Questions tagged [vibration]

Vibration of mechanical systems is a field studied by mechanical engineers and civil engineers

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57 views

On rectangular section beam properties of plate stiffeners

I am trying to understand the expression of the vertical dynamic stiffness $K_T$ and the rotational dynamic stiffness $K_r$ which appears in this paper where they consider a semi-infinite plate ...
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1answer
48 views

Does an ultrasonic horn increase displacement?

Reading the Ultrasonic Horn Wikipedia article, it states: An ultrasonic horn is a tapering metal bar commonly used for augmenting the oscillation displacement amplitude provided by an ultrasonic ...
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50 views

What is the possible reason for a huge discrepancy between measured vibration by vibration meter kit and a vibration transmitter?

I work in a pump station and I've noticed that when I measure the bearing vibration by a vibration meter, the measured value differs from what is shown on the computer monitor (2.5 mm/s measured ...
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22 views

Adding tension to a model of a Timoshenko beam?

I am interested in modeling a Timoshenko beam: https://en.wikipedia.org/wiki/Timoshenko%E2%80%93Ehrenfest_beam_theory However, I would also like to add tension to the beam so that it can vibrate like ...
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22 views

Model for dynamic plate deformation

I would like to gather ideas to model the dynamic behaviour of a plate with variable thickness. The assumption are: Small deformations. The plate is all made of the same material with variable ...
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1answer
80 views

Why does my trimmer feels heavier when it is operating and its fully charged?

I have a Philips trimmer which when fully charged feels much heavier than when it is not charged. Also , the blades move much faster when it is fully charged I.e it’s weight , speed of blades kind of ...
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41 views

Ride Comfort Estimation using Accelerometers

I've been trying to find established/novel methods for calculating ride comfort using accelerometers and recently I came across this paper which uses ISO 2631 standard to get an objective measure of ...
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1answer
53 views

How do engineers reduce vibration of system with multiple known natural frequencies? How do they design the isolation system for specific frequencies?

I have a system that is pretty much a chamber that needs to sit on the ground. I measured the transmissibility of the chamber vs the ground (output/chamber acceleration over input/ground acceleration) ...
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1answer
43 views

Forced vibration of beam

I was watching a video that derives the forced vibration response of a beam. The link to the video is https://www.youtube.com/watch?v=6VuLZDgRhZ4&list=PLMXj6GKKnHI6Lftj7CXr9WusMkXi5s9yH&index=...
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1answer
57 views

Wierd faulty gearbox FFT

I am working with a public dataset (mentioned in few papers) of vibration measurements of broken and healthy gearbox under various load. Most of the measured channels posses the same parameters no ...
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1answer
16 views

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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25 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
49 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
16 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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24 views

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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47 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
125 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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15 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
138 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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165 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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67 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
75 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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31 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
170 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: ...
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2answers
45 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
185 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
45 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
24 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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36 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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54 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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25 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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12 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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18 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
87 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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27 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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29 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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53 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
94 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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36 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
746 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
45 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
30 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
76 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
41 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
33 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 ...