"Cave Fills"

[dumpsterDiver]

What happens to the Young's modulus during Work hardening?

Answers


Best Answer: Hardening changes the shape of the stress strain curve by increasing the elastic region and decreasing the plastic region. The slope in the elastic region (Young's modulus) remains the same in both cases. To generate a strain hardened stress-strain diagram you essentially draw a line parallel to the elastic region and to its right in order to truncate the graph. The ultimate stress in the diagram will stay the same meaning the tensile strength will not change.

Source(s):Stress–strain curve - Wikipedia, the free encyclopedia

 

[cool_hardware52]

What happens to the Young's modulus during Work hardening?

Answers


Best Answer: Hardening changes the shape of the stress strain curve by increasing the elastic region and decreasing the plastic region. The slope in the elastic region (Young's modulus) remains the same in both cases. To generate a strain hardened stress-strain diagram you essentially draw a line parallel to the elastic region and to its right in order to truncate the graph. The ultimate stress in the diagram will stay the same meaning the tensile strength will not change.

Source(s):Stress–strain curve - Wikipedia, the free encyclopedia

Exactly. *IF* cave fills are "work hardening" tanks, and I see no evidence that they are, the effect would be to make the tanks more elastic, not less.

Tobin

 

[Charles2]

What is the test pressure for a LP 2400 psi tank with a "+" rating?

What is 90% of that value?

Test pressure for a 3AA or 3AL tank is 5/3 of the 'service pressure'. In this case, the 'service pressure' is 2400 psi -therefore- 'test pressure' is 4000 psi.

"+" rating is a different issue entirely.

90% of 4000 psi is 3600 psi. There is nothing in the manufacturers' or the DOT's literature to suggest that 90% of test pressure is OK. It is merely my own 'red line'.

There is a part of the DOT specification for 3AL cylinders that requires the manufacturer to proof test three cylinders to either 100,000 cycles at the 'service pressure' or 10,000 cycles at the 'test pressure'. Also, three cylinders must be pressurized to failure and must not fail at less than 2.5 times the 'service pressure'. These tests, although not required for 3AA (I think), should give some comfort to those who occasionally find their tanks 'cave filled'.

 

[Kairoos]

What I would like to see is someone compare a 300 BAR European tank to the most similar (in dimensions) American tank. So looking at the weight of the steel, the thickness in different areas, composition, etc.

If our friends across the pond can fill tanks with the same composition and steel thickness to 4351psi I wouldn't be so concerned about "cave fills".

 

[kensuf]

Should have been around when Steamboat in Branford had chill fills. The vat was chilled to 40 degrees, and you would get big fill,but those tanks left in the sun would blow burst disks or extrude O-rings.

Ahh Dustin's old ice bath. I loved getting to table rock and having more gas in my tanks than when I started.

 

[cool_hardware52]

What I would like to see is someone compare a 300 BAR European tank to the most similar (in dimensions) American tank. So looking at the weight of the steel, the thickness in different areas, composition, etc.

If our friends across the pond can fill tanks with the same composition and steel thickness to 4351psi I wouldn't be so concerned about "cave fills".

It's well to remember that each "controlling authority" DOT, CT etc. will set it's own standards, design criteria and performance criteria. That will impact the materials, the heat treatment (temper) etc. Assuming that "Euro" cylinders are the same tanks as North American cylinders, but stamped with a higher working pressure is a mistake IMO.

Tobin

 

[cool_hardware52]

Test pressure for a 3AA or 3AL tank is 5/3 of the 'service pressure'. In this case, the 'service pressure' is 2400 psi -therefore- 'test pressure' is 4000 psi.

"+" rating is a different issue entirely.

Ok, but what is the test pressure used to maintain a "+" rating?

Tobin

 

[Kairoos]

It's well to remember that each "controlling authority" DOT, CT etc. will set it's own standards, design criteria and performance criteria. That will impact the materials, the heat treatment (temper) etc. Assuming that "Euro" cylinders are the same tanks as North American cylinders, but stamped with a higher working pressure is a mistake IMO.

Tobin

That is why I said someone should compare the weight, thickness, and composition. If the steel composition is exact, and the weight is the same, or very close, and the thickness is the same, or extremely similar, then it would be safe to say that these cave fills are not hurting the cylinders. If we find that the euro cylinders are thicker, and/or made of a different steel composition, well that certainly is something to add into this discussion.

 

[cool_hardware52]

That is why I said someone should compare the weight, thickness, and composition. If the steel composition is exact, and the weight is the same, or very close, and the thickness is the same, or extremely similar, then it would be safe to say that these cave fills are not hurting the cylinders. If we find that the euro cylinders are thicker, and/or made of a different steel composition, well that certainly is something to add into this discussion.

Not without understanding the design criteria, and performance standards. You could have two tanks with very similar weight, thickness etc. that were designed to satisfy different criteria. Are the cycles to failure the same? Is the retest protocol the same? etc.

Tobin

 

[CuzzA]

Are tank manufacturers really making different tank for the US and EU? I would think the best business model would be to make one size tank and change the stamp to satisfy the regulations for where ever they are going, rather than make two very similar tanks. Build one tank that will satisfy both governments and stamp appropriately.