7 votes

In vibration study, should the reference be necessarily the mean/equilibrium position?

It can be arbitrary. It just simplifies the mathematics significantly. However the end result should be the same.
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4 votes

In vibration study, should the reference be necessarily the mean/equilibrium position?

So you need a point, "zero point" as you really want the amplitude of the displacement as the conditions vary. if you use a moving point to measure another moving point then you have to ...
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2 votes

What is the best time interval in condition monitoring programs for checking rolling bearings?

I know of no global standards for vibration monitoring. Like all preventive/predictive maintenance items, these things need to be equipment-specific. These are the same considerations you would apply ...
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2 votes

Where does all the inherent vibrations in an internal combustion or jet engine come from?

The common denominator in ICE and jet engines is probably imbalances of rotating masses. ICE's have additional vibrations which are due to the firing of the different cylinders. The firing itself is a ...
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2 votes

Where does all the inherent vibrations in an internal combustion or jet engine come from?

From out-of-balance forces, caused by rotating and / or reciprocating masses. Lots of published theory about this. A quick google search gave the following: https://www.researchgate.net/publication/...
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2 votes
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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

As an equipment supplier, your responsibility is to avoid the resonance to occur between the equipment and its support, whether a skid or a frame that is to be supplied by you. It might be a problem ...
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2 votes

What frequency is the low frequency vibration of normal buildings from like elevator or ventilation motor? To avoid equipment resonance vibration

The major source of vibration especially in modern light floor structures with +25ft spans is the floor vibration under foot traffic. foot traffic frequency is about 1.25 hertz. so most of the modern ...
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2 votes

In vibration study, should the reference be necessarily the mean/equilibrium position?

Any point in a wave can be arbitrarily chosen as the reference and it wouldn't change the frequency and amplitude. but it would change the phase of the wave which is essential in complex analysis and ...
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2 votes

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

Assuming that the model is adequate and appropriate, then to answer your second question: Which frequency out of those five is right? All of those modes and frequencies are possible in the structure....
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2 votes

A problem from Damped free Vibrations

I think your math is taking you to the right place. Looking at the this sketch from the problem statement, it does not look like $\dot{x}(0) = 0$ when $\phi_0=\pi/2$; for example see here. Perhaps ...
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A problem from Damped free Vibrations

UPDATE: after your comment I sat down and derived it myself (I couldn't make it out from the image), and I realised that your assumption that $\phi_0= \frac{\pi}{2}$ is not valid. I prefer the ...
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2 votes
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natural period of vibration for the system - positive and negative work

When you compress the spring by $dx$ the energy stored in the spring is given by: $$E_s = \frac{1}{2} k \cdot (dx)^2$$ By raising to the square power, the energy quantity becomes positive and that ...
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2 votes
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Natural Frequency of a Shear Frame

The basic unit of the natural frequency is $Hz$, $cycle/s$, or just $1/s$. Let's check the results by using "$m$" and "$mm$" as the base unit - 1. Use $m$ as the base unit: $\...
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1 vote
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Positioning accelerometer on a cantilever beam

In both cases it would be best to place the accelerometer as far as possible from the fixed point. However IMHO, for an adequate approximation of the natural frequency (assuming the damping is not ...
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1 vote

Calculate Vibration Velocity and Acceleration from Triple Axis Accelerometer

If you are not aware of vector math then perhaps now is the time. You can use vectors to represent the direction of all three component accelerations as a single magnitude along with a direction with ...
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1 vote

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

It depends what you think should be the frequency of the external force, which will cause it to vibration. If the frequency of the external force is overlapping with any of the natural frequencies, ...
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1 vote
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Interpretation of results in a spring mass dashpot system subjected to harmonic excitation force

I think the confusion is due to the fact that you have not understood the significance of "The response of a system assuming sufficient time has been passed and the complementary part of the ...
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1 vote
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Control System Response

The logarithmic decrement is not applicable to the overdamped systems because there are no oscillations. Also, there is not (at least to my knowledge) an equivalent to the logarithmic decrement ...
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1 vote
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Force Transmitted to the support (Vibrations)

In the analysis you are referring to the authors are only concerned about the amplification of the excitation force (they are not concerned about the total force). I.e. they only care about the ...
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1 vote

A question on resonance

There are many ways that your movement could have increased the sway of the scaffolding. The scaffolding has planks that virtually act as an airfoil and like an airfoil they can experience what is ...
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1 vote

A question on resonance

The wind was the initial excitation of the scaffold. If it was a gust (not a sustained wind), then the response could be characterized as free vibration with initial conditions (the gust from the wind)...
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1 vote
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Does an ultrasonic horn increase displacement?

Disclaimer: Even though I posted a relevant link (in a comment to the question ) which can answer the exact question asked, I am not familiar enough with continuum mechanics to actually explain it. ...
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1 vote

Reducing vibration coming from the floor while at sleep

I know there was someone who had a few blog posts about a similar issue and ultimately settled on low-cost anti-vibration pads. Myself, I was theorizing if one could float a bed frame on a thin layer ...
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  • 111
1 vote

Vibrations analysis 7x rpm

The impeller blades will always make a vibration. Unless you see an increase in the amplitude of this peak in your spectrum, you may just be seeing normal operational vibration. Monitor it for ...
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