Empathy List Archives

NM

Nathan Millard

Tue, May 30, 2017 4:46 PM

Hi All,
In CREO Simulate (previously known as ProMechanica) I used the maximum
strain energy and maximum Von Mises stress as my convergence criteria. I
first look for a plateau in the strain energy value as the order of the
elements increases. Next I look for a plateau in the value of the stress as
the order of the elements increases. This method is what my instructor
taught us and has worked well for me in the past.

I'm now using ANSYS. I've created a simple model; a quarter of a rod with
symmetry constraints and an applied axial load at one end so as to mimic a
full rod that is fixed at one end and loaded at the opposite end; material
is steel. I am again using max strain energy and max Von Mises Stress as my
convergence criteria. But this time instead of increasing the order of the
elements as CREO is programmed to do I increase the number of elements in
the model. I then plot the number of elements vs the max strain energy and
max stress.

I've noticed that the max stress converges very quickly (I compared it to
hand calculations). However the strain energy does not converge. It instead
approaches zero.

Is this normal behavior in ANSYS? Is strain energy not the appropriate
convergence criteria to use? If it is not what is the appropriate criteria
to use?

Thanks.
Nathan Millard
M.S. Mechanical Engineering Student
California State University, San Jose

Hi All, In CREO Simulate (previously known as ProMechanica) I used the maximum strain energy and maximum Von Mises stress as my convergence criteria. I first look for a plateau in the strain energy value as the order of the elements increases. Next I look for a plateau in the value of the stress as the order of the elements increases. This method is what my instructor taught us and has worked well for me in the past. I'm now using ANSYS. I've created a simple model; a quarter of a rod with symmetry constraints and an applied axial load at one end so as to mimic a full rod that is fixed at one end and loaded at the opposite end; material is steel. I am again using max strain energy and max Von Mises Stress as my convergence criteria. But this time instead of increasing the order of the elements as CREO is programmed to do I increase the number of elements in the model. I then plot the number of elements vs the max strain energy and max stress. I've noticed that the max stress converges very quickly (I compared it to hand calculations). However the strain energy does not converge. It instead approaches zero. Is this normal behavior in ANSYS? Is strain energy not the appropriate convergence criteria to use? If it is not what is the appropriate criteria to use? Thanks. Nathan Millard M.S. Mechanical Engineering Student California State University, San Jose

BH

BenZ Hagege

Tue, May 30, 2017 4:54 PM

Hi Nathan,

Nice methodology with ProE :) Don't worry with ANSYS as it uses the L2-norm
of the residual vector for forces to tend to 0 + max disp. correction to
tend to 0 at the same time , by default. So it's equivalent to your
previously used methodology (convergence of disp/strain energy+
forces/stresses).

What variable did you use for "strain energy" in ANSYS ? Of course it
should NOT tend to 0...

Benjamin onthemystery HAGEGE, Eng. & Ph.D. Arts & Métiers
*Own Compagny : NABLA.Expertises
*Academic job 1 : Collaborator of french Minister of Research (for Research
Tax Credit)
*Academic job 2 : Associate prof. @ www.utc.fr / Dpt Mechanical Engineering

2017-05-30 18:46 GMT+02:00 Nathan Millard nathan.millard@sjsu.edu:

Hi All,
In CREO Simulate (previously known as ProMechanica) I used the maximum
strain energy and maximum Von Mises stress as my convergence criteria. I
first look for a plateau in the strain energy value as the order of the
elements increases. Next I look for a plateau in the value of the stress as
the order of the elements increases. This method is what my instructor
taught us and has worked well for me in the past.

I'm now using ANSYS. I've created a simple model; a quarter of a rod with
symmetry constraints and an applied axial load at one end so as to mimic a
full rod that is fixed at one end and loaded at the opposite end; material
is steel. I am again using max strain energy and max Von Mises Stress as my
convergence criteria. But this time instead of increasing the order of the
elements as CREO is programmed to do I increase the number of elements in
the model. I then plot the number of elements vs the max strain energy and
max stress.

I've noticed that the max stress converges very quickly (I compared it to
hand calculations). However the strain energy does not converge. It instead
approaches zero.

Is this normal behavior in ANSYS? Is strain energy not the appropriate
convergence criteria to use? If it is not what is the appropriate criteria
to use?

Thanks.
Nathan Millard
M.S. Mechanical Engineering Student
California State University, San Jose

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Hi Nathan, Nice methodology with ProE :) Don't worry with ANSYS as it uses the L2-norm of the residual vector for forces to tend to 0 + max disp. correction to tend to 0 at the same time , by default. So it's equivalent to your previously used methodology (convergence of disp/strain energy+ forces/stresses). What variable did you use for "strain energy" in ANSYS ? Of course it should NOT tend to 0... Benjamin onthemystery HAGEGE, Eng. & Ph.D. Arts & Métiers *Own Compagny : NABLA.Expertises *Academic job 1 : Collaborator of french Minister of Research (for Research Tax Credit) *Academic job 2 : Associate prof. @ www.utc.fr / Dpt Mechanical Engineering 2017-05-30 18:46 GMT+02:00 Nathan Millard <nathan.millard@sjsu.edu>: > Hi All, > In CREO Simulate (previously known as ProMechanica) I used the maximum > strain energy and maximum Von Mises stress as my convergence criteria. I > first look for a plateau in the strain energy value as the order of the > elements increases. Next I look for a plateau in the value of the stress as > the order of the elements increases. This method is what my instructor > taught us and has worked well for me in the past. > > I'm now using ANSYS. I've created a simple model; a quarter of a rod with > symmetry constraints and an applied axial load at one end so as to mimic a > full rod that is fixed at one end and loaded at the opposite end; material > is steel. I am again using max strain energy and max Von Mises Stress as my > convergence criteria. But this time instead of increasing the order of the > elements as CREO is programmed to do I increase the number of elements in > the model. I then plot the number of elements vs the max strain energy and > max stress. > > I've noticed that the max stress converges very quickly (I compared it to > hand calculations). However the strain energy does not converge. It instead > approaches zero. > > Is this normal behavior in ANSYS? Is strain energy not the appropriate > convergence criteria to use? If it is not what is the appropriate criteria > to use? > > Thanks. > Nathan Millard > M.S. Mechanical Engineering Student > California State University, San Jose > _______________________________________________ > Xansys-temp mailing list > Xansys-temp@xansystest.info > http://xansystest.info/mailman/listinfo/xansys-temp_xansystest.info > If you are receiving too many emails from XANSYS please consider changing > account settings to Digest mode which will send a single email per day. > > Please send administrative requests such as deletion from XANSYS to > xansys-mod@tynecomp.co.uk and not to the list >

BO

Buyukisik, Osman (GE Aviation, US)

Tue, May 30, 2017 4:57 PM

Hi Nathan,
I think you are looking at the strain energy density (sigma*epsilon), not the volume integral of it. Energy density may very well approach zero as you decrease the element size (volume), but the volume integral of it will not. I think :-)
Osman
GE Aviation
LEAP HPT Design

-----Original Message-----
From: Nathan Millard [mailto:nathan.millard@sjsu.edu]
Sent: Tuesday, May 30, 2017 12:46 PM
To: xansys-temp@xansystest.info
Subject: EXT: [Xansys] Should strain energy be used as convergence criteria in ANSYS?

Hi All,
In CREO Simulate (previously known as ProMechanica) I used the maximum strain energy and maximum Von Mises stress as my convergence criteria. I first look for a plateau in the strain energy value as the order of the elements increases. Next I look for a plateau in the value of the stress as the order of the elements increases. This method is what my instructor taught us and has worked well for me in the past.

I'm now using ANSYS. I've created a simple model; a quarter of a rod with symmetry constraints and an applied axial load at one end so as to mimic a full rod that is fixed at one end and loaded at the opposite end; material is steel. I am again using max strain energy and max Von Mises Stress as my convergence criteria. But this time instead of increasing the order of the elements as CREO is programmed to do I increase the number of elements in the model. I then plot the number of elements vs the max strain energy and max stress.

I've noticed that the max stress converges very quickly (I compared it to hand calculations). However the strain energy does not converge. It instead approaches zero.

Is this normal behavior in ANSYS? Is strain energy not the appropriate convergence criteria to use? If it is not what is the appropriate criteria to use?

Thanks.
Nathan Millard
M.S. Mechanical Engineering Student
California State University, San Jose

Xansys-temp mailing list
Xansys-temp@xansystest.info
http://xansystest.info/mailman/listinfo/xansys-temp_xansystest.info
If you are receiving too many emails from XANSYS please consider changing account settings to Digest mode which will send a single email per day.

Please send administrative requests such as deletion from XANSYS to xansys-mod@tynecomp.co.uk and not to the list

Hi Nathan, I think you are looking at the strain energy density (sigma*epsilon), not the volume integral of it. Energy density may very well approach zero as you decrease the element size (volume), but the volume integral of it will not. I think :-) Osman GE Aviation LEAP HPT Design -----Original Message----- From: Nathan Millard [mailto:nathan.millard@sjsu.edu] Sent: Tuesday, May 30, 2017 12:46 PM To: xansys-temp@xansystest.info Subject: EXT: [Xansys] Should strain energy be used as convergence criteria in ANSYS? Hi All, In CREO Simulate (previously known as ProMechanica) I used the maximum strain energy and maximum Von Mises stress as my convergence criteria. I first look for a plateau in the strain energy value as the order of the elements increases. Next I look for a plateau in the value of the stress as the order of the elements increases. This method is what my instructor taught us and has worked well for me in the past. I'm now using ANSYS. I've created a simple model; a quarter of a rod with symmetry constraints and an applied axial load at one end so as to mimic a full rod that is fixed at one end and loaded at the opposite end; material is steel. I am again using max strain energy and max Von Mises Stress as my convergence criteria. But this time instead of increasing the order of the elements as CREO is programmed to do I increase the number of elements in the model. I then plot the number of elements vs the max strain energy and max stress. I've noticed that the max stress converges very quickly (I compared it to hand calculations). However the strain energy does not converge. It instead approaches zero. Is this normal behavior in ANSYS? Is strain energy not the appropriate convergence criteria to use? If it is not what is the appropriate criteria to use? Thanks. Nathan Millard M.S. Mechanical Engineering Student California State University, San Jose _______________________________________________ Xansys-temp mailing list Xansys-temp@xansystest.info http://xansystest.info/mailman/listinfo/xansys-temp_xansystest.info If you are receiving too many emails from XANSYS please consider changing account settings to Digest mode which will send a single email per day. Please send administrative requests such as deletion from XANSYS to xansys-mod@tynecomp.co.uk and not to the list

NM

Nathan Millard

Tue, May 30, 2017 5:50 PM

In ANSYS Mechanical when you click on "Solution" in the project tree you
get a list of solutions drop down menus. In the Energy drop down menu you
can select strain energy. The result after running the analysis is a fringe
plot that shows the strain energy at each element.

On Tue, May 30, 2017 at 9:57 AM, Buyukisik, Osman (GE Aviation, US) <
osman.buyukisik@ge.com> wrote:

Hi Nathan,
I think you are looking at the strain energy density (sigma*epsilon), not
the volume integral of it. Energy density may very well approach zero as
you decrease the element size (volume), but the volume integral of it will
not. I think :-)
Osman
GE Aviation
LEAP HPT Design

-----Original Message-----
From: Nathan Millard [mailto:nathan.millard@sjsu.edu]
Sent: Tuesday, May 30, 2017 12:46 PM
To: xansys-temp@xansystest.info
Subject: EXT: [Xansys] Should strain energy be used as convergence
criteria in ANSYS?

Hi All,
In CREO Simulate (previously known as ProMechanica) I used the maximum
strain energy and maximum Von Mises stress as my convergence criteria. I
first look for a plateau in the strain energy value as the order of the
elements increases. Next I look for a plateau in the value of the stress as
the order of the elements increases. This method is what my instructor
taught us and has worked well for me in the past.

I'm now using ANSYS. I've created a simple model; a quarter of a rod with
symmetry constraints and an applied axial load at one end so as to mimic a
full rod that is fixed at one end and loaded at the opposite end; material
is steel. I am again using max strain energy and max Von Mises Stress as my
convergence criteria. But this time instead of increasing the order of the
elements as CREO is programmed to do I increase the number of elements in
the model. I then plot the number of elements vs the max strain energy and
max stress.

I've noticed that the max stress converges very quickly (I compared it to
hand calculations). However the strain energy does not converge. It instead
approaches zero.

Is this normal behavior in ANSYS? Is strain energy not the appropriate
convergence criteria to use? If it is not what is the appropriate criteria
to use?

Thanks.
Nathan Millard
M.S. Mechanical Engineering Student
California State University, San Jose

Xansys-temp mailing list
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xansys-mod@tynecomp.co.uk and not to the list

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If you are receiving too many emails from XANSYS please consider changing
account settings to Digest mode which will send a single email per day.

Please send administrative requests such as deletion from XANSYS to
xansys-mod@tynecomp.co.uk and not to the list

In ANSYS Mechanical when you click on "Solution" in the project tree you get a list of solutions drop down menus. In the Energy drop down menu you can select strain energy. The result after running the analysis is a fringe plot that shows the strain energy at each element. On Tue, May 30, 2017 at 9:57 AM, Buyukisik, Osman (GE Aviation, US) < osman.buyukisik@ge.com> wrote: > Hi Nathan, > I think you are looking at the strain energy density (sigma*epsilon), not > the volume integral of it. Energy density may very well approach zero as > you decrease the element size (volume), but the volume integral of it will > not. I think :-) > Osman > GE Aviation > LEAP HPT Design > > -----Original Message----- > From: Nathan Millard [mailto:nathan.millard@sjsu.edu] > Sent: Tuesday, May 30, 2017 12:46 PM > To: xansys-temp@xansystest.info > Subject: EXT: [Xansys] Should strain energy be used as convergence > criteria in ANSYS? > > Hi All, > In CREO Simulate (previously known as ProMechanica) I used the maximum > strain energy and maximum Von Mises stress as my convergence criteria. I > first look for a plateau in the strain energy value as the order of the > elements increases. Next I look for a plateau in the value of the stress as > the order of the elements increases. This method is what my instructor > taught us and has worked well for me in the past. > > I'm now using ANSYS. I've created a simple model; a quarter of a rod with > symmetry constraints and an applied axial load at one end so as to mimic a > full rod that is fixed at one end and loaded at the opposite end; material > is steel. I am again using max strain energy and max Von Mises Stress as my > convergence criteria. But this time instead of increasing the order of the > elements as CREO is programmed to do I increase the number of elements in > the model. I then plot the number of elements vs the max strain energy and > max stress. > > I've noticed that the max stress converges very quickly (I compared it to > hand calculations). However the strain energy does not converge. It instead > approaches zero. > > Is this normal behavior in ANSYS? Is strain energy not the appropriate > convergence criteria to use? If it is not what is the appropriate criteria > to use? > > Thanks. > Nathan Millard > M.S. Mechanical Engineering Student > California State University, San Jose > _______________________________________________ > Xansys-temp mailing list > Xansys-temp@xansystest.info > http://xansystest.info/mailman/listinfo/xansys-temp_xansystest.info > If you are receiving too many emails from XANSYS please consider changing > account settings to Digest mode which will send a single email per day. > > Please send administrative requests such as deletion from XANSYS to > xansys-mod@tynecomp.co.uk and not to the list > > _______________________________________________ > Xansys-temp mailing list > Xansys-temp@xansystest.info > http://xansystest.info/mailman/listinfo/xansys-temp_xansystest.info > If you are receiving too many emails from XANSYS please consider changing > account settings to Digest mode which will send a single email per day. > > Please send administrative requests such as deletion from XANSYS to > xansys-mod@tynecomp.co.uk and not to the list >

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Should strain energy be used as convergence criteria in ANSYS?