Learning Forum

[Amirmkr]

Hi,

I have defined a 3d model of a 2 link manipulator with a revolute joint in the middle. The joint is MPC184 as specified in Solution Information. I want to find the node number of 2 nodes corresponding to MPC184. And find the "Nodal displacements included in the overall nodal solution."

2linkmpc184.wbpz

[Rohith Patchigolla]

As an Ansys Staff member, I am not allowed to download the attachments.
Could you please post some images describing the problem?
Best regards Rohith

[Amirmkr]

Hi Rohith I have a 2 link manipulator as below:
It has a joint in the middle and a fixed end.

As specified in https://www.mm.bme.hu/~gyebro/files/ans_help_v182/ans_elem/Hlp_E_MPC184.html , I want to obtain "Nodal displacements included in the overall nodal solution." In order for that I would like to have access to the nodes corresponding to MPC184, and using command APDL, achieve the rotational displacement.

[Amirmkr]

I think the following command is what I want:
esel,s,ename,,184
etable,rotate,nmisc,9
but it gives this error: Select one or more elements before pressing the ElementNumber button

[Rohith Patchigolla]

What exactly are you trying to find?
If its the displacements of nodes attached to the MPC184 element, you can use the below script.
esel,s,ename,,184
NSLE
prnsol,u,comp
allsel,all
NMISC9 corresponds to Z component of evolved e3 axis at Node i (https://ansyshelp.ansys.com/account/Secured?returnurl=/Views/Secured/corp/v211/en/ans_elem/Hlp_E_MPC184weld.html)
Please clarify.
Also, please paste the part of your solver output showing the error.
Best regards Rohith

[Amirmkr]

Thanks a lot Rohith I do not have any error anymore.
I can obtain the nodal displacement of the MPC184 revolute joint using the following command:
set,list
/output,2link,eig
*do,I,1,9
SET,,I
esel,s,ename,,184
NSLE
prnsol,dof,comp
allsel,all
*enddo
/output,term

And below is the output of one mode:

***** POST1 NODAL DEGREE OF FREEDOM LISTING *****

LOAD STEP=1SUBSTEP=9
FREQ=138.29LOAD CASE=0

THE FOLLOWING DEGREE OF FREEDOM RESULTS ARE IN THE GLOBAL COORDINATE SYSTEM

NODEUXUYUZROTXROTYROTZ
10100.64164E-004 0.19108E-003 0.36662E-001-0.54793E-002 0.28098E-001-0.15030E-003
10110.64164E-004 0.19108E-003 0.36662E-001-0.54793E-002 0.28098E-001-0.15030E-003

Although the joint is a revolute joint and it only rotates around local Z axis (Y in global coordinate as shown in the geometry figure), the output shows rotational displacement around other axes as well. In order to obtain the joint rotation around local Z, don't you think I need to obtain the rotation of E1I wrt E1J around local Z, if yes, would you please give me the command?

Thanks
Amir

[Amirmkr]

Hi In modal analysis, for MPC184 where Local z-axis is axis of revolute, I have written the code below to get the joint rotation around local z axis (e1i & e1j):
set,list
/output,2link_axes,eig
*do,I,1,9
SET,,I
esel,s,ename,,184
ETABLE,v1,NMISC,1
ETABLE,v2,NMISC,2
ETABLE,v3,NMISC,3
ETABLE,v4,NMISC,10
ETABLE,v5,NMISC,11
ETABLE,v7,NMISC,12

PRETAB,v1,v2,v3,v4,v5,v6,v7
*enddo
/output,term

it gives the following output for all the modes.


***** POST1 ELEMENT TABLE LISTING *****
STATCURRENTCURRENTCURRENTCURRENTCURRENTCURRENT
ELEMV1V2V3V4V5V7
2631.00000.69944E-014 0.42828E-0301.00000.69944E-014 0.42828E-030

Why is that constant, even though, the rotation of the joint is obvious in the picture?

[Rohith Patchigolla]

You can obtain the rotations in a local csys by simply using RSYS command.
Step 1: Create a local csys which has the same orientation as the Joint csys and give it an APDL name, say "mycsys"

Step 2: Add RSYS,mycsys command before PRNSOL
rsys,mycsys
esel,s,ename,,184
NSLE
prnsol,dof,comp
allsel,all
This should give you the rotations in local co-ordinate system. Hope this helps.
Best regards Rohith

[Amirmkr]

Hi How to assign APDL name to the coordinate system? I don't have the section.
Thanks

[Amirmkr]

Hi rgpatchi
APDL name for coordinate system is a new section that is from version 18.2 onwards, but our university has ANSYS 18.1. How can I assign an apdl name to the coordinate system in workbench without needing for an update?

[Rohith Patchigolla]

If you would like to use 18.1, instead of using APDL name for the coordinate system, In the details of the Coordinate system, you can switch the Definition -->"Coordinate System" --> Manual and Input a "Coordiante System ID" (say 21 --> need to be careful so that this number doesn't clash with any program generated csys IDs corresponding to other coordinate systems)


Then the Post Processing script changes to,
rsys,21
esel,s,ename,,184
NSLE
prnsol,dof,comp
allsel,all

Hope this helps.
Best regards Rohith