All Springer/NP/PCP Air Gun Discussion General > Engineering- Research & Development

Request for FEA Analysis

**rsterne**:

This is a request for anyone who has the ability to run an FEA Stress Model for a very simple cylindrical HPA reservoir....

The material is 2024-T3 Aluminum, Yield Strength 50,000 psi (345 MPa) and Tensile Strength 70,000 psi (483 MPa).... It is magically machined in a single piece from a 1.250" OD with a 1.000" ID, so the walls are 0.125" thick.... The flat ends are 0.250" thick.... One end has a square internal corner, the other has a 0.125" radius (the same as the wall thickness).... The Working Pressure is 300 Bar (4,350 psi) and the FEA is to be run at 900 Bar (13,050 psi)....

I know that several GTA members have the ability to do this, and I would appreciate it if one or more of you could please run this test for me.... I put a square inside on one end and a radius on the other, so that only one FEA run would be required.... Thanks in advance....

Bob

**WobblyHand**:

--- Quote from: rsterne on May 15, 2023, 03:16:33 PM ---This is a request for anyone who has the ability to run an FEA Stress Model for a very simple cylindrical HPA reservoir....

The material is 2024-T3 Aluminum, Yield Strength 50,000 psi (345 MPa) and Tensile Strength 70,000 psi (483 MPa).... It is magically machined in a single piece from a 1.250" OD with a 1.000" ID, so the walls are 0.125" thick.... The flat ends are 0.250" thick.... One end has a square internal corner, the other has a 0.125" radius (the same as the wall thickness).... The Working Pressure is 300 Bar (4,350 psi) and the FEA is to be run at 900 Bar (13,050 psi)....

I know that several GTA members have the ability to do this, and I would appreciate it if one or more of you could please run this test for me.... I put a square inside on one end and a radius on the other, so that only one FEA run would be required.... Thanks in advance....

Bob

--- End quote ---

Not to be a joker, but I think you could do this. You have FreeCAD and the FEM workbench. If you need help, I'd be glad to help you get going.

This is a nice test case, since it gets rid of the threads. 1/8" walls at 900 bar! I think one has to do a nonlinear simulation for this. Do you know of a place to find the stress vs strain for 2024T3 all the way out to fracture? I found the MIL-HBK-5J, which has curves for this for 2024T3, but they have two curves, one for longitudinal L and one for LT, do you know which curve is more appropriate?

When I simulated the "other tube" with 3.5mm walls, the simulator had convergence problems at 75 MPa (750 bars). At 70 MPa, the simulator converged.

I can make a model and do a linear sim, that one will be easy. For a nonlinear sim, could use some guidance...

**rsterne**:

I had a brief look, and decided it was beyond me at present, as I am still having problems constraining simple drawings.... If you can do this, it would be much appreciated.... The calculator I use, compliments of Lloyd Sikes, tells me the safety margins for the Hoop Strength are 2.5:1 to Yield and 3.5:1 using Tensile, at 300 bar.... It will do threaded or pinned (thick) end plugs, but not machined, and has no ability to add an internal radius.... The 2X wall thickness for the ends is a guess, if the stress in the middle (where it should be the highest) is greater than the hoop stress, they will need to be thicker (eg. 3X wall thickness = 0.375")....

While we're talking units, remember that 900 bar is "only" 90 MPa.... ;)

Bob

**WobblyHand**:

--- Quote from: rsterne on May 15, 2023, 04:20:13 PM ---I had a brief look, and decided it was beyond me at present, as I am still having problems constraining simple drawings.... If you can do this, it would be much appreciated.... The calculator I use, compliments of Lloyd Sikes, tells me the safety margins for the Hoop Strength are 2.5:1 to Yield and 3.5:1 using Tensile, at 300 bar.... It will do threaded or pinned (thick) end plugs, but not machined, and has no ability to add an internal radius.... The 2X wall thickness for the ends is a guess, if the stress in the middle (where it should be the highest) is greater than the hoop stress, they will need to be thicker (eg. 3X wall thickness = 0.375")....

Bob

--- End quote ---

Honestly, I think this is still a bit beyond me, but I have stubbornly kept plodding ahead. I don't know if you want to follow along or not, but here is the quick model I made of 1/4 of the cylinder. You may want to see how I did it. It's really just a 1/4 circle sketch, with lines to close the area, with the correct radius, then padded to length of 5.5". Then I made a sketch of the inside, using the symmetry. So the height is equal to the ID/2, and the length is 5.5-2x0.25 = 5". Then I added a constraint preserving fillet, and set the radius to 1/8". Once the sketch was constrained. I used the grooving tool, and revolved the sketch about the correct axis. My model is converted to metric, because when I was learning the tool, all the videos were metric. So all the imperial dimensions are metric in my model. This is what a 1/4 of your magically machined model looks like. Let's see if I can attach the model. It's small. I will change the extension to zip. Just change it back to FCStd.

**rsterne**:

You had me at "L" vs "LT", so I had to look it up.... The Longitudinal (L) direction is the direction the material is rolled or extruded in.... The Long Transverse (LT) direction is across the width of the plate (and I would assume around the circumference of a tube).... The Short Transverse (ST) direction is across the thickness of the plate (radially, across the wall of a tube?).... It the part is made in such a way you cannot tell the direction (eg. a round rod), then they just use "T" for Transverse.... Here is a chart on 2024-T3 showing the stress/strain relationships at different temperature.... I would only use the room temperature data....

https://icme.hpc.msstate.edu/mediawiki/index.php/Aluminum_2024-T3_Stress-Strain_and_Fatigue_Life_Data.html

Bob

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