Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin vibrationem ("shaking, brandishing"). The oscillations may be periodic, such as the motion of a pendulum—or random, such as the movement of a tire on a gravel road.
Vibration can be desirable: for example, the motion of a tuning fork, the reed in a woodwind instrument or harmonica, a mobile phone, or the cone of a loudspeaker.
In many cases, however, vibration is undesirable, wasting energy and creating unwanted sound. For example, the vibrational motions of engines, electric motors, or any mechanical device in operation are typically unwanted. Such vibrations could be caused by imbalances in the rotating parts, uneven friction, or the meshing of gear teeth. Careful designs usually minimize unwanted vibrations.
The studies of sound and vibration are closely related. Sound, or pressure waves, are generated by vibrating structures (e.g. vocal cords); these pressure waves can also induce the vibration of structures (e.g. ear drum). Hence, attempts to reduce noise are often related to issues of vibration.
I designed a spring and mass system (damping unknown) that is vibrated by applying a sinusoidal force to the mass using an electrodynamic shaker.
The mass is estimated to be 100 Kg.
The spring is actually 4 springs, each with a k value of 63.55 N/mm, supporting a platform (one spring at each...
I posed this thought experiment elsewhere, so the tone may seem a bit odd. It's based on what I've been reading on physical chemistry, atmospheric radiation and thermal physics. Just wondering if my interpretation is on the money or if I've made any incorrect assumptions.
"Time for another...
Mods, I hope I'm not breaching any guidelines here, haven't had any responses in General Physicsand thought perhaps the question might be more at home here.
I understand that CO2 molecules absorb infrared at 2.7, 4.3 and 15 microns, this makes them become vibrationally excited (rocking...
I understand that CO2 molecules absorb infrared at 2.7, 4.3 and 15 microns, this makes them become vibrationally excited (rocking, stretching, bending, I don't know all the modes).
I have a few questions from this point:
1. When the CO2 molecule re-emits that energy is it obliged to do so...
1. A rigid uniform slender beam weighing 8kg is hinged at A and is in dynamic motion. A spring of stiffness 4.5kN/m and a damper giving a viscous resistance of 35Ns/m is connected at B. The beam carries a flywheel of mass 28kg at a distance of 0.9m from A. The beam, AB is 1.2m long, Find the...
Mechanical ad Electrical vibration EASY question please help?
In Boyce and Diprima textbook it says that:
mu'' + ku = 0 .
Then it says the general solution of this is:
u = Acos (w^2)t + B sin (w^2)t , where w^2 = k/m
It provides no explanation how it arrives at this. Where does...
Homework Statement
I am asked to provide an anti vibrational support mount for equipment mounted on turbo-prop aircraft. The equipment has a mass of 40kg.
the vibrational response of the equipment to the environmental disturbances will need ot satisfy a safety limit prescribed by the...
1. A mass attached to the lower end of a vertical spring causes the spring to extend 25mm to its equilibrium position. The mass is then displaced a further 20mm and released. A trace of the vibration and time measurements are taken. From these measurements it can be seen that the displacement...
Homework Statement
The solution to the Initial value problem, x''+2x'+5x=0, is the sum of the steady periodic solution x_sp and x_tr. Find both.
Homework Equations
The Attempt at a Solution
I already found x_sp ( the particular solution). It is (-44/533)cos(7t)+(14/533)sin(7t).
r^2+2r+5=0...
need a tutorial on how to model piezometric material in ansys.. i am working on a project related to piezometric control of vibration..please need it very urgently!
When we have vibration excitation then the radius of nucleus is define like:
R=R_0[1+\sum^{\infty}_{\lambda=0}\sum^{\lambda}_{\mu=-\lambda}\alpha_{\lambda\mu}Y^{\lambda}_{\mu}(\theta,\phi)]
where \alpha_{\lambda,\mu}=\alpha_{\lambda,-\mu} and \alpha_{\lambda,\mu}=\alpha_{\lambda,\mu}(t)...
Hi,
I am a bit confused about somethings.
I want to determine the mode shapes of a free-free beam.
I assume that I can use the following?
1. the Euler-Bernoulli theory
2. the generalised wave equation
3. modal analysis
With modal analysis I can use the eigenvalue problem to finally...
Hi..
I'm trying to do the damped vibration analysis of a cantilevered beam. Although i am choosing no damping in subdomain settings menu, it solves the problem as if the material is damped (the result is a damped vibration signal).
Is this is a bug or am i missing something?
Thanks in advance
Hello MechEs (or anybody else who'd care to reply)
I'm about to get a small, but fairly sensitive analytical scale recently (down to 0.01 mg) and now I'm trying to figure out a way to dampen ambient vibration from the room and its surroundings (people walking around, HVAC, etc.)
I've got a...
1.A 2-meter long wire vibrates with a frequency of 330 Hz when the tension is 500 N. What is the new frequency if the tension on the wire is doubled?
i have no idea how to solve this,, help..
Hi all,
I have a question, I am trying to do to measure the stress on human feet while standing on a vibrating platform. The platform was placed on top of a cam and the cam was driven by a motor. I know most of the parameter, i.e. frequency, speed, acceleration but how can i calculate the...
hi all..
How can i describe initial conditions or initial forces in comsol(like wave forms such as ramp or parabolic)? I couldn't find it in the manual.
in ansys, i do it in time steps(in solution options).(like t=0, F=10 t=0.001 F=0)
I tried to give initial displacements to the points but...
Homework Statement
The slender rod AB of weight W_{AB} is attached to two identical collars, each of weight W. The system lies in a horizontal plane and is in equilibrium in the position shown when the collar A is given a small displacement and released. Calculate and plot the period of...
Homework Statement
Determine the max and min values of x and their times from 0 to 2s
initial conditions X0 = 0, V0 = 1m/s
http://img266.imageshack.us/img266/2198/figure1.jpg
Homework Equations
Undamped force vibration:
m\ddot{x}+kx = F0sin\omegat
Damped force vibration:
x =...
1. SDOF Systems Governing Equation m(dx^2/dt^2) + c(dx/dt)+ kx = F(t)
how do i get this equation below?
Free Critically damped Vibration x(t) = e^(wt) [x(0)(1+wt) + (dx/dt)(0) t]
(dx/dt is x with 1 dash on top)
Homework Statement
A child on a playground swings through a total of 42 degrees. If the displacement is equal on each side of the equilibrium position, what is the amplitude of this vibration?
(Disregard frictional forces acting on the swing)
The Attempt at a Solution
I know amplitude is the...
Does anyone know of any really good resources on high turbulant flow/velocity induced vibration in piping systems (in particular this is a very high flow PSV off of a large vessel and they are concerned with dramatic pipe vibration when it relives) also it would be nice if the recommended...
an astronaut in space sits on a chair that vibrates horizontally at the end of a spring. the spring has a 1200-N/m spring constant, the amplitude of vibration is 0.50 m and the speed of the chair as it passes through equilibrium is 2.0 m/s.
also devise another method to determine the mass, you...
Hey, so I just ripped the two permanent magnets out of an old seagate hard drive, and have a breadboard for my electronics class to practice with logic chips, and figured id wrap some wire around one of the magnets and see what happens.
I got around 10 turns of the wire about the magnet, and...
I Have been studying a problem involving a two mass/spring system. I have been analysing the system and finding out the frequency at which the vibration of Mass 1 is absorbed by Mass 2 and spring 2. The problem can represent a quarter car system where Mass 1 is the unsprung mass (wheel...
Homework Statement
Known :
- Material : Tungsten
- Property : G7 - Drill, you can see the picture in here :
http://www.accuromm.com/drills.html"
- Other information you can find here :
1...
so u = -cos(t) + sqrt(3)sin(t)
so the Wo = 1, and R =2, but how do i find delta?
tan(del) = sqrt(3)/-1, but the answer has it as
u = 2cos(t-2pi/3)
i can't get the 2pi/3 no matter what i do...
thanks
if we have a machine is running at 6,000 rpm. It is vibrating at 1 mil Pk-Pk. Calculate the velocity & acceleration of the vibration in mm/s & mm/S2. Explain the calculation.
can anybody provide me the formulas?
Hi,
I have a simple question to ask: What is the Eigenfrequency mean in vibration? I am confused and can anyone here explain to me or provide me some useful link?
I am trying to use comsol to analyse the vibration frequency from a plate, which was mount on top of 4 camshafts. These...
Homework Statement
in this vibration system find ratio of (m/m1) so that (point A) would not move and will stay stationary.
point A distance from left end of spring is 0.25 of total length of spring.
all surfaces are frictionless.
the problem is in indie numbers:
The Attempt at a Solution...
Hi,
Can anyone recommend a text for Vibration. My university recommends Mechanical Vibrations by S.S Rao but it has received bad reviews. I am an undergraduate in my second year and prefer the sound of a book that makes this less complicated...?
Thanks
Will
Hi,
Suppose we have a fixed-fixed beam with a distributed force acted in between -on a part of the beam.
I have found out the fundamental mode of vibration i.e calculated the fundamental resonant frequency of the above case.
But there will be higher order mechanical modes too.. In case...
Hi.. I have a question about natural fvibration.
Every object has natural frequency and modes of vibration.
Let us consider a simple cantilever beam for our discussion.
and Let's say its first 4 modes of vibration are at 3, 6, 10 and 20 kHz respectively.
(I made up these frequency values)...
Hi All,
I need some basic info of He closed cycle cryos..(like working principle, etc)..
I have a compressor, which compress He gas and passed into a cryo's coldhead. So He gas expands in side the coldhead and cools the coldhead..then it again passes into compressor..so the cycle repeats..
I...
[b]1. When seven people whose average mass is 83 kg sit down in a car they find that the car drops down 0.87cm lower on its springs. Then they get out of the car and bounce it up and down. The acceleration of gravity os 9.8m/s^2.
What is the frequency of the car's vibration if its mass (empty)...
A string of length 0.29 m is fixed at both ends. The string is plucked and a standing wave is set up that is vibrating at its second harmonic. The traveling waves that make up the standing wave have a speed of 115 m/s. What is the frequency of vibration?
fn=n(v/2L)
I tried...
helo guys,i'm new here hope to gain knowledge from this forum.i currently doing a project about design of turbofan engine.now i have to do preliminary stress and vibration analysis for the turbine blade.i'm not very good at stress and vibration and have search the internet about it but couldn't...
Homework Statement
A parallel plate capacitor is used as a vibration sensor. The plates have an area of 100cm^2, the dieelectric is air, and the dist between the plates is given by
d(t)=1+.01 sin(200 t) mm
A constant voltage of 200 V is applied to the sensor. Determine the current...
Homework Statement
A vibration platform oscillates up and down with an amplitude of 10.4 cm at a controlled variable frequency. Suppose a small rock of unknown mass is placed on the platform. At what frequency will the rock just begin to leave the surface so that it starts to clatter...
oscillation question -- vibration topic
Book is asking me to prove that ξ = 1 corresponds with the smallest value of c such that no oscillation occurs.
Says let λ = -b (b is a positive number)
and that's all I'm given.
I'm not even sure I understand how you can tell there is no...
hello everyone. can u help me on my homework? here are the questions..
--What physical quantity in a vibration is altered when a speed of sound dies away?
--Would you expect the speed of sound in Singapore and Britain to be the same, if each place had the same temperature? Why?
thank u...
Hi,
Does anyone know how to calculate the vibration in a pipe with water flowing through it? I have no idea where to start or what formula to use.
Any help would be appreciated. Thanks.
Homework Statement
A tuning fork vibrating at 512 hertz falls from rest and accelerates at 9.81 m/s^2. How far below the point of release is the tuning fork when waves of frequency 485 Hz reach the release point? take the speed of sound in air to be 340 m/s. (don't forget it takes the sound...