Questions tagged [vibration]
The vibration tag has no usage guidance.
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Do internal / external stresses affect modal frequency?
Imagine a cantilevered beam, fixed on one end and with a tension line connecting the other end to ground (e.g. perpendicular to the length of the beam).
If I increase the tension, does the modal ...
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0answers
23 views
How to state the PSD value (random vibration)
In random vibration analysis, the load is given as a PSD (power spectral density). The values are often $G^2/Hz$, but I have an example where the PSD is a pressure $Pa^2/Hz$. The value is written as $(...
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1answer
32 views
Shock/Isolation mounting under tension
I want to secure a box (roughly 20kg in total) that contains electronic equipment to the underside of a flat steel structure. We can weld onto the underside.
The steel structure has a high chance of ...
0
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1answer
31 views
Vibrations analysis 7x rpm
im monitoring an overhung pump 19kw . and it shows a high peak at 7x rpm . on Thrust Vertical DE of pump.
what does it mean ?
2
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2answers
52 views
Need Help to Remove Sway from Steel Post + Glass Panels
I have spanned ~15' with 2x 10mm tempered glass panels. They're connected in the middle with a 1.5" x 1.5" 16-gauge, 316 stainless steel post filled with concrete. This post has a 316 base welded on ...
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2answers
279 views
Stiffness of a cantilever beam
I am working on calculating the stiffness of a cantilever beam by applying a distributed load. I wanted to ask if the distribution of the load on the beam effects its stiffness.
For eg., if I apply a ...
2
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1answer
43 views
How to allow only one mode of resonance in a cantilever beam
So I am designing a MEMS structure consisting of cantilever arrays.
For my problem, I want the cantilevers to vibrate only at their 1st mode of resonance and reject all the other modes of resonance ...
2
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3answers
49 views
Resonance vs flutter
Is there any difference between resonance and flutter. Both of them are related to overlap of external excitation frequency and Natural frequency then increase in amplitude even inifite amplitude ...
0
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2answers
46 views
Vibration table for tests (7-200Hz) from extruded aluminium profiles bolted together - good idea (?)
I need to design a vibration table (approx. 1000mx1000mm) to test products between 7-200Hz.
I was wondering if it is recommended to make the table structure from standardised, extruded aluminum ...
0
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3answers
58 views
Mechanical vibration: 2 springs attached horizontally to a wheel at a vertical distance a above the center, find the natural frequency of the system
Context: introductory mechanical vibrations, 300-level engineering. ISBN13: 978-0-13-287169-3
See problem solution below
As seen in the "Potential Energy" section, the author writes that the ...
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0answers
19 views
Frequency domain analysis of steering system of a car
Can anyone share the equations involved, or some relevant theory material for frquency domain analysis of steering rack and pinion using bode plot?
0
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1answer
23 views
time interval selection for RMS of vibration
What is the general practice for selecting time interval for RMS calculation for vibration data (mm/s)
Should it be linked to the the frequency of the motor or the sampling rate?
Thanks!
0
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1answer
25 views
Amplitude RMS vs Amplitude in understanding vibration
I am reading this paper, which talks about dealing with mechanical noise.
When characterizing their existing noise, it says the following:
The integrated RMS vibrations up to 1 kHz on the mixing ...
1
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2answers
76 views
Analizing Vibrations Influence on Dynamic Weighing
I have a very sensitive scale used for dynamic weighing (by dynamic I mean that the scale and load cells are actually beneath a belt conveyor that actively weight product when it´s being transported ...
2
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2answers
109 views
How can I measure the vibrations of a solid object?
I want to measure the vibrations of a solid object (a tuning fork, a bone conducting headphone, the chest during singing) and to isolate them from the vibrations of the air. So I am looking for a ...
0
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1answer
48 views
Base Driven Tuning Fork Mechanical Response Spectrum
I am new to vibration analysis/simulation etc. so I may be missing something very basic here so please forgive me if I'm explaining things poorly or not making sense.
To familiarize myself with ...
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2answers
36 views
How to measure number of strokes in a small space
I have read about a device called drumometer, which measures the number of strokes of hitting drum stick.
I think this is almost the same, but instead, I would like to measure the number of strokes/...
1
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1answer
47 views
Need to produce vibration amplitude of 200 um (approx) at natural (resonant) frequency, can be any frequency between 100 to 150 Hz
In order to conduct study, I need to produce controlled vibrations with amplitude (maximum) approx 200 um (micro) at frequency between (100-150) Hz. Vibration amplitude must be controlled with input ...
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1answer
41 views
Measuring beats/bounce in a closed cubed glass
Suppose that we have a $2$ by $2$ by 2 $cm^3$ closed box, made up of glass, with thickness $0.1 cm$. Yes, it is a very small box. Let's say in that box there is a ball (also made with glass) with ...
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1answer
59 views
Mechanical vibrations: kinetics of kinematics?
In books of dynamics, I normally see topics in kinematics and then in kinetics, and finally a last chapter on mechanical vibrations dealing with SDOF and MDOF systems. But I do not see any book ...
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1answer
19 views
Vibe Table: Increase Peak Force Capability?
I'm driving a small, benchtop vibe table (shaker) with two Crown DSI-1000 PA's, and also cleaning my signal with a DBX 231s EQ. Currently running the system at 6.8 GRMS, but I'm looking to increase my ...
0
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1answer
61 views
Analytic expressions of the kinetic and potential energy [closed]
A homogeneous rigid circular disc (radius R, mass ms, center point S) rolls without a slip on a plain with a small angle of inclination alpha against the horizontal. A point mass MG is fixed on the ...
2
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1answer
53 views
Rigid circular disc equation of motion
I am working on an assignment and I have a doubt in a step in my problem. Could someone please help me understand it?
Question and its solution is:
.
My doubt is in the part which is underlined. How ...
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1answer
59 views
Twin cylinder engine opposed cylinders
Hoping this is the best area to ask this, mostly in the DIY and hobby world I've seen 2 engines coupled together to make a twin engine some so this for the zen of doing, but others do it to align the ...
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1answer
53 views
Predicting frequencies, decays, levels, and phases of modes of a circular membrane (drum head)?
I have been working on some acoustic synthesis software for modelling several acoustic instruments. I am using the principle of modal synthesis, where every mode of vibration is individually ...
1
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1answer
252 views
What does 1 x rpm or 2 x rpm or 3 x rpm in vibration analysis mean?
a description for virbation monitoring of industrial bearings states:
peak amplitues at 1 x rpm
should be an indicator for a fault in my case. Can somebody explain me what I have to understand ...
2
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0answers
49 views
Determining the load on a pump vibration isolator
It seems to me that pump vibration isolators need to support:
The weight of the pump
The weight of the water in the pump
The weight of the water (only) in the drop to the pump
The supplier of ...
2
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1answer
142 views
How to work out the damping or deflection curve from deflection angles?
I have a crane boom that is rotating and when it is stopped suddenly, the boom flexes back and fourth several times. I have measured the angles between each deflection and have $3.16 ^\circ$, $2.42 ^\...
3
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1answer
52 views
Rayleigh damping in structural mechanics
In structural mechanics, we often approximate a partial differential equation by a system of ordinary differential equations in matrix form
$$\boldsymbol{M}\ddot{\boldsymbol{q}}(t)+\boldsymbol{B}\dot{...
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1answer
70 views
Is it possible to calculate the shear wave velocity in lab using ultrasonic test?
I have an ultrasonic testing equipment that can only measure the direct and semi-direct ( (a) and (b) in the image below):
I can measure compression wave velocities fairly easily, but I would like to ...
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0answers
789 views
Equivalent spring of beam supported by springs
My professor gave us yesterday a problem to calculate the equivalent spring of the system shown in the attached figure. The problem: a cantilever beam supported by two springs $k_1$ and $k_2$ located ...
3
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0answers
55 views
Optimal size and shape for a steel target?
Problem
I'm building a steel target for long-range rifle shooting. For those unfamiliar, the purpose of the steel is to produce a loud "PING" when the bullet strikes the target. It's very fun.
Since ...
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0answers
15 views
How to find the maximum misalignment from vibration?
Consider the system in the (drawn in Paint) image. Assume that there is an input acceleration at the ground defined by a PSD. This acceleration can be in any axis. Points A and B are initially aligned ...
2
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1answer
152 views
Mechanical vibration of objects
Do you happen to know relevant references in the literature that model the mechanical vibrations of a solid object (preferably antennas) by means of complex representations as a function of time?, i.e....
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0answers
41 views
Applying modern control systems to real mechanical engineering problems
My aim was to damp the vibration of a stepper motor ( Nema 8 ) using only spring systems. I have taken modern control course and I wanted to apply it here.
So I first analyzed my open loop system and ...
3
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3answers
82 views
Do vibrations affect inductive sensors?
As the question states, do vibrations cause any influences on inductive sensors? For example, do vibrations on rail, from a locomotive, affect signalling equipment?
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0answers
25 views
Plot zero-pole from frequency response matrix
I've represented with Matlab a system with three degrees of freedom. I'm trying to plot a pole-zero map from my Frequency Response Matrix H(w) in the case of Damped-...
3
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2answers
121 views
Simple mass spring damping system sizing K, and C factors
I have come across a problem, which has troubled me for some time now. What needs to be done is the following:
A mass on a rod 0.6m (mass less) has a mass of 1 kg attached at the end of it. The rod ...
2
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3answers
94 views
Units for vibration measurements
I am conducting research to determine vibration limits for cultural heritage objects (e.g. art, small sculpture, ceramics). The vibration source can be, for example, transport, construction in or next ...
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1answer
78 views
Modal Testing and Frequency Response Interpretation
I'm studying vibrations in a gearhead, for which I have a general dynamic model of 12 degrees of freedom (only translational coordinates) and I have calculated its natural frequencies.
Now I want to ...
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1answer
32 views
Is it possible to measure x & y displacement components with a single point (out-of-plane) vibrometer?
Originally I was going to use accelerometers, but they are to big for the disk I'm trying to measure.
Basically I have a set of planetary gears for which I need to measure the vibrations in the x and ...
0
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1answer
97 views
Undamped forced vibration for a multi dof system
I'm trying to determine the amplitude vs the excitation frequency of a multi dof dynamic system. I'm very confused from reading different methods, although I understand there's a very general one, ...
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2answers
66 views
Strategies for cable vibration: eigenvalues are suitable?
This is a theoretical question.
It is known that in "classic" vibration analysis natural frequencies can be found by solving an eigenvalue problem, from the undampened vibration equation like
$\...
2
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0answers
32 views
Combining critical speeds for a shaft of variable cross-section
I am looking to determine the critical speed for a shaft with universal joints at each end, where the halves are joined by telescoping profile members. I can calculate the critical speed of each ...
3
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2answers
87 views
Can a thing resonate whilst exposed to white noise?
Imagine some thing put in the presence of loud pure white noise, say at a level that might come from a teenager's HI-FI set to annoying. And the thing is like a champagne glass, sheet metal box or ...
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1answer
310 views
Determining damping ratio empirically?
I'm an engineering coop at a vibrations consultant. I was given a graph plotting a series of applied frequencies against a floor's acceleration response to them. I was asked to find the natural ...
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2answers
44 views
Why is the spin velocity of a gear irrelevant if perfectly balanced?
Going through some theory about epicyclic gears I came accross a comment that says that the spin velocity of the gear irrelevant if perfectly balanced, I don't understand why this might be true, is it ...
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1answer
349 views
How do I represent equations of motion of a dynamic system in State Space?
I'm going through some vibration theory and I need to represent the equations in state space for vibration control.
The main forced general equation of motion is:
$$\mathbf{M{\ddot q}+{\Omega_c}G{\...
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1answer
54 views
Best format to plot vibration data?
I am about to present my work on vibrations to a NVH specialist at work and he is supposed to help me.
I have calculated PSD's, now my question (subjective, I know) is how should I plot the data? I'...
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1answer
41 views
Reed played by the wind [closed]
I am trying to build a reed instrument played by the wind (kind of like these aeolian instruments: Eerie musical instruments played by the wind from around the world but using reeds rather than ...
