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Questions tagged [vibration]

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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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37 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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Random Vibration: Does Segmenting Bandwidth Affect Validity of Response?

Important bits in bold. I'm planning to conduct some preliminary workmanship vibration testing on a new aerospace device. Unfortunately, this 'product' is too heavy for my small ED shaker table to ...
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35 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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14 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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39 views

Finding constraint condition + Kinetic and Potential Energy

I am trying to find the Kinetic and Potential energy of the slider-crank mechanism shown in the fig. I am not sure what I have calculated is correct or not. I would be glad if somebody could confirm ...
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58 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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Eigen-Modes for a homogenous, non-conservative mechanical system

$$ M\,\ddot{y}+D\,\dot{y}+K\,y=0\\ y=\begin{bmatrix} y_1&y_2&\cdots&y_f \end{bmatrix}^\top\\ M=M^\top>0,\quad D=D^\top,\quad K=K^\top\geq0 $$ Equations show a homogeneous non-...
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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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27 views

20g 11 msec shock

Is there any reliable procedure to estimate a constant acceleration acting on a body (for structural calculation) in case it is subjected to a momentary shock? I'm assuming it is possible to ...
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21 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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Polymers: Creep modulus failure criteria

I am developing a polymer component that is under statical, vibration and temperature loads and is made out of PA66 GF35 (polyamide 6.6 with 35 wt% short glass fiber). The component needs to ...
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1answer
34 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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26 views

Reducing mechanical vibration in an actuator design

I've been building a simple screw driver actuator. The actuator uses a coreless DC motor, attached to an aluminum beam coupling. This is connected to a plastic coupling which presses a drill bit into ...
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1answer
25 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
39 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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45 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
33 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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297 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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38 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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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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autocorrelation function of mechanical displacement

I was wondering if there any work in the literature that has been done on the form of the autocorrelation function of mechanical displacement of an object.
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114 views

natural frequency of floating body

guys i was doing this problem and i approached it like this: $$restoring force + m \bigl( \frac{d^2x}{dt^2}\bigr) = 0$$ $$restoring force = \rho \cdot A\cdot x\cdot g $$ so, now $$\omega_n= \...
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1answer
123 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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41 views

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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What should be the step type for a non-linear model in abaqus?

I have a non-linear model which has a nonlinear axial and rotation connection. I am going to do a dynamic analysis on it. What should be the step type for this model? Explicit? Implicit? or Modal ...
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24 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
100 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
68 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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1answer
55 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
45 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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Detecting potholes through Vibrations

To begin with, please excuse my little knowledge, I'm currently a data science student and unfortunately have very little knowledge of physics, engineering, DSP but I am willing to learn. Currently, ...
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2answers
47 views

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
24 views

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
85 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
109 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
191 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
41 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
38 views

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 ...
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3answers
118 views

How do I measure vibration of a moving object?

I want to measure the vibration of a rollercoaster cart while it is riding down the tracks. Handheld dataloggers with a pin on them won't work. I'd need something I can attach or place inside of the ...
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2answers
54 views

will a force with same frequency as natural frequency make system resonance (in multi-dof)?

assume we have a multi-dof system and a force is applied with same frequency as one of the natural frequencies. will this system be resonant in any circumstances? (system is undamped).
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23 views

Why does Experimental Modal Analysis need a reference signal?

I need to conduct a vibration experiment with 3 accelerometers for a gear box. I'm reading the theory of mainly how to perform the vibration analysis but I don't understand why EMA needs a reference ...
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2answers
39 views

Vibration of annular sector plate

The deflection of the sector is assumed in the following form But I don't know why they assumed G(θ) in the following form and how to compute η.Can somebody help me? Thanks.
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1answer
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What does natural frequencies with multiplicities m=1,2 or n mean?

If I have a planetary gear set consisting of one sun and N planets, what does it mean if it says that typical vibration modes of 6 natural frequencies always have multiplicity m = 1 for different N, ...
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What does multiplicity of a multiple natural frequency mean?

I'm doing some vibration tests on planetary gear sets and a lot of the information I´ve read mentions a lot about mode shapes and multiplicities of the natural frequencies. I understand how one can ...
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2answers
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How to get natural frequencies from accelerometer measurements?

I will be performing some tests and measuring the vibrations of a planetary gearbox. The accelerometer I will be using stays attached to the gearbox and saves the data into a log, which is available ...