ladder frame torsion FEA

[willsie]

Using generative structural analysis I'm trying to set up a pure torsion case for a ladder frame as shown in the attached image.

I think I need to restrain the part somehow, but everything I try fails.

 

[solid7]

You should be able to use the 'clamp' function on the two round faces at the bottom end of your ladder. This will provided a restrained condition.

If you need more restrained surface area than that, (such as if your ladder is part of an extension ladder, or restrained by a grip area) what you can do is to explode the solid, split the side legs at a particular length, and then join the whole thing back together. Now, the area that you split will appear as a separate face on the solid, and you can clamp just that area. (this method also works when appying different pressures across a surface)

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Catia Design|Catia Design News|Catia V5 blog

 

[willsie]

Thanks for the reply it was very informative. I'm quite experienced with v5, but new to the GSD function .

I have run 2 cases. The first was clamping the end faces on one end and the other where I clamped diagonally opposite faces. Neither quite give me what I want as the clamped ends show zero deflection.

In the pure torsion case I am trying to achieve I would like to see the zero deflection point at the c of g of the frame with all 4 corners showing deflections created by the 2 couples applied to the frame.

As the c of g is in space I'm thinking I need to create a restraint at this point, but how? A virtual restraint?

Or am I barking up the wrong tree.

As a matter of interest the frame is a simplification of a ladder frame chassis.

I have a FEA v5 tutorial book from SDC publications, but it doesn't specifically cover this point.

Is there any other literature available that may help me?

 

[solid7]

Can you create a solid sphere around the CoG, and use it to apply your clamp? (It's possible to do this and use it as a restraint, but I don't know what the actual result will be)



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Catia Design|Catia Design News|Catia V5 blog

 

[willsie]

I've managed to apply the case I wanted by adding small pads to the inside surfaces of the frame longitudinals and adding restraints to them.

the following image shows that my analysis indicates zero deflection of the frame along the longitudinal and transverse axes through the c of g.



I'm assuming these pads being very small relative to the overall structure will have an insignificant affect on the analysis.

I couldn't get the cut faces or seperate sphere to work.


J