Reaction moments are only applicable to element with nodes having degrees of freedom in rotation. This is not the case for solids as they only have 3 degrees of freedom per node (3 translations, but no rotation). So how can we get reaction moments on fixed faces of Solid Bodies?
Have you ever tried imposing symmetry for shell elements in SolidWorks Simulation 2012 or older? If you have then you would probably know it is a very tedious process and requires exact knowledge of what the symmetry condition actually does to impose it for shells. The built-in symmetry condition does not work because it requires the symmetry to be applied on a face (which is also the cutting plane), whereas the shells are cut along an edge and not a face. The actual process of imposing this boundary condition was actually published in a previous blog post, “Use of Symmetry in Shell Elements“.
If you tried imposing symmetry boundary condition in SolidWorks 2013, pay close attention to the icon for symmetry plane selection. Did you notice any different between Simulation 2012 and 2013?
When using Shell elements in your Simulation studies it is important to define the offset of your shell to ensure that the geometry accurately represents the 3D model.
The default offset selection in a shell definition is Middle Surface. Therefore the defined thickness will have half of the material on either side of the surface. If you require all of the material on one side or the other, the Top or Bottom surface can be applied. The direction is defined by the orientation of the mesh. If the Top offset was selected, then the material will start from the Top surface of the mesh (part colour) and go below. If the Bottom offset was selected, then the material will start from the Bottom surface of the mesh (orange colour) and be above. Flipping the mesh or adjusting the offset definition may be required.
In SolidWorks 2012 and prior, the orientation was verified after meshing the model by comparing the mesh to the offset setting. New in SolidWorks 2013 is the ability to render the thickness in 3D to graphically see if the offset is correct. Please watch the following video to see this new functionality.
Imagine a manhole cover in a pressure vessel that needs to be bolted to a flange in the pressure vessel. This usually requires a number of bolts to hold the two pieces together. Furthermore, same type of bolts may be present in the assembly at various locations. Imagine having to define all these bolt connectors for a simulation. I am sure this is going to give nightmares to people trying to simulate multiple bolts using SolidWorks Simulation.
You will be happy to learn that SolidWorks Simulation has a smart feature which could reduce the effort in the definition of these bolt connectors.
SolidWorks simulation provides two options to solve the set of FEA algebraic equations; iterative or direct solution methods.
The iterative solver, FFEPlus, uses approximate techniques to solve the problem. It assumes a solution and then calculates the associated errors. The iterations continue until the errors become acceptable.
The direct solver, Direct Sparse, solves the set of equations directly without any approximations and hence there are no errors associated with the solution process. There will still be discretization errors which are present both in iterative or direct solvers.
A solver may be selected changing the study properties from the study feature tree. Read More »
My SolidWorks Simulation 2013 pick of the day is the new functionality for obtaining beam joint reactions. Now it is possible to list reaction forces and reaction moments at beam joints that have fixed translations or rotations.
After the simulation is completed, right click on Results and choose the List Result Forces. Now you can pick the joints you want to view the reaction forces on. The reaction forces and moments will be displayed in call outs on the screen with a graphical representation on the joint.
Watch the video below to see this feature in action.
My SolidWorks Flow Simulation 2013 pick of the day is the new leakage browser functionality.
Hidden within the lids creation tool is the leakage tracking functionality. It helps you quickly locate holes or displacement gaps within the flow models.
The tool works by selecting a pair of faces, one on the inside of the flow domain and one on the outside of the flow domain and then finds a connecting path between the two faces. The only way to get from one face to the other would be through a hole or a gap.
This tool can really help debug issues with flow domains which would have required a lot of manual effort in the previous releases.
Watch the video below to see the tool in action.
A number of people are quite reluctant to use shell elements vs. solid elements. Shell elements can be a huge time save since they allow the modelling of thin features with relatively much fewer elements than solid elements. They are also easier to mesh and less prone negative Jacobian errors which might occur when using extremely thin solid features. Here is a comparison of Solid and Shell elements for a fairly simple model. The figure below show the Solid (on the left), Thin Shell (in the centre) and Thick Shell (on the right) elements. All the three are subjected to same loadings and fixtures.
A simple static study reveals that we get the same results for all the three cases.
However, the shell elements Read More »
There are some improvements I would like to talk about for beam element in SolidWorks 2012.
Let’s use the particle separator model as example. The machine has solid and shell elements. The majority of the structure has beam elements. At the bottom, 4 plates are meshed as solids.
Usually when you get this error, it is related to the geometry of the model (assuming the boundary conditions are done correctly).
There are two things you can check in the model:
1. Look for “edge-edge” or “point-face” contacts as they are considered invalid contacts under Flow Simulation.
2. Make sure the lids fully enclose the internal volume. The concept above applies here as well. If the lid is created with edge-edge contact to the main body, this is a problem. This is why the default “create lids” command in Flow Simulation will generate a lid body interfering with the opening.
If you are using FloXpress, you won’t see the error message if your geometry is not properly setup. Most likely FloXpress just won’t start.
The “check geometry” tool is actually very useful. I check it before I apply any boundary conditions (too bad FloXpress doesn’t have this capability).