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Questions tagged [vibration]

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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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23 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
32 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
31 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
52 views

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
279 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 ...
2
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1answer
43 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 ...
2
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3answers
49 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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46 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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58 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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0answers
19 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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1answer
23 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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1answer
25 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
76 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
109 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
48 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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36 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
47 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
41 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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1answer
59 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
19 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
61 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 ...
2
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1answer
53 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
59 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
53 views

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
252 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 ...
2
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1answer
142 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
52 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{...
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1answer
70 views

Is it possible to calculate the shear wave velocity in lab using ultrasonic test?

I have an ultrasonic testing equipment that can only measure the direct and semi-direct ( (a) and (b) in the image below): I can measure compression wave velocities fairly easily, but I would like to ...
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0answers
789 views

Equivalent spring of beam supported by springs

My professor gave us yesterday a problem to calculate the equivalent spring of the system shown in the attached figure. The problem: a cantilever beam supported by two springs $k_1$ and $k_2$ located ...
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0answers
55 views

Optimal size and shape for a steel target?

Problem I'm building a steel target for long-range rifle shooting. For those unfamiliar, the purpose of the steel is to produce a loud "PING" when the bullet strikes the target. It's very fun. Since ...
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0answers
15 views

How to find the maximum misalignment from vibration?

Consider the system in the (drawn in Paint) image. Assume that there is an input acceleration at the ground defined by a PSD. This acceleration can be in any axis. Points A and B are initially aligned ...
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1answer
152 views

Mechanical vibration of objects

Do you happen to know relevant references in the literature that model the mechanical vibrations of a solid object (preferably antennas) by means of complex representations as a function of time?, i.e....
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Applying modern control systems to real mechanical engineering problems

My aim was to damp the vibration of a stepper motor ( Nema 8 ) using only spring systems. I have taken modern control course and I wanted to apply it here. So I first analyzed my open loop system and ...
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3answers
82 views

Do vibrations affect inductive sensors?

As the question states, do vibrations cause any influences on inductive sensors? For example, do vibrations on rail, from a locomotive, affect signalling equipment?
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0answers
25 views

Plot zero-pole from frequency response matrix

I've represented with Matlab a system with three degrees of freedom. I'm trying to plot a pole-zero map from my Frequency Response Matrix H(w) in the case of Damped-...
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2answers
121 views

Simple mass spring damping system sizing K, and C factors

I have come across a problem, which has troubled me for some time now. What needs to be done is the following: A mass on a rod 0.6m (mass less) has a mass of 1 kg attached at the end of it. The rod ...
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3answers
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Units for vibration measurements

I am conducting research to determine vibration limits for cultural heritage objects (e.g. art, small sculpture, ceramics). The vibration source can be, for example, transport, construction in or next ...
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1answer
78 views

Modal Testing and Frequency Response Interpretation

I'm studying vibrations in a gearhead, for which I have a general dynamic model of 12 degrees of freedom (only translational coordinates) and I have calculated its natural frequencies. Now I want to ...
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1answer
32 views

Is it possible to measure x & y displacement components with a single point (out-of-plane) vibrometer?

Originally I was going to use accelerometers, but they are to big for the disk I'm trying to measure. Basically I have a set of planetary gears for which I need to measure the vibrations in the x and ...
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1answer
97 views

Undamped forced vibration for a multi dof system

I'm trying to determine the amplitude vs the excitation frequency of a multi dof dynamic system. I'm very confused from reading different methods, although I understand there's a very general one, ...
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2answers
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Strategies for cable vibration: eigenvalues are suitable?

This is a theoretical question. It is known that in "classic" vibration analysis natural frequencies can be found by solving an eigenvalue problem, from the undampened vibration equation like $\...
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0answers
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Combining critical speeds for a shaft of variable cross-section

I am looking to determine the critical speed for a shaft with universal joints at each end, where the halves are joined by telescoping profile members. I can calculate the critical speed of each ...
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2answers
87 views

Can a thing resonate whilst exposed to white noise?

Imagine some thing put in the presence of loud pure white noise, say at a level that might come from a teenager's HI-FI set to annoying. And the thing is like a champagne glass, sheet metal box or ...
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1answer
310 views

Determining damping ratio empirically?

I'm an engineering coop at a vibrations consultant. I was given a graph plotting a series of applied frequencies against a floor's acceleration response to them. I was asked to find the natural ...
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2answers
44 views

Why is the spin velocity of a gear irrelevant if perfectly balanced?

Going through some theory about epicyclic gears I came accross a comment that says that the spin velocity of the gear irrelevant if perfectly balanced, I don't understand why this might be true, is it ...
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1answer
349 views

How do I represent equations of motion of a dynamic system in State Space?

I'm going through some vibration theory and I need to represent the equations in state space for vibration control. The main forced general equation of motion is: $$\mathbf{M{\ddot q}+{\Omega_c}G{\...
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1answer
54 views

Best format to plot vibration data?

I am about to present my work on vibrations to a NVH specialist at work and he is supposed to help me. I have calculated PSD's, now my question (subjective, I know) is how should I plot the data? I'...
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1answer
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Reed played by the wind [closed]

I am trying to build a reed instrument played by the wind (kind of like these aeolian instruments: Eerie musical instruments played by the wind from around the world but using reeds rather than ...