Simulation 2020: Is a bolt stiff like an engine or flexible like your hands?

by Shaun Bentley

Simulation 2020:

Is a bolt stiff like an engine or flexible like your hands?

In all versions of SOLIDWORKS Simulation, Remote Loads can be created using two connection types: Rigid and Distributed.

Figure 1 - Remote Load distributed connectors

Figure 1 – Remote Load

Now with Simulation 2020, we can use these same two options with Bolt and Pin connectors as well.

Bolt and Pin distributed connectors

Figure 2 – Bolt and Pin connectors

DISTRIBUTED CONNECTORS COMPARISON STUDIES

To see the difference between these options, I’ve run a few comparison studies to illustrate what they are doing.  Can you tell the difference between these two stress plots?

Stress PlotsThe picture on the left was created using a RIGID connection type (available in 2019 and prior).  Notice this plot looks almost identical to setting up a study using prescribed displacements (right; see figure 3).

Figure 3 - Rigid Bolt vs Prescribing displacements

Figure 3 – Rigid Bolt vs Prescribing displacements

The RIGID option has behavior that is similar to mounting an engine inside a vehicle.  The engine is stiff compared to the vehicle frame so we can simplify the engine as a point-mass and use rigid bars to connect it to the frame.  The engine stiffens the frame considerably.

What about these two stress plots?  Is there much of a difference?

More Stress PlotsThe picture on the left was created using the new DISTRIBUTED connection type which you can see is practically equivalent to simply applying a uniform load to the faces in this case (right; see figure 4).

Figure 4 - Distributed bolt vs. uniform load

Figure 4 – Distributed bolt vs. uniform load

The DISTRIBUTED option has behavior like your bodyweight hanging from a pull-up bar.  Your hands don’t add any stiffness to the bar.

Does a bolt behave more like the engine, or is it more flexible like your hands?

This last stress plot (figure 5) shows a physical bolt being modeled, meshed, and shrunk into place (this is a common FEA technique to model bolts with preload directly) so we can compare.  What do you think?

Figure 5 - Bolt model with temperature shrinkage trick

Figure 5 – Bolt model with temperature shrinkage trick

The new DISTRIBUTED option seems to do a better job in this case, but the choice can sometimes be a tricky one.  For more technical information, these elements were inspired by the Distrubuted and Kinematic coupling elements used in Abaqus.

Interested in learning more about what’s new in SOLIDWORKS 2020, check out our collection of videos here.

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