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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:
Regions cannot be created within Assembly Mode.
This can be annoying at times as you must
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. 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.
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