Workbench 12 help example - meshing question

[StructuresDan]

Hi all,

Attached is a screen grab of the clip used as an example in the ANSYS DesignModeler help in Workbench 12.

I understand that the part is composed of three surface bodies and is then exported to Mechanical where it is meshed but I don't know how it has been meshed. It looks like that although the surface thicknesses have been specified in DesignModeler, Mechanical has meshed them using a pure 2D mesh of 0 thickness elements. When I mesh the clip.agdb file in Mechanical it uses solid elements through the thickness.

Many thanks

Dan

 

[flash3780]

If the geometry is specified as sheet bodies, it is meshed as sheet bodies. However, for your viewing pleasure, Ansys applies a thickness to the mesh (when in meshing mode) to represent the thickness of the part. When you view the part in results mode, it appears as a sheet body again. You can output temperatures at the top (TTOP), bottom (TBOT), or in the middle of the sheet.

 

[StructuresDan]

Hi flash3780

Thanks for your reply.

I have imported the ANSYS clip geometry into Mechanical and meshed it accepting all defaults. You are right when I mesh it that ANSYS gives it a thickness. I have applied a couple of loads to the clip handles and constrained it at the spring (as per the example).

I've run the analysis and when I look at the solution and plot the resulting total displacements I still see a thickness. How is this?

Many thanks,

Dan

 

[flash3780]

Ahh, I got it. Got to "View" and unclick "Thick Shells and Beams" to change the display.

 

[StructuresDan]

Excellent, thanks flash3780!

I am a step nearer to being able to do what I want now.

Another question... If the clip and spring had been modelled as solids (albeit with small thicknesses) how would you extract the surfaces? For this example and having checked the DesignModeler file the parts had been modelled as surfaces from the off.

If you use mid-surface extraction to convert a solid to a surface then the clip and spring won't be in contact since there will be a gap between the clip mid-surface and the spring mid-surface. Which will mean than the contact won't be detected.

The other option I guess would be to use the thin/surface functionality in DesignModeler?

I've tried using this for two thin solid models which are in contact and tried to extract the surfaces so that they remain contacted but I am the error "ansys operation would result in illegal t surface body". Any ideas?

Cheers.

 

[flash3780]

You might consider using the "Surface from Faces" command in DesignModeler. You can then choose the faces that are touching and define the direction of the thickness properly.

 

[StructuresDan]

Am using Workbench 12. I'm presuming that you mean the "Thin/Surface" tool and the "faces to keep" option?

I have a 4mm thick panel with three bonded c section stiffeners attached, currently the stiffeners and panel is modelled as a solid. I'm trying to create a shell representation of the panel so that I can apply a distributed load and work out the tip deflection. I wanted to start with this basic example before I go on to more complicated shell examples.

I can shell the stiffeners using the Thin/Surface command by selecting the three outer c section faces, selecting direction Inwards and thickness = 0. But when I try and shell the panel by selecting the lower face (which the stiffeners are connected to) DM won't complete the action and tells me that the operation would result in illegal T surface bodies.

I'm sure this is quite a straightforward thing to do but I am really struggling!

Any ideas where I am going wrong?

Cheers.

 

[flash3780]

You might try Concept/Surface from Faces option in DesignModeler. It does a good job of extracting surface geometry.
You can also extract midplanes, but I've had DesignModeler fail on some things that I felt it should have been able to handle.