Questions tagged [vibration]
Vibration of mechanical systems is a field studied by mechanical engineers and civil engineers
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How to interpret the phase plot from an accelerometer on vibrating machinery
Attached is a plot of amplitude vs frequency and on the inset phase vs frequency. I have constructed this phase plot via $\arctan\left(\frac{Im}{Re}\right)$
How can I interpret the phase plot or ...
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1answer
37 views
Can I use loadcell for vibrating force measurement?
Is it possible to use a load cell to measure a force that is vibrating? The idea is to measure that force that is getting into the load cell in a sweep of frequencies and vibration is NOT a noise. ...
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35 views
Estimation of Beam Displacement from Acceleration
Hi Engineering Exchange,
I have a beam with pinned-pinned boundary conditions (free to rotate but not free to translate). A legacy computer analysis provided me with the maximum mid-span acceleration ...
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1answer
22 views
Are the modal participation factors bounded for shock response spectrum analysis?
Recently dug myself into the theory of shock response spectrum analysis, but one thing is not clear for me.
The theory says that the peak response of the structure can be calculated as the product of ...
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1answer
42 views
Deriving equation of motion of a 1 degree of freedom system
Before solving this system, note that the rigid bars $\mathrm{\overline{OA}}$ and $\mathrm{\overline{OB}}$ are rotating about point $\mathrm{O}$, not their respective CGs. To account for this two ...
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41 views
Air - rectangular membrane system vibration and natural frequency
I'm struggling with the following problem:
The boundary conditions are $w(x,y) = 0$ around the edges.
I am supposed to find the natural frequencies of the system as a whole, and find the solution ...
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1answer
28 views
Linear actuator with low vibration and low noise
Which kinds of linear actuators offer the lowest levels of noise and vibration?
I am looking for an actuator with these properties that can push a load vertically on the cm scale. Velocity, accuracy ...
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1answer
23 views
Is shock spectrum always obtained for an undamped single degree of freedom system?
I am reading a textbook on fundamentals of vibrations and it has a very brief introduction to shock spectra. It mentions that
For comparison purposes, it is customary to use the response of an
...
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3answers
524 views
Three-phase versus single-phase operation of a generator
My generator (a Fermont MEP-803A, 4 cyl diesel, 10kW rated) can run in three distinct modes:
Single-phase 120V, in which one terminal is hot, and another is neutral
Single-phase 120V/240V, in which ...
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2answers
79 views
Relation between natural frequency and the thickness
If I have a solid material, let's say two bricks, one of which is thicker and I do modal/vibration testing. What would be the relation between thickness and natural frequency of any of them, is there ...
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2answers
57 views
How do those “dipole-shaped” weights attached to sections of electrical power lines work?
I see these frequently on tall power lines like the one in the image below, sometimes a single one at each end, sometimes pairs as are shown here. Sometimes on one side of the tower but not the other.
...
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1answer
24 views
Estimating the quality factor (decay properties) of an object's vibrational modes?
I am attempting to model the acoustic behaviors of a circular membrane (drum head). I know that software like ANSYS will give me the modes of vibration pretty easy from a simulation.
But what if I ...
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72 views
which kind of accelerometer/vibration sensor are suitable for sensing vibration of building floor caused by human foot strike?
I want to count human presence in a room through vibration sensing of concrete floor. For this I want an accelerometer with low frequency detection capability. I have used ADXL-345 which is not much ...
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1answer
51 views
How to compare multiple data acquisition systems?
For an application of displacement measurement under 1 kHz, I have 3 options to choose from. The application is automotive. Unfortunately I don't have deep electronics knowledge and the catalogues ...
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22 views
Translation of vibrational motion in the 15-20 Hz range
Is anyone familiar with how to create a "shaking" fluidized bed. With vibrational amplitude in the 2" range and Hz 15-20?
I'm constructing a vibrational fluidized bed dryer for the purpose of drying ...
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57 views
How to compare two acceleration sensors side-by-side?
I have a single axis analog capacitive acceleration sensor (from PCB Piezotronics) which is very reliable but expensive. Now I need more axis, unfortunately can not afford buying anymore. So I have ...
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29 views
Formula natural frequency double wall
I started with a book (pdf see here: https://www.pdhonline.com/courses/m104/m104_new.htm)
In this book there is the following formulla found
$$f_0 = 170 / \sqrt{M_1 * t / (1 + M_1 / M_2)}$$.
The ...
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1answer
264 views
Car's shock absorbers' damping ratio
I'm trying to find a suitable shock absorber for a small ATV with a specific value (to be determined later). But everywhere I look, no one seems to be giving the damping ratio of the shock absorbers.
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2answers
3k views
What is the difference between washer and O-ring? what is their advantages over the other?
I am designing a hydrophone, from the piezo buzzer. To hold the circular piezo plate, I have designed a mechanical fixture. I need to use washer/o-ring to make it leak-proof. I am confused about which ...
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41 views
Would a cross correlation between vibrations in the X and Y directions help determine vibrations in the Z direction?
I have a 2D vibration sensor that can only measure in the X and Y directions, and it is mounted on top of a motor that is fixed into place, as shown in a rough sketch below.
Would I be able to work ...
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1answer
59 views
Which kind/model of sensor is appropriate for detecting vibration at one end of 1000 m steel block?
We have to detect vibration/sound produced at rail track for upcoming train at 1000 m distances . So which sensor is appropriate here? thanks.
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3answers
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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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50 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
37 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 ...
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1answer
124 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 ?
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2answers
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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
2k 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 ...
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1answer
49 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 ...
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3answers
392 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 ...
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2answers
54 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 ...
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3answers
287 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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25 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?
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29 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!
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30 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 ...
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2answers
91 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 ...
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2answers
331 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 ...
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1answer
90 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
39 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/...
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1answer
75 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
43 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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93 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
22 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 ...
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1answer
65 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 ...
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1answer
80 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
136 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
105 views
Modelling acoustic instruments — 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 ...
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1answer
2k 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 ...
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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 ...
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1answer
358 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 ^\...
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1answer
67 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{...
