Pro/MESH, Pro/FEM-POST
Ask the EXPERT

                              Andrew Bax

 

Enhancements to Pro/MESH and Pro/FEM-POST

Both Pro/MESH and Pro/FEM-POST were functionally enhanced with release 17. The primary additions to Pro/MESH are the abilities to set up modal analyses and create beam elements along an edge or curve without datum points. Enhancements to Pro/FEM-POST include the animation of structural or modal analysis results and the ability to create edge graphs of the solution results along multiple edges simultaneously. (Refer to the Pro/ENGINEER Release Notes for discussion of other enhancements.)


Hard points

QUESTION: What is the significance of hard points in Pro/MESH and when would I use them?

ANSWER: Hard points are datum points created in Part or Assembly Mode and later specified as a node at the location of the meshed solid model. Hard points can be used for a number of things. You can use them to tweak the mesher in order to get the mesh refinement that you desire in a particular location.

I have also seen hard points used to calculate stress levels for a particular location. For example, you may want to perform some fatigue calculations on shaft that is case hardened. You’ve probably observed a part that first shows fatigue cracks inside an oil lubrication hole that is below the case-hardened surface. In such a case you could place a datum point inside this lubrication hole to ensure that a node will be placed there by Pro/MESH.


Applying symmetry boundary conditions

QUESTION: I want to apply symmetry boundary conditions. Does the Along Surf option inside of Pro/MESH do this for me?

ANSWER: The Release 17 Pro/Mesh User’s Guide implies that using the Along Surf option will apply symmetrical boundary conditions. It does, but only for models meshed with parabolic tetrahedrons (in general, linear tetrahedrons should never be used). Along Surf only constrains the translational degree of freedom normal to the surface that you select.

For shell models (which have X, Y, and Z translational and X, Y, and Z rotational degrees of freedom), two other rotational degrees of freedom need to be constrained in addition to the translation degree of freedom that would be constrained with the Along Surf option. These rotational degrees of freedom would be around the other two axes that are not constrained translationally. For example, if the X direction is to be constrained in translation, the rotational direction about the Y and Z axes would need to be constrained for proper symmetrical boundary conditions on shell elements. For this reason, I always use the 6 Components option in Pro/MESH when applying symmetrical boundary conditions and explicitly identify which degrees of freedom I would like constrained.


Making regions within Pro/MESH

QUESTION: I occasionally have problems making regions. Sometimes creating a region works, while other times I get an error. Why would this occur?

ANSWER: Regions are a very important function within Pro/MESH. Regions allow you to apply loads as well as mesh controls and constraints on only a portion of a surface instead of the entire surface. They also allow you to split surfaces in order to create surface pairs. Unfortunately, there are some limitations in creating regions within Pro/MESH that are not documented in the Release 17 Pro/MESH user’s Guide. The limitations are the following:

  1. Regions cannot be created within Assembly Mode. This can be annoying at times as you must
  1. Regions cannot be created from datum curves or cosmetic features that were copied or mirrored another datum curve. This limitation is not always obvious. Pro/MESH won’t give you an error message when you try to do this, so it appears as though the region was created. the problem is that a region was created, but from the geometry of the original datum curve and not the copied one.
  2. Multiple regions cannot be created from a single operation. The most Pro/MESH can do in one operation is divide one surface into two . This limitation becomes problematic when you have multiple closed curves that were created as one feature. When you select the datum curve to use as the region’s boundaries, Pro/MESH will give a Partial load region aborted. Geometry could not be constructed error without further explanation. Essentially, Pro/MESH has tried to create many split surfaces within one operation. which it cannot do as of release 17.

Andrew Bax is senior analysis engineer for DRD Technology Corporation in Tulsa, Oklahoma. He can be reached at 918-743-3013 or abax@drd.com.