Beam Elements in Simulation

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!

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