Have you defined plasticity in the material model for the beam? If you have
plasticity and then turn on the NlGeom on then plasticity will effect your
results as wel.
Br
Ali
-----Original Message-----
From: ***@yahoogroups.com [mailto:***@yahoogroups.com] On Behalf Of
Dave Lindeman
Sent: 11. november 2010 22:28
To: ***@yahoogroups.com
Subject: Re: [Abaqus] Straight beam under pure bending
The solution with NLGEOM=NO may agree with the theoretical values, but
with deformations that large, they'll both be wrong.
If you form an 80 mm long beam into a circle, then the radius of
curvature should be 12.73 mm. The maximum vertical displacement in the
beam should then be equal to the diameter of this circle -- 25.48 mm.
Your value (30.86) is approximately 20% larger than this. If you
increased your load from 0.1 N mm to your estimated value of 0.109 N mm,
then your values would start getting pretty close.
Regards,
Dave
-------------------------
Dave Lindeman
Lead Research Specialist
3M Company
3M Center 235-3F-08
St. Paul, MN 55144
651-733-6383
Post by Cheng-Kong WuDave,
Thank you for the quick respose.
The beam is 80 mm long, 8 mm wide and 0.048 mm thick. The applied moment is 0.1 N-mm.
When NLGEOM is off, the maximun vertical displacement is about 229 mm
compared to the theretical value 231 mm. The stress/strain results were
almost identical to the theretical value. The auto compute scale factor
is only about 0.03.
From some articles, if the beam was going to form a circle, the the
radius of curvature can be calculated by L = 2 * pi *rho, where L is the
length of the beam and rho is the radius of curvature. The bending
moment required can be calculated by M = EI/rho, and is about 0.109
N-mm. From this, I think my applied moment is close to this value, and
the deformed shape should looked similar to a circle. I turned NLGEOM on
and the maximum vertical displacement was 30.86 mm, and the stress and
strains were 5-10% off. Do you know any equation that can describe the
displacement field for large deformation?
Thank you!
Cheng-Kong
Subject: Re: [Abaqus] Straight beam under pure bending
Date: Thursday, November 11, 2010, 1:20 PM
(1) When plotting the deformed
shape with NLGEOM off, make sure the
displacement scale isn't being exaggerated (i.e., set the
deformation
scale to "1.0" in the "Common Options" dialog box.
(2) Theoretical beam solutions are based on small
deformation theory.
If the loads your are applying are large enough that
NLGEOM=YES is
required, then the theoretical solution will be very
inaccurate. Since
you describe your deformed shape as "almost in a circle",
then large
deformation effects are definitely important.
Regards,
Dave
-------------------------
Dave Lindeman
Lead Research Specialist
3M Company
3M Center 235-3F-08
St. Paul, MN 55144
651-733-6383
Post by Cheng-Kong WuDear all,
I have a beam bending problem that I cannot figure out
and need some advice.
Post by Cheng-Kong WuI tested two composite beams, one made of steel and
aluminum and under
Post by Cheng-Kong Wusmall deformation. The theoretical stress and strain
correlate very well
Post by Cheng-Kong Wuwith the ABAQUS results.
I tested another composite beam (Copper + Polyimide)
under a small
Post by Cheng-Kong Wumoment. One abaqus model without NLGEOM and one with
NLGEOM. The
Post by Cheng-Kong Wudeformed shape was quite different. The one with
NLGEOM resulted almost
Post by Cheng-Kong Wuin a circle but the one without have a very large
deformation. The
Post by Cheng-Kong Wudeisplacement, stress/strain results of the model
without NLGEOM
Post by Cheng-Kong Wucorrelate very well with the theoretical values (delta
= ML^2/2EI,
Post by Cheng-Kong Wuepsilon = y/rho). However, I think the one with NLGEOM
turned on is more
Post by Cheng-Kong Wureasonable, but the correlation was not good, why?
I searched the internet and my books for large
deformation theoretical
Post by Cheng-Kong Wuresults, but did not find what I want. Could anyone
provide some
Post by Cheng-Kong Wusuggestions?
Thank you for your time!
Cheng-Kong
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