# Questions tagged [vibration]

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

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### Can I use logarithmic decrement to get damping ratio when given data is acceleration?

Since I was going to get the damping ratio from time domain, the first thought was using logarithmic decrement method. But I'm not sure if I can use it when the given data is acceleration-time. Can I ...
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### Some questions at interpreting FRF from vibration test

Currently going through impact hammer test of cantilever beam(200mmx20mmx2mm) which is made of particulate composite(Epoxy/PZT/CB). Hammer sensitivity is 2.25mV/N and accelerometer sensitivity is ...
• 1
44 views

### Vibrating hollow sphere

I would like to make a hollow sphere that can vibrate like a tuning fork. It should go like this: Place the sphere on a table Strike the sphere with something like a spoon The sphere vibrates (...
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34 views

### How would you handle the rebalancing of a bearing cage?

I am a intern who was tasked with finding the correct amount to mill off (in an angle) of a bearing cage (basically an annulus with gaps in it to hold the balls or rollers) to bring it back into ...
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34 views

### Is there explicit expersion for the natural frequency of a cantilever timoshenko beam?

I am trying to find a closed form solution for the natural frequency of cantilever Timoshenko beam. In mechanical vibration (Rao, 5th edition) he outlined the details to include the Effects of Rotary ...
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### Finding the best fit between Ansys model results and measurd values to optimize the parameters

I have the final element model of an experimental rig respresenting a vibrating system. The time domain results from both are known. I need to reduce the error between the results/find the best fit ...
31 views

### How to Design System for Resonating Tuning Forks from Base

I have seen videos like this where two tuning forks with matched frequencies are attached to resonant chambers and the sound from one fork can be used to resonate the other fork. I am interested in ...
64 views

### Induce vibration on metal ball

Suppose that I have a hollow, metal ball that lies on a table. How do I induce a vibration on this ball? I want to be able to control the frequency, so it is a forced vibration (not natural vibration)....
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60 views

### Changing the relative equilibrium position for a 2-mass spring-mass system

I am trying to solve a double spring-mass system that is positioned vertically (I currently have the pendulum at an angle of 0 in my code below). I derived the system of ODE's required, and I get this ...
31 views

### Ansys Pedestrian-Induced Vibration on Bridge

I have a concrete girder box bridge that is 40 m long and 4 meters wide, and I would like to simulate the response of the bridge using Ansys random vibration for pedestrian traffic. What are ...
55 views

### How to balance an irregular shape on a motor shaft?

I have an irregular shaped object about 100g in weight and 3x3x3 cm in size that I'd like to mount on a shaft (eg of a small motor) and spin. The trick is, I'd like it to be pretty close to perfectly ...
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### what kind of Vibration Motor should I choose and how can I achieve my goal?

I'm building a vibration table for testing the durability of a metal rack, I want the vibration motor to create an even and average vertical displacement to the table, what kind of Vibration Motor ...
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64 views

### Topology optimization issue (or not an issue, which is the issue)

I am currently doing some work in topology optimization regarding optimizing for the dynamic compliance of a beam structure but I am running into some issues. Well actually I am not running into some ...
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1 vote
48 views

### Controlled oscillation of a piano string by electromagnetic, mechanical, or other means

What would be a good way to actively control the loudness of an acoustic piano note over time after the note has already been struck by the hammer, such as by actively changing the amplitude of a ...
51 views

### Standing desk sway stabilization

I have a standing desk that sways when I'm typing and it is in the standing position. I've read numerous things online about this and can't find any actionable information for stabilizing the desk. It ...
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### modal analysis of a wind turbine

I have to do a vibration mechanics project for university and I was thinking of doing the modal analysis of a wind turbine, only I don't know how to evaluate the results I get. With what I should ...
20 views

### How can I know the linearity/nonlinearity from the FRF result?

It's a FRF of neat PA 11 obtained by vibration test. (Mind that g is not a gram but the acceleration) Explanation says that for the excitation level of 5g, the FRF is strongly modified and the peak's ...
1 vote
68 views

### What are the unknown sources of vibration in this Rotax 914 propulsion system

(This might be a little out of score for SE.Engineering, so close if appropriate.) I have a drivetrain setup where I have been performing a vibration analysis. Below is a diagram of the system. There ...
• 223
40 views

### vibration "amplifier" structure to place an accelerometer

I want to catch very small vibrations with an accelerometer. Is there any structure that can amplify the vibrations, such as springs or something to place the accelerometer on? The accelerometer will ...
13 views

### Boundary condition of vibrating flange in ANSYS mechanical

I have a structure with both sides a having flange. The vibration comes to plant from one of the flanges. The structure has it's own fixed support on its bottom, bearing its weight. I assumed force is ...
1 vote
164 views

### Do sound waves caused by a vibrating machines correlate to the vibration waves of the machine itself?

I'm a computer engineer, so please excuse my lack of mechanical knowledge :). We have a machine that has large electrical motors causing massive amounts of vibrations, the machine also consists of ...
75 views

### Mechanism for fast vibration

What mechanisms can be used to apply fast vibration to an object? One way is this. What are some other ways to do it? I'm looking to go as fast as possible - 100s of Hz if possible. Thankyou
1 vote
76 views

### Effect of bracing on a music instrument top - is FEM modal analysis enough to predict this?

I'm currently building a music instrument (string instrument), and I am at the step where one applies certain braces to the soundboard. Since I actually don't know how the bracing will affect the ...
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1 vote
202 views

### Does Bending Stress Affect Natural Frequency?

I have been researching about the factors that affect natural frequencies, particularly about the effects of stresses. Most of what I have found only discusses compressive and tensile stresses though, ...
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### How can I measure RPM of an encased refrigerator compressor. I would like the resultant RPM reading as a variable DC output

I understand that there are very expensive meters that do this ; ex: Ono Sokki FT-7200 or FLuke, but I need a cheaper alternative.
37 views

### What methods can be used to stabilize a vibratory bowl used for orientation

I have a project where we are using a vibratory bowl to feed in parts to an assembler. The issue I am having is that the calibration sticker on the side is very out and a single line is very difficult ...
80 views

### Preliminary way to estimate damping quality factor (Q) from a SolidWorks FEM

I am analyzing the modal response of a structural FEM for a spacecraft structures course. I'm using Solidworks Simulation Premium. Need first mode to be above 40Hz and the damping Q-factor (quality ...
57 views

### How to measure the beat phenomenon in amplitude of vibration waveform?

I have time series of 3 signals, and I found the amplitude of vibration waveform would display the so-called beat phenomenon, which means the amplitude at different time is not always equal, and the ...
210 views

### How is the fundamental frequency of a large rotating body determined?

Okay, I understand that "large" is relative. I'm referring to the 60" diameter 5000 rpm counterrotating flywheels I've postulated in this question. When I was taking flying lessons in ...
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### Can you explain mathematical and mechanics formulation of equation in Junker 1969 paper on self-loosening of fastener by vibration?

Can you help me to understand how the first equation in the paper 'New Criteria for Self-Loosening of Fasteners Under Vibration' by GH Junker, 1969 is derived? I'm not able to understand the ...
59 views

### (Why) does the sound of propeller planes change with increasing distance?

I recently heard a propeller plane, and then very shortly after a jet like noise. After I did some probability calculations, I conjectured that probably these two events are timely correlated. I also ...
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### 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 ...
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### 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 ...
1 vote
297 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 ...
1 vote
313 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,...
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313 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 ...
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55 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 ...
111 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 ...
2k views

### 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 ...
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99 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 ...
99 views

### "$\theta_A$" 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 ...
217 views

### 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 ...
121 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). ...
158 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 ...
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1k 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 ...
420 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 ...
64 views

### 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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501 views

### 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 ...