Wall thickness of reactor 2

[9one]

We need to build an open ended CS reactor vessel to test a new rock breaking cartridge we have designed. The vessel is to simulate a 1/2" dia by 12" deep hole drilled in a rock. Since rocks are far from uniform we believe this approach will allow us to get a sense of the pressure develobed within our reactor which will allow us to compare several different designs to determine best design for the cartridge. This reaction is quite short, 20 ms. max so we would outfit the reactor with strain gauges and sample at a relatively high rate, ie: 5 to 10k s/s. Pressures developed could easily be 100,000 psi and we would want a safety factor of 4 to feel safe with the system (all components are within a blast shield for added safety). This vessel must withstand many repetitions of this test but not be so thick so as not be able to give us good data from our strain gauges. Any help or suggestions will be sincerely appreciated. Thanks in advance.

 

[metengr]

9one;
If you want some advice, conduct field testing of various cartridge designs on actual rock out in the desert southwest instead of trying to simulate this with a steel vessel.

 

[JoeTank]

Sounds more like a cannon barrel design rather than a pressure vessel.

Joe Tank

 

[9one]

Thanks for your response "meteng"".
Our problem with breaking rocks to test designs is that we have only a subjective sence of the effects of our cartridges on a given rock. Since no 2 rocks require the same energy to break we have no accurate way of comparing differences between cartridge designs. Initiating the cartridges in a vessel and measuring the resultant pressures seemed to us as a way around this problem which would allow us to tune the design for optimum results.

 

[9one]

Thanks JoeTank.
You are correct in the form of this "Reactor Vessel" as being cannon like. The difference is that the cartridge contains a self stemming feature which is designed to contain most of the energy within the "vessel" upon initiation This is important to maximize the efficiency of the propellant to gain the max. breaking power when used in rock. We fully expect the stemming to fail at some point however the idea is to maximize the pressure inside the "vessel" before failure. We can alter the materials and geometry of the "stemming components" to tune the system for the highest yield.

 

[prex]

I have no experience of such a calculation, but this should be a problem to be solved based on an energy balance.
The energy absorbed per unit volume in the deformation of the cylindrical portion of your cannon is easily calculated as 9[σ]²/16E (the factor 9/16 accounts for the longitudinal stress, that's half the circumferential one).
As the stress may be considered constant over the cylinder and assuming you can go up to yield stress, this would equal some 0.3 J/cm³ for a common steel (to be reduced if you want a factor of safety).
Now if you can determine with sufficient accuracy the mechanical energy released by the explosion, you'll determine the thickness from the volume of steel required to absorb that energy.
This procedure should be safe as not all the energy of the explosion will go into the cylinder: a non negligible portion is likely absorbed by this self stemming feature (and possibly some will go out before the stem closes?).

prex

http://www.xcalcs.com

: Online tools for structural design

http://www.megamag.it

: Magnetic brakes for fun rides

http://www.levitans.com

: Air bearing pads

 

[arto]

Would you want to use a test setup to measure "Copper units of Pressure" {CUP)~psi or "Lead units of Pressure" like they do on ammo cartridges? I believe Hatcher's Notebook has some of the details

 

[deanc]

http://scitation.aip.org/getabs/ser...00123000001000135000001&idtype=cvips&gifs=yes

Also do a Google on "gunbarrel fatigue stress"

http://www.globalsecurity.org/military/systems/munitions/explosives-compositions.htm

This site has all kinds of interesting data.