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There are multiple benefits of using a Split Line (Insert > Curve > Split Line) feature for SW Simulation.  When you want to apply an attribute in Simulation, such as a fixture, load or mesh control, to only a portion of the face and not the entire face, a split line will break up that face to be able to do what you want.  New in 2010 is the ability to have many closed profiles in a sketch to use in a Split Line feature yielding multiple new faces.  But previously in 2009 or before, you could only do this for a single sketch profile.  And since I know that many of you are using 2009 or earlier, I will try to help out with a tip for multiple closed sketch profiles.  (I could go on about why for Simulation at least you should be using the latest version 2010, but I'll have to leave that until another blog post.)


In 2009 or earlier, have you ever gotten this error (see screenshot below): "Rebuild Errors: There should only be one profile in the sketch."  All you wanted to do was to project these four sketch circles onto the face of this plate.

image1.jpg


You could create a multitude of Split Line features to get the four breaks that you want (see screenshot).
image2.jpg
 
Go on a feature diet with a Wrap instead!  Create as many sketch profiles as you want, and then go to the Wrap feature (Insert > Features > Wrap) and choose Scribe as the Wrap Parameter as shown in the screenshot.
image3.jpg

This will break up the face for you with only one Wrap feature (see below), which now you can use in your Simulation studies.  The one down side is that you can only split a single face with a Wrap feature.  Did I happen to mention that with SW 2010, you can use a Split Line feature to split multiple faces with multiple closed sketch profiles!  SW 2010 is the real deal.

image4.jpg

 

Copyright © 2009 Dassault Systèmes SolidWorks Corp. All rights reserved.
Do not distribute or reproduce without the written consent of Dassault Systèmes SolidWorks Corp.
When doing the  first training lesson from the SolidWorks Simulation manual, the results summary  table (on page 64 of the 2009 book) is meant to illustrate the impact of the  model discretization, or element size, on the data of interest.  In this  example, the max displacement changes only in the fourth decimal place while the  max von Mises stress changes much more.  In general, this same trend is true: displacement will always be the most accurate value calculated  in a static analysis, thus discretization has a minimal effect, whereas stress is the least accurate value.  If you have ever wondered  why, I will try to explain:

What is being  solved in a structural analysis as the unknown is the displacement, the vector  equation given as: {u}=[K]^-1{f}.  Its accuracy is of the same order as the  order of the element, so a high quality mesh will yield 2nd-order accurate  displacements.  A derivative is taken to calculate the strains, thus lowering  the order by 1, so for high quality elements is 1st-order accurate.  More calculations are done to the strains to scale them by the elastic modulus and  averaging the Gaussian points to nodal values (or element values), so error is introduced in this process, but its order of accuracy is maintained, so for high  quality elements stress is 1st-order accurate.  So you can see that stress values are always the least accurate quantities and why extra care should be  taken in obtaining accurate stress results.

Here is a flowchart  type of order of calculations to illustrate this a little  better:

element_accuracy.jpg

Have you been to a roll-out by your local reseller where they covered what's new in the 2010 SolidWorks release?  There's a lot more than they can share in that short amount of time.  In the new 2010 release of Simulation, there are a lot of great hidden gems that are not immediately obvious.  Here is a short list of some of those gems:


1) A great anhancement has been the handling of bonded contacts for a mixed meshing with beams and shells (I assume the same is true with beams and solids too but I haven't really checked yet, maybe a later update on this).  Someone had sent me a model with about 400 beams making up a large rectangular building and then he had the walls done as shells.  He didn't create any contact definitions besides the global bonded contact, meshed and ran it... AND IT WORKED!  The compatible meshing between beams and shells works like a charm.  To me, I think this shows how the Simulation product team is working to make analysis easier for all to use!

(2) I also like the fact now that you can Edit the definition of results plots without first having to show the plot.  Definitely makes it much faster to make changes.
(2a)- Also in the graphics window for results, you can get rid of the plot details and the legend in the Chart Options.  I don't think you were able to do this before.


(3) Defining shell elements by selecting faces of a solid body is welcomed back.  Thanks Simulation team!  Remember though that the shell definition still assumes that it's defined at its mid-plane.  With composite shells though that is not the case for 2010, you can now define the direction of the stack up or also by setting a positive or negative ratio 0±0.5.

(4) Defining bodies as either Rigid or Fixed in Nonlinear, like in the example of an O-Ring, helps to speed up the analysis.  We're only interested in the rubber gasket so one can make the bottom fixed and the top rigid; then simply move that rigid part down a specified amount to just touch the bottom fixture.  Model and videos: http://bit.ly/1l7l2I (342 kB)

5) NAFEMS Benchmarks... Help > SolidWorks Simulation > Validation > NAFEMS Benchmarks.  NAFEMS is an international organization who promotes the proper usage of computational analysis for engineering.  Models are here: <install directory>\SolidWorks\Simulation\Examples\Verification

6) An geometric entity can be both be used as a selection and a reference when defining a load or restraint.  There are countless number of times that have I wanted to do this in the past.  This enhancement is along the same lines as not having to select a face before selecting the hole wizard tool.

7) Backup after both meshing and solved a study to be able to recover the settings and data should there be a problem during this critical phase of a study.  This can be handy in those crucial times when you just can't lose your work!
Click Options (in the Standard SW toolbar) or Tools > Options.  On the System Options tab, click Backup/Recover and select Save auto-recover info after meshing and after running a simulation study.

8) I've found automatic contact definition works much faster than in the past, especially when you have a gap between bodies.  Another enhancement to contacts is that you can drag contact definitions from static studies to nonlinear studies and vice versa. Note: Make sure that these contact definitions are available to both study types.

9) The units available for displacement plots match the units provided in the SolidWorks application. The units are am, nm, micron, mm, cm, m, micron, mil, in, and ft.

By using an Annotation, you can display the weight of your assembly (or part) in the graphics window, which is awesome for when you are making design changes or optimizing it for weight.  Here is the procedure:

1. Insert > Annotations > Note
1.bmp

2. Drop the annotation on the screen where you want, and then over in the property manager, select the Link to property button.
2.bmp

3. Choose the File properties button.
3.bmp

4. "Weight" under Property Name, and "Mass" under Value / Text Expression, and then OK.
4.bmp

5. Back to the "Link to Property" dialog, use the pull down to select "Weight."
5.bmp

6. Here is an example of the result (the 164.11).  You can add text around it and change the Font format as well.

6.bmp

 

Copyright © 2009 Dassault Systèmes SolidWorks Corp. All rights reserved.
Do not distribute or reproduce without the written consent of Dassault Systèmes SolidWorks Corp.

I'm looking for people to make comments about how they've been able to successfully relate analysis setup or results to people that don't have a solid background in FEA / simulation, let's just say the average lay person.


Here's some recent examples to help get the creative thinking in motion:


a) Did you know that people can blow about 2 psi.  Helps to explain pressure drop.


b) Supercritical fluids, like highly pressurized CO2, are used to extract substances like caffeine from coffee beans.  Just cool to know because before yesterday I didn't know how they decaffeinated coffee.


c) Changing the force on a linear static analysis just linearly scales the resulting values (as long as they stay below the yield strength are they valid) so all the colors on the model stay the same, no additional run/study is required.

How do you calculate the bolt preload for Bolt connectors in SW Simulation?

pre-load.bmp
I'm going  to try to make this super easy for you all.  Here is a link to two PDF  files, one for USA bolts and the other for Metric bolts, where the values of Ats (Tensile Stress Area, length^2) and Sp (Proof Load Strength, force/length^2) are  provided in one document.  These two parameters are even colored in the tables so that they can be found  more easily.

To calculate the  Axial Preload, Fi, use this equation:
For a permanent  connection: Fi = 0.90 * Ats * Sp
For a reusable  connection: Fi = 0.75 * Ats * Sp
For those  of you who want to input a torque, T, then it gets a little more complicated:
With a nut:  T = k * Fi * Dn
Without a nut: T = 1.2 * k * Fi * Dn
where k is the Friction Factor, and Dn is the nominal (major) diameter, which  can be found in the tables in the PDF files.

The friction factor, k, is difficult to estimate in a real world  application, so for practical usage recommended values are suggested  below:
Non-plated, k = 0.30
Zinc-plated, k = 0.20 - 0.28
Lubricated, k = 0.18
Cadmium-plated, k = 0.12 - 0.15
Default (No  information / not provided / unknown), k = 0.20
After  running the study, check the forces on the bolts by  right-clicking the Results folder and choosing the "List Pin/Bolt/Bearing Force"  item.  Typically the absolute value of the axial force on the bolt should be  about the value of the preload that was entered.  If the axial load on any of  the bolts is nearly zero, then that means that the bolt was not properly  preloaded and so the bolt is loose, which can cause real problems!

Here are two practical  examples:

(a) 1/4" -  20 UNC Bolt Grade 5

Ats = 0.031822 in^2 and Sp = 85000 psi

So, for a  permanent connection, the bolt preload is calculated be

  • Fi = 0.90 * 0.031822 in^2 * 85000 psi = 2430 lbf


(b) M10  x 1.25 x 40 - 9.8

Ats = 61.199 mm^2 and Sp = 650 MPa

So, for a reusable connection,  the bolt preload is calculated to be

  • Fi = 0.75 * 61.199 mm^2 * 650 MPa = 29800 N

Just one more thing before I finish this blog about Bolt Connectors...

A feature for the bolt connectors (for releases 2008 and greater) allows the bolt to go through more than two components.  If you have this case, then make sure that you open up the Advanced Option and turn on the "Bolt Series" flag and select the cylindrical faces of the holes for all the other parts that are sandwiched in between.

bolt_series.bmp

This meshing tech tip is perfect for when you really want to control the mesh through the whole volume or thickness of only a portion of a part.  Mesh controls on a surface may not propagate through the entire thickness of the part, which in some cases may be necessary for accuracy.  What you should do is use the Split feature!

You can create a multibody part from either a 2D sketch or a 3D surface as a "Trim Tool" for Insert > Features > Split.  If you've already created a Simulation study, make sure you right-click on the study name and choose Update Components.  This will update the component that you split with more than one body, and since they are probably the same material, you can just drag-and-drop the material from Body 1 to the rest of the bodies.

Apply a mesh control to one of the split bodies and you can control the mesh on that entire volume!  Here is an example of a mesh control on a portion of a cube, where on the left it shows a compatible mesh and on the right an incompatible mesh.  (Note: This example was not used for any real problem but just as a proof of concept for myself.)

 

Meshing - compatible & incompatible.gif

Joe Galliera

3GB switch question

Posted by Joe Galliera Employee Oct 8, 2009

Using more memory is definitely an advantage in Simulation. There seems to be a lot of confusion in the industry about what's commonly called the Windows “4GB memory limit.” When talking about performance tuning, people are quick to mention the fact that an application on a 32-bit Windows system can only access 4GB of memory. But what exactly does this mean?


By definition, a 32-bit processor uses 32 bits to refer to the location of each byte of memory. 2^32 = 4.2 billion, which means a memory address that's 32 bits long can only refer to 4.2 billion unique locations (i.e. 4GB).


In the 32-bit Windows world, each application has its own “virtual” 4GB memory space. (This means that each application functions as if it has a flat 4GB of memory, and the system's memory manager keeps track of memory mapping, which applications are using which memory, page file management, and so on.)


This 4GB space is evenly divided into two parts, with 2GB dedicated for kernel usage (i.e. used by Windows OS), and 2GB left for application usage. Each application gets its own 2GB, but all applications have to share the same 2GB kernel space.


To be able to extend this to 3GB for applications, such as SolidWorks Simulation, then here is how you do it:

 

Enable the 3GB switch on Windows  XP

  • Right-click My Computer. Click Properties.
  • In the System Properties dialog box, click the  Advanced tab.
  • On the Advanced tab, under Startup and Recovery,  click Settings.
  • In the Startup and Recovery dialog box, under  System startup, click Edit. The Windows boot.ini file will be opened in  Microsoft® Notepad.
  • Create a backup copy of the boot.ini file by doing a "Save As..." to a different  location. Note: Boot.ini files may vary from computer to computer. 
    Select the following line in the boot.ini file:

multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP  Professional 3GB" /noexecute=optin /fastdetect

  • Press Ctrl+C to copy the line and then press Ctrl+V  to paste it immediately above the original  line. This will be the default  selection, if you don't want to boot to the 3GB environment by default, then copy it below the original line instead.
    Note: Your text string may be different from the text  string in this solution, so be sure to copy the text string from your boot.ini  file, and not the text string included here.
  • Modify the copied line to  include "3GB" (you can change anything within the quotation  marks to be descriptive), as shown in the following example:

multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="WinXP  Pro 3GB" /noexecute=optin /fastdetect /3GB /userva=2900

 

Note: Do not overwrite any existing  lines. I set the timeout for my menu to be 8 seconds (instead of 30),  which is plenty enough to make a menu selection during the boot process.  To do this, just change the line to:  timeout=8

  • Save and close the boot.ini file.
  • Click OK to close each dialog box.
  • Restart your computer.
  • During startup, you be presented with a menu to have the option of which environment to boot.

Note: If problems occur during startup, you may need  to update some of your drivers.

Enable the  3GB switch on Windows Vista and Windows 7 (32-bit)

  • Right-click Command Prompt in the Accessories  program group of the Start menu. Click Run as Administrator.
  • At the command prompt, enter "bcdedit /set  IncreaseUserVa 3072"
  • Restart the computer.

Disable the 3GB switch on Windows  Vista and Windows 7 (32-bit)

  • Right-click on Command Prompt in the Accessories  program group of the Start menu. Click Run as Administrator.
  • At the command prompt, enter "bcdedit /deletevalue  IncreaseUserVa"
  • Restart the computer.

 

For more information on the 3GB switch,  refer to the following Microsoft MSDN article:

http://msdn2.microsoft.com/en-us/library/ms791558.aspxhttp://msdn2.microsoft.com/en-us/library/ms791558.aspx

 

More on BCDEdit at: http://www.windows7home.net/how-to-use-bcdedit-in-windows-7/

Joe Galliera

Got Simulation?

Posted by Joe Galliera Employee Sep 24, 2009
Got  Simulation?  I think the following video (link below) clearly demonstrates how design analysis has lead the way in improving the safety of everyday products.   The video shows from many angles how dramatic a head-on collision can be, but in a typical modern day automobile, being able to walk away from it is something  that we may take for granted!

You may ask: Why should I choose to begin my blog with this post?  The straightforward answer is simulation should be just another step in today's engineering design process.  People frequently will hear me say that a design is not complete without simulation, because it is my true feeling that design analysis/validation is something that is misunderstood by a majority of people.  Everybody needs to be doing more simulation, they just don't know it.  It is my duty to share my personal experiences about  why simulation is integral in the design process... and there will be many tips about the SolidWorks Simulation products provided along the way!

Title slide reads:  "In celebration of the Insurance Institute for Highway Safety's 50th  Anniversary, a 1959 Chevrolet Bel Air was crashed into a 2009 Chevrolet  Mailbu."

Download ZIP of WMV video: http://bit.ly/XgCG0 (11.5  MB)