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Hi Jay,
The design check is done
using von Miser stress
In the photos showing
the factor of safety distribution, the software takes the part or assembly to
the first material yield point, then stops. (weakest link) The red
area(s) show the area(s) on the part that yielded first. A part that is mostly
orange in a FOS display state, shows a pretty well balanced stress absorption by
the part. The chart on the right, in the FOS display state, shows the red
as being at the max FOS shown in the top left hand text.
The display state
showing Static displacement, I have set to show the real amount of
deformation that the part or assembly should have at the
time, one area or another of the part or assembly has yielded. I can
change the deformation scale for a bigger effect, to better understand what is
moving. But I've not done that in a while, since are parts tend to not give all
that much, and I'm going after a more realistic display. The red shows the
area the has moved the most under load. That doesn't necessarily mean that, the
red area yielded, just moved. In some cases the material around and/or
under the red area gave way. I see this sort of thing when I run FEA work on 2
to 1 heads. I can animate the displacement to show how the progression of
stress is applied as you dive deeper into the abyss or get munched on by
Kraken.
The scale for the Static
displacement charts you see, are URES: (Resultant Displacement), and it was set
to metric meters. That is the default display state, and since I've been looking
at FOS, static strain, and static stress mostly, I usually just leave it on that
setting. I can set it to show how far the part or assembly moved in a particular
axis, in some cases.
The blue bands you speak of on the upper and lower outer surface of the
acrylic cylinder, is matching what you see on my blown dome FEA work. In the
bonded on retaining ring area. That area is not under much stress. If you
look at how the middle is coming in, of which forces the bending part to bind on
the inside seating edges, against the seating material, it will all come clear.
The outer mating edges would actually lift off the mating surface just a
bit. This is also what we see on basic flat, and conical frustum windows,
as well as many domes, like mine.
Regards,
Brent
From: Jay K. Jeffries
Sent: Saturday, August 29, 2009 5:48 AM
Subject: RE: [PSUBS-MAILIST] FEA Work on Acrylic CT for
KLH-500 Brent You have an
enigma around the top and bottom of your cylinder, note the two thin blue
bands. Something like this usually points out that you might have an issue
with your model. Looking at the numbers along the right side of the image,
is this deflection? What are the units? R/Jay Resepectfully, Jay K.
Jeffries Andros
Is., Bahamas Save
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