CAD and analysis programs need to work together. Regardless of how the geometry gets to the analysis program, the important thing is it gets there easily and can be quickly analyzed. That smooth transfer and analysis are how companies are cutting product lifecycle time and increasing profits.

Jean Thilmany, Senior Editor

You’ve created your CAD design, but you’re not done. You need to analyze the geometry to ensure air or fluid will flow through it correctly, that it can withstand a certain amount of pressure, that it’s structurally solid, or that it meets a host of other specifications.

The important thing is that the model needs to be analyzed within the analysis software.

CAD and analysis software work together much better than in the past, when CAD models had to be exported, then imported into the analysis software that then required engineers make even more changes before they could be read.

Today, CAD and analysis integration is key. But it’s not everything. The way modeling and analysis work together depends on the type of work you do and the physical forces you need to analyze. Sometimes geometry is imported directly from the CAD package. Sometimes geometry is created within the analysis software itself.

Because these needs vary, some products–like Comsol multiphysics analysis software–contain two engines for creating and managing geometry. Once the geometry exists within Comsol, the software can solve for more than one physical effect that acts on the geometry at the same time.
Comsol’s CAD import module–as the name implies–directly imports CAD geometry. Or, users can create their own geometry directly within the multiphysics software.

Regardless of how they get CAD into the analysis system, engineers and analysts will need to select the physical phenomena they want to apply. For this, they’ll need to mesh their designs. The mesh, which looks like a net over the model, creates nodes that the analysis software applies mathematical formulas to and studies.

“Some of our users analyze designs that are generated within a design department. That could be a product that’s close to being released,” says Lorant Olasz, Comsol’s technical product manager working with CAD. “Those geometry files are not drawn for simulation, so they come with some challenges for analysis.”

In those cases, the existing model will need to be meshed and, often, simplified, for analysis.

“But, in the end, we provide tools that allow you to work as if the geometry had been drawn directly within Comsol,” he adds. “You shouldn’t feel like, ‘I’m importing something and it’s not going to work!’ It just works,” Olasz says.

Electrical engineers can also analyze their printed circuit board designs in Comsol. The recently upgraded software now has the tools to generate geometric objects from the 2D layouts of ECAD files, group them into easy-to-use selections for simulation setup, and automatically take care of the geometric complexity inherent to ECAD formats before meshing.

All multiphysics analysis tools offered by Comsol can be run on the imported CAD model. Engineers need not worry they won’t be able to solve for, say, both structural and fluid-flow within the same, imported model, Olasz adds.

Both CAD import and the CAD design kernel allow users to import and then repair geometries, “and if you’re using the design kernel you have a few extra g operations like fillets or the option to thicken the surface of a solid,” he said.

The CAD Import Module supports the import of a variety of different file formats including the Parasolid and ACIS formats, and standard formats like STEP and IGES. Users import their files by saving them in any of these formats. The import module also allows users to import the native file formats of a number of CAD systems, such as Inventor, Creo Parametric, and SolidWorks. The optional file import for Catia V5 provides support for importing the native file format for this system.

Sometimes, for various reasons, engineers will choose to make preliminary, or even final designs directly within the analysis tool, he says.

At the beginning of the design process, for instance, engineers sometimes quickly create a model directly within their analysis software, which they use to test and analyze the feasibility of several ideas and variations. This makes it easy to find the geometry needed to meet fluid-flow and other specifications before designers commit to modeling the part in-depth within a CAD package, Olasz says.

“If you don’t need all the details, sometimes it’s faster to quickly draw something in your analysis package rather than try to simplify a complex assembly and take out the components not needed before you analyze it,” he says. “It really depends on the workflow you’re in.”

Designing directly within the analysis tool is often done if the piece will never be created in real life. The geometry still needs to be analyzed for other purposes.

A model eye

Take the case of the human eye. One company recently created an exact digital replica. They don’t intend to actually create a human eye. Though researchers are experimenting with 3D printed organs, they haven’t yet moved to experimenting with the eye. Instead, the model is used to study the human eye with the intent to change it with laser treatment. Or, as many middle-aged humans like to think, to perfect it.

Engineers at the company, Kejako, in Switzerland, created and imported 3D geometries pertaining to the human eye. Once the geometry was in Comsol software, they worked on that model some more. They were studying how laser treatment might work for aging eyes.

Let’s face it, almost everyone will need reading glasses or bifocals or specialized contact lenses as they age thanks to presbyopia. There is an operation that can decrease dependency on reading glasses and like, but as with all surgeries, it’s invasive and comes with risk.

Presbyopia is very common in middle age and older adults as it’s due the loss of elasticity in the lens of the eye that comes with aging, according to the National Eye Institute, part of the National Institute of Health. In 2015, 1.8 billion people around with world had presbyopia, according to researchers publishing in the journal Ophthalmology in 2015.

Younger people who still have soft and flexible lenses within their eyes, can adjust their eyes easily to focus on close and distant objects. That’s why they don’t have to hold their restaurant menus at arm’s length to read them.

David Enfrun cites research that finds presbyopia will affect 2.3 billion people across the globe in 2020. He theorizes, probably correctly, that quite a few of them will resist wearing reading glasses or bifocals because they think the look will immediately age them, he says.

Enfrun is Kejako’s chief executive officer. His company is at work on a method to fend off the need for reading glasses and do away with the need for the invasive surgery that can correct presbyopia.

To that end, two years ago engineers at the company built a 3D model of the human eye that they use to determine how the eye changes over time.

“We built a full-eye multiphysics 3D model with consideration for mechanics, fluidics and optics,” Enfrun said. “We have imbedded in our multiphysics model everything necessary to simulate visual accommodation, explain the root causes of the occurrence of presbyopia, and to test any potential solution,” Enfrun says.

Computational modeling enables the company to validate their concept before it goes to clinical trial, he adds.

With the help of the model, researchers and engineers were able to brainstorm a list of potential solutions to presbyopia and model the way those solutions would affect the human eye, Enfrun says.

The company is now moving forward with a concept of what it calls phakorestoration, which is a series of laser eye surgeries. They begin when a patient first develops presbyopia and continues until the patient develops cataracts. Kejako plans to soon bring phakorestoration to market.

To create the accurate 3D model of the eye that led to the creation of phakorestoration, several physics phenomena were considered as were the eye’s material properties, said Aurlien Maurer, research and development engineer at Kejako, who lead the project. Always acting within the eye are many different types of physics, such as the fluidics of the aqueous human; optical behavior of the lens and cornea material; and refractive index, which involves modeling the muscle ligaments as they deform the lens.

“We wanted to model the entire eye and adapt its properties to look at different outcomes,” Maurer says.

The Kejako researchers used geometries from statistical measurements and optical coherence tomography imaging techniques, which they then translated into a 3D geometry. Then they imported that information into Comsol. When the geometry was within the analysis software they modeled the mechanical elements of the eye, including the complex muscle ligaments that pull the lens into shape, and the viscoelastic properties of the vitreous fluid that fill the eye.

Once the Kejako tool is released, clinicians will be able to use the standard OCT imaging to image a patient’s eye. They’ll then send that information to Kejako, where a team can create a personalized 3D parametric full-eye model of the individual’s eye. The model is then further optimized and customized and a phakorestoraction procedure particular to the patient is created.

The procedure tells doctors how to perform the laser surgery on that particular eye and can detail when it will likely need to be done next, after the patient’s lens changes and needs further accommodation.

Comsol
www.comsol.com