value and even that (max-max) value remain correct but the shape of the signal is not as I am willing.
is there is a way to input directly the displacement by time? I read the guide but nothing there.
a lot of article could handle that but they did not show the way.
Please advice
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Hi Mohammed,
thank you for your quick answer. Generally, vibrometer measurements on rotating objects are more difficult compared to stationary vibrating objects. The major drawback is the increased noise level, caused by speckle effects due to the object rotation in combination with the surface roughness. "Speckle noise" is increasing with rpm rate and concentrates in "speckle peaks" at multiples of the rpm rate, leading to a typical comb-sprectrum. The amplitudes of the speckle peaks are nearly constant over the measurement band width. So it is much harder to detect a vibration , especially when it is correlated with the rpm rate, which is mostly the case. In that case the vibration signal is on top of a speckle peak. If the vibration amplitude is big enough (say 3 xor 5 x of the speckle peak height), then its easy to detect. But when the vibration amplitude is in the same range as the height of the speckle peak, it is nearly impossible to detect. Furthermore, an investigation of the vibration signal in time domain is virtually impossible- independant if you look at velocity or displacement data, because of the high noise level. Especially the displacement signal will additionally increase or decrease continuously, because the vibrometer will acquire the part of the circumferential veloctiy, which is projected on to the laser beam.
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Dear all.
Since I am working on the establishment of a Lab for vibration measurement and signal processing for rotating machinery, I would highly appreciate based on your experience what should be included (bought) as equipment.
Thanks all
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Mohammed, this is a how-long-is-a-piece-of-string question. It is very difficult to give a useful answer without knowing more details, such as:
1. What is the scale of machinery you are studying? Power stations and mega-ships, micromotors or something in between? If you are studying non-portable systems, you will need a portable lab. If you are studying large systems, the rpms will be lower, which affects your choice of suitable accelerometers and signal analysers. If you are studying tiny systems where the vibrations are small, you may need vibration isolation platforms to get usable measurements.
2. How many people does the lab need to accommodate and how many experiments do you plan to run at once? Is the lab for research only or will it also be used for teaching?
3. Do you want to study the effects of loading? If so, you will need to consider braking devices, dynamometers or other forms of loading systems.
4. Laboratories usually provide calibration services, at the very least for the lab users, but often for outside clients as well. What level of calibration do you intend to provide? Do you just want secondary calibration to verify that your equipment is operating correctly or do you want primary calibration to check the secondary calibrators? Calibration and traceability are important in any research work, but they are particularly important in any forensic or expert witness work.
5. Do you need ventilation and/or cooling systems for combustion engines?
6. Do you need soundproofing for noisy equipment or vibration isolation for shaky equipment to avoid disturbance to other building occupants?
7. Do you plan any destructive testing? If so, you may need safety enclosures and other safety equipment.
8. What is your budget? How much floor area do you have? Are you adapting an existing lab space or creating a new one from scratch?
9. Do you plan to make acoustic measurements as well as vibration measurements?
10. Vibration studies may need to measure the modes of vibration as well as the amplitudes. High-speed video and/or strobes may be needed for this. Laser interferometry may also be needed. Appropriate lighting will be needed for video work.
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Any structures like the bridge, railway suspension, beam, building. With damage occurred, it is expected that the vibration mode will be different.
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Hi, you can also check our dataset from the Hardager Bridge.
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I am interested in studying the vibration level classification to determine the damage to a machine using the random forest classifier. Based on the accuracy and computational cost, what is the best feature extraction method that can be used in this case?
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So I am beginner in Random vibration research. I have gone through some theory like ergodicity, stationarity, PSD etc.. related to Random Vibration. I am trying to model a very basic SDOF system subjected to random vibration.
I am trying Python. I have already modelled a harmonically loaded linear vibration system. For that I just needed to solve the equation of motion. But I am confused regarding incorporating randomness. How and where I use
How can I move about ? What are the baby steps that I should take ?
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There are two ways-
1. Spectral simulation method- Find output spectral density (So) using harmonic transfer function and input (force) spectral density (Sf). Then calculate the required mean square response (MS) from the area under Sf curve over required frequency band using the numerical integration of Sf function.
2. Time domain method- First you are required to generate the time-domain force f(t) signal using ‘wgn’ function in the MATLAB and save it as data file. Then solve the equations of single DOF system in by using f(t) as input with MATLAB solvers such as ode45.
The white-noise produced by the ‘wgn’ is essentially the band-limited and max frequency is equal to half of the sampling frequency. The ideal white-noise has infinite variance but ‘wgn’ requires to specify it as follows.
Var of wgn = Spectral Ht of white noise required (N^2/rad/s)* sampling frequency(rad/s)/2
In your case choose the sampling time (dt) such that, dt<=1/(2*10*fn), this ensures that the generated white-noise contains the highest harmonic of frequency 10*fn. Where fn=sqrt(k/m)/(2*pi). The factor more than 10 can be used but it is sufficient for lightly damped single dof system.
Then Sampling freq (Hz) = 1/dt.
3. SIMULINK is convenient for this use and it is not required to save the signal f(t). The blocks ‘Band Limited White Noise’ and ‘WGN’ can be used.
Hope this will help.
Note that. the suggestion presented by Chandrashekhar Dharankar.
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Hello
I am working with piezoceramic actuator to vibrate the flexible substrate but I am confused how to determine the resonant frequencies under loading condition? I am using function generator and amplifier and observe the vibration from the oscilloscope. I know that Network analyzer would help to determine the resonant frequency. But how to do that using NA, if anyone knows, please help.
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If you're already observing the vibration with an oscilloscope (and I'm assuming a transducer or accelerometer?) then why not just take an FFT of that signal if all you need is the resonant frequency? Don't trust the built in FFT function on a scope, those typically don't use enough points to be useful. Transfer the data to a computer and do it there. If you need the complex impedance then use a NA measuring a sweep of the reflection.
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Why vibration levels under certain defect condition get reduced than healthy state vibration ?
In the Graph below
Blue line represents healthy state vibration of a machine
Red line represent the defect state of the machine
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What machine fault was introduced?
Some machine faults could behave like that it is not allowing the shaft to move and could reduce max amplitude of the vibrations.
What are the values of the RMS of velocity for this measurements?
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I need the basics for including energy loss in Hamilton formulation for Finite element analysis for vibration of viscoelastic materials. The papers I read use complex modulus to represent viscoelastic losses or convolution integrals. Can someone give me a link where the formulation starts from Hamilton's principle?
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Have you got answer about it?
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Hello everyone
I want to use the finite element method to solve the differential equation of the bending vibration of a euler bernouli beam you can recommend me the most efficient version of the finite element method
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I recommend the Spectral Finite Element Method.
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Hi all,
As far as I know, to distinguish the core-mechanism of UV-Vis spectrum and Raman spectrum, we can attach UV-Vis spectrum with Oscillation and Raman spectrum with Rovibronic State (Rotational - Vibrational - Electronic State) word.
However, I am having a vague distinction between Oscillation in the UV-Vis spectrum and Vibration in the Raman spectrum.
Can you clarify this for me?
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I am not sure what you mean by "oscillation".
The core mechanism of UV-Vis absorbance is the induction of electric dipole transitions between the electronic states of an atom/molecule/solid by photons of appropriate energy/frequency.
The core mechanism of Raman is inelastic scattering of photons by coupling to vibrations of bonds in a molecule/solid, or also rotations in the case of a molecule (although less commonly studied).
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The system should generate high-frequency vibration. I want to component or mechanism use to generate.
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You can use a simple DC motor which rotates a half disk (you can buy both of them as a vibration motor) and a variable DC power supply( or dimmer ) to change RPM of motor. If you want to make linear vibration, you can use a simple speaker and a pulse generator program (PC or mobile app) to generate a sine wave with arbitrary frequency.
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Can anyone suggest how to calculate what type of bands present in the sample if we collect Raman spectra?
Recently I take the Raman spectra of my sample it shows three intense peaks in the range of 180, 570 and 640 and one small peak around 400 so how to interpret this and what type of vibration present in the sample?
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The principle of operation of Raman spectroscopy is based on the measurement of the shift in frequency (or energy) of the scattered light following its incidence on a sample.
The frequency of most of the scattered light is similar to that of the incident light. But a fraction of the scattered light is at a different frequency. This shift in frequency gives rise to the effect referred to as Raman
scattering. The difference in frequency between the incident and scattered light is termed Raman shift.
In response to your question, a number of significant information can be obtained from the Raman spectra with peaks fitting techniques which are both qualitative and quantitative in nature.
In our studies, when I was examining composite materials commonly used in organic electronics, for example blends of polymers/polymers or polymers/fullerenes for light emitting diodes (LEDs) or solar cells, their identification and characterisation are important.
The qualitative analysis of Raman spectra can also be used to map composite materials. The intensities of peaks (or bands) observed in OSCs active layer thin films, for example, have been shown to correlate with the concentrations of the functional groups in active layer molecules yielding them. So it can be possible to identify a distribution of composite components in a mapped image.
Probing the nature of conformation of nanodomains of composite materials within thin films can also be achieved using Raman spectroscopy. Such knowledge is useful for understanding the impact of thin film nanodomains on the performance of OSCs.
So depends of your samples definition and type of substances used, different fitting techniques on peaks can give you a different interpretation.
Analytical software like “OriginPro” or integrated Raman apparatus softwares like WiRE3 for Renishaw inVia Raman can also be helpful to have Gaussian distribution or a mixture of other fitting techniques to find out peaks numerical parameters.
I hope that’s helpful. 🙏
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I want to calculate vibrational reorganization energy for the ground and excited state, associated with corresponding normal modes.I also want to plot reorganization energy Vs frequency .I have attached one such example. Can anyone suggest me how to calculate vibrational reorganization energy with normal modes using gaussian ?
Thank you in advance.
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Interested!
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Can the current and voltage generated by the piezoelectric vibratory energy harvester be measured experimentally?In other words, can we measure the power generated by the piezoelectric vibration energy collector ?
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There are two options:
1. (Easier) Measure the voltage of a resistor placed into the piezoelectric eletrical terminals. Then, you have the value of the resistor and the measured voltage. Thus, it is possible to calculate the current by I=V/R.
2. (Harder but more comprehensive) Connect a frequency analyzer equipment into the terminals of the piezoelectric device. Then, it is possible to extract the frequency response (gain as function of frequency). Usually, frequency analyzers can provide voltage gain as function of frequency. You can also use a resistor as load in this case.
I hope this helps
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Hi All
I want to simulate an ambient vibration to be used as an input to a Numerical Model. I want this to represent the vibrations occurred to the building through the wind, vehicle/human movement, etc.
The sole purpose of simulating this ambient vibration is to input it to the numerical model in order to find out the natural frequencies, mode shapes and damping ratios of the building through Operational Modal Analysis
Thank you
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