# Questions tagged [vibration]

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

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### What is the physical and mathematical meaning of nonsymmetric mass, damping and stiffness matrix of a linear fluid-solid interaction modeling problem?

Suppose the problem of the subsonic flow over a simply-supported rectangular plate as bellow. According to the assumptions of incompressible, inviscid and irrotational flow, and using perturbation ...
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### Whirl and angular speed of Jeffcott rotor model

So it just doesnt make sense for me that ω and dθ/dt angular speeds can be different.(My book states that it can and it usually is) It doesnt make sense simply because harmonic excitation doesnt ...
32 views

### What is the mechano-acoustic effect of off-centering the black paste on tabla-drum skins?

Tabla is a musical instrument composed of two drums, the Bayan (left on picture) and the Dayan (right on picture). A unique feature of the tabla is the tuning [black] paste called the gab, applied to ...
36 views

### Understanding the units of columns in MaFaulDa Dataset

Recently I am learning about the MaFaulDa machine failure database. I am wondering about the unit of column zero (tachometer signal) measured by Monarch Instrument MT-190 (as announced by database ...
22 views

### Gravitation Potential Energy on Sector Gears

Find an equivalent spring stiffness for a system using Energy Methods. The problem is, I do not understand when gravitational potential energy should be taken into account. Let's see the examples ...
1 vote
49 views

### Natural Frequency of a Shear Frame

Hi I've been stuck on a problem for one of my exam revisions, we were asked to identify the natural frequency of the following structures I know that the equation for the stiffness is as follows Left ...
62 views

### Sign Convention for Energy Methods in Vibration Analysis

Find the equivalent spring stiffness of the system below. I was able to solve it using Newton's second law and got the result below. $$k_{eq} = \frac{mgl}{2} - \frac{k_1 l^2}{16} - k_2 l^2$$ However,...
41 views

### Contradiction of bandwidth and damping

I am studying control theory and mechanical vibrations. From control theory aspect, I know that bandwidth and response time is inversely proportional, which means bandwidth and damping as well. But in ...
32 views

### How does vibration monitoring with engine power differ?

How do engineers design vibration monitoring for motors with different wattage? What effect does power have on vibration? I consulted manufacturers of these vibration monitoring and did not see any ...
18 views

### Design of the parameter of a transfer function so that output can reduce to zero

Here is a transfer function. $$G_2(s) = \frac{Y(s)}{F(s)} = \frac{M_1s^2+K_1}{(99s^2+30000+K_1)(M_1s^2+K_1)-K_1^2} = \frac{M_1s^2+K_1}{99M_1s^4+(99K_1+30000M_1+K_1M_1)s^2+30000K_1}$$ The output to the ...
44 views

### Forced vibration single degree of freedom system

so for the Single Degree of freedom system, I obtained the equation in blue, where I think the equation below in black is missing the ‘m*a’ from F=ma? So I see that there is one ‘m*a’, but is that ...
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### Spring and damper in series, equation of motion

For the motion in fig 4.1 (a), please check the description of this system in the images above, everything should be there. I get it, assuming the positive direction is downward, the spring tension is ...
43 views

### frequency of oscillation of the disk

The mass m is suspended by a string from a disk circular homogeneous of mass mc and radius R, as illustrated in figure 24. The disk is restricted from rotating by a spring attached to it at a distance ...
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### "$\theta_A$" and "$J_A \theta_A$" in the opposite direction

The system represented in the figure is composed of two rigid assemblies articulated in two points and connected to several springs as indicated. Each beam segment weighs 2 kgf/m, and the 5 kgf weight ...
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### Positioning accelerometer on a cantilever beam

What is the appropriate position to place an accelerometer, along the length of a cantilever beam, for the follwing two cases: The beam is under sinusoidal excitation at the free end. The beam ...
99 views

### Dynamic equilibrium equations

The system represented in the figure consists of a 2 kg pulley to which two springs and a rigid square with 10 kg/m are connected, which in turn is articulated at point B (System is in the xz plane). ...
42 views

### Net force exerted by spring

I want to find the exact net force exerted by the spring between pt. P and C, when it is compressed till point P with some mass, m attached to it and released (assuming spring goes to pt. C after its ...
211 views

### Calculate Vibration Velocity and Acceleration from Triple Axis Accelerometer

Looking for very specific support developing a simple Python script to take the time series X,y,z tuple readings from a triple axis accelerometer and output a meaningful measure of vibration for ...
57 views

### Resonance of 4 cylinder engine

Let’s say I have a 4-Cylinder, in-line engine where all pistons start from the same point, Could I have more than speed where resonance occurs? I read on a book that systems have more than one natural ...
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### Total Kinetic Energy of a System with a Body Inside Another for Lagrange's Equation

Suppose a bus with mass $m_1$ moving horizontally with velocity $\dot{x}_1$, and a person with mass $m_2$ running with velocity $\dot{x}_2$ inside the vehicle. What is the total kinetic energy of the ...
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### Equations of Motion for the Multi Degree of Freedom (MDOF)

I was watching the video: Equations of Motion for the Multi Degree of Freedom (MDOF) Problem Using LaGrange's Equations from Good Vibrations with Freeball However, I didn't understand how to obtain ...
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### natural period of vibration for the system - positive and negative work

A 10kg block is suspended from a cable wrapped around a 5kg disk, as shown in the figure. If the spring has a stiffness constant of k=200N/m, determine the natural period of vibration for the system ...
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### Unbalanced forces on an Engine

so I have a 4 Cylinder inline engine configuration. How would I identify the speeds at which vibrations due to unbalanced forces are acting? I have data such as RPM and Force and Moments acting
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### Particular Solution of Multiple-Degree-of-Freedom Systems

I was going through some Vibration examples on how to solve multiple-degree-of-freedom systems and I have noticed that they usually assume a particular solution with just one trigonometric function (...
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### How can I find the right resonant frequency of a chassis?

Structures have infinite DOFs, so it possess infinite mode shapes. How can we find the right resonant frequency out of the infinite resonant frequencies so that we can save our structure? For example, ...
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### A problem from Damped free Vibrations

Problem: I can understand the problem physically that the block is pulled by some amount X so that its displacement at t=0 is X. It is then released from that position so that its velocity at t=0 is ...
1 vote
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### How to analyse results of vibration isolation test

I performed some tests with vibration isolators and have computed the PSD. The natural frequency of the isolators is 110 Hz in the axial direction. So my question is, should I expect to see noise ...
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### how to interpret plots in ISO 10816-8?

In ISO 10816-8 for reciprocating compressors, there are some plots that show the allowable RMS vs. frequency for every part of a compressor. However, in the text of the standard, it is mentioned that ...
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### Interpretation of results in a spring mass dashpot system subjected to harmonic excitation force

Consider a spring mass dashpot system subjected to a harmonic excitation force of $$F(t)=F_0 sin(\omega t)$$ The response of a system assuming sufficient time has been passed and the complementary ...
1 vote
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### Control System Response

How does one find the zeta value or the frequency of an over damped response curve. I am used to determining things by using the log-decrement equation. Does that apply here even though there is no ...
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### Force Transmitted to the support (Vibrations)

Consider the spring mass dashpot system shown below which is acted upon by a harmonic excitation force F(t). The reference is taken at the equilibrium position of the system when no F(t) was present. ...
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### What is the best time interval in condition monitoring programs for checking rolling bearings?

The time intervals between observing or measuring the vibration of rolling bearings in industrial plants are so important in condition monitoring programs. For instance, some experts measure the ...
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### Where does all the inherent vibrations in an internal combustion or jet engine come from?

I am trying to understand that why does a piston engine produce vibrations? What is the source of it and how will it cause the whole internal combustion engine to vibrate in response? Will jet engines ...
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### What frequency is the low frequency vibration of normal buildings from like elevator or ventilation motor? To avoid equipment resonance vibration

Recently I am building equipment. It is as large as two refrigerators with aluminum extrusion frame. Unfortunately, it has visible resonance vibration. After measuring I find on the floor there is a ...
285 views

### In vibration study, should the reference be necessarily the mean/equilibrium position?

When we determine the natural frequency of free vibration for a system, we start of by defining a reference from where displacements will be measured. I have usually seen in books, taking the ...
1 vote
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### Pre requisites for a course in vibration for a Mechanical Engineering Bachelors Degree [closed]

Can anyone please tell me what parts of differential equations, linear and partial I need to revise properly before I take a course in vibrations , in Dynamics, our course in vibrations mainly deals ...
81 views

### A question on resonance

This is to settle a debate. I was working on a scaffold next to a building, as the wind blew, the scaffolding would sway. As I stood there I was trying to maintain my stability, but my movements ...
1 vote
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### On rectangular section beam properties of plate stiffeners

I am trying to understand the expression of the vertical dynamic stiffness $K_T$ and the rotational dynamic stiffness $K_r$ which appears in this paper where they consider a semi-infinite plate ...
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### Does an ultrasonic horn increase displacement?

Reading the Ultrasonic Horn Wikipedia article, it states: An ultrasonic horn is a tapering metal bar commonly used for augmenting the oscillation displacement amplitude provided by an ultrasonic ...
1 vote
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### What is the possible reason for a huge discrepancy between measured vibration by vibration meter kit and a vibration transmitter?

I work in a pump station and I've noticed that when I measure the bearing vibration by a vibration meter, the measured value differs from what is shown on the computer monitor (2.5 mm/s measured ...
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### Adding tension to a model of a Timoshenko beam?

I am interested in modeling a Timoshenko beam: https://en.wikipedia.org/wiki/Timoshenko%E2%80%93Ehrenfest_beam_theory However, I would also like to add tension to the beam so that it can vibrate like ...
24 views

### Model for dynamic plate deformation

I would like to gather ideas to model the dynamic behaviour of a plate with variable thickness. The assumption are: Small deformations. The plate is all made of the same material with variable ...
94 views

### Why does my trimmer feels heavier when it is operating and its fully charged?

I have a Philips trimmer which when fully charged feels much heavier than when it is not charged. Also , the blades move much faster when it is fully charged I.e it’s weight , speed of blades kind of ...
1 vote
53 views

### Ride Comfort Estimation using Accelerometers

I've been trying to find established/novel methods for calculating ride comfort using accelerometers and recently I came across this paper which uses ISO 2631 standard to get an objective measure of ...
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### How do engineers reduce vibration of system with multiple known natural frequencies? How do they design the isolation system for specific frequencies?

I have a system that is pretty much a chamber that needs to sit on the ground. I measured the transmissibility of the chamber vs the ground (output/chamber acceleration over input/ground acceleration) ...
1 vote
65 views

### Forced vibration of beam

I was watching a video that derives the forced vibration response of a beam. The link to the video is https://www.youtube.com/watch?v=6VuLZDgRhZ4&list=PLMXj6GKKnHI6Lftj7CXr9WusMkXi5s9yH&index=...
59 views

### Wierd faulty gearbox FFT

I am working with a public dataset (mentioned in few papers) of vibration measurements of broken and healthy gearbox under various load. Most of the measured channels posses the same parameters no ...
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### Sign of torque in torsional vibration of a shaft

In the example problem below, how were the signs of the torques at x = 0 and x = L found? At x = 0, the direction of pulley rotation is unspecified but the direction is assumed to be positive. And at ...