SolidWorks Simulation 2016 - Intermittent Fixtures

What's New in SolidWorks Simulation 2016?

When a designer runs a simulation, basic parameters such as material, contact sets, fixtures and external loads are essential in defining the problem and achieving accurate results.  New to SolidWorks Simulation 2016 is the concept of intermittent fixtures that adds additional functionality to yield accurate results. 

Consider the following slide-clip assembly:

We can use a 2-D simplification of this model to run the simulation analysis as shown below:

  This simulation is setup to slide the clip into a locking position, then holding it in the locking position for a few moments before applying a lateral force to unlock the clip and slide it out.  The displacement over time curve is shown below:

The clip slides in over 0.5 seconds, hold in the lock position momentarily before retracting to its original position.  The lateral force is applied after the clip is in the lock position.  The lateral force is applied to the point as shown below:

It is not necessary to have the lateral force active throughout the simulation.  It is only required after the clip has moved into in the lock position and before it is about to slide out.  With intermittent fixtures, designers now have the ability to turn a fixture on and off.  

In this case we have the fixture deactivated from 0 seconds to 0.6 seconds before it is activated to move the point in the lateral direction.  After it has moved the point it is turned off at 0.77 seconds and remains off for the rest of the simulation study.  Turning a fixture on and off is useful to help avoid artificial stresses applied to the model and to ensure accurate loads applied. 

We know with confidence that the simulation has been performed correctly and that the stresses seen through each time step is correct.

SolidWorks Simulation 2016 - Contact Sets

Contact Sets - New in SolidWorks Simulation 2016

When a designer is putting together an assembly there may be a few missed mates which will cause the part to be free and unrestrained.  Usually the designer will need to go back and find the missing mate to fully restrain the assembly.  This is a similar concept to contact sets in simulation where a designer must define contact sets or the connection conditions between elements.  This was typically a difficult task that involved looking through the model to find the missing contact set. 

Consider a crane tower as shown:

We will setup a simulation study for this crane tower where it is fixed on the ground and experiencing horizontal and vertical loads at the top.  

Before running the study, the designer now has a new tool to help check for free moving bodies.  This tool is found by right clicking Connections then selecting “Find Underconstrained Bodies”

With the new tool selected, the designer may use the tool by selecting “calculate”.  This allows the software to run a simplified analysis to find whether there are under-restrained bodies.

The results return by isolating and clearly highlighting bodies of interest and showing all modes in which it is under-constrained.  In this case, Body 1 is shown as free floating and can move in every direction. 

This is a problem for the simulation analysis.

Upon closer inspection it was determined that this crane tower was originally modeled with a small gap between the elements to account for welding and tolerances. 

Usually the designer would need to create individual contact sets to account for the gap, however also new to SOLIDWORKS SIMULATION 2016 is the ability to accommodate small gaps.  This option is found under Connections> Component Contacts > Global Contact > Edit definition

Under the component contact option, the designer now has the ability to include “Non-touching faces” by selecting a gap size to treat as bonded.

This is one more tool to help designers be more efficient and effective when using SolidWorks Simulation by spending less time finding missing contact sets and more time analyzing the results.  

New in SolidWorks Simulation 2016 - Ability to section the mesh

New in SOLIDWORKS  Simulation 2016

  SolidWorks Simulation is a great tool to test your part in a virtual environment to understand how it behaves under loading conditions.  Consider the following simple hook:

We are going to run a simple simulation study on this hook to determine how it behaves.  The hook is fixed at the eyelet at the top and it is experiencing a 1000 N force downward. 

By running the finite element analysis we get our results

We see that the hook is experiencing a maximum stress of 12Mpa at the expected location.  As part of the simulation process, the software ‘meshes’ the part by breaking it into small elements to prepare it for analysis.

  New to SolidWorks Simulation 2016 is the ability to section the mesh.  This may be done before or after the analysis, as long as the part is meshed, you can section it.

Sectioning will show all the elements intersecting the plane of choice.  This ability ensures that you have the desired mesh density at any location in your model.  Areas of high stress concentration will require higher mesh density for accurate results.  Using mesh sectioning you can now see how the mesh is distributing throughout the entire model.  

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