Mesh Bolted Connections

[Anonymous]

In an assembly i have created bolted connections with the design accelerator, but when i attempt to mesh the assembly i get an error saying... "Surface Meshing.  Fetaure too small to be resolved at the current mesh setting.  Try to adjust the mesh element size in the indicated area.  If this does not help, consider checking the model for validity, overlaps and self-intersections." 

The bolted connection has interferences at that location and i have tried making the mesh in this spot extremely small without success.

How can i fix this?

[JDMather]

Can you simplify the anaylsis by removing the fasteners and using constraints?

[Anonymous]

I could do that, but i would like to see the stresses on the bolts as well.

[blair]

Use the split-face tool to create circular areas to represent your flasher/fastner. Then apply the correct force to simulate the value of the torqued faster(s).

[blair]

Should have used spell-check: flat-washer/fastners

[randym1982]

What I've found with FEA in Inventor is that the standard Hex Head bolts aren't usable due to the head detail included.  I can't remember if it's the chamfer on the top of the head or the land under the head.  What I usually do is perform a save as on the content center part and then sketch under the head starting from the flat landing and extrude the hex shape to the top surface of the head.  This creates a simple hex with thickness for the head which doesn't cause meshing issues. 

Question for Autodesk here..... any chance the content center parts could be recognized and automatically simplified in the FEA module?  Would save a bunch of time and headaches for me.  My longer term solution is going to be to create my own simplified bolt library (ipart) and use that in my assemblies rather than content center.

Randy

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[blair]

This is  a standard problem with all FEA programs. When working with assemblies, when you mesh, you require the mesh-nodes to match. The basis of all FEA requires the forces to pass along the nodes, much like litle cubes. All the loads are passed to the adjoining cube at the corners.

For a thin plate, you would require at least 2 cubes for the thickness. You can't have a material with a single cube as you don't have the nodes at the corners to measure or transfer the loads/forces.

Trying to do FEA with fastners adds to the model. You have corners and points which require finer meshes. There are some great books out there about FEA.

[randym1982]

Blair,

Are you using a round head to simulate your bolts then to minimize mesh elements?  I am not familiar with the split face tool, you mention applying a force to simulate torqued fasteners, does that result in an accuratly represented pre-loaded fastener?  That is something I have struggled with, my latest FEA task is rather large with joints between sections. I set a "seperation" contact between the flanges so that the bolts take the load rather than the flange.Using this method I am not getting the effect of bolt preload from the fasteners that hold the joint together.  Also you mention good books available for FEA.  Are there any specific ones you would recommend that focus on Inventor FEA?

Randy

Core i7 930 (OC'd to 3.96 GHz HT off watercooled)

12 GB DDR3-PC16000 GSkill Trident RAM

WD Caviar Black HDD SATA3

GTX 280

Asus P6X58D-Premium Mobo

Inventor 2010 Pro

Windows 7 x64 Pro

Trend Micro Internet Security

[blair]

We use flat washers under all our bolt heads. If you are using just a bolt-head only you could use a hex shape when you use the Split-Face tool.

You should have no problems calculating the "clamp-force" for your specific size fastner and torque used.

There are a number of books on Amazon

You might kick around the Autodesk/Algor site as well: http://download.autodesk.com/us/algor/userguides/index.html

[henderh]

Hi Randy,

  I have a couple workarounds and I logged your wish about automatic simplification of standard components as 1342136.

  1)  Instead of doing a save-as on the CC part and editing the fastener, you can edit the CC part directly if you choose to place "As Custom" (see image attachment)

  2)  This workaround has its drawbacks (as with nearly any workaround) but we can create a preload in the bolt by cutting out a section of the shaft (make sure the cut is wide enough that an automatic bonded contact won't be made).  Add forces to the newly created faces for the preload (see image attachment)

Hope this helps.

Best regards, -Hugh 

[randym1982]

Hugh,

Thanks for the tips.  I hadn't used the place as custom feature before, I'll have to try that.

Randy

[jasonrecords]

---

@henderh wrote:

Hi Randy,

  I have a couple workarounds and I logged your wish about automatic simplification of standard components as 1342136.

  1)  Instead of doing a save-as on the CC part and editing the fastener, you can edit the CC part directly if you choose to place "As Custom" (see image attachment)

  2)  This workaround has its drawbacks (as with nearly any workaround) but we can create a preload in the bolt by cutting out a section of the shaft (make sure the cut is wide enough that an automatic bonded contact won't be made).  Add forces to the newly created faces for the preload (see image attachment)

Hope this helps.

Best regards, -Hugh 

--------------------------------------------------------------

Hugh,

concerning your work around, for a bolted joint what kind of contact types would be needed between:

1) bolt and clamped parts

2) bolt and nut

2) between the multiple clamped parts?