What is nonlinear simulation? Most people don’t know. So, I’ll lay it out as simply as I can.

First, let’s talk about the linear solver. When the linear solver runs, it solves for the end result. Only the end result. The solver doesn’t recognize any of the in-between steps. Most people notice this when they create an animation where you would expect some intermediate interaction between parts. “Why didn’t the hook go over the latch?” Is a question I hear all too often when customers create animations from linear simulations. When you have a hook going over a latch, you would expect some interaction between the two components. The reason the two components don’t move like you would expect is because a linear solver only focuses on the end result. So, we only have two points to work with – The start point and the end point. The animation interpolates between the two. The middle is missing.

The nonlinear solver goes about the problem in a different way. Instead of having two points, A and B, the nonlinear solver will solve the in-between steps. The solver marches through time solving these intermediate steps. However, this time isn’t real time. It’s merely a parameter used to describe the relation between the intermediate steps. So, it’s often referred to as pseudo time. This approach comes in handy in a few different situations.

Boundary nonlinearity – Just like the latch example. You have two parts that interact with one another. When the situation arises where you would like to study the steps in-between start and finish, you might want to treat the simulation nonlinearly.

Geometric nonlinearity – When a part deforms so much that its spacial orientation significantly changes, it often helps to solve with little steps. This sort of nonlinear simulation can be dealt with using Simulation Standard. To turn this option on, click, “Large displacement” under properties.

Material nonlinearity – When a material doesn’t have a straight stress-strain curve, you can’t go from point A to point B without the in-between steps. This is because the path from point A to point B is crooked. Have you ever stretched rubber so far that it became easier to stretch? Well, how could you ever solve THAT with a linear solver? You have one force and two or more displacements. Think about it. There are a few different types of material non-linearity, so I won’t go into it too deeply. but they apply to rubbers, plastics, metals after yield and so forth.

So, when someone tells you, “This problem is nonlinear,” don’t change the subject. It’s not as complicated as it sounds.

As a member of the Technical Support Team at Symmetry Solutions, each year we are required to be recertified by SolidWorks.  Part of the recertification test is focused on new functionality and features for the latest release of SolidWorks.  As you may or may not know, there is a “What’s New” file for every new release of the software that documents these changes.  You can access this file from your help menu in SolidWorks.  Like many, I am one of those people that scan the document for some highlights when I install each new release.  However, since my recertification test was approaching, I thought I would give it a more thorough read.  You know what I discovered (again)?  There is a lot of good information in that document.  I won’t try and summarize the entire thing, but here is one tip that I think may be useful if you are in the process of updating hardware:

“You can transfer a license from a computer even if SolidWorks is no longer installed on that computer. You can download and run SolidWorks Activation Wizard from the SolidWorks customer portal to transfer the license.”

So now when you get that annoying message about “Activation Count Exceeded” because you forgot to transfer the license off of your old computer, you no longer need to call technical support to resolve the problem.

Note, the tool is new and currently only applies to SW2011 installations.

Take some time and read through the “What’s New” document (again).  It may not be the most fun reading material available, but I recommend it for all SolidWorks users, as it can help you get the most from your software.

P.S.  You will be happy to know that all the members of your SolidWorks Technical Support Team here at Symmetry Solutions passed their recertification test.

If you use the Complete Search as the basis for your search card, you may want to change the default value for some of the check boxes like “Display Folders” or “Search all versions.”  The method to do this is not clear in the Administration Guide for 2011 and isn’t explained in the Help.  It’s not hard, just hard to find!

1. Open the Card Editor and open the search card.
2. Go to the Card menu and select Default Values.
3. In the Default values window, select “Click here to add variable.”
   Scroll down and select the variable such as Find Files, Find Folders, or Search Previous Versions.
4. Click in the Value column and enter 0 to uncheck.
5. Repeat for any other variables.

The other day a customer called in and wanted to show in a drawing one of the components of an assembly in a dashed state. I thought this to be a nice feature to have but did not know if it was possible. So I started looking into this and I stumbled upon Component Line Font from the right click menu. This allows you to change the default setting for Visible Edges, Hidden, Tangent Edges and Crosshatch.

Once you unselect ”Use document defaults” you can change the Line style or Line thickness setting for each. You can also set it to change for all views or just the selected view. Once you have applied this and click on “OK” the drawing will update. As I show in the picture below, the top component is dashed and the bottom one is solid line.

A rubber band stretches over a can.  Simple, right?  But when the rubber band is half the size of the can, simulating that sort of expansion over a large body becomes an enormously complex task.   It was day one of Advanced Non- linear Simulation Training in Chicago.  By the dumb expressions on our faces, Jandra Novak, our Czechoslovakian instructor, knew that we were stumped.  “Try this.” He said.    

We watched as he proceeded to silently work.  We all leaned forward and closed our laptops.  He entered values into the software.  No words, just numerical values.  It’s a language we all speak.  

Without getting into too much detail, simulating the rubber band going over the can was not possible.  The size difference was too great for any simulation software to handle.  What Jandra did, was simple.  He shrank the can and placed it in the center of the rubber band.  Then, he made the can grow.  The rubber band expanded as it came into contact with the can.

To any non-super-nerd it was all just numbers.  But to us, it was physics.  Glorious physics.  (It’s as close to reading the code from The Matrix as I’ll ever get.)  

He clicked “Run” and we waited.  

As we reviewed the result, I leaned back in my chair and had only one simple thought:  I understood everything that just happened. 

I’m smart.

As I walked into O’Hare,  I grabbed my ticket and looked down.  C33.  Gate C33, I thought.  For those of you who have never been, O’Hare is one of the largest airports in the country.  Getting to gate C33 was no small chore.  It took 3 miles of walking to get to.  As I reached the end of the terminal, I read C30, C31, C32.  No C33.  Confused, to say the least, I asked, “Excuse me miss, where is gate C33?”  

“Let me see your ticket,”  she replied.

I passed it across the counter.  I watched her type for what felt like an eternity.  

“C33 is your seat number.  You’re 5 miles away from your gate.”   

Defeated, I plopped down in gate 32.  I leaned back and had only one simple thought:  I’ve got a lot to learn.

-Nick Luyster, Applications Engineer (Simulation)