Questions tagged [vibration]
Vibration of mechanical systems is a field studied by mechanical engineers and civil engineers
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Sign of torque in torsional vibration of a shaft
In the example problem below, how were the signs of the torques at x = 0 and x = L found? At x = 0, the direction of pulley rotation is unspecified but the direction is assumed to be positive. And at ...
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18 views
Boundary Conditions of a Stepped Beam
I would like to ask about the boundary conditions to be considered in a stepped beam. For a cantilever beam wherein the one end is fixed while the other end is free to oscillate along the z-axis, we ...
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1answer
46 views
Vibration following an impact
This high-speed video shows a cymbal's response to impact. I'm interested in how the observed vibration relates to the modes and frequencies that an eigenvalue vibration analysis would predict. My ...
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1answer
15 views
Derivation of expression for strain in a beam that experiences transverse vibrations
I was watching
this video (the link to the video is https://www.youtube.com/watch?v=AoxTyIJprg8&list=PLMXj6GKKnHI6Lftj7CXr9WusMkXi5s9yH&index=60) which is part of a course on mechanical ...
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How to solve stress/strain constitutive equation for system of springs and dampers with a Coulomb friction element added in?
I am attempting to solve the stress/strain constitutive equation for a system of springs, dampers, and a Coulomb friction element. Basic examples for such constitutive equations can be found in this ...
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39 views
Is there an analogy between mechanical vibrations and electromagnetic waves
Recent questions about analogies between mechanical and electrical systems and about electromagnetic waves from a conductor made me wonder whether there is an analogy between the mechanical vibrations ...
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2answers
113 views
Vibration damping a bed from mechanical vibrations
Note: I understand the very nature of this question is about gross approximations on an incredibly complex topic, but even educated 'guesstimates' would be very helpful
I have already seen these two ...
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13 views
How do you exclude the connections between mechanical shaker and specimen?
to apply any kind of vibration, shock input using a mechanical shaker to any specimen, you first need to connect the speciment to the shaker, that sometimes needs some connectors that could weight as ...
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1answer
60 views
Deflection Equation of a Stepped Beam
Help out a college student.
How do you derive the deflection equation y(x) of the shown stepped cantilever beam in the figure? Each segment has a unique Young's modulus and moment of inertia. The ...
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47 views
How to use Spectroid app to measure low frequency vibrations?
Need to measure how low frequency (vibration) changes when going through different materials. The only possible way found is by using Spectroid app. However, have no idea of what settings to set up. ...
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65 views
A mechanical system with coupled oscillators and dampers
I found here Coupled oscillators, the last one on this page, a system named by the author "Vehicle Suspension System". But I am not sure this modelizes a suspension for a vehicle.
I am ...
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1answer
69 views
Creating an isolate bed environment for sleeping (to reduce mechanical vibration from floor)
Having a serious issue with mechanical vibration in my home (I call it "mechanical" because its nature is not from sound, but rather from some sort of a device - for clear image whats ...
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28 views
Shell Breathing Modes and Base Excitation
I have been reviewing "Vibration of Continuous System" by S. Rao as part of self-studying to help with work. I started reviewing the chapter regarding shells and noticed that shells have ...
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6answers
147 views
Reducing vibration coming from the floor while at sleep
having an interesting issue here. Imagine you live above some mental dude who starts a vibrating device and frames it against its ceiling - my floor (for your imagination, see example of this at the ...
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1answer
33 views
What's the meaning of 'Total acceleration effective'?
I'm reading a document describing the procedure to do a random vibration test. In it, a PSD (Power Density Curve) curve is defined, and there's a note at the bottom of the curve:
...
3
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2answers
44 views
Damp vibration on phone attached to car seat
I'd like to create a 3d printed system to damp the vibrations on the phone when we are on the road. The idea is to be able to hold the phone for my little kid when we travel
First I tried a spring ...
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2answers
97 views
Are there any instructions on how to install and run Natran-95?
there is a source code for Natran-95 on Github. I need to install it on Window 10
but searching on the web there is no clear tutorial on installation. while I click on the nastran.exe on this package ...
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37 views
how do i keep static deflection in a spring at a minimum upon applying gravity in a mass spring system without altering the response?
i modelled a simple mass spring damper system (with a vertical orientation) with base excitation in solidworks. After applying all necessary parameters, i plotted responses with and without gravity ...
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1answer
39 views
How does Nonlinear Viscous Damping work? In what way are Viscous Dampers typically nonlinear?
Viscoelastic materials like metal cables/wires/strings/webs/beams can be modeled with a variety of combinations of springs and dampers as described here.
For example, one simple common structure to ...
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1answer
21 views
Is stroboscope a substitution for accelerometer testing? [duplicate]
given that handy stroboscope can also check translational vibration of parts, is it a substitute for a test that can be done by accelerometer for stationary vibrating equipment?
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2answers
35 views
Is stroboscope a useful device to control the translational vibrations?
There is few material on net related to stroboscope applications. since it is an optical device, it is best used to control the vibrations of rotary devices like turbine blades electromotors etc.
but ...
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0answers
53 views
Effect of frequency resolution on the frequency spectrum of impulse force delivered by an electromagnetic shaker
this is a part of my parameter study for the experiment (a vibration analysis with a force impulse input). This specific part studies the frequency resolution effect on the spectrum. The input (i.e.: ...
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0answers
24 views
Can concepts like “critical damping” or “resonant frequency” be applied to more complex systems than just a spring and damper in parallel?
I am trying to do some modeling analysis by representing materials with parallel systems of springs and dampers. In the simplest case with just one spring parallel to a damper, we have the traditional ...
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18 views
correcting mode shape for modal damping
I have mode shapes and eigen frequencies from FE simulation. I have modal matrix and eigen frequencies corresponding to each mode. The mode shape is mass normalized. I am required to correct each ...
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0answers
10 views
Quantifying the amount of structural/hysteretic vibrational damping that occurs in proportion to deformation? (ie. Based on how “bent” something is?)
Three different conceptual types of vibrational damping forces are described here:
Viscous: $f(t) = -c \cdot v$
Coulomb: $f(t) = -c \cdot \text{sgn}(v)$
Structural: $f(t) = -c \cdot |x| \cdot \text{...
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14 views
Can cross correlation be used to see if filtering of a signal has changed it too much?
I am filtering a signal, and want to check if I am not over filtering it , I wanted to use cross correlation , but I am not sure if it is a good technique. usually I get something like the following ...
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1answer
78 views
Non-observable effect of low-pass filter on the Transfer function (of Vibration measured with Laser scanner)
I have to study the effect of low-pass filters (if any) on the outcome of the experiment. And the experiment here is to measure the vibration of a (metal) specimen by hitting the said specimen with ...
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0answers
26 views
Vibration measurement of rotating blade
In a vibration measurement of a rotating blade, I have the following information. The vibration signal is measured using an ICP accelerometer which has the following specification
Measurement range: ...
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5answers
5k views
Why are engine blocks so robust apart from containing high pressure?
Lately, I've been pondering why some engine blocks are so bulky, I always thought intuitively it was because they had to last a long time whilst containing thousands of combustion cycles but the more, ...
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0answers
28 views
How to take the engineering FFT of Signal in Matlab?
All,
The FFT function in matlab gives a theoretical mathematical FFT of the signal, and is not scaled to units and is real imaginary and not amplitude-frequency
is there an alternative way of FFT to ...
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1answer
42 views
I need a solution to a problem. I could not figure out myself how to do it [closed]
I was trying to solve this problem. But I could not figure out how to do it. Please help or provide a hint how can I solve it?
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0answers
49 views
How to find nodes of an undamped free-vibrating 2 DOF pitch and bounce system
I am working on a 2DOF non-forced pitch and bounce model for an engineering project.
I've found the values for my natural frequencies, and the initial conditions which make the system resonate in a ...
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2answers
87 views
Why does the frequency of a bottle filling up changes?
Today as I was filling up a bottle of water, and I could hear the distinctive change in pitch that signals that the bottle is near filling up, I started wondering what equation determines the ...
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0answers
33 views
I don't understand a simulation result of frequency vibration analysis of ultrasonic tranducer
I am building a ultrasonic transducer like this (with double-exponential (75%-25%) match and 2 ring PZT8 50x20x6.5 (for the moment I do not take account of pre-stress on bolt) :
When I simulate the 2 ...
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3answers
616 views
Can gravity be a driving force for a spring-mass system?
If a spring-mass system is undergoing free vibration (oscillating up and down), then does it imply that there is no gravity?
My tutor always consider gravity when finding the Equation of Motion for ...
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2answers
43 views
Coulomb damping time calculation
I'm designing a movable cover on rails under a spring and with added friction to dampen the movement. The model that describes it's movement the best is Coulomb damping model. The cover is moved from ...
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1answer
28 views
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
59 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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1answer
40 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
27 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
48 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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1answer
53 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
35 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
726 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 ...
3
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2answers
123 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
62 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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3answers
85 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
54 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 ...
