Hi,

Guest

SK

Shiraz Khan [KHSH]

Tue, Jan 16, 2024 5:44 AM

Hi Xansers,

I am trying to find the weld stresses (weld shear and weld tension) using the forces output in 3 -directions (Fx, Fy and Fz) using FSUM/PRNLD command in Ansys post-processing with APDL.

The mesh (SHELL281, 8 noded quadratic elements) is uniform in size (=10mm) across the model and the weld is simulated using "CPINTF" command in Ansys. So, two set of nodes of the model where there is a weld are connected through couplings (one by one in a loop).

During postprocessing, I am selecting one node set from a weld (couplings between two set of nodes) and after each node selection, I write the forces Fx, Fy and Fz in a text file. I know the spacing between nodes so for each node I get Fx, Fy and Fz and I calculate the resultant force causing shear (two directions) and I do a SRSS of forces Fx, Fy and Fz (square root of sum of squares) - which gives shear force per unit element length (distance between two nodes) using the former and unit force (SRSS) per unit element length using the latter.

I then pick a size of weld and calculate throat, then dividing this shear force per unit length of element by the throat which gives me the shear stress and same for the unit stress (SRSS of Fx Fy and Fz per unit element length per throat). Then compare these values with allowable as min.[0.4Sy (base material),0.3Su] (outlined in AWS D1.1 table 2.3)

Problem is that I have a mid-side node and it connects two elements whereas the corner nodes connects 4 elements. And when I calculate the weld stress using a full penetration weld (size equals to plate thickness) the weld fails. There is high force on one of the midside nodes. I do not understand why it happens and what can I do to avoid this high force. If I exclude that node, then I need a less size of weld (15mm plate thk will require 8mm groove weld) and all is hunky-dory.

Shall I mesh with linear elements and see the forces so that I only have corner nodes to get the Fx, Fy and Fz for these nodes?

FYI, the coupling or cpintf command generates coupling between midside nodes also (in WB) which I can see in Ansys Classic if I save the db and rst file in WB and then open the same in Ansys Classic.

Best regards,

Shiraz Khan

Senior Engineer

Topsoe

Hi Xansers,
I am trying to find the weld stresses (weld shear and weld tension) using the forces output in 3 -directions (Fx, Fy and Fz) using FSUM/PRNLD command in Ansys post-processing with APDL.
The mesh (SHELL281, 8 noded quadratic elements) is uniform in size (=10mm) across the model and the weld is simulated using "CPINTF" command in Ansys. So, two set of nodes of the model where there is a weld are connected through couplings (one by one in a loop).
During postprocessing, I am selecting one node set from a weld (couplings between two set of nodes) and after each node selection, I write the forces Fx, Fy and Fz in a text file. I know the spacing between nodes so for each node I get Fx, Fy and Fz and I calculate the resultant force causing shear (two directions) and I do a SRSS of forces Fx, Fy and Fz (square root of sum of squares) - which gives shear force per unit element length (distance between two nodes) using the former and unit force (SRSS) per unit element length using the latter.
I then pick a size of weld and calculate throat, then dividing this shear force per unit length of element by the throat which gives me the shear stress and same for the unit stress (SRSS of Fx Fy and Fz per unit element length per throat). Then compare these values with allowable as min.[0.4Sy (base material),0.3Su] (outlined in AWS D1.1 table 2.3)
Problem is that I have a mid-side node and it connects two elements whereas the corner nodes connects 4 elements. And when I calculate the weld stress using a full penetration weld (size equals to plate thickness) the weld fails. There is high force on one of the midside nodes. I do not understand why it happens and what can I do to avoid this high force. If I exclude that node, then I need a less size of weld (15mm plate thk will require 8mm groove weld) and all is hunky-dory.
Shall I mesh with linear elements and see the forces so that I only have corner nodes to get the Fx, Fy and Fz for these nodes?
FYI, the coupling or cpintf command generates coupling between midside nodes also (in WB) which I can see in Ansys Classic if I save the db and rst file in WB and then open the same in Ansys Classic.
Best regards,
Shiraz Khan
Senior Engineer
Topsoe

PS

Parameshwarayya S Mathapati

Tue, Jan 16, 2024 6:13 AM

There is option to select only edge nodes

check help manual will get

Use fir selecting edge nodes

NSEL,,EDGE something like this

Regards

Paramesh

On Tue, 16 Jan, 2024, 11:16 am Shiraz Khan [KHSH] via Xansys, <

xansys-temp@list.xansys.org> wrote:

Hi Xansers,

I am trying to find the weld stresses (weld shear and weld tension) using

the forces output in 3 -directions (Fx, Fy and Fz) using FSUM/PRNLD command

in Ansys post-processing with APDL.

The mesh (SHELL281, 8 noded quadratic elements) is uniform in size (=10mm)

across the model and the weld is simulated using "CPINTF" command in Ansys.

So, two set of nodes of the model where there is a weld are connected

through couplings (one by one in a loop).

During postprocessing, I am selecting one node set from a weld (couplings

between two set of nodes) and after each node selection, I write the forces

Fx, Fy and Fz in a text file. I know the spacing between nodes so for each

node I get Fx, Fy and Fz and I calculate the resultant force causing shear

(two directions) and I do a SRSS of forces Fx, Fy and Fz (square root of

sum of squares) - which gives shear force per unit element length (distance

between two nodes) using the former and unit force (SRSS) per unit element

length using the latter.

I then pick a size of weld and calculate throat, then dividing this shear

force per unit length of element by the throat which gives me the shear

stress and same for the unit stress (SRSS of Fx Fy and Fz per unit element

length per throat). Then compare these values with allowable as min.[0.4Sy

(base material),0.3Su] (outlined in AWS D1.1 table 2.3)

Problem is that I have a mid-side node and it connects two elements

whereas the corner nodes connects 4 elements. And when I calculate the weld

stress using a full penetration weld (size equals to plate thickness) the

weld fails. There is high force on one of the midside nodes. I do not

understand why it happens and what can I do to avoid this high force. If I

exclude that node, then I need a less size of weld (15mm plate thk will

require 8mm groove weld) and all is hunky-dory.

Shall I mesh with linear elements and see the forces so that I only have

corner nodes to get the Fx, Fy and Fz for these nodes?

FYI, the coupling or cpintf command generates coupling between midside

nodes also (in WB) which I can see in Ansys Classic if I save the db and

rst file in WB and then open the same in Ansys Classic.

Best regards,

Shiraz Khan

Senior Engineer

Topsoe

Xansys mailing list -- xansys-temp@list.xansys.org

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There is option to select only edge nodes
check help manual will get
Use fir selecting edge nodes
NSEL,,EDGE something like this
Regards
Paramesh
On Tue, 16 Jan, 2024, 11:16 am Shiraz Khan [KHSH] via Xansys, <
xansys-temp@list.xansys.org> wrote:
> Hi Xansers,
>
> I am trying to find the weld stresses (weld shear and weld tension) using
> the forces output in 3 -directions (Fx, Fy and Fz) using FSUM/PRNLD command
> in Ansys post-processing with APDL.
>
> The mesh (SHELL281, 8 noded quadratic elements) is uniform in size (=10mm)
> across the model and the weld is simulated using "CPINTF" command in Ansys.
> So, two set of nodes of the model where there is a weld are connected
> through couplings (one by one in a loop).
>
> During postprocessing, I am selecting one node set from a weld (couplings
> between two set of nodes) and after each node selection, I write the forces
> Fx, Fy and Fz in a text file. I know the spacing between nodes so for each
> node I get Fx, Fy and Fz and I calculate the resultant force causing shear
> (two directions) and I do a SRSS of forces Fx, Fy and Fz (square root of
> sum of squares) - which gives shear force per unit element length (distance
> between two nodes) using the former and unit force (SRSS) per unit element
> length using the latter.
>
> I then pick a size of weld and calculate throat, then dividing this shear
> force per unit length of element by the throat which gives me the shear
> stress and same for the unit stress (SRSS of Fx Fy and Fz per unit element
> length per throat). Then compare these values with allowable as min.[0.4Sy
> (base material),0.3Su] (outlined in AWS D1.1 table 2.3)
>
> Problem is that I have a mid-side node and it connects two elements
> whereas the corner nodes connects 4 elements. And when I calculate the weld
> stress using a full penetration weld (size equals to plate thickness) the
> weld fails. There is high force on one of the midside nodes. I do not
> understand why it happens and what can I do to avoid this high force. If I
> exclude that node, then I need a less size of weld (15mm plate thk will
> require 8mm groove weld) and all is hunky-dory.
>
> Shall I mesh with linear elements and see the forces so that I only have
> corner nodes to get the Fx, Fy and Fz for these nodes?
>
> FYI, the coupling or cpintf command generates coupling between midside
> nodes also (in WB) which I can see in Ansys Classic if I save the db and
> rst file in WB and then open the same in Ansys Classic.
>
> Best regards,
> Shiraz Khan
> Senior Engineer
> Topsoe
> _______________________________________________
> Xansys mailing list -- xansys-temp@list.xansys.org
> To unsubscribe send an email to xansys-temp-leave@list.xansys.org
> 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
>

NH

Nelson Ho

Tue, Jan 16, 2024 6:16 AM

Hi Shiraz,

With srss after recombination the nodal forces are not written to the file.

Consequently, it may give a wrong result.

Try using presol,f which takes into account the forces at the nodes at the

weld for each element at the interface. Forces are written to element db.

Thanks,

Nelson

On Mon, Jan 15, 2024 at 9:46 PM Shiraz Khan [KHSH] via Xansys <

xansys-temp@list.xansys.org> wrote:

Hi Xansers,

I am trying to find the weld stresses (weld shear and weld tension) using

the forces output in 3 -directions (Fx, Fy and Fz) using FSUM/PRNLD command

in Ansys post-processing with APDL.

The mesh (SHELL281, 8 noded quadratic elements) is uniform in size (=10mm)

across the model and the weld is simulated using "CPINTF" command in Ansys.

So, two set of nodes of the model where there is a weld are connected

through couplings (one by one in a loop).

During postprocessing, I am selecting one node set from a weld (couplings

between two set of nodes) and after each node selection, I write the forces

Fx, Fy and Fz in a text file. I know the spacing between nodes so for each

node I get Fx, Fy and Fz and I calculate the resultant force causing shear

(two directions) and I do a SRSS of forces Fx, Fy and Fz (square root of

sum of squares) - which gives shear force per unit element length (distance

between two nodes) using the former and unit force (SRSS) per unit element

length using the latter.

I then pick a size of weld and calculate throat, then dividing this shear

force per unit length of element by the throat which gives me the shear

stress and same for the unit stress (SRSS of Fx Fy and Fz per unit element

length per throat). Then compare these values with allowable as min.[0.4Sy

(base material),0.3Su] (outlined in AWS D1.1 table 2.3)

Problem is that I have a mid-side node and it connects two elements

whereas the corner nodes connects 4 elements. And when I calculate the weld

stress using a full penetration weld (size equals to plate thickness) the

weld fails. There is high force on one of the midside nodes. I do not

understand why it happens and what can I do to avoid this high force. If I

exclude that node, then I need a less size of weld (15mm plate thk will

require 8mm groove weld) and all is hunky-dory.

Shall I mesh with linear elements and see the forces so that I only have

corner nodes to get the Fx, Fy and Fz for these nodes?

FYI, the coupling or cpintf command generates coupling between midside

nodes also (in WB) which I can see in Ansys Classic if I save the db and

rst file in WB and then open the same in Ansys Classic.

Best regards,

Shiraz Khan

Senior Engineer

Topsoe

Xansys mailing list -- xansys-temp@list.xansys.org

To unsubscribe send an email to xansys-temp-leave@list.xansys.org

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 Shiraz,
With srss after recombination the nodal forces are not written to the file.
Consequently, it may give a wrong result.
Try using presol,f which takes into account the forces at the nodes at the
weld for each element at the interface. Forces are written to element db.
Thanks,
Nelson
On Mon, Jan 15, 2024 at 9:46 PM Shiraz Khan [KHSH] via Xansys <
xansys-temp@list.xansys.org> wrote:
> Hi Xansers,
>
> I am trying to find the weld stresses (weld shear and weld tension) using
> the forces output in 3 -directions (Fx, Fy and Fz) using FSUM/PRNLD command
> in Ansys post-processing with APDL.
>
> The mesh (SHELL281, 8 noded quadratic elements) is uniform in size (=10mm)
> across the model and the weld is simulated using "CPINTF" command in Ansys.
> So, two set of nodes of the model where there is a weld are connected
> through couplings (one by one in a loop).
>
> During postprocessing, I am selecting one node set from a weld (couplings
> between two set of nodes) and after each node selection, I write the forces
> Fx, Fy and Fz in a text file. I know the spacing between nodes so for each
> node I get Fx, Fy and Fz and I calculate the resultant force causing shear
> (two directions) and I do a SRSS of forces Fx, Fy and Fz (square root of
> sum of squares) - which gives shear force per unit element length (distance
> between two nodes) using the former and unit force (SRSS) per unit element
> length using the latter.
>
> I then pick a size of weld and calculate throat, then dividing this shear
> force per unit length of element by the throat which gives me the shear
> stress and same for the unit stress (SRSS of Fx Fy and Fz per unit element
> length per throat). Then compare these values with allowable as min.[0.4Sy
> (base material),0.3Su] (outlined in AWS D1.1 table 2.3)
>
> Problem is that I have a mid-side node and it connects two elements
> whereas the corner nodes connects 4 elements. And when I calculate the weld
> stress using a full penetration weld (size equals to plate thickness) the
> weld fails. There is high force on one of the midside nodes. I do not
> understand why it happens and what can I do to avoid this high force. If I
> exclude that node, then I need a less size of weld (15mm plate thk will
> require 8mm groove weld) and all is hunky-dory.
>
> Shall I mesh with linear elements and see the forces so that I only have
> corner nodes to get the Fx, Fy and Fz for these nodes?
>
> FYI, the coupling or cpintf command generates coupling between midside
> nodes also (in WB) which I can see in Ansys Classic if I save the db and
> rst file in WB and then open the same in Ansys Classic.
>
> Best regards,
> Shiraz Khan
> Senior Engineer
> Topsoe
> _______________________________________________
> Xansys mailing list -- xansys-temp@list.xansys.org
> To unsubscribe send an email to xansys-temp-leave@list.xansys.org
> 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
>

R

rickfischer51@sbcglobal.net

Tue, Jan 16, 2024 9:52 PM

Its not clear to me if you are doing the following, but I think its necessary to get good results. First, you need to select only elements on one part. Then select only nodes on that part that are on the weld. Next, perform an FSUM,RSYS. this should give you accurate weld reactions. Second, it does not appear that you are considering moments in the weld group. You will get these from the FSUM command, but to be accurate, you must place a local coordinate system at the centroid of the weld group, get the global coordinates of the origin of that csys (*get,xx,cdsy,actsys,loc,x, etc) and set that location as the summation point (spoint,,xx,yy,zz). Hope this helps.

Its not clear to me if you are doing the following, but I think its necessary to get good results. First, you need to select only elements on one part. Then select only nodes on that part that are on the weld. Next, perform an FSUM,RSYS. this should give you accurate weld reactions. Second, it does not appear that you are considering moments in the weld group. You will get these from the FSUM command, but to be accurate, you must place a local coordinate system at the centroid of the weld group, get the global coordinates of the origin of that csys (\*get,xx,cdsy,actsys,loc,x, etc) and set that location as the summation point (spoint,,xx,yy,zz). Hope this helps.

MV

Mitch Voehl

Wed, Jan 17, 2024 8:23 AM

Shiraz,

Rick Fischer brought up some important points. Be sure to consider his suggestions.

Also, be aware that quadratic elements have differing stiffness at the corner nodes vs the midside nodes. This is due to the quadratic functions used for displacement interpolation within the element. As a consequence, interpreting the nodal forces (and reaction forces) for quadratic elements can be somewhat complicated. I suspect this is why you are seeing higher forces on the midside nodes relative to the adjacent corner nodes.

Read the theory manual for SHELL281, as well as the section explaining quadratic elements and their shape functions. Then, create a very simple problem involving only a couple elements, connected via coupling, with a simple straight forward load(s), and review the nodal forces so you can understand how these elements work.

--

Mitch Voehl

CEO and Engineering Consultant

Summit Analysis, Inc.

78748 410th Ave

Lakefield, MN 56150

Specializing in the use of ANSYS (R) finite element analysis software

On 01/15/2024 11:44 PM CST Shiraz Khan [KHSH] via Xansys xansys-temp@list.xansys.org wrote:

Hi Xansers,

Best regards,

Shiraz Khan

Senior Engineer

Topsoe

Xansys mailing list -- xansys-temp@list.xansys.org

To unsubscribe send an email to xansys-temp-leave@list.xansys.org

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

Shiraz,
Rick Fischer brought up some important points. Be sure to consider his suggestions.
Also, be aware that quadratic elements have differing stiffness at the corner nodes vs the midside nodes. This is due to the quadratic functions used for displacement interpolation within the element. As a consequence, interpreting the nodal forces (and reaction forces) for quadratic elements can be somewhat complicated. I suspect this is why you are seeing higher forces on the midside nodes relative to the adjacent corner nodes.
Read the theory manual for SHELL281, as well as the section explaining quadratic elements and their shape functions. Then, create a very simple problem involving only a couple elements, connected via coupling, with a simple straight forward load(s), and review the nodal forces so you can understand how these elements work.
--
Mitch Voehl
CEO and Engineering Consultant
Summit Analysis, Inc.
78748 410th Ave
Lakefield, MN 56150
Specializing in the use of ANSYS (R) finite element analysis software
> On 01/15/2024 11:44 PM CST Shiraz Khan [KHSH] via Xansys <xansys-temp@list.xansys.org> wrote:
>
>
> Hi Xansers,
>
> I am trying to find the weld stresses (weld shear and weld tension) using the forces output in 3 -directions (Fx, Fy and Fz) using FSUM/PRNLD command in Ansys post-processing with APDL.
>
> The mesh (SHELL281, 8 noded quadratic elements) is uniform in size (=10mm) across the model and the weld is simulated using "CPINTF" command in Ansys. So, two set of nodes of the model where there is a weld are connected through couplings (one by one in a loop).
>
> During postprocessing, I am selecting one node set from a weld (couplings between two set of nodes) and after each node selection, I write the forces Fx, Fy and Fz in a text file. I know the spacing between nodes so for each node I get Fx, Fy and Fz and I calculate the resultant force causing shear (two directions) and I do a SRSS of forces Fx, Fy and Fz (square root of sum of squares) - which gives shear force per unit element length (distance between two nodes) using the former and unit force (SRSS) per unit element length using the latter.
>
> I then pick a size of weld and calculate throat, then dividing this shear force per unit length of element by the throat which gives me the shear stress and same for the unit stress (SRSS of Fx Fy and Fz per unit element length per throat). Then compare these values with allowable as min.[0.4Sy (base material),0.3Su] (outlined in AWS D1.1 table 2.3)
>
> Problem is that I have a mid-side node and it connects two elements whereas the corner nodes connects 4 elements. And when I calculate the weld stress using a full penetration weld (size equals to plate thickness) the weld fails. There is high force on one of the midside nodes. I do not understand why it happens and what can I do to avoid this high force. If I exclude that node, then I need a less size of weld (15mm plate thk will require 8mm groove weld) and all is hunky-dory.
>
> Shall I mesh with linear elements and see the forces so that I only have corner nodes to get the Fx, Fy and Fz for these nodes?
>
> FYI, the coupling or cpintf command generates coupling between midside nodes also (in WB) which I can see in Ansys Classic if I save the db and rst file in WB and then open the same in Ansys Classic.
>
> Best regards,
> Shiraz Khan
> Senior Engineer
> Topsoe
> _______________________________________________
> Xansys mailing list -- xansys-temp@list.xansys.org
> To unsubscribe send an email to xansys-temp-leave@list.xansys.org
> 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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