Tricks for Producing Averaged Results for Surfaces or Volumes In ANSYS Mechanical

Occasionally it may be a requirement to report average values of stress or strain from an ANSYS Mechanical analysis. There are tricks to do this either for a group of nodes/elements on a face or elements within a specific volume.

Depending on the requirement, the goal may be to simply report either :

– “Average” stresses on a face (based on nodes)
– “Average” stresses on a face (based on elements)
– “Average” stresses on a volume (based on elements)

Technique 1 : Reporting weighted area average nodal stress Continue reading

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Transferring Deformed Geometry Between ANSYS Applications

Often there is a need to export the deformed geometry from ANSYS Mechanical. Possibly to a 3D printer to show to customers, or maybe a new CAD geometry file is needed that can be used for drawings or further design evaluation. Starting with Release 17, Mechanical offers two options for users for doing this task.

Exporting STL (Standard Tessellation Language) files from the deformed results is one option. The STL file may be opened within ANSYS SpaceClaim Direct Modeler and reverse engineered to create deformed solid geometry from the STL facets. Continue reading

Slip Slidin’ Away! Modifying Friction Coefficients During a Mechanical Simulation

There are situations in which it may be necessary to tweak friction coefficient in a nonlinear contact analysis during the simulation. Currently, the ANSYS Workbench GUI does not support this capability directly; however, it is possible to vary the friction coefficient using a command object.

The ANSYS documentation has several references of doing this as listed under the Help section; Mechanical APDL > Material Reference > Nonlinear Material Properties > Contact Friction as shown below.

image1

This section on the documentation describes defining contact friction using TB,FRIC which is a material property used with current technology contact elements. It can be used to define coefficient of friction for both isotropic or orthotropic friction models. It further discusses varying friction coefficient in a multiple load step scenario, as well as implementing user defined friction  using TB,FRIC with TBOPT = USER.

The example presented here will show how to use commands object within Workbench to vary friction coefficient. The friction coefficient is defined via the TB,FRIC command. To define the friction that is function of temperature, time, normal pressure, sliding distance, etc. you can use the TBFIELD command in conjunction with the TB,FRIC. In this example presented, the friction is varied with time (to simulate it’s change through the load step).

Below is a graphic of the nonlinear contact between the Aluminum housing and steel ring gear.
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The command object used to modify friction as a function of time is shown below.
image3

This command object uses the information in the table below to modify friction :

Time                Friction Coefficient
0                      0
0.2                  0.1
0.4                  0.3
0.6                  0
0.8                  0.15
1                      0

As an example of the friction can vary, notice the friction coefficient is zero for time = 0.6 and time = 1.0.

During the run, the output controls under Analysis Settings was set to Yes for Nodal Forces, Contact Miscellaneous and General Miscellaneous.

A quick look at the contact results confirms our findings. The contour plot for contact friction stress shows zero results for time = 0.6 and 1 which makes sense, since the friction coefficient is essentially zero at these time points.
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Another sanity check is to check for reaction force through the frictional contact with the extraction method set to contact element option; this also reveals zero (nearly zero reaction force at these time points). The very small discrepancy noted on the reaction force is due to a few overlapping nodes on a boundary condition.
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