vibration along a steel bar 4

[proddesign]

what is the best grade of steel for vibration transmitting? If there is a vibration at one end of a steel bar, we want that to travel the length of the bar and be reproducable. We know just about any material will do this but to have the best for the job wouldnt hurt. Higher or lower carbon content? does stainless do better or worse, does zinc plating help? etc...

I appreciate any info on this subject

Thank you,
Bryan

 

[prex]

Strange question: I suppose that a high elastic limit material would be the best, as the dissipation of energy should be lower. Zinc plating has nothing to do with this, as the elastic modulus is much lower than that of steels. A hardening surface treatment could possibly help, but I'm not sure.
My opinion is that the way the bar is held at ends is much more important in transmitting the elastic vibratory energy, unless you have a very very long bar.

prex

http://www.xcalcs.com

Online tools for structural design

 

[Maui]

Materials that are most effective at transmitting heat would also be appropriate for this application. You'll want to use aluminum. I would recommend using an alloy in as hard a condition as you can purchase locally.


Maui

 

[proddesign]

thank you for responding so quickly...i've put a little more thought into it since this morning.
The bar would be open on the ends and be held along the length of the bar by something with varying consistency such as soil...so the sound vibration would constantly be dampend as it travelled the length of the bar.

I am wondering if using a hollow pipe rather than a solid bar would increase the sound vibrations' distance due to the added ambient noise inside the tube. I guess i'll have to play with that to see.

Still learning

Thanks again,
Bryan

 

[scornaby]

You probably want to use a material with an infinite fatigue life. Aluminum may crack and break with time. An inexpensive low carbon steel may be your best bet, as long as you are not inducing much stress.

 

[EnglishMuffin]

There is a new material that has just been developed called liquidmetal. It's not steel, but it seems to have an extremely high coefficient of restitution. This suggests to me that it would be good for vibration transmission. See

http://www.liquidmetal.com.

On this site, they have a bouncing ball demo, the video portion of which appears to me to be faked. However, it might be of interest.

 

[pjhype]

Assuming that the vibration transmissibility is related to the speed of sound in the material, your should pick a material with a high elastic modulus and low density, since the speed of sound in a material is equal to the square root of the elastic modulus divided by the density. Steel will have a speed of about 5000 m/s. Aluminum will be slightly less. On the high end, carbon and beryllium fibers will give you about 12,000 m/s, however when you bind them with epoxy, the speed will be much lower. There are new materials called "buckytubes" that will give you a speed of about 22,000 m/s, however, these materials are still in development.

pj

 

[EnglishMuffin]

proddesign :If it was you who gave me the star, you might be interested in this thread : thread330-65326 which I started about liquidmetal. But whether there is really a correlation between coefficient of restitution and internal damping, or vibration transmission, I really don't know. It would be interesting to find out.

 

[proddesign]

Sorry EnglishMuffin,
It wasn't me, but i'd be more than happy to star it...
i'm still new to the site and wasnt sure of the proper etiquette

that liquidmetal is pretty interesting...not sure how cost efficient it is...yet
(always use the "yet"...DVD players were seen as not cost efficient either till 5 years later...still waiting on that thin panel big screen TV to get down to $200)

The actual use of what i'm looking for is a bar/tube (1 in. OD +/- ) that can withstand being driven into the ground with a sledge hammer (1-4 ft) and have optimal sound transmission in order to set a microphone on the bar and hear the sounds under the earth's surface. They make devices called probe bars that are steel but they arent designed for this specific application (acoustically). I was wondering if a certain material or grade would be best for this situation.

There has been a lot of great responses...high elasticity, hard grade of aluminum, low carbon steel.

I can see the users jerking on the bar trying to get it out of the ground when they are done...so something easily bendable wouldnt be too good.

The acoustic difference from one material to another (within a certain group) may not be noticable to the human ear but to be able to say its the best for the situation gives marketing another attack angle.

Thank you all, for your help on this subject,
Bryan

 

[EnglishMuffin]

Actually - I don't think it deserves a star - it was just a shot in the dark. But I'm not complaining !