# Mechanical vibration and shock control

1. Sep 8, 2008

### sri.karmarkar

Please could anyone help me on the topic "Controlling the vibration and shocks received by elctronic-mechanical components"?

2. Sep 8, 2008

### FredGarvin

Sure. Take a year or two of college classes and then learn more under a mentor in the field.

Can you be a bit more specific with your request?

3. Sep 8, 2008

### sri.karmarkar

I will start learning on the topic and will be enquiring where i get strucked. I will try to mention the topic more specific.

The first query from me
"What is natural frequency and how it can be obtained or estimated?".

4. Sep 8, 2008

### FredGarvin

The natural frequency is a vibration mode that is inherent to all structures. It is the frequency that the structure will vibrate at if the body is given a single impulse. In other words, it is the frequency that the body will vibrate at on its own, without an external forcing of any kind other than an initial "push."

Natural frequencies are calculated as well as measured through various techniques such as modal analysis.

5. Sep 8, 2008

### sri.karmarkar

Thanks fred.
Where can i get an example of calculating the natural frequency by modal analysis?

6. Sep 8, 2008

### rbeale98

try this
http://cp.literature.agilent.com/litweb/pdf/5954-7957E.pdf [Broken]

Last edited by a moderator: May 3, 2017
7. Sep 8, 2008

### sri.karmarkar

Thank you so much rb.. let me go through this.

8. Sep 8, 2008

### sri.karmarkar

How the materials fails when it is subjected to excitation?
what are the influencing factors?
Material fails is it because of lone factor "excitation frequncy reaches more than the natural frequency?".

9. Sep 9, 2008

### FredGarvin

The influencing factors are the basics of fatigue and strength of materials. If you excite a structure's natural frequency, it can take no time at all for that structure to reach its fatigue life. It gets amplified by the fact that the alternating stresses can be quite a bit higher than one would expect at any other operating point. Take a look at a basic S-N diagram to get an idea about this.

[quote="sri.karmarkar]Material fails is it because of lone factor "excitation frequncy reaches more than the natural frequency?". [/quote]
The point to be worried about is when the excitation frequency matches the natural frequency. If you are above or below it, you shouldn't need to worry about it. Even if you do reach the natural frequency, sometimes it's not a big deal due to the design or the system's ability to dmpen vibrations. Still if you are close to the natural frequency, you need to know what the result will be. You can't ignore it. This is why we do things like shaker and modal testing.