Locking a displacement in a rotated plane

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zjuv9021 posted this 13 October 2018

All,

I want to first rotate an object 15 degrees (for an example), and then make a displacement/force  towards the fixed end but have the entire pipe locked within that 15 degree rotated plane as I displace it towards the fixed support, please see diagram below:

How can I go about doing this exercise in Mechanical for any "X" degree I choose to rotate this pipe?

Regards,

Zach

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zjuv9021 posted this 13 October 2018

Edit, I don't want the entire pipe locked in the new plane, only a certain length.... Would I just have to create an outer tubing that encompasses this pipe and then cut it to the desired shortened length and "lock it"?

SandeepMedikonda posted this 13 October 2018

Hi Zack, Please see if this post helps.

Regards,
Sandeep

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peteroznewman posted this 13 October 2018

Create a Remote Point scoped to the end face of a cantilevered beam. Create a displacement, scoped to that remote point and apply a rotation about X to the remote point leaving all others free, and if you have Large Deflection on, you will get a circular looking displacement of the beam. If you also set Z = 0 instead of leaving that free, the end point will move slightly along the Y axis as the tube bends to the applied angle. Do that in step 1 of a two step solution. You can set X=0 if you want or leave it free.

Then in step 2, You can apply a force to the Remote Point in the Y direction and push the end further along the line Z=0, because the displacement in step 2 will holding the angle at the same value as well as hold Z=0.

Regards,

Peter

 

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zjuv9021 posted this 15 October 2018

Thank you. I'm still a little confused.

Please see diagram below of what I would like to achieve:

I would like to ultimately be able to vary the degree and then constrain movement within the bottom layer (pink/salmon colored, frictionless or rigid as I don't care about it's deformation, currently), then apply an axial displacement on the tubing to see the characteristics/behavior that occur within the free movement plane. 

I hope this helps clarify. Any input on how to best approach this physical problem is greatly appreciated.

Kind Regards,

Zach

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peteroznewman posted this 15 October 2018

Zach,

One aspect of FEA modeling that may not be obvious to a new user is the idea of of the zero stress state of a part. You show in blue, Axial Displacement #1, with a curved shape that you want to push axially and contact the yellow part. The problem is that the tube started out life as a straight tube. That is the shape it is in when it is manufactured. You have to bend it into the curve shown in blue before you start to push it axially. While you could draw the tube as curved in the CAD system and mesh it and start to push it axially, that simulation would behave differently than a tube that started out straight in a horizontal line, was bent into the curve and then pushed axially. The reason it will behave differently is the state of stress in the tube after it is bent will affect how it deforms when it makes contact with the wall.

You have been drawing straight tubes and trying to bend them, so maybe you already understood this concept.

When you take a straight tube fixed at one end and apply a 90 degree rotation to the other end face, you can get a nice circular shape. There is an APDL command snippet that allows the current position of a specific degree of freedom of a node to be fixed at the current position. That could be used on the end of a straight tube along the X axis after it has been bent into a curve to hold the node fixed in X at whatever value that was, while moving the node in the Y coordinate from wherever it was at the end of step 1.

When you say axial, you mean that it is following the path of the tube in a channel in the salmon part. I can imagine modelling the salmon part as a two-piece rigid form. Initially, the right part with the concave face is retracted way to the right. The left part with a convex face is fixed and the straight blue tube is pulled down to make contact with the left part in step 1. In step 2, the right part of the salmon form is translated to the left into place as shown above. In step 3, the tube is pushed and now has a path to follow, and freedom above the salmon part to deform as it makes contact with the yellow part.

Regards,
Peter

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zjuv9021 posted this 15 October 2018

Thanks Peter.

Could I wrap the salmon part around the tubing, in essence creating an outer tubing wrapped around the manufactured one, rotate the end of the straight tube a fixed degree (e.g. 30 degrees), and then lock the salmon wrapped tubing in my second step and then displace or push my manufactured tubing through this locked tubing path?

Thank you,

Zach

peteroznewman posted this 15 October 2018

Zach,

Yes, you could have a salmon tube outside the blue tube. You could move the salmon tube into position, carrying the blue tube with it and fix the salmon tube then push the blue tube.

Regards,

Peter

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