Discussion:
Help needed-Warning on numerical singularity for a piezo device
Rahul Shukla
2007-11-03 06:14:19 UTC
Permalink
Hi all
I am doing simulation of piezoelectric device and facing the following
warning while trying to calculate the voltage from the input
displacement to the device.

***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING NODE
PIEZOT-1.1 D.O.F. 9 RATIO = 1.60624E+014

***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING NODE
PIEZOB-1.1 D.O.F. 9 RATIO = 1.0436E+014.

This warning message is consistent for both the piezos for same DoF 9.
Here I am not understanding the node no.

My first question is that
what is numerical singularity?
second,
How can I overcome the above warning?

I shall be obliged.
Thanks.

Best regards,
-Rahul.
cnjrq
2007-11-03 20:26:48 UTC
Permalink
hi all,

I think your model must be going through some rigid body motion. Try
sufficiently constraining the model. As ABAQUS tries to solve for stiffness
matrix, the model must have appropriate boundary conditions. If there is
rigid body motion, it will result in singular stiffness matrix. Thus no
solution will be obtained.

Regards,

JAWED QURESHI,
Leeds, UK
Post by Rahul Shukla
Hi all
I am doing simulation of piezoelectric device and facing the following
warning while trying to calculate the voltage from the input
displacement to the device.
***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING NODE
PIEZOT-1.1 D.O.F. 9 RATIO = 1.60624E+014
***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING NODE
PIEZOB-1.1 D.O.F. 9 RATIO = 1.0436E+014.
This warning message is consistent for both the piezos for same DoF 9.
Here I am not understanding the node no.
My first question is that
what is numerical singularity?
second,
How can I overcome the above warning?
I shall be obliged.
Thanks.
Best regards,
-Rahul.
--
View this message in context: http://www.nabble.com/Help-needed-Warning-on-numerical-singularity-for-a-piezo-device-tf4742522.html#a13566534
Sent from the Abaqus Users mailing list archive at Nabble.com.
Rahul Shukla
2007-11-06 04:09:24 UTC
Permalink
Hi Jawed
I agree what you say. I am sure from this side, this is not the issue.
I have found that this error may also come from the overconstrain in
the model if any. I have checked and removed all the possibilities I
know but still the warning exist.

If you see carefully here it is particularly asking for DOF 9 which is
concerned with piezo only. Most probably from electrical BC's point of
view. Let's see.
Thanks for the comment.
-Rahul.
Post by cnjrq
hi all,
I think your model must be going through some rigid body motion. Try
sufficiently constraining the model. As ABAQUS tries to solve for stiffness
matrix, the model must have appropriate boundary conditions. If there is
rigid body motion, it will result in singular stiffness matrix. Thus no
solution will be obtained.
Regards,
JAWED QURESHI,
Leeds, UK
Post by Rahul Shukla
Hi all
I am doing simulation of piezoelectric device and facing the following
warning while trying to calculate the voltage from the input
displacement to the device.
***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING NODE
PIEZOT-1.1 D.O.F. 9 RATIO = 1.60624E+014
***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING NODE
PIEZOB-1.1 D.O.F. 9 RATIO = 1.0436E+014.
This warning message is consistent for both the piezos for same DoF 9.
Here I am not understanding the node no.
My first question is that
what is numerical singularity?
second,
How can I overcome the above warning?
I shall be obliged.
Thanks.
Best regards,
-Rahul.
--
http://www.nabble.com/Help-needed-Warning-on-numerical-singularity-for-a-piezo-device-tf4742522.html#a13566534
Post by cnjrq
Sent from the Abaqus Users mailing list archive at Nabble.com.
bahadoor sabet
2007-11-03 16:47:40 UTC
Permalink
Hi,
NUMERICAL SINGULARITY means that there is an exact solution for the shape function you are using in the modeling (read more if FEM tutorials) . the problem is come from the way you defined your matrix .

my problem is when I assign 10 for surface charge, the strain in PZT is much bigger than I expected. tell me if you know abou it.

Thanks
Sabet


----- Original Message ----
From: Rahul Shukla <***@yahoo.com>
To: ***@yahoogroups.com
Sent: Saturday, November 3, 2007 2:14:19 PM
Subject: [ABAQUS] Help needed-Warning on numerical singularity for a piezo device













Hi all

I am doing simulation of piezoelectric device and facing the following

warning while trying to calculate the voltage from the input

displacement to the device.



***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING NODE

PIEZOT-1.1 D.O.F. 9 RATIO = 1.60624E+014



***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING NODE

PIEZOB-1.1 D.O.F. 9 RATIO = 1.0436E+014.



This warning message is consistent for both the piezos for same DoF 9.

Here I am not understanding the node no.



My first question is that

what is numerical singularity?

second,

How can I overcome the above warning?



I shall be obliged.

Thanks.



Best regards,

-Rahul.














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BenZ
2007-11-05 13:07:41 UTC
Permalink
Have you defined the zero potential somewhere ?
Have you defined anisotropic behavior with very low constants ??

benz
Post by Rahul Shukla
Hi all
I am doing simulation of piezoelectric device and facing the
following
Post by Rahul Shukla
warning while trying to calculate the voltage from the input
displacement to the device.
***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING NODE
PIEZOT-1.1 D.O.F. 9 RATIO = 1.60624E+014
***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING NODE
PIEZOB-1.1 D.O.F. 9 RATIO = 1.0436E+014.
This warning message is consistent for both the piezos for same DoF 9.
Here I am not understanding the node no.
My first question is that
what is numerical singularity?
second,
How can I overcome the above warning?
I shall be obliged.
Thanks.
Best regards,
-Rahul.
Rahul Shukla
2007-11-06 03:59:30 UTC
Permalink
Hi Benz
Many thanks for ur comments.
Yes I have defined zero potential on the desired places in various
steps as we normally do for electrical actuators and sensors.
Also, yes piezo constants are always very low in magnitude. Normally
of the order of 10e-9. This I have given as their properties.
Plz let me know if you would like to know any other info.
Waiting for your comments.

-Rahul.
Post by BenZ
Have you defined the zero potential somewhere ?
Have you defined anisotropic behavior with very low constants ??
benz
Post by Rahul Shukla
Hi all
I am doing simulation of piezoelectric device and facing the
following
Post by Rahul Shukla
warning while trying to calculate the voltage from the input
displacement to the device.
***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING
NODE
Post by Rahul Shukla
PIEZOT-1.1 D.O.F. 9 RATIO = 1.60624E+014
***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING
NODE
Post by Rahul Shukla
PIEZOB-1.1 D.O.F. 9 RATIO = 1.0436E+014.
This warning message is consistent for both the piezos for same
DoF 9.
Post by Rahul Shukla
Here I am not understanding the node no.
My first question is that
what is numerical singularity?
second,
How can I overcome the above warning?
I shall be obliged.
Thanks.
Best regards,
-Rahul.
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