SimSolid Faster than FEA, Just as Accurate. What’s Not to Like?
Roopinder Tara posted on July 09, 2019 |

It’s no fun to get a part or assembly ready for simulation. You have to spend hours eliminating details that, if left in, would choke the solver with a ridiculous number of tiny elements. It’s tedious and time consuming. Then you request a mesh and cross your fingers. Being conscientious, you probably check the mesh, because you know not all meshes are created properly.

This two-step process, first simplifying the model and then meshing it, accounts for most of an engineer’s time spent on simulation. In fact, studies have shown that this accounts for up to 70 percent of the time spent in FE modeling and analysis.

Engineering.com readers are familiar with SimSolid, which provides an alternative to traditional finite element analysis methodology. SimSolid does not require model simplification or meshing. Instead, SimSolid uses a proprietary mesh-free method, which works directly on the original CAD geometry.

“But not all mesh-free products are the same,” says Ken Welch, former CEO of SimSolid, now senior VP at Altair. “Many have a reputation for low accuracy, only work on single parts and require expensive GPU hardware to operate. SimSolid is different. It was written from the ground up to be a large assembly solver, runs on standard desktop or laptop PCs and provides accurate results in seconds to minutes.”

We catch up with Welch, co-founder of SimSolid, after the larger simulation vendor Altair acquired his company last October. Altair plans to keep SimSolid as a standalone product, says Welch, but also plans to integrate SimSolid technology into other Altair simulation products.

Fasteners automatically modeled with SimSolid include bolts and rivets. SimSolid also models spot welds, laser welds and fillet welds. (Picture courtesy of SimSolid.)

Fasteners automatically modeled with SimSolid include bolts and rivets. SimSolid also models spot welds, laser welds and fillet welds. (Picture courtesy of SimSolid.)

Altair SimSolid shines bright with assemblies, and even brighter with recent releases, as it now provides an expanded set of advanced fasteners such as bolts, welds, rivets and bushings. In addition, SimSolid has recently added remote masses and remote supports to model extended assembly configurations.

Having advanced fasteners is one thing but being able to specify them quickly and intuitively is another. “Since SimSolid only works on full 3D CAD geometry, fasteners are easier to apply, and this is extended further by several automation workflows. With assemblies that have a large number of fasteners, the ability to handle them more or less automatically can be a huge timesaver all by itself,” says Welch.

Every Day is Weldsday

Welds are a huge pain to analyze. With your typical simulation product, an enormous number of tiny elements are required to model a weld. You might be tempted to ignore the weld, but that could be a big mistake. Often, the weld is critical. Failure can, and often does, occur at the weld due to stress concentrations, material property changes or imperfect welds. Fatigue can also play a significant part in a weld failure.

With SimSolid, weld modeling is much easier, according to Welch. CAD weld definitions, commonly represented as indicator parts consisting of solid tubes or wedges, are recognized and converted automatically.

“A single fillet weld dialog provides all necessary inputs,” says Welch. “Users simply need to specify the weld diameter and which parts to convert, or even better SimSolid can examine all parts and propose which ones are suitable to convert. Once the user verifies the selection, SimSolid will replace each CAD weld tube part with its mechanical equivalent. The original geometry representing the weld is suppressed. All welds can be created at one time using this method.”

“I’ve seen weld modeling go from weeks to minutes using this method,” Welch adds.

Automotive chassis model with welds represented as cylindrical tubes. A complete automotive chassis could have hundreds of welds. (Picture courtesy of Altair.)
Automotive chassis model with welds represented as cylindrical tubes. A complete automotive chassis could have hundreds of welds. (Picture courtesy of Altair.)


Welds shown in green. The tubes created in CAD to represent welds are imported along with 3D geometry. (Picture courtesy of Altair.)
Welds shown in green. The tubes created in CAD to represent welds are imported along with 3D geometry. (Picture courtesy of Altair.)

SimSolid examines all assembly parts and suggests which ones are actually welds. In one step, geometry representing a weld is suppressed and replaced with mechanically equivalent weld definitions, according to Altair. (Picture courtesy of Altair.)
SimSolid examines all assembly parts and suggests which ones are actually welds. In one step, geometry representing a weld is suppressed and replaced with mechanically equivalent weld definitions, according to Altair. (Picture courtesy of Altair.)

May the Forces Be with You

One final consideration for large assemblies is understanding complex load paths. SimSolid provides a simple one-dialog interface to display reaction force and moment vectors for any combination of supports, connections or parts. Components can be selected individually or in groups and forces/moments can be summed to quickly understand load balance and free body forces.

Complex load paths. SimSolid provides a dialog interface to display reaction force and moment vectors for a combination of support, connection or parts. Components can be selected individually or in groups and forces/moments can be summed to understand load balance and free body forces. (Picture courtesy of Altair.)
Complex load paths. SimSolid provides a dialog interface to display reaction force and moment vectors for a combination of support, connection or parts. Components can be selected individually or in groups and forces/moments can be summed to understand load balance and free body forces. (Picture courtesy of Altair.)

All About Speed, But Accuracy Matters

Analysis is all about managing trade-offs between speed and solution accuracy. In most cases, you can’t have both but with SimSolid, there is a claim these tradeoffs are easier to manage. Take, for example, the analysis of a golf club driver. Along with mass, center of gravity and coefficient of restitution, golf club manufactures pay close attention to the sound that is made when their club heads strike the golf ball. In recent years, these companies have been able to correlate the club head’s natural frequencies with the sound it makes when it strikes the ball and modal analysis has become an important part of the club head design process.

The challenge is that golf driver heads generally have very complex geometry which are constructed of non-uniform thickness thin-walled materials. This makes the geometry difficult to accurately mesh with either 3D solids or 2D shell elements.

In order to validate results, a comparison modal analysis was done with both SimSolid and traditional FEA. Detailed result settings were used – 6 adaptive solution passes for SimSolid and 1.93 million second order TETS for the reference FE analysis.

Solution results for all modes were mostly within 0.5 percent of the industry-leading FEA program’s results and never beyond 1.5 percent, per a SimSolid report. However, the savings in model preparation were dramatic. Instead of hours with the FEA solution, SimSolid took under a minute. All told, the FEA solution took 27 times longer to model and analyze.

“Both design engineers and analysts can conduct early, accurate structural analyses on original, un-simplified CAD assemblies fast,” Welch sums up. “We get the accuracy, but in much less time.”

To learn more about SimSolid and download a free trial, visit Altair.


Altair has sponsored this post.  All opinions are mine.  --Roopinder Tara


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