Posts Tagged ‘Meshing’

Simulation tips for Flip Shell Elements

Thursday, August 1st, 2013

Have you ever worked on a complicated Simulation study with many thin components meshed with shell elements?  If you have, you’re familiar with the face colors for shell elements – silver for the top face, orange for the bottom face.  The face colors provide a visual link from the 2-Dimensional representation of our part back into 3-D space.  At some time, you may have encountered ‘top’ and ‘bottom’ faces in the mesh being adjacent to one another, or a mis-alignment of the shells.  To re-align the shell mesh, select a face from the graphics window, move the cursor to the Mesh icon in the Simulation feature tree, RMB on Mesh, and choose ‘flip shell elements’.

2013-0801a Flip Shell Elements

Now that you know what to do, here are three tips for dealing with shell alignment in your mesh.  The first is to use a Simulation default option to align the shells.  From your pull-down menu, choose ‘Simulation… Options…’ then click on the ‘Default Options’ tab and then click ‘Mesh’.  On this options page, check the box for ‘Automatic re-alignment for non-composite shells’.

2013-0801b Flip Shell Elements

With this Simulation option set and the shells being automatically aligned, you may still want to flip the orientation of the shells in your mesh.  I’ve already described the procedure to manually flip the shells, and that requires a lot of mouse travel.  My second tip is to set up a Keyboard Shortcut for the ‘flip shell elements’ command.  With either a part or assembly open, you can access the Customize options via ‘Tools… Customize…’, choose the ‘Keyboard’ tab, and then set the Category to ‘Simulation’.  This is a much faster option than moving your mouse to access the command.

2013-0801c Flip Shell Elements

Finally, the third tip for ‘flip shell elements’ is to set up a Mouse Gesture for accessing the ‘Flip Shell Elements…’ command.  Mouse Gestures, like Keyboard Shortcuts, are accessed through your Customize menu.

2013-0801d Flip Shell Elements

Regardless of whether you choose a keyboard shortcut or a mouse gesture, both options will greatly reduce your mouse travel when you use ‘Flip Shell Elements’.  What other mouse travel reducing tips do you have?  Now go make your products better – faster – with SolidWorks Simulation!

Bill Reuss

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

Beam Elements in Simulation

Wednesday, December 21st, 2011

One of the things that we emphasize in our Simulation Training classes is simplifying the model. It’s an easy concept to understand – the simpler the model, the faster you’ll get results! For designs that use SolidWorks’ weldment functionality, Simulation will automatically make one of the most significant idealizations of a model. 3-D geometry is idealized into a 1-D finite element for the mesh, a Beam element.

Here is a simple example where two standard c-channel structural members come together at what could become a welded joint (left side). Notice how Simulation has automatically meshed the structural member with beam elements (right side)! In Simulation 2012, you now have the option to render the beam mesh on the structural member geometry – a welcomed enhancement!
2011-1216b SW Beam Mesh-w630-h630

In Simulation, the purple spheres represent the ‘joint’ where the two or more beams are connected. There are also options for each beam’s end condition –rigid connection, hinged connection, etc.
2011-1216d Beam End Conditions-w630-h630

How should you handle the automated power of Simulation with weldments? I say ‘handle with care’! Let’s assume that you have one of these c-channels as a simply supported beam – fixed at one end with a load applied at the other. The standard, cantilever beam that we all know and love from our Engineering studies! Recall that the deflection of the end of the beam is calculated by the following equation:
Deflection = (F * L^3) / (3 * E * I)
Where F is the force acting at the end of the beam, L is the length of the beam, E is Young’s Modulus for the beam material and I is the Moment of Inertia for the cross section of the beam.

This is valid, assuming the beam has a uniform cross section throughout its length. What if there are holes cut through the beam? In this scenario, the cross section of the beam is not uniform throughout the length – which is a critical assumption for the deflection of a simply supported beam. In this scenario, Simulation does not recognize the holes and still meshes the structural member with a Beam element.
2011-1216c Edit Joints-w630-h630

In my opinion, you have two options for proceeding with the analysis. The first option is to recognize that using a Bea for the structural member is not an accurate representation of the model, but proceed with the analysis to obtain a baseline result. If this particular structural member does not significantly contribute to the overall strength of the model, you may choose to proceed based on these results. The second option would be to treat the structural member as a solid body. With this method you will obtain more accurate results with your analysis, especially if the structural member contributes to the overall strength of the model.

So the next time you’re reviewing your analysis results, be sure to review the assumptions made by both you and by Simulation. Once you’ve verified that all of the assumptions are valid, or at least that you can accept them, you will be well on your way to making sound decisions based upon your Simulation results. Now go make your products better with SolidWorks Simulation!

Bill Reuss

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

Mesh Failure Diagnostics, Part 2

Monday, May 16th, 2011

Last month, I wrote about Mesh Control and described a process using the Simulation Advisor to fix mesh errors.  If you prefer to operate without the proverbial ‘phone-a-friend’ option, you can always turn the Simulation Advisor off by un-checking the box in your Simulation Options, as shown.  When you uncheck this box, you still have the option of accessing the Simulation Advisor from the Command Manager by selecting the appropriate Advisor in the pull-down menu.

2011-0512a Sim Advisor Off

When an assembly failed to mesh in Simulation 2010, you had to know your assembly components well to determine which part(s) failed to mesh.  Recall that the Simulation Feature Tree looked like this:

2011-0512b 2010 Mesh Failure

With SolidWorks Simulation 2011, however, we now have a visual indication for which parts failed to mesh in the Simulation Feature Manager Design Tree.  Notice all of the component icons that are colored red?  Simulation 2011 provides this visual feedback to let you know where the mesh failures occurred.  If you right-click on any of those parts and select ‘Create Mesh’, this will start the Mesh Control dialog for the selected part.  Apply a mesh control and click ‘OK’ to mesh the part.  Using this method, you have to apply mesh controls to a single part at a time.  If you control-select several of the red (failed) parts from the Simulation Feature Manager Design Tree, you need to right click on the Mesh folder and select ‘Apply Mesh Control’.  Note that when you choose this method, you will need to recreate the mesh for the entire assembly.

2011-0512d RMB Create Mesh

Bill Reuss

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

Mesh Control: As Easy as 1-2-3

Wednesday, April 13th, 2011

When is the last time you saw this warning dialog when meshing?  If your primary responsibilities include FEA, chances are it was as recently as yesterday.

2011-0412a Mesh Failed

As we continue to design and analyze increasingly complex models, our need to access mesh controls will increase proportionally.  Wouldn’t it be nice if accessing those tools were made simple?  Amazingly enough, they already are!  At the conclusion of a failed mesh, just click on the Mesh Failure Diagnostic button.

2011-0412b Failure diagnostics

Yes, it is that simple to access the Mesh Failure Diagnostic tools.  You’ll notice that this opens up the Simulation Advisor in the Task Pane.  The Simulation Advisor is a great tool for beginning and experienced Simulation users, alike.

Here are the 1-2-3’s of using the Simulation Advisor for applying mesh controls.
1. Select one of the parts from the list of ‘failed to mesh’ parts.
2. Click the Mesh Control button.
3. Apply the local mesh control desired to the part by either changing the slider bar or typing a value for the mesh control you wish to apply.

2011-0412d Mesh Control 123

Now click the green check mark to OK your mesh controls.  SolidWorks Simulation will mesh the component you just applied mesh control to.  Notice that you can apply mesh control to several components in one step by adding (clicking) more components to the ‘Selected Entities’ dialog box.  Another nice feature is that the Simulation Advisor window will stay open as long as you have parts that failed to mesh, allowing you to continue applying controls until your entire model has meshed.  Try using the Simulation Advisor the next time you encounter a model that is difficult to mesh!

Bill Reuss

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

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