Short duration pressure impulses

[TMD]

Anyone have any experience with short duration pressure impulses and the effects they have on steel enclosures? I'm trying to make a "scientific" connection between strain and pressure pulses of less than 1 ms duration. Empirically, a steel enclosure can withstand, without permanent deformation, a much higher pressure if the duration is sufficiently short. Any references (books, papers, websites....) you can direct me to?

 

[JAE]

Is this for something like a blast force applied to structures? If so, I think there are some design manuals/criteria that I've seen from the US Air Force on blast mitigation and design. The Corps of Engineeers also deals with this. I'm sorry I can't offer anything specific other than that.

 

[TMD]

JAE: Thanks for that.

To answer yoru question, we are looking at gas explosions inside steel enclosures for explosion-proof (flameproof) certification.

 

[GregLocock]

You could use an acosutic excitation of a dynamic FE model. I'd add the fluid/structure coupling is quite difficult to get right, and that during an explosion the air itself is quite non linear, as typically the wavefront is moving at several M. So stick with the army guidelines!

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[MikeHalloran]

Are you sure you're not just looking at the low pass filter in your strain gage amplifier?



Mike Halloran
Pembroke Pines, FL, USA

 

[Ron]

Can you not use a relief valve with a flame arrestor on it?

As for the explosion pulse, a lot of the force is attenuated based on volume and rebound compression of the air after the initial pulse. Since your pulse period is so short, it can be approximated like the impact of a falling object that has a short impact duration....i.e., the force is significantly reduced by the length of time that the impact occurs.

 

[JStephen]

A gas explosion inside an enclosure is not necessarily the same as an explosion from, say, TNT. If I remember correctly, the knock in a car engine is when you have combustion propagating by shock wave rather than by a flame front, which is much smoother and slower.

The Welding Research Council did a study on storage tanks, specifically trying to determine if the tops of the tanks would blow off before the shell pulled loose from the bottom. You might look into that kind of work and see how the pressures were modeled there.