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2010 Simulation Studies Enhancements

Tuesday, December 1st, 2009

Hey everyone! Back for another 2010 Simulation What’s New Blog. This one covers a little bit of everything.

Auto-Recover
There is now an option to backup and recover mesh and solution data. To set this up, go to Tools, Options. On the System Options tab, select Backup/Recover. You will see the option to “Save auto-recover info after meshing and after running a simulation study”.

Sim Studies 0

If you use this option, keep an eye on how large your backup folder gets. I can imagine this could make this blow up pretty fast.

Solver Window Improvements
Similar to the changes that were made to the mesh progress window, the Solver Window has been upgraded as well. You can opt to see a condensed solver window like this:

Sim Studies 1

or a more extensive solver window like so:

Sim Studies 2

Fatigue Analysis
You now have to be in a fatigue study to enter an S-N curve. Not sure of the reasoning for this one yet. I wonder how it will affect the creation of custom materials. It is now possible to use the stress values from a specific solution step of nonlinear and linear dynamic analysis for fatigue studies. In a damage plot, damage is now shown as a percentage versus a fraction as it used to be.
A new Fatigue Check Plot has been added to static studies for Simulation Professional seats. It alerts you to areas of the model that may need further investigation due to fatigue issues. It is a “blue is good, red is bad plot” so the red area should get further attention in the form of a fatigue analysis. A single constant-amplitude fatigue event, either fully-reversible or zero based, is used to generate the plot.

Design Study
A new Design Study has been added. This is basically a combination of the old Design Scenarios and the Optimization module. Just as before, the user specifies variables, ranges and goals and the software goes through all the possible combinations to determine the best solution. There is an extensive tutorial on how to use this in the What’s New Document for further investigation.

Offsets for Composites
Previously, the software always positioned the surface used to define the composite shell in the center of the stackup. Now, it can be positioned either in the center, top, bottom or anywhere in between. This is done by specifying an offset ratio. An Offset Ratio of zero, places the surface at the center of the shell. 0.5 places it at the top surface of the shell. -0.5 places it at the bottom of the shell. Interpolation between these values can place the shell anywhere in between as well.

Sim Studies 3

Beams
Beams are now supported for Nonlinear Studies. They have improved the Neutral Axis Detection. Many of you may have noticed that Simulation previously had a hard time detecting beam lengths that were relatively short compared to their width. Anything with a length to width ratio of less than 3 was an issue. The Define Beam Neutral Axis command allows the user to over-ride this. It is now possible to edit the Torsional Rigidity and Shear Factor for Beams. Beams can now be bonded to curved shells and sheet metal bodies. Beam information can also now be added to reports and saved out as an edrawing.

That wraps up this blog entry. As always spay and neuter your pets and if you have any questions, refer to the 2010 What’s New Document or contact us on the support line. See you next time!


Seth Bischoff

Seth Bischoff
CAE Support Engineer
3DVision Technologies

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Posted in COSMOSWorks, General, Tips & Tricks, Uncategorized | No Comments »

Meshing Enhancements in Simulation 2010

Monday, November 16th, 2009

Back for another addition of Simulation 2010 What’s New. Today’s episode covers meshing enhancements. Enjoy!

Curvature-based mesher
There are some improvements to the curvature-based mesher. Compatible meshing is now supported for touching solid faces. Previously, all curvature based meshes were incompatible. The curvature-based mesher now checks for interferences between components. If there are interferences, the following dialog pops up:

Mesh 3

Clicking “Yes” puts you into the interference detection dialog box. The curvature mesher handles small features better than it did in previous versions.

Mixed Meshing
The mesh is now compatible between shells and beams that act as stiffeners.

Memory Usage
The mesher now uses memory more efficiently. The following chart from the What’s New document shows the results of running an h-adaptive mesh on Windows XP 32 bit:

Mesh 2

Shell mesh
You can again define shells by selecting the surface of a solid body. This is something that they took away in the 2009 version. In 2009, only sheet metal of surface bodies could be defined as shells. Enough people must have complained to get them to bring this back.

Mesh Progress Window
They have changed the look of the Mesh Progress Window. It now shows memory usage, elapsed time, the number of components that failed to mesh, and mesh progress.

Mesh 1

That wraps up the discussion of mesh imporvements in Simulation 2010. As always, if you have any questions about anything discussed here, refer to the What’s New documentation or direct questions to us on the support line. See you next time!


Seth Bischoff

Seth Bischoff
CAE Support Engineer
3DVision Technologies

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Posted in COSMOSWorks, Tips & Tricks, Uncategorized | No Comments »

2010 Simulation Interface Enhancements

Tuesday, November 10th, 2009

Hey everyone! SolidWorks 2010 is out! There are a lot of small improvements in SolidWorks Simulation. There is nothing earth shattering but there are a lot of long over-due improvements that make Simulation friendlier to use. I will try to put together a series of short blogs that outline the highlights. This entry will cover interface enhancements.

Study tree feature names are now more descriptive. It used to be, unless you manually renamed your features, you had to edit a feature to tell what you had actually applied. This is no longer the case. Most features have descriptions in parentheses next to them in the feature tree.

2010 blog 1

If you hover over an item in the Simulation feature tree, an even more detailed description pops up.

2010 blog 2

2010 blog 3

Hovering over a symbol in the design window also pops up the details.

2010 blog 4

Fixtures, loads, and connectors can now be organized into folders. To do this, right click on Connections, Fixtures, or External Loads and select Create New Folder. Items can then be dragged into the new folder.. When using the Connectors dialog box, and connectors that are created while the dialog box pushpin is depressed will be placed in a new folder. If this is not wanted, the items can be dragged out of the folder back into the general connections folder.

It is now possible to group edit like features. For instance, if you have 25 identical bolt connectors, you can either ctrl select or shift select all the bolts you would like to edit, right click, select edit feature, edit a value in the dialog box, and accept the change. The change will be applied to all the selected connectors.

These may seem like relatively simple interface changes but I think they will make Simulation much more user friendly. As always, if you have any questions about any of the enhancements discussed here, the What’s New documentation is a great source or I would be happy to answer your questions on the support line.

Seth Bischoff

Seth Bischoff
CAE Support Engineer
3DVision Technologies

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Thermal Resistance definition for thermal contact

Friday, July 31st, 2009

In thermal analysis of assemblies, SolidWorks Simulation lets you define thermal contact resistance values. This allows you to model the thermal effect of a layer of a material which is too thin to mesh in 3D. However, the user needs to input the value of the resistance. Here is a primer on how to calculate the thermal resistance:

 glue-layer2

The expected value is either the total or distributed resistance, respectively in K/W or (K.m²)/W in the SI unit system.

The basic formula for temperature drop in a thin layer of material between two parts is given by:

DT = q * [t / (k * A)]

where:

DT = temperature drop at the contact zone in K

q = heat power flowing through the contact in W

t = thickness of the layer in m

k = thermal conductivity of the layer material in W/(mK)

A = surface area of the contact in m²

 

The total thermal resistance is t/(k*A) and the distributed resistance is t/k.

heat-flow2 

Thermal conductivity required to have a given thermal resistance

You can also determine the thermal conductivity required to have a given thermal resistance.

For a material of constant thickness, the total thermal resistance is Rt =  t/(k*A) and the distributed resistance is Rd = t/k.

With:

t = thickness of the layer in m

k = thermal conductivity of the layer material in W/(mK)

A = surface area of the contact in m²

Therefore, you can calculate the required thermal conductivity k to use in a material of thickness t to have the thermal resistance you need: k =  t/(Rt*A) or k = t/Rd.

Vikram Vedantham

Vikram Vedantham
CAE Technical Specialist
3DVision Technologies

Posted in COSMOSWorks, Uncategorized | No Comments »

Quick Tips for Less Painful Motion Analysis…

Wednesday, July 29th, 2009

I was working on a Motion issue today and thought I would share a few tips that help me set up a Motion Analysis:

Mate all components into their initial position.
Components are expected to move (obviously!!!!) so generally, you want to be able to drag the assembly (in SolidWorks) through the motion you expect to achieve in SW Motion. Once this is done, add a couple of extra mates to lock the assembly into its desired initial position. These can be suppressed within the Motion analysis but they are always there so you can get back to where you started.

Position the model in the graphics window as you would like it to appear in you Motion analysis.
I typically position the assembly as I would like to see it and then create a specific view just for Motion. To create a new view, hit the spacebar to bring up the Orientation View list and select New View which is in the upper left hand corner.

Do these two things before creating the Motion study. It can be tricky to move components or get the appropriate view after the Analysis is created so doing a little pre-analysis footwork can save some headaches.

Start with a simplified version of your assembly.
If dealing with a complex assembly, it can be tough to wrap your head around everything necessary to get everything set up properly within Motion. When possible, I will suppress components, get the partial assembly to run properly, and then reintroduce components. This isn’t always possible but can be very helpful when it is.

Seth Bischoff

Seth Bischoff
CAE Support Engineer
3DVision Technologies

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Posted in 3D CAD, COSMOSWorks, SolidWorks, Tips & Tricks | No Comments »

Connections in Assembly Frequency Analysis

Tuesday, July 28th, 2009

If you have tried to run any type of frequency analysis on an assembly, you may have noticed that the only types of contact conditions available to you are Bonded and Free. The No Penetration contact condition is not available. The reason for this is that constant stiffness and mass matrices are a requirement for frequency analysis. No Penetration allows components to come together or to separate during the course of an analysis which would represent a change in the stiffness matrix. This also precludes the use of bolt connectors in an assembly frequency analysis as bolt connectors utilize No Penetration contact conditions.

There are two methods around this. The first is to replace the bolt connectors with bonded contacts at the necessary locations. The second option is to apply free contact between the connected components and utilizing pin connectors. The first method generally makes the model overly rigid resulting in higher than actual natural frequencies. The second method leans the other way. While these methods do not provide completely accurate results, they typically bound the true frequencies.

P.S. This is also the case for Modal Time History, Harmonic, and Random Vibration Linear Dynamic analysis. As stated above, Bonded and Free contacts are also typically suitable assumptions in these cases as well.

Seth Bischoff

Seth Bischoff
CAE Support Engineer
3DVision Technologies

Posted in COSMOSWorks, SolidWorks, Tips & Tricks, Training | No Comments »

Reviewing boundary conditions

Thursday, May 28th, 2009

Thank you, Richard Wand (MJ Engineering – http://mjengineering.com/) for showing this cool trick!! And thank you Tony Tsao (SolidWorks Corporation) for reminding me to blog about this after the Simulation Tips and Tricks Webinar!!

In numerous instances, I have had the need to revisit some of the conditions that I set up on a simulation study. For instance, going back and checking what I applied on one bolt!! Or checking the value of a pressure load that I set up on the model. Usually, the quickest way to do this would be to right click on the item in the simulation tree, and select Details. This would pop-up a window that shows the definition of that item.

details1

What is cool is the fact that you can lock this pop-up window down using the push-pin on the top right corner of the window.

details-2

Thereafter, clicking any entity on the simulation tree would bring up its corresponding definition in the pop-up window. Try doing this by walking through some of the items you have already set up in your Simulation tree (such as connections, external loads, fixtures, etc.).

Another way of getting  a quick summary of any portion of the pre-processing is to generate a report and choose to only include a specific item (such as external loads) in the report. Publishing the report would list out all the external loads that were setup in the study.

Remember: Reviewing boundary conditions is a necessary step before running the analysis, and when troubleshooting erroneous results!!

Vikram Vedantham

Vikram Vedantham
CAE Technical Specialist
3DVision Technologies

Posted in COSMOSWorks, Tips & Tricks | No Comments »

How to Correct a Singular Matrix Error Message

Thursday, May 14th, 2009

Here is an error message that I get on a fairly regular basis on the support line:

pic1

This is a pretty simple problem to solve. This error means that the model is not sufficiently restrained to allow the solver to reach a solution. This could be caused either by a lack of restraints or incorrect contact conditions. To trouble shoot this, right click on the study name and select Properties. In the solver box, there will be an option that says “Use soft spring to stabilize model”.

pic2

This option artificially stabilizes the model by attaching a soft spring element to every node in the model. This stabilizes the model just enough to allow the solver to come up with a solution. Re-run the analysis after activating the soft spring option. You will probably get a large displacement error message. Click No. Clicking Yes will activate the large displacement flag which will apply the load in small steps. This is not what we are going for here. We just want to see where the model is inadequately restrained.

pic3

Once the solver finishes, animate the results by right clicking on one of the result plots and selecting Animate. This should show you what is happening with the model. You may see movement that you would not expect. All degrees of freedom need to be restrained, even if motion is not expected in a given direction. Add the additional restraints or contact conditions then re-run the analysis. Once the analysis is behaving as expected, make sure you deactivate the soft spring option. The soft spring elements can slightly affect your stress results so always deactivate the soft spring option before trusting your results.

Seth Bischoff

Seth Bischoff
CAE Support Engineer
3DVision Technologies

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Posted in COSMOSWorks, Tips & Tricks | No Comments »

Transition Layers in Mesh Control

Tuesday, May 5th, 2009

While practising for the upcoming Simulation Premium training class this week that I am going to teach, I came across an instance where I wanted to control the number of layers for the growth of mesh size. Prior to 2009, the Mesh Control utility in Simulation permitted the user to specify the number of layers to grow from the local element size to the global element size. This functionality is gone in 2009. That confused me as much as some of the attendees at the COSSUG meeting two weeks ago in Columbus, OH.

Well, the solution is tricky to get to, but is available in 2009!!

Apparently, the two options available now are the desired local element size, and a ratio called a/b. The ratio was defined previously as the desired Aspect Ratio (or a measure of skewedness of the elements). In 2009, the definition has been re-written as the ratio of the element size in one layer to the element size in the preceding layer.

Now, that got me thinking about how to back-calculate and hence control the number of layers. So here is the solution:

The general expression that dictates mesh sizes can be stated as:

equation

 Here is an example:

Suppose I want the local size to be 0.2mm and the global size to be 0.3456mm, and the number of layers to be 3. I can calculate the a/b value by substituting these numbers into the above equation. I end up with a value of 1.2, which would yield the desired result in the mesh. If I want the number of layers to be 10, I can re-calculate the equation, and the new a/b value is 1.056.

As a generalized observed rule, the smaller the a/b value, the slower the growth rate.

So pull out those calculators, and start punching away!! The functionality is still there.

Vikram Vedantham

Vikram Vedantham
CAE Technical Specialist
3DVision Technologies

Posted in COSMOSWorks, Tips & Tricks | No Comments »

Summary of FEA 101 at COSSUG

Friday, April 24th, 2009

As promised, here is a summary of the FEA 101 session that Richard conducted at the COSSUG meeting in Westerville, OH this week:

The session involved a basic discussion of what the finite element method is, and why a user should opt for it. The fundamentals of finite elements were established as a process of breaking down a structure into smaller segments in order to capture its response to loading conditions. This breakdown relates to the process called meshing where the model now is made up of elements and nodes (corner points on elements). The roots of this process were traced back to the mathematics that governs stresses and strains. 

eq11
 
Rearranging the terms, 

eq21                                                                                                                                                

In other words, it can be said that any structure behaves very similar to a spring mass system, where F is the external force, k is the stiffness of the structure (contributed by the material and the geometry), and x is the displacement response to the instigating force.

The above principles were extended to the displacements of the nodes created in the mesh, thus depicting the deflection of the structure to the applied loads. Once the resulting deflections are determined, the strains and subsequently the stresses are captured in the geometry.

The discussion moved on to understanding the different meshes that can be created inside Simulation, and how the nature of the geometry (solid structures v. sheetmetal v. weldments) dictates the type of mesh to be created. The topic of converged results crept into the picture here, and hence the topic of refining meshes progressively to study stress/energy norm convergence was brought up.

The different steps in setting up a finite element problem were discussed in good detail:

1. Definition of the study – determining the type of analysis to perform based on the desired results (static, non-linear, linear dynamics for stresses and deflection, thermal for temperature, frequency for resonant frequencies, etc.)

2. Material – determining the type of material to use, its underlying assumptions, and the required material properties for the type of study

3. Fixtures (Restraints) – specifying the locations in the geometry where the structure is constrained from freely moving

4. Connections (contacts/connectors) – locating areas of existing/potential contact and also connecting multiple bodies together with virtual fasteners

5. External Loads (forces/pressure etc.) – indicating regions where the load acts on the design, and the nature of the loads

6. Meshing, running the analysis and viewing the results

Finally, there was a good amount of time invested in understanding what SimulationXpress offers (the free FEA introductory tool inside every seat of SolidWorks), and what its limitations are.

The seminar ended on a summary of some neat tips and tricks shown at SolidWorks World this year. The discussion on the limitations of SimulationXpress will form the basis of the first part of FEA 201 next week, which will help lead into the full-blown Simulation Portfolio.

I will post some key take-aways from the session in my next post!!

Vikram Vedantham

Vikram Vedantham
CAE Technical Specialist
3DVision Technologies

Posted in COSMOSWorks | No Comments »

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