Creo Elements/Direct Finite Element Analysis Frequently Asked Questions


This section answers the frequently asked questions concerning Creo Elements/Direct Finite Element Analysis.

Table of Contents

  1. Disc space for scratch directories to perform analyses
  2. Deactivate Finite Element Analysis
  3. Material databases
  4. I cannot see the mesh or any symbols related to Finite Element Analysis
  5. Select a study
  6. Delete a study
  7. Where are the studies and the LBCs in the drawlist
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  8. Mesh condition to get larger mesh size
  9. Constraints and Displacements for one geometrical entity
  10. Odd symbol positions on a face of a hole
  11. How can I get 'better' results
  12. How can I create my own materials database
Question: What is the suggested disc space for using Finite Element Analysis?
Answer: The space needed depends on the size of the part to be examined and especially on the number of degrees of freedom. That is - simply speaking - the number of nodes in the mesh.

Depending on this number the following disc space for static analyses are required:

no of nodes (non) Space -------------------------------- -------- non < 5 000 135 MB 5 000 <= non < 20 000 700 MB 20 000 <= non < 50 000 1500 MB 50 000 <= non < 100 000 2500 MB Or using a formula: non / 30 = disc space in Mega Byte

These are approximate values.


Question: Can Finite Element Analysis be deactivated?
Answer: Yes.

Question: Where can I find materials?
Answer: You can find various material databases in personality/DesignAdvisor/DA_matdb5.1.


Question: I can not see any symbols that I have created within Finite Element Analysis?
Answer: Use the show button in the viewport. On the bottom of the menu you will find various buttons related to Finite Element Analysis.

Question: How can I select a study?
Answer: Either using the Structure Browser and clicking on a study or by clicking on a LBC in the viewport which belongs to the study.

Question: How can I delete a study?
Answer: In the Study menu choose menu item 'delete' and select the studies to be deleted.

Question: Where are the LBCs in the Drawlist Browser?
Answer: They are not there. Studies and LBCs only appear in the Structure Browser.

Question: Why can I not define a larger mesh size than the default element size with a mesh condition?
Answer: The mesher itself does not have these capabilities.

Question: How can different constraints and displacements being applied to one geometrical entity? For example a displacement on an edge. While one face that contains the edge is constraint in a direction perpendicular to this displacement.
Answer: The MSC/NASTRAN solver can not handle two different coordinate systems on one node. Therefore a combination of constraints and displacements can be achieved by using the same local coordinate system for these LBCs.

Question: There are odd positions of symbols - especially forces - if applied to the inside of a cylindrical face. What is it?
Answer: Symbols are displyed so that they are on a face - not inside the object. Often they are displayed symmetrically and therefore might overlap themselves so that their meaning is not always clear. In these cases scaling the symbols and changing the length in the settings menu gives reasonable results.

Question: I am not sure wether the calculated values are correct. How can I make sure to have correct values?
Answer: a) The mesh quality is responsible for the quality of the result values. Refining the mesh increases the accuracy of the calculated results. This can be done by reducing the global mesh size which affects the whole part, or by using mesh conditions in certain areas. Mesh conditioning is absolutely necessary in areas of high stress concentrations.

Rules for controling the mesh quality:

Using quadratic h - elements:
  1. Reduce the global mesh size to obtain a regular looking mesh and to avoid elements which are too flat.
  2. Locally increase the number of elements in areas of high stress concentration. Mesh conditions on radii shound be at maximum half of the size of the radius (=> 3 elements spanning a 90 degree blend).
  3. All areas which are important for transmitting forces through the part should be at least 2 elements thick.
  4. Significant further refinements should lead to converging results.

Using p - elements:
  1. Reduce the global mesh size to obtain a regular looking mesh and to avoid elements which are too flat.
  2. Mesh conditions should only be used if necessary.
  3. With p - elements there is an error estimation as a dataset which can be displayed as a contour.

b) It is essential that the loads and boundary conditions are applied as realistic as possible.

Question: How can I create my own materials database?
Answer: test_materials.dat is an example database which you can use as a template. Please refer to DA_matdb.html