A:Procision handles: uniform and non-uniform loading,
non-uniform loading is applied by defining control points (ie. 3 locations
on a surface with set values of LOAD/UNIT AREA) and the magnitude is interpolated
linearly in-between. In addition, it presently supports bearing loads around
holes and suspended loads.
A: Torsion (or moments) is applied either as a set of
forces (manual technique) or using a suspended load.
A: Suspended loads allow you to pick a point in space
and either a set of surfaces or a REGION to react the
load upon. For example, if moments are applied to the suspended point,
PROCISION calculates the force distribution that needs to be applied to
the surface.
A: You can use the PICKINFO option to display numerical
result values at any DATUM point or part location. The GRAPH function may
also be used to display result values along a user specified line or part
edge. These items can be output to an HTML file.
A: Choose command Print from File menu in the appropriate
application.
A: Yes, though contours are shown as color bands. Choose
Options -> color ramp -> number of colors in the color plot.
A: Vector plot results are not currently available.
A: First create the region; for a REGION-SURFACE, you
must form a closed loop of datum curves (even if the region joins up to
a surface edge). To select the region, use query select (to be safe), pick
inside the region, and use NEXT until the parent surface of the region
highlights. The region itself may or may not become visible during this
selection process, in fact it may appear when one of the component datum
curves becomes highlighted. Ignore any appearance of the region symbols.
ACCEPT the selection when the parent surface is highlighted. Once
you do that then the region should appear.
A: Yes, merge is fine, in fact some people like to use
merge even if it is a single part. Note also that different
material properties may be assigned to different subparts.
A: Traction Boundary Condition Error is an absolute measurement of error in the solution. PROCISION is unique in its ability to provide such an absolute (versus an estimated) measurement.
If you consider a part surface which is not loaded, then the tensile stress normal to the surface, right on the surface, must be zero. Similarly, the shear stresses tangent to the surface, right on the surface, must also be zero. On a loaded surface, the stress must equal the applied load. Therefore, we have a known or target value for these components of stress, all around the part boundary.
Traction stress components can also be calculated from
the computed stress solution (using standard stress transformation functions).
Thus, we have known values, and calculated values of these stresses. The
difference in these values is Error. This value of error can be displayed
as a color fringe plot, showing the user the quality of his solution.
A: Yes, and a free Verification Manual is available. You may download
the manual in postscript format from:
verif.ps . Alternatively,
contact your local Rand office for a hardcopy.
A: The final message that PROCISION gives is based upon
the examination of several parameters, primarily convergence of strain
energy within 1% and convergence of traction error within the user set
%. Note that convergence of traction error is based on the CHANGE in error
not the absolute value of error. Therefore it is possible for the solution
to be considered converged if increasing accuracy ceases to cause a reduction
in error. The best approach to determine solution quality is to examine
the convergence graphs of strain energy and vonmises stress, and especially
the traction error contour plots. The rule of thumb for examining the traction
error plots is that the displayed fringe plot should be all in the blues
(different shades of blue is okay), any greens, yellows, etcetera indicate
a non-ideal solution (of stresses) therefore the splitting scheme should
be ammended. This should be done regardless of PROCISION's final message.
A: Result not improving may be due to a singularity in
the model. The message is issued when increasing accuracy causes the error
to INCREASE. Examine the convergence and error results. Also look for "HOT
SPOTS" in the stress results this may suggest where the difficulty is.
If you have high traction stress in some areas that can guide you whether
more splits are required. (Typically solutions are pretty good when
this message is issued with 0 non converged, but you always want to check
using the tools included).
A: Yes, it is implemented.
A: Probably the best way to accomplish this is to save
the plot as a graphics format and use an image editor to add the text.
Please notice that some basic information, such as the displayed result type,
is already printed into the file if it is saved from Procision application.
A: Yes, choose Options -> background -> white.
A: Whenever possible, apply loads to surfaces or surface regions, as you want to avoid singularities (infinite stresses).
A load applied to a point or edge will give an infinite stress in theory (stress=force/area, so if area =0 ...).
PROCISION seems to be forgiving sometimes of line loads but they should be avoided.
Point or line constraints have the same problem, as well constraints of a region ( a surface or part of a surface with tangent neighboring surfaces) the edge of a region also may form a singularity.
One use for edge constraints is if you need to model a pinned constraint... I.E. a simply supported beam... If you make the end surfaces IMMOVABLE, that is welded (i.e. fixed-fixed beam)...
To Model a simply supported beam you could do the following:
1) (Approximate) Apply fixed constraints to the top or bottom edge of each end face.. Since the axial direction is now constrained only at a line, Moments cannot be reacted at the ends... the structure will pivot about the line. (In solids analysis there are no rotational degrees of freedom... I.e. to carry a moment you need to contrain a surface area). This method will give fair results, but to more correctly match beam theory:
2) Create Datum curve lines midway (or neutral axis position)
on each end-face (the line should correspond to the desired pin axis).
Create REGION-CURVEs from these lines, and constrain the regions as immovable.
This will give you the best representation.
A: If you run only to converge on displacement, then in general only displacement results are reliable. If you want stress results, you must converge on TRAC BC ERR.
Stresses are more difficult to calculate than displacements, basically displacements are converted to strains which are converted to stresses... You can see that Stress has error of Order 2 whereas displacement Order 1. (This is not only in PROCISION. All analysis software does the same thing.)
The main item always to examine to determine solution
quality is the Von Mises convergence graph, and the Stress - Trac BC ERR
contour plot.
A: Due to PROCISION's high speed and low resource usage, employing symmetry is not always the best approach. However, regular symmetry may be used in the same fashion as any solid element (FEM) model. Providing that geometry & LOADS are symmetric, you may cut the part along the mirror plane(s) and apply displacement constraints to the cut surface(s) normal to the surface to model symmetry.
Some analysis tools have Cyclic Symmetry and Axi-symmetric
modules; PROCISION has not implemented anything similar to date. Axi-symmetric
can be simulated by cutting a small pie-wedge and treating like normal
symmetry. For now cyclic symmetric problems should be modeled in their
entirety (of course regular symmetry can be used if applicable).
A: With some experience the best partitioning techniques will become more intuitive. The new user should concentrate on verifying the solutions accuracy using the convergence graphs, and especially the traction BC error fringe plot. The rule of thumb for these error plots is that the part should be shaded all in the blues (different shades of blue are okay, but greens, yellows, etcetera, indicate a non-ideal solution, and modification of the splitting scheme is required).
Section "Summary of Splitting Methodology" of the User's Guide should be used as a guideline for all analyses.
Some additional tips include:
1) When possible split parts normal
to the part surface.
2) Use the volume rule for your initial strategy, the
results from the first run will guide you on how to add more splits (if
necessary).
- Split non-coverged subparts which are at high accuracy
level
- Split the part in areas of high traction stress error
- Split the part so as to divide areas of high stress
from areas of low stress
- Do not be afraid to have lots of subparts