For explicit dynamics smaller elements means smaller stable time steps. If the problem is quasi-static you could use mass scaling to increase the stable time step some. Fewer ties steps may help since there will be less steps for the hourglass displacements to accumulate.
Some items in my library on the subjects you mention are:
- Design by analysis of vessels: "Criteria of the ASME Boiler and Pressure Vessel Code for Design by Analysis in Sections III and VIII, Division 2", ASME, 1969
- FEA: "Concepts and Applications of Finite Element Analysis", Robert D. Cook...
I only have ASME Section III handy right now, but the definition it gives (NB-3213.10) is below.
"Cases arise in which a membrane stress produced by pressure or other mechanical loading and associated with a discontinuity would, if not limited, produce excessive distortion in the transfer of...
No, that is not ok. I've given a lot of hints but short of doing it for you (which I won't do), I can't provide much help by one or two sentence exchanges every couple days. It would be beneficial for you to find somebody local (in your office?) to teach you.
The constraints do not look right. The real pipe can grow radially. See the comments by corus in the other thread for some advice on constraints. The constraints do prevent rigid body motion (since the pipe didn't fly off the screen). Also, I'm guessing your temperature distribution is...
Assuming this is related to your thread Thermal Stress Analysis Constraints then you have already done the system level stress analysis with restrained free end expansion (in CAESAR II).
What criteria are you using to evaluated the acceptability of the stresses you calculate?
Yes. W = mg (as you show), or m = W/g = 11500 kN / 9.8 m/s^2 = 11500 kN * (1000 kg-m/s^2/1 kN) / 9.8 m/s^2 = 1.17e6 kg
If you are already working with weight a quick way to do the natural frequency calculation is omega=sqrt(k/m)=sqrt(k/(W/g))=sqrt(k*g/W)=sqrt(5e6 kN/m * 9.8 m/s^2 / 11500 kN) ~...
B31.1 does not specifically address stresses due to through wall gradients (but it isn't a bad idea to look at them). Part of my point was that determining the stresses is one thing, but then once you find them what is your acceptance criteria (what failure modes are you protecting against)?
I think you have the units wrong in both checks above. 1 N = 1 kg-m/s^2 or 1 kN = 1000 kg-m/s^2. You should probably also go through and double check that your units are consistent in the ANSYS model as well.
1) It would be hard for anyone to say if your calculated frequency in reasonable without have some idea of mass, stiffness, geometry, and other info about your model.
2) Certainly you can use combin14 to model a spring. Probably the more interesting thing is determining the appropriate spring...
The sum of all reactions still have to be the same to satisfy equilibrium, but the the loads on each member and the individual support reactions will vary based on stiffness of the members.
Start with something simple like two springs in parallel. Vary the stiffness of one of the springs and...
