Questions tagged [vibration]

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

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How can I find the right resonant frequency of a chassis?

Structures have infinite DOFs, so it possess infinite mode shapes. How can we find the right resonant frequency out of the infinite resonant frequencies so that we can save our structure? For example, ...
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A problem from Damped free Vibrations

Problem: I can understand the problem physically that the block is pulled by some amount X so that its displacement at t=0 is X. It is then released from that position so that its velocity at t=0 is ...
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How to analyse results of vibration isolation test

I performed some tests with vibration isolators and have computed the PSD. The natural frequency of the isolators is 110 Hz in the axial direction. So my question is, should I expect to see noise ...
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how to interpret plots in ISO 10816-8?

In ISO 10816-8 for reciprocating compressors, there are some plots that show the allowable RMS vs. frequency for every part of a compressor. However, in the text of the standard, it is mentioned that ...
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Interpretation of results in a spring mass dashpot system subjected to harmonic excitation force

Consider a spring mass dashpot system subjected to a harmonic excitation force of $$F(t)=F_0 sin(\omega t)$$ The response of a system assuming sufficient time has been passed and the complementary ...
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Control System Response

How does one find the zeta value or the frequency of an over damped response curve. I am used to determining things by using the log-decrement equation. Does that apply here even though there is no ...
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Force Transmitted to the support (Vibrations)

Consider the spring mass dashpot system shown below which is acted upon by a harmonic excitation force F(t). The reference is taken at the equilibrium position of the system when no F(t) was present. ...
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What is the best time interval in condition monitoring programs for checking rolling bearings?

The time intervals between observing or measuring the vibration of rolling bearings in industrial plants are so important in condition monitoring programs. For instance, some experts measure the ...
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Where does all the inherent vibrations in an internal combustion or jet engine come from?

I am trying to understand that why does a piston engine produce vibrations? What is the source of it and how will it cause the whole internal combustion engine to vibrate in response? Will jet engines ...
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What frequency is the low frequency vibration of normal buildings from like elevator or ventilation motor? To avoid equipment resonance vibration

Recently I am building equipment. It is as large as two refrigerators with aluminum extrusion frame. Unfortunately, it has visible resonance vibration. After measuring I find on the floor there is a ...
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In vibration study, should the reference be necessarily the mean/equilibrium position?

When we determine the natural frequency of free vibration for a system, we start of by defining a reference from where displacements will be measured. I have usually seen in books, taking the ...
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Pre requisites for a course in vibration for a Mechanical Engineering Bachelors Degree [closed]

Can anyone please tell me what parts of differential equations, linear and partial I need to revise properly before I take a course in vibrations , in Dynamics, our course in vibrations mainly deals ...
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A question on resonance

This is to settle a debate. I was working on a scaffold next to a building, as the wind blew, the scaffolding would sway. As I stood there I was trying to maintain my stability, but my movements ...
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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
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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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1answer
79 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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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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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
93 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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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
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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
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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
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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
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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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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
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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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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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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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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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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
405 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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501 views

How to use Spectroid app to measure low frequency vibrations?

I need to measure how low frequency (vibration) changes when going through different materials. The only possible way I found is by using Spectroid app. However, I have no idea of what settings to set ...
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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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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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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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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
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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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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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332 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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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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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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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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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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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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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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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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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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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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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: ...