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1answer
13 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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0answers
38 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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1answer
57 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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0answers
51 views

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-...
2
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1answer
41 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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0answers
25 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 ...
0
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1answer
17 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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0answers
10 views

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
27 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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0answers
19 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 ...
1
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1answer
21 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 ...
2
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0answers
18 views

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
29 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 ^\...
2
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1answer
43 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{...
1
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1answer
31 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 ...
1
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0answers
129 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 ...
3
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0answers
37 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
10 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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0answers
21 views

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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0answers
79 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= \...
2
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1answer
104 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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0answers
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 ...
3
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3answers
63 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
12 views

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 ...
2
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0answers
23 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-...
3
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2answers
88 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 ...
2
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3answers
66 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 ...
1
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1answer
51 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 ...
0
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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 ...
0
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1answer
40 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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0answers
30 views

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, ...
3
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2answers
41 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 $\...
2
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0answers
23 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 ...
2
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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 ...
1
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1answer
69 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 ...
1
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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 ...
1
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1answer
176 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{\...
0
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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'...
1
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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 ...
0
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3answers
106 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 ...
0
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2answers
46 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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0answers
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 ...
0
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2answers
38 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.
2
votes
1answer
43 views

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, ...
3
votes
1answer
71 views

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 ...
0
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2answers
861 views

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 ...
4
votes
1answer
103 views

How to simulate the Natural Frequencies of a Planetary Gearbox?

I have a dynamical model of a planetary gearbox of the form: $\mathbf{M{\ddot q}+{\Omega_c}G{\dot q}+{[K_b+K_m-\Omega_c^2K_\Omega]q}=T(t)+F(t)} $ $K_b$: bearing stiffness symmetrical matrix $K_m$: ...
5
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0answers
196 views

Is a 3 Hz beat frequency from my neighbor's HVAC a sign of a malfunction?

I'm being annoyed by a pulsating hum which comes from my neighbor's HVAC system. I read up a little on the design of HVAC systems and I came to a tentative conclusion that what I'm hearing is a ...
0
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0answers
75 views

Threaded rod length

Here is my "piston rod" on the right of the picture; On the bottom is a base that sits within a CAST ALUMINUM gas piston's dish area. That is then welded in place to the gas piston face and ground ...
1
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0answers
861 views

How to get mass normalized mode shapes?

I have an MDOF system with 4 degrees of freedom with forced input at one of the dof (4th dof)(it is a sinusoidal wave with a particular frequency expected to be generated using a shaker); displacement ...