Elmer-FEM vs CalculiX - Simple Static Problem

Get the files at Google-Drive

1. In this lesson we will use geometry in .STEP file. There is a steel cantilever (E=29e6 psi) with 1500 lb applied to the tip as pressure directed along Y axis. See this first: http://youtu.be/FIKBtefm-es

2. Elmer uses Opencascade kernel to deal with STEP and when you will open the model, all dimensions will be scaled to millimeters although you use something different when saving. In this problem we will use Imperial units and scaling factor=0.03937 (1/25.4) to scale initial mesh coordinates to "inches". I am adding this line to the "Free text" at the "Simulation" section of .sif file

3. Default type of elements in Elmer is linear one, what is giving weird results even for good meshing.
It is why we need to add "element=p:2" to the "solver" section of .sif file. I am doing it manually in this sample. Also I am correcting Young's modulus to be counted in "psi" to be compatible with "inches". Other values and constants doesn't necessarily to be changed (for static problem).
In this example I use "Direct Solver" for linear solution and 1 iteration at "Nonlinear" section (steady state, linear). Specially for Elmer you need to follow log file when making solution to be sure that it is converged. Otherwise the results can be weird.

4. Elmer GUI is still in development and it saves all data in the xml file. When you corrected .sif file manually and save it, it will come back to previous state when you will load your project again from xml file. Sometimes it can be hard to figure out what is happen. Check .sif file every time before running solver, because solver uses just .sif , not xml. Learn Elmer Model Manual of actual version for command language and use it.
Elmer is good and correct scientific software but it requires some knowledge about console applications principles, to be successful with it.

No comments:

Post a Comment