Questions tagged [vibration]
Vibration of mechanical systems is a field studied by mechanical engineers and civil engineers
102
questions
0
votes
1answer
19 views
Is shock spectrum always obtained for an undamped single degree of freedom system?
I am reading a textbook on fundamentals of vibrations and it has a very brief introduction to shock spectra. It mentions that
For comparison purposes, it is customary to use the response of an
...
6
votes
3answers
314 views
Three-phase versus single-phase operation of a generator
My generator (a Fermont MEP-803A, 4 cyl diesel, 10kW rated) can run in three distinct modes:
Single-phase 120V, in which one terminal is hot, and another is neutral
Single-phase 120V/240V, in which ...
3
votes
1answer
41 views
Relation between natural frequency and the thickness
If I have a solid material, let's say two bricks, one of which is thicker and I do modal/vibration testing. What would be the relation between thickness and natural frequency of any of them, is there ...
2
votes
2answers
52 views
How do those “dipole-shaped” weights attached to sections of electrical power lines work?
I see these frequently on tall power lines like the one in the image below, sometimes a single one at each end, sometimes pairs as are shown here. Sometimes on one side of the tower but not the other.
...
1
vote
1answer
22 views
Estimating the quality factor (decay properties) of an object's vibrational modes?
I am attempting to model the acoustic behaviors of a circular membrane (drum head). I know that software like ANSYS will give me the modes of vibration pretty easy from a simulation.
But what if I ...
1
vote
3answers
62 views
which kind of accelerometer/vibration sensor are suitable for sensing vibration of building floor caused by human foot strike?
I want to count human presence in a room through vibration sensing of concrete floor. For this I want an accelerometer with low frequency detection capability. I have used ADXL-345 which is not much ...
0
votes
1answer
38 views
How to compare multiple data acquisition systems?
for an application of displacement measurement under 1 kHz, I have 3 options to choose from. the application is automotive. unfortunately I don't have deep electronics knowledge and the catalogues ...
0
votes
0answers
22 views
Translation of vibrational motion in the 15-20 Hz range
Is anyone familiar with how to create a "shaking" fluidized bed. With vibrational amplitude in the 2" range and Hz 15-20?
I'm constructing a vibrational fluidized bed dryer for the purpose of drying ...
0
votes
0answers
30 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 (...
2
votes
0answers
53 views
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 ...
0
votes
0answers
18 views
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 ...
0
votes
0answers
22 views
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 ...
1
vote
1answer
115 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.
...
3
votes
2answers
2k 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 ...
0
votes
2answers
39 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 ...
1
vote
1answer
51 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.
2
votes
3answers
70 views
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 ...
1
vote
0answers
48 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 $(...
0
votes
1answer
37 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 ...
0
votes
1answer
76 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 ?
2
votes
2answers
65 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 ...
1
vote
2answers
1k 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
votes
1answer
48 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
votes
3answers
201 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 ...
0
votes
2answers
52 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 ...
0
votes
3answers
159 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 ...
0
votes
0answers
23 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?
0
votes
1answer
29 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!
0
votes
1answer
29 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 ...
1
vote
2answers
84 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 ...
2
votes
2answers
238 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 ...
0
votes
1answer
79 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 ...
0
votes
2answers
39 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/...
1
vote
1answer
63 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 ...
1
vote
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 ...
1
vote
1answer
85 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 ...
0
votes
1answer
20 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 ...
0
votes
1answer
65 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
votes
1answer
70 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 ...
0
votes
1answer
112 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 ...
1
vote
1answer
77 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 ...
1
vote
1answer
1k 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
votes
0answers
71 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
votes
1answer
282 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
votes
1answer
59 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
vote
1answer
87 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
vote
0answers
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 ...
4
votes
1answer
105 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 ...
1
vote
0answers
20 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 ...
3
votes
1answer
174 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....
