Reference points in ABAQUS.

[verfet]

Hello.

I'm new to Abaqus and I am trying to topology optimize a wind turbine rotor hub. I am trying to apply surface traction(uniform distribution,general traction, Global CSYS) and in order to choose the direction of the load i created a reference point to define the vector.
Unfortunately, an error occured at the outputfile.'The system detected some Nodes in the model which are not connected to an element.'I m pretty sure these nodes are the reference points, but i cannot find anything similar in the manual.

Any idea?
thanks in advance.

ps.sorry for my english

 

[IceBreakerSours]

Did you couple the reference point to a node or nodes on the turbine?

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[verfet]

thanks for the response!

I tried coupling the RP to the surface but i got the same error.
Now,I am trying in the menu of surface traction ,inserting the coordinates, instead of creating Reference Points and insert those, and it seems to work!

But, what if i whould like to apply a moment on the center of mass?Do i have to create a reference point at the same coordinates as the center of mass and apply the moment?In that case, at which surface should i couple the reference point?

Thanks.

 

[IceBreakerSours]

If there is a node at the center of mass (CoM), simply use that node to apply the moment. Otherwise, couple (see kinematic coupling) a reference point (which does not have to be located near the CoM) to the CoM.

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[verfet]

Dear IceBreakerSours,
Many thanks for your interest.

Im aware of the kinematic coupling(constraints->coupling->'select the constraints control points'.I choose the RP->'Select the constraints region type.surface or node region'.I select Node region->'select points for the surface nodes'.But seems impossible to select the CoM).
If i select a surface an try to apply the moment at the reference point i get the same error as mentioned.
This is the model in which i try to apply the moment.
Link

thanks.

 

[IceBreakerSours]

Why worry about CoM in the first place? You can create a reference point anywhere you want. Then, assign a kinematic coupling between the ref node and the surface of interest. That's it.

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[corus]

Using the CoM might not work anyway as this may only have 3 translational freedoms and not the rotational freedoms you require. Associate the reference point in the part module, at whatever location, and then you can apply your forces/moments to that RefPt.

 

[verfet]

You are both right!It worked.
I link an image pictured where i assigned the kinematic coupling between the reference point and the surface.
Link
I m not sure if a reference point,coupled with a surface, is appropriate to apply a moment.I supposed that the moment must be applied on the axis of rotation not on a surface.That's the reason why i tried to couple the reference point to a point(specifically the CoM) and then apply the moment on the reference point.

Thanks you both for your time.
Promise it's my last question