Static Equivalent Model Reduction in Ansys Mechanical

Editor’s note: Content revised on 10/21/1024

The original version of this post incorrectly estimated the isolated cantilever (Equation (5) of slide 5) deflection using shear and moment estimates (Equations (1) and (2)). This should always match the fixed-fixed beam solution of (Equation (4)). Comments that accompanied this error were also incorrect and corrected here. Please see the PDF for details.

Ansys Mechanical users are often asked to simulate the structural response of a simple area in a complex geometry. One way to do this is to reduce the model to a static equivalent model reduction – creating a simplified model that acts close enough to a larger, more complex representation. Although this seems simple enough at first glance, years of providing tech support to customers doing static equivalent model reduction have taught us that it can be tricky, and users need to be aware of some subtleties.

PADT’s Alex Grishin, PhD, recently put together a presentation to dive into what he has learned about static equivalent model reduction over the years and how to quickly get a model that gives useful and accurate results. You can find the PowerPoint below, as well as a zip file containing the sample Ansys Mechanical model he used.

Static Equivalent Model Reduction of the Lip on a Rubber Diaphragm

Here is the model that Alex used. It’s a rubber diaphragm held in a retainer, and what the user needs to know is the load and stress on the lip that the rubber diaphragm is glued to.

The PowerPoint covers:

• Background on the problem
• Some hand-calcs to show how over-simplification can get you into trouble
• A list of common mistakes
• A full model
• A linearly elastic simplification
• Two statically equivalent model reduction model of the retainer
• A summary

And here is the ZIP file with the model and the MS Excel file Alex used:

This presentation is an example of how PADT’s engineering team combines an understanding of fundamental engineering principles with the leading simulation tools from Ansys. It would be easy to just import the CAD model, put some pressure loads on, and run it. However, an approach that includes some looks at some basic equations can help us make sure we are modeling the real situation.

This is one of the many reasons why companies around the world use PADT’s simulation consulting team to supplement their own engineering teams. Reach out today, and let’s talk about how we can help.