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Summary: Mechanica contact analysis

Level 1

Summary: Mechanica contact analysis

Thanks for all your replies. After some trial and error I've learned a
few more things about Mechanica. Using contact analysis was a given for
our problem but options such as mesh refinement and multi-pass had
differing effects which could prove useful in some situations. Using mesh
refinement can increase the accuracy in the immediate area of the contact
and high stress gradients but where stress gradients aren't so steep a
normal run without mesh refinement seems to give acceptable results. Mesh
refinement takes much longer to run so if you're just looking for rough
numbers and general areas of high stress not using mesh refinement will
save time. Multi-pass also takes longer but once again depending on your
purpose you may get away with single-pass. I also found that using a
plotting grid of 6 or 8 gives a much smoother appearance in the output
although at the expense of time. I would say running with the default of
4 gives pretty good results but if a high resolution image is required
(say for a report) you may want to spend the extra time and use 6 or 8.
Plotting grid doesn't change the actual stress levels but it does change
the way the output looks on the screen. High stress gradients also look
better with a higher plotting grid number. Another thing that I learned
was that when doing contact analysis it is important to set the legend
properly to see all the stress areas that may affect the design. The
default legend gives you an indication of the top stress levels but tends
to wash out the lower level gradients by making them all one colour. By
lowering the maximum stress value shown in the legend you can get more
insight into the stress distribution. Lastly, using the "contour" option
when viewing results can point you to stress areas that you can't see
easily from a shaded image, even with cutting or capping surfaces. With
contour mode the model is transparent but allows you to see the stress iso
lines so you can more easily see inside the part and zero in on areas on

Anyway that's what I gleaned from this exercise. If anyone disagrees with
any of my statements please let me know.


Mark Dolata

CenterLine (Windsor) Ltd. - Automation Components Division


Re: Summary: Mechanica contact analysis

Very good explanation.

My only comments are related to the plotting grid value.

1) The run time should not be affected very much by changing the plotting grid number, just the results file sizes. I am surprised that this is the case for your model. And yes, your output resolution is absolutely better with a higher plotting grid value.

2) Also, the maximum stress reported in results can increase if you increase the plotting grid value. I have proven this to myself in the past with a test model.

Randy Speed
President and CEO
Speed Consulting, LLC
(972) 938-0490 ph (972) 937-2319 fax

Re: Summary: Mechanica contact analysis


Thanks for clarifying this. I was under the impression that the plotting
grid was just for visuals but I checked the documentation and you are
right it actually affects the results that are reported. In high gradient
areas you could probably miss some high values if you used too coarse a
plotting grid.

Thanks for the feedback.


----- Forwarded by Mark Dolata/CenterLine/CA on 02/02/2006 12:06 PM -----

"Randy Speed" <>
02/02/2006 11:50 AM
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