Well, I have since modeled it as a 3D Solid.
Pressure only cases match up with expected results from Lame equations for stresses in thick cylinders.
Temperature only cases match up with expected results as well from the equations found in the journal paper below.
Stresses were determined...
Sorry if that was not clear.
The total is including contributions for the temperature caused by the temperature gradient as well as the pressure load.
For example, the thermal contributions are around 75 ksi, while the pressure contributions are around 18 ksi. (total of around 93 ksi)
The...
Because I have modeled it as a 2D surface, I believe it is measuring it at the midplane (Ro-Ri)/2. I modeled it at the midplane because when you apply thickness to the material properties, it extends out in both directions (from what I have read).
I believe this is the source of error, because...
Ah. Well, after playing around with the coordinate system, I found that there were issues with the nodes RCID versus the ACID.
So, now I have achieved a similar functioning model to yours. I changed the geometry based on the Timoshenko equation during design.
At the Max P and Max T...
How odd. I reconfigured the RBE3 to have the 23 DOF for the three nodes, but there is still an error.
In the F06 file, the OLOAD RESULTANT matrices for each subcase has approximate zeroes everywhere.
However, there are two sections with error messages. One concerning the UM set. The other...
@nlgyro
So, the best I can understand this is to set up the center (20000) as a dependent node in 123456. Then add every point on the circumference to the independent set in 123. Then, to achieve a similar looking RBE3, add the three separate points that are 120deg apart to the dependent set in...
Thanks @Couch_King
If I knew everything, I wouldn't be here. Was fortunate enough to have some good folks that know this topic better than I do share their advice.
Very thankful to the people who share their knowledge here!
Interesting slideshow on RBEs. I am not sure I fully understand what it is saying though.
It looks like it is saying make 3 nodes the independent terms in an RBE for all 6 DOF, then, for every other node, make it the dependent term for those three independent terms in all 6 DOF.
That must not...
@nlgyro
That is fantastic! A few follow ups.
I was wondering how to consider Thermal Stress as a function of the geometry (Ro, Ri). That is how I found the original equation I used. I suppose it is not 100% necessary as the results you obtained and the theory line up quite nicely.
Can I ask...
This is supposed to be a generic component used in liquid rocket engines. The pressure and temperature data is taken from one engine in particular as an example of loading environment. These temperatures are given to be what temperature the inner wall experiences after heat transfer has been...
I added the 3-2-1 method of constraints on both of the ends. This works out to 6 constrained points.
The stresses vary through the length of the pipe like you would expect. However, the stresses are still not as high as I calculated.
Thanks SWComposites, I see that now as I have played with it...
Ro: 0.233 in
Ri: 0.172 in
When constructing the geometry, averaged these to get the midplane radius and applied thickness in material properties.
R: 0.2025 in
L: 0.9320 in
t: Ro-Ri = 0.0610 in
Meshed with QUAD4 elements (100 around the circle, 100 down the length)
Material Properties of...
Update:
Was going to try the plane strain, but tweaked a few more parameters and ran it with the 3-2-1 BC.
Stress induced by the pressure in the tangential direction (Hoop Stress) has a 0.05% error between theoretical versus FEA results. NICE!!!
Varying the temperature causes no change in the...
The analytical solution is about an order of magnitude higher than the FEA results. Which makes me think there is an error with inputs. Alas, the inputs were double-checked and were correct.
Currently, I have the reference temperature and the initial temperature both set at 70 deg F. So, I...
When you say symmetry, do you mean turning the 3D problem into a 2D one? Or just cutting the problem in half. I understand people take symmetrical geometries/loads and will sometimes cut them in half to reduce complexity of the problem.
Also, I have the pressures applied to the internal face of...
Update:
Tried this 3-2-1 method of constraining the model found in this forum that seemed to work for other people.
https://www.eng-tips.com/viewthread.cfm?qid=176220
https://www.eng-tips.com/viewthread.cfm?qid=178234
The stress found was uniform throughout and in a positive realistic value...
Yes, the mesh is indeed pretty fine. It is set up that way because of the number of data points needed from the output of this analysis.
Thanks for the suggestion. I will experiment with some other elements. I have just read that 2D Shell elements tend to be quite good at idealization for...
Sure thing! Attached just 2 snapshots of the model in wireframe and smooth shaded.
To elaborate, there are 100 elements down the length of the model and 100 elements that follow the circular path. So it ends up being 10,000 elements used.
I thought it was interesting that the von Mises stress...
Hoping to find someone that knows a bit more than I do on this matter.
I currently have a cylindrical geometry modeled and meshed with 2D Quad elements. This has been assigned Titanium material properties and a specified thickness. I have several load cases of combinations of internal pressure...
