How can I change the connector types in different steps 1

[ardalansv]

Hello,
I want to change the behavior of the connector in abaqus after a step. First I want to translate a box toward another one using translator connector then I want to change its behavior at the second step to MPC pin. I have read that I can do it using field variables but I do not know how can I use it. Please feel free for any sugestions.
Thanks.
Ardalan

 

[akabarten]

Hi,

I want to translate a box toward another one using translator connector

1st connector degree of freedom is free and controlled with user motion, other 5 DOFs are blocked.

change its behavior at the second step to MPC pin

MPC pin blocks all translational DOFs (1, 2, 3) and free rotational DOFs (4, 5, 6)

I think connector definition below will make the trick.
In first step DOF 1 is controlled by *CONNECTOR MOTION and move by 10[mm] and DOFs 2, 3, 4, 5, 6 use high stiffness to constrain move.
In second step DOF 1 is still controlled by *CONNECTOR MOTION but does not move since is always in the same position, DOF 2, 3 are still locked due to high stiffness and DOF 4, 5, 6 are unlock due to very low stiffness.

**------------------------------------------------------------------------------
**
*NODE
 1, 0.0, 0.0, 0.0
 2, 1.0, 0.0, 0.0
**
*ELEMENT, TYPE=CONN3D2, ELSET=connector-SECT
 1, 1, 2
**
*ORIENTATION, NAME=Connector-ORI, SYSTEM=RECTANGULAR
 ... lines to define connector coord. system ...
**
*CONNECTOR SECTION, ELSET=connector-SECT, BEHAVIOR=connector-BEH
 CARTESIAN, CARDAN
 Connector-ORI, Connector-ORI
**
**------------------------------------------------------------------------------
**
** x-trans : not defined --> controled with *CONNECTOR MOTION
** y-trans : lock, never switch
** z-trans : lock, never switch
** x-rot   : lock (FV=0.0) --> free (FV=1.0)
** y-rot   : lock (FV=0.0) --> free (FV=1.0)
** z-rot   : lock (FV=0.0) --> free (FV=1.0)
**
*CONNECTOR BEHAVIOR, NAME=connector-BEH
*CONNECTOR ELASTICITY, COMPONENT=2
** E [force/disp]
          1.0e+06
*CONNECTOR ELASTICITY, COMPONENT=3
** E [force/disp]
          1.0e+06
*CONNECTOR ELASTICITY, COMPONENT=4, DEPENDENCIES=1
** E [moment/rad], freq, temp, FV1
          1.0e+06,     ,     , 0.0
          1.0e-06,     ,     , 1.0
*CONNECTOR ELASTICITY, COMPONENT=5, DEPENDENCIES=1
** E [moment/rad], freq, temp, FV1
          1.0e+06,     ,     , 0.0
          1.0e-06,     ,     , 1.0
*CONNECTOR ELASTICITY, COMPONENT=6, DEPENDENCIES=1
** E [moment/rad], freq, temp, FV1
          1.0e+06,     ,     , 0.0
          1.0e-06,     ,     , 1.0
**
**------------------------------------------------------------------------------
**
*NSET, NSET=connector-FV-NSET, ELSET=connector-SECT
**
*INITIAL CONDITIONS, TYPE=FIELD
 connector-FV-NSET, 0.0
**
*AMPLITUDE, NAME=step-FV-AMP, TIME=TOTAL TIME
**          time,            FV1
             0.0,            1.0
          1000.0,            1.0
**
*AMPLITUDE, NAME=connector_load-AMP, TIME=TOTAL TIME
**          time,           disp
             0.0,            0.0
            10.0,           10.0
           100.0,           10.0
**
**------------------------------------------------------------------------------
**    STEP 1
**------------------------------------------------------------------------------
**
*STEP
*DYNAMIC, EXPLICIT
** blank, time
        , 10.0
**
*CONNECTOR MOTION, AMPLITUDE=connector_load-AMP, TYPE=DISPLACEMENT
 connector-SECT, 1, 1.0
**
** use FV1=0.0 stiffness
*FIELD, NUMBER=1, AMPLITUDE=step-FV-AMP
 connector-FV-NSET, 0.0
**
*END STEP
**
**------------------------------------------------------------------------------
**    STEP 2
**------------------------------------------------------------------------------
**
*STEP
*DYNAMIC, EXPLICIT
** blank, time
        , 90.0
**
*CONNECTOR MOTION, AMPLITUDE=connector_load-AMP, TYPE=DISPLACEMENT
 connector-SECT, 1, 1.0
**
** use FV1=1.0 stiffness
*FIELD, NUMBER=1, AMPLITUDE=step-FV-AMP
 connector-FV-NSET, 1.0
**
*END STEP
**
**------------------------------------------------------------------------------

Regards,
Bartosz

VIM filetype plugin for Abaqus

https://github.com/gradzikb/vim-abaqus

 

[ardalansv]

Thank you so much akabarten.

 

[ardalansv]

Dear Akabarten,
I have figured out a more complicated situation that I cannot model. At first, two nodes should translate without any rotation with respect to each other using a coordinate system (axial connector), then at the second step they can translate and rotate with respect to an axis of another coordinate system (cylindrical connector). The issue I have is that as I use the connector displacement at the first step, the first node reaches the second node then, at the second step I want the nodes to stay at the same place (so I have to propagate the movement) and have a cylindrical joint (translate and rotate wrt one axis) however the csys for the translation is different than the cylindrical joint. I want to simulate this in static not the dynamic. I would appreciate if you can help.
Regards,
Ardalan

 

[akabarten]

Hi,

I did not get whole description of your problem, but here couple of my thoughts.

two nodes should translate without any rotation with respect to each other using a coordinate system (axial connector)

AXIAL connector does not constrain rotation, TRANSLATOR will do the job.

I understand in first step we can move along one axis of 1st coordinate system and in second we can move and rotate along one axis of different coordinate system.
Do the coordinate system move in space at any time? If they are fixed respect to global coordinate system maybe you do not have to use connectors and *BOUNDARY conditions in local coordinate system (*TRANSFORM) will do the job.

We need to turn off TRANSLATOR and turn on CYLINDRICAL.
To remove connector we can use *CONNECOTR FAILUR of CONNECOTR DAMAGE but the problem is with activation of CLINDRICAL in 2nd step.
I do not know such option. Maybe combination of connector and boundary conditions will do the job.

Some kind of sketch how the bodies should move will be helpful for me.

Regards,
Bartosz

VIM filetype plugin for Abaqus

https://github.com/gradzikb/vim-abaqus

 

[ardalansv]

Dear Bartosz,
Here you can find an attachment showing what I want to simulate. Briefly, the distance between point 1 and 2 is becoming zero, then at the second step, point 1 and 2 can rotate and translate along another coordinate system which is different. The thing is that in this simulation all the coordinate systems are different than the global one.
I hope you can now understand what is my issue. Please let me know if I need to explain in more details. Also, I should mention I am using connector displacement not the bc since I want to see the effect of lowering the distance between points on both.
Regards,
Ardalan

 

[ardalansv]

Dear Bartosz,
Simply if it was possible to define two different connectors using different coordinate systems and activated at the different steps, this was possible. But unfortunately, abaqus is not letting me define two different connectors between same nodes, also as you stated too, I do not know any way to activate the connectors at different steps.
As I mentioned and you corrected me, I want to use a translator connector using a coordinate system, then having the same nodes rotate and translate along another coordinate system.
Regards,
Ardalan

 

[akabarten]

Hi,

Thanks for the sketch, it is really helpful, however I still have some doubts.
1. In 1st step we have movement of both nodes (1 & 2) at the same time, am I right?
2. In step 2 is it possible to get non zero distance/angle between the nodes along axis cylindrical system or are they have the same movement?

Regards,
Bartosz

VIM filetype plugin for Abaqus

https://github.com/gradzikb/vim-abaqus

 

[ardalansv]

Dear Bartosz,

Thats right at the first step we have motion of both nodes with the translator connnector.
Answering your second question, I should say right now I figured out that I can couple a third point to the box one and connect that point via another connector to the existing connector and assign the cylindrical motion to the second connector. Briefly, there is a translator connector connected to another cylindrical connector and the end of connectors are coupled to the boxes. at the first step I use a BC on the cylindrical connector to make the U1 and UR1 motions zero (Just translation in the translator connector is happening) and at the second motion I propagate the motion in translator connector as what it was and modify the cylindrical connector and make the both motions free. It seems logical to me more but the issue that I am faced with is the zero pivot and overconstrain error in the model. I should mention that the direction of the coordinate systems are different so I do not know how I could fix this issue.
For no confusion, using the first connector both nodes are getting closer to each other then the sliding and rotation of the second node with respect to the first node is allowed but with respect to another coordinate system. I did not know that I should use chain connector or disjoint connector for making two consecutive connected connectors and I am using disjoint connector.
Please help me solve the issue of using two connected connectors and let me know there would be any difference if I use chain connectors instead of two different disjoint connectors.

Regards,

Ardalan