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Questions tagged [vibration]

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

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27 views

Please,i am not sure if it is a bearing defect , could someone help me?

This pump has shown high vibration level on axial orientation (pump side). The picture represents velocity spectrum on horizontal. Some peaks matches BPFI. I had no training on vibration analysis (...
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How to compare two acceleration sensors side-by-side?

I have a single axis analog capacitive acceleration sensor (from PCB Piezotronics) which is very reliable but expensive. Now I need more axis, unfortunately can not afford buying anymore. So I have ...
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How can I develop the displacement imposed frequency response function?

in theoretical vibration books , almost all of them to my knowledge, the FRF function is always developed for a system of SDOF or MDOF being excited with a unit force. but in FEM softwares there is ...
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Formula natural frequency double wall

I started with a book (pdf see here: https://www.pdhonline.com/courses/m104/m104_new.htm) In this book there is the following formulla found $$f_0 = 170 / \sqrt{M_1 * t / (1 + M_1 / M_2)}$$. The ...
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29 views

Car's shock absorbers' damping ratio

I'm trying to find a suitable shock absorber for a small ATV with a specific value (to be determined later). But everywhere I look, no one seems to be giving the damping ratio of the shock absorbers. ...
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958 views

What is the difference between washer and O-ring? what is their advantages over the other?

I am designing a hydrophone, from the piezo buzzer. To hold the circular piezo plate, I have designed a mechanical fixture. I need to use washer/o-ring to make it leak-proof. I am confused about which ...
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36 views

Would a cross correlation between vibrations in the X and Y directions help determine vibrations in the Z direction?

I have a 2D vibration sensor that can only measure in the X and Y directions, and it is mounted on top of a motor that is fixed into place, as shown in a rough sketch below. Would I be able to work ...
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37 views

Which kind/model of sensor is appropriate for detecting vibration at one end of 1000 m steel block?

We have to detect vibration/sound produced at rail track for upcoming train at 1000 m distances . So which sensor is appropriate here? thanks.
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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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45 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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36 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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54 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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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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553 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 ...
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47 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 ...
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101 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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51 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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92 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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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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28 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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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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79 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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149 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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69 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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38 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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55 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
42 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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70 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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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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63 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 ...
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61 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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80 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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67 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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510 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 ...
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1answer
201 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
54 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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79 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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1k 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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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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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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164 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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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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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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130 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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112 views

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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87 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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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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118 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, ...