Over the last couple of months, we’ve been running a series of customer events up and down the West Coast showcasing some of the new features that have been introduced into SolidWorks 2011, and having a little fun at the same time.
However, I find that I don’t really get a feeling for how new features in software are going to work for me until I get back to my desk and start working on real models and real problems, so over the next couple of weeks, I’ll showcase a couple of things that were introduced in SolidWorks 2011 that I already can’t live without in my day-to-day work.
When doing stress or thermal analysis of a part or assembly using SolidWorks Simulation, you can now activate a new analysis scheme – 2D simplification.
This means that if you can characterize the behavior of the model by taking a planar slice through it, you can now represent the problem much more simply, and get your answer much faster.
Over the last few weeks, I’ve run into a couple of situations where this has helped me out tremendously.
One of them was with the design of a simple bracket for a CO2 cylinder. I was hoping to use SolidWorks to develop a simple one-piece bracket that would deform to accept the cylinder, and then, through the elasticity of the material, retain the bottle.
To analyze this situation is a complex proposition. Firstly, the bracket is undergoing significant deformation, which makes this a nonlinear analysis. A simple linear approach to stress analysis assumes that the stiffness of the structure does not significantly change throughout the loading process – this is what we call the small deformation assumption. If a significant shape change does occur, generally the stiffness of that shape is also changing significantly, therefore a linear static analysis may not capture the accurate behavior, and a nonlinear analysis is required.
In this example, there is also a chance that if the material is over-deformed, it could suffer permanent deformation. If this happens, it would hamper the effectiveness of the bracket. Nonlinear analysis will also allow us to analyze post-yield material behavior.
The problem with nonlinear analysis is that it is computationally intensive. As little as ten years ago, during my undergraduate engineering class, I recall being told that we didn’t need to know much about performing nonlinear analysis, as it was too difficult for most analytical methods and software packages at that time. We’ve come a long way since then, but nonlinear analysis still typically takes 10-100 times longer than a linear analysis of the same complexity.
The great thing about the 2D simplification methodology is that if the shape and loading conditions can be characterized as being plane stress, plane strain, or axisymmetric, we can greatly simplify the model, and significantly improve the time it takes to get the analysis completed.
I tried two methods of simplifying the analysis. In the first I analyzed a representative 3d slice of the model. I meshed this part with what I considered to be a good mesh, and ran the analysis. It gave me satisfactory results , but took 15 minutes to complete, and meshed with 61,000 degrees of freedom (a good estimate of the number of systems of equations the software has to solve).
I then tried the same analysis with the 2D simplification tool. This methodology, available when you start a new static, thermal or nonlinear study (and available if you have a SolidWorks Simulation Professional or SolidWorks Simulation Premium license) asks you to select a plane or face to use as the representative slice of the model. I selected a plane that ran through my bracket.
I then applied exactly the same conditions as I’d defined in my 3D analysis, and ran this one. It gives very similar results, but does so with 12,000 degrees of freedom, and in around 45 seconds.
In completing this design, I needed to run innumerable studies, modifying the shape, thickness and gap spacing of my bracket after each one, until it performed exactly as I needed. The ability to use 2D simplification to run a series of analyses in less than a minute each allowed me to quickly iterate to my best design. After just one project, I’d estimate that the 2D analysis in SolidWorks has saved me at least 8 hours of design/analysis time.
Even better, you can even push out an output video, like that linked below, that allows us to display the results in a 3D format!