Using External Data in ANSYS Mechanical to Tabular Loads with Multiple Variables, Part 2

ANSYS Mechanical is great at applying tabular loads that vary with an independent variable. Say time or Z.  What if you want a tabular load that varies in multiple directions and time. In part one of this series, I covered who you can use the External Data tool to do just that. In this second part, I show how you can alternatively use APDL commands added to your ANSYS Mechanical model to define the tabular loading.

PADT-ANSYS-Tabular-loads-2

Mechanical Meshing Enhancements in ANSYS 18 and Beyond – Webinar

ANSYS Meshing is a general-purpose, intelligent, automated high-performance product that helps engineers to produce the most appropriate mesh for accurate, efficient multi-physics solutions.

With the release of ANSYS version 18 earlier this year, engineers were introduced to a variety of new and innovative enhancements that help improve the quality of their meshing, and speed up the simulation process.

Join PADT’s Simulation Support Manager Ted Harris, for an in depth look at new mechanical meshing capabilities made available in ANSYS 18.0, 18.1 and 18.2!

This free webinar will cover a variety of new and improved capabilities within the latest version of ANSYS, including:

  • Improved diagnostics/mesh metrics
  • More flexible mesh controls
  • New physics preference for Hydrodynamics
  • and much more!

Don’t miss this informative presentation – Secure your spot today!

If this is your first time registering for one of our Bright Talk webinars, simply click the link and fill out the attached form. We promise that the information you provide will only be shared with those promoting the event (PADT).

You will only have to do this once! For all future webinars, you can simply click the link, add the reminder to your calendar and you’re good to go!

AZBigMedia.com: The do’s and don’ts of pitching a startup

One of the coolest things I get to do often is to listen to startups pitch their companies. Every single one is an educational experience where I also get to feed off of the passion and drive of entrepreneurs. The problem is, more than half of the pitches I hear are bad. Sometimes it is the delivery, but public speaking is hard for most people, and I can go beyond that. What gets to me is when the speakers just make silly mistakes in what should be a very simple task. After a couple of recent discussions with others who hear many pitches, I have come up with a list of The Do’s and Don’ts of pitching a startup.

Phoenix Business Journal: ​A few thoughts after 100 blog posts

The post “A few thoughts after 100 blog posts” is my 100th guest blog article for the Phoenix Business Journal. That is a lot of 500 or so word rants and missives. Because I like round numbers, and I did write a lot of posts, I figured it would be ok to be a little self-indulgent and go introspective on the whole experience, and talk directly to you, my occasional reader.

Getting to Know PADT: Our Offices in Four Other States

This is the fourth installment in our review of all the different products and services PADT offers our customers. As we add more, they will be available here.  As always, if you have any questions don’t hesitate to reach out to info@padtinc.com or give us a call at 1-800-293-PADT.

Updated on 4/6/2018: Added a paragraph on our efforts in Austin, Texas and modified California to reflect our growth there. 

Based in the ASU Research Park in Tempe Arizona, PADT has thrived and grown in the technologically oriented East Valley of the Phoenix Metro area. When people think about the company, they think about Phoenix and Arizona. Phoenix is even in the company name. What many people do not realize is that PADT has thriving sales and support offices in four other states. If we updated our name, it would be Southwest Simulation, Design, and Additive Technologies. However, SWSDAT is even worse than PADT! Worse yet, people might think we are from Switzerland.

As the company has grown so has our sales and support territory for the products we sell. And the best way to provide outstanding support to their high-technology customers is to be part of the local technology community. So starting with Colorado in 2010, the company has been investing in the communities that are allowing it to grow. Below is a brief overview of each office and what makes them unique.

PADT Colorado

Arizona and Colorado are like siblings, so alike in some ways, totally different in others. The Rocky Mountain state was the first state that saw significant growth for PADT outside of Arizona, so it was an obvious place to start growing. The bulk of our business there is around selling and supporting Stratasys Additive Manufacturing equipment. And to be blunt, it has been a great location for our engineering staff who literally could not take the heat of Arizona. Located in Littleton just south of Denver, we are close to our large Aerospace customers, and a quick drive to Boulder, Fort Collins, Colorado Springs, and Golden where we also have clusters of customers.

The high-tech nature of the industry in the state fit perfectly with PADT’s strengths. From launch vehicles to mining, to cell phone cases, we have fit right in with our growing customer base. And part of our fitting there is the fantastic location on Littleton Blvd right next to the Arapahoe County courthouse. We rent a suite on the second floor a cool mid-century building that is walking distance from light rail and restaurants – a great location. If you ever visit, ask to see the bathroom and kitchen, both are a blast from the past.

PADT New Mexico

Our largest customer outside of the Phoenix area is the combined Sandia National Lab, and Los Alamos National Lab, and Kirtland’s Air Force Research Lab. All are located in New Mexico and are a major focus for us for Additive Manufacturing and ANSYS sales and support. That is why our New Mexico office is so important. It is located in the Sandia Research Park, right outside the Eubank entrance to Sandia National Lab.

The office provides a nice space for training as well as a location to hold office hours and meet with users who may be in locations we are not authorized to visit. Many of our non-lab customers are in that same park or nearby. This office has been a great base of operations for our continued growth in the state. This office may have the best views of any in the PADT family. Many of us also feel it also offers the best Mexican food options.

PADT Utah

Utah has a small but very active technology community, and PADT’s presence in the state is growing quickly. Our office in Murray at the I-15 and 5300S is only 9 miles due south of downtown Salt Lake City. If you have not visited, the space is actually one of our more enjoyable offices to work in. One large room houses the sales and engineering team as well as a host of 3D Printers, supplies for maintenance, and a cool sitting area.

Working with so many customers in Utah leads to a lot of driving, tech companies seem to be evenly distributed along the I-15 corridor, so the local team does a lot of driving. However, the office is a great central location for meeting with customers and seminars and as a starting point for those drives to Provo, Park City, and Ogden as well as destinations in-between. As our business in Utah continues to grow, we may soon have to expand this office.

PADT California

Our newest second most recent location is in Southern California, Torrance in particular. If New Mexico has the best views, this one probably has the worst… unless you like refineries. However, it is a central location that has served us well for almost two years now. Just down the street from our largest customer, Honeywell Aerospace, it is the ultimate home base for such a freeway dominated territory. Our local staff can get there fairly easily from their homes, and when the rest of us visit, its location near LAX is very convenient.

Our focus in that office right now is Simulation. Particularly ANSYS sales and support. Our SoCal customers like to drop by when they are in the neighborhood, and the PADT team there is constantly on the road out visiting them. It works great for our customers nearby, but since that office covers from San Diego North to San Luis Obispo, a random collection of coffee shops serve as an office for SoCal almost as much as our Torrance base.

Our growth in the region is quick, and we look forward to opening more satellite offices across an area that is larger in population and real estate than some countries.

Since publishing this article, we have added two new sales people to PADT California that will be working from home offices as well as dropping into Torrance as needed.  They are based in Pasadena and San Diego, giving us better coverage of the South and North part of the region.

PADT Texas

When people look at PADT and where we are located, they almost always say “You should open an office in Austin, the tech community there is a perfect fit for your skills and culture.” We finally listened and are proud to announce that our newest location is in Austin Texas. This new office will be initially focused on ANSYS Sales and Support across the great state of Texas. We have had customers for other products and services in the state for decades and are pleased to have a permanent local presence now.

We have hit the ground running.and have a growing group of customers who are now enjoying PADT’s famous support. We hope to add engineers and more salespeople as we increase our efforts in Texas.  Right now we are trying to get them to understand that Arizona Cowboys are real cowboys.

 

Serving our Customers Better

Sometimes technology allows people to connect fairly well. However, nothing beats being local. The best way for PADT to support our customers is to not just be there for them technically, but also to be part of the communities they reside in. And that community spreads across the Southwestern United States, and we are proud to be members of the Colorado, New Mexico, Utah, and Southern California technical communities. People innovate everywhere, so we are there, local, to make innovation work for them.

All Things ANSYS Episode 005 – Getting to know convergence better and hidden gems in the ANSYS product family

Published on: September 25, 2017
With: Tom Chadwick, Ted Harris, Eric Miller
Description: In this episode your host and Co-Founder of PADT, Eric Miller is joined by PADT’s Senior CFD Engineer Tom Chadwick,  and Simulation Support Manager Ted Harris for a discussion on convergence with both FEA and CFD solutions, as well as a look at some of their favorite hidden gems in the ANSYS tools set. Learn about some beneficial ANSYS capabiliites you may not be aware of!
Listen:
Subscribe:

 

Phoenix Business Journal: ​While AI, IoT, and automation are taking over we forgot about genetic engineering

The big technologies right now are Artificial intelligence, the Internet of Things, and the automation of everything from manufacturing to our automobiles. These advanced technologies will transform how we live our lives.  But ” While AI, IoT, and automation are taking over we forgot about genetic engineering.”  This is something everyone, especially those in tech, need to stay on top of.

What we Learned at the Geomagic Conference about Design X and Control X

On September 11th and 12th Mario Vargas (Hardware Manager for PADT Inc.) and I (James Barker, Application Engineer for PADT Inc.) attended Convergence 2017 in Los Angeles, CA.  This event is held by 3D Systems and is the America’s Software Partner Meeting.  Many strategic partners were in attendance from all across the USA, Canada, and Latin America.  We were able to learn about some new enhancements to Geomagic that will help you with Inspection or Reverse Engineering BIG time!  The first day of meetings we heard from Vyomesh Joshi (CEO of 3D Systems referred to as VJ).  He mentioned that 3D Systems has committed 17% to R&D and after going to this event it is apparent!  VJ briefly talked about each of their software options.  The 1st being Control X and how Polyworks currently has the edge for inspection software but after this next software release, he and other 3D Systems employees seemed confident that they could surpass Polyworks.  The 2nd software he talked about was Freeform which allows users to freely design parts by using a haptic device.  This software would be great for creating custom shapes on a whim.  If you haven’t tried a haptic device, you need to!  It will blow your mind as a designer with the freedom you get by using the haptic device and this Freeform Software.  The 3rd software he talked about was Cimatron which aids in the design of mold and die design.  Of the top 10 largest USA mold makers, 7 of them use Cimatron Software.  The 4th software is something new that will be released later this month.  I would love to tell you more about it but can’t….  sorry!

A little about why Mario and I attended this convention, PADT Inc. offers 3D Scanning as both a service and also as hardware or software you can buy.  We use both Geomagic Design X and Geomagic Control X and have experts that are scanning parts for customers for either inspection results or for reverse engineering purposes at our Tempe, AZ office.  The scanner that we use is a CMM quality scanner from Zeiss.  This scanner is capable of scanning 5 million points per scan!  We also offer 3D Systems Capture and Capture Mini scanners which are great tools for reverse engineering.  Each time they scan a part they are capturing about 1 million points per scan.  I am located in the Salt Lake City, Utah office and have a Capture Mini scanner that anyone wanting to see and demo, can come look at and evaluate at our office.  Same holds true for the Capture scanner and Zeiss scanner in our Tempe, AZ Headquarters.  Since we offer these services, we love knowing what new tools are available with these product releases.

Jumping back to the conference, on September 12th, there were breakout sessions.  We chose to go to the Geomagic Design X session to see what enhancements have been made.  This software is the preferred software in all of the industry for reverse engineering parts.  There were many different vendors/partners in the room we were at.  There was even a rep from Faro who prefers to sell Geomagic Design X software with each Faro Arm that he sells because this software is so powerful.  The neat thing about this software is all of the improvements that have been made to it.  If you are accustomed to designing parts with Solidworks, Solidedge, NX, Catia, Pro-E or any of the other CAD software, you will be able to use this software with ease.  Every command that you execute within Design X is editable just like the major CAD software.  You have the ability to create sketches on planes or to make life even easier, there are wizards that automatically create sketches and perform a command like an extrusion or revolve that is editable after completing the wizard.  After you have finished reverse engineering your parts within Design X, you can live transfer your new CAD data over to the above-mentioned CAD software.  Once you have imported this data into NX or Solidworks, you can again edit any of the sketches that were created within Design X but now in your software of choice!  I would love to show you how powerful this software is.  There is a reason why it is the preferred reverse engineering software in the industry.

Geomagic Control X session was next.  It also happened to be the last session of the day.  To be honest, I have only used Design X so I was looking forward to learning more about this software.  From all the demo’s that I have seen in the past from this software, it appeared really hard to use.  That is all changing with this new software release and is the reason why VJ is confident that it will compete and could exceed Polyworks as the preferred software for inspection.  The biggest thing that stuck out to me was the ability to set up a workflow for scanned data for inspection so that you can create your inspection reports.  The idea is that if you have a part that needs to be inspected for quality, you 3D scan the part and then import the CAD file.  By overlaying the scanned data over the CAD data you can show the deviation within the 2 parts and you are able to have different views in a 3D PDF to share with others the actual quality of the part.  As you are assigning your GD&T to this first inspection file, you are creating the first steps of the workflow.  There are many options for the workflow that you can create and 3D Systems has made it easy to create the workflow.  I feel that the power of this software is when you can open up the results of the first inspection report and do a split screen on your monitor to show the 100th or 1,000th part side by side and see how that part deviates from the first.

I had a great time in California at this event even though all of our time was spent at the hotel.  The streets looked nice from the window on the 11th floor.  Maybe next time we will venture out!  If anyone from 3D Systems is reading this, let’s go out to eat next time instead of eating at the hotel for breakfast, lunch, and dinner!  Although the view from the dining room was nice!

If you have any questions about 3D scanning whether it is for Inspection or for Reverse Engineering, let us know at PADT Inc.  We look forward to helping you.

Announcing Nerdtoberfest 2017 – Save the Date!

We are excited to announce the return of our annual fall open house, Nerdtoberfest! PADT will be opening it’s doors to the public for a celebration of all things engineering and manufacturing in Arizona.

More information, along with a full event agenda will be made available soon, however in the meantime you can secure your spot now by clicking the link below.

Join us:
Where:  7755 S Research Dr, Tempe, AZ 85284

When: Thursday, October 26th 2017

What Time: 5:00 PM – 8:00 PM MST

Standard Roof Rack Fairing Mount Getting In Your Way?! Engineer it better and 3D Print it!

It is no mystery that I love my Subaru. I bought it with the intention of using it and I have continually made modifications with a focus on functionality.

When I bought my roof crossbars in order to mount ski and/or bike racks, I quickly realized I needed to get a fairing in order to reduce drag and wind noise. The fairing functions as designed, and looks great as well. However, when I went to install my bike rack, I noticed that the fairing mount was in the way of mounting at the tower. As a result, I had to mount the rack inboard of the tower by a few inches. This mounting position had a few negative results:

  • The bike was slightly harder to load/unload
  • The additional distance from the tower resulted in additional crossbar flex and bike movement
  • Additional interference between bikes when two racks are installed

These issues could all be solved if the fairing mount was simply inboard a few more inches. If only I had access to the resources to make such a concept a reality…. oh wait, PADT has all the capabilities needed to take this from concept to reality, what a happy coincidence!

First, we used our in-house ZEISS Comet L3D scanner to get a digital version of the standard left fairing mount bracket. The original bracket is coated with Talcum powder to aid in the scanning process.

The output from the scanning software is a faceted model in *.STL format. I imported this faceted CAD into ANSYS SpaceClaim in order to use it as a template to create editable CAD geometry to use as a basis to create my revised design. The standard mounting bracket is an injection molded part and is hollow with the exception of a couple of ribs. I made sure to capture all this geometry to carry forward into my redesigned parts, which would make the move to scaled manufacturing of this design easy.

Continuing in ANSYS SpaceClaim, as it is a direct modeling software instead of traditional feature-based modeling, I was able to split the bracket’s two function ends, the crossbar end and fairing end, and offset them by 4.5 inches, in order to allow the bike rack to mount right at the crossbar tower. I used the geometry from the center section CAD to create my offset structure. A mirrored version allows both the driver and passenger side fairing mount to be moved inboard to enable mounting of two bike racks in optimal positions. The next step is to turn my CAD geometry back into faceted *.STL format for printing, which can be done directly within ANSYS SpaceClaim.

 

After the design has been completed, I spoke with our 3D printing group to discuss what technology and material would be good for these brackets, as the parts will be installed on the car during the Colorado summer and winter. For this application, we decided on our in-house Selective Laser Sintering (SLS) SINTERSTATION 2500 PLUS and glass filled nylon material. As this process uses a powder bed when building the parts, no support is needed for overhanging geometry, so the part can be built fully featured. Find out more about the 3D printing technologies available at PADT here.

Finally, it was time to see the results. The new fairing mount offset brackets installed just like the factory pieces, but allowed the installation of the bike rack right at the tower, reducing the movement that was present when mounted inboard, as well as making it easier to load and unload bikes!!

I am very happy with the end result. The new parts assembled perfectly, just as the factory pieces did, and I have increased the functionality of my vehicle yet again. Stay tuned for some additional work featuring these brackets, and I’m sure the next thing I find that can be engineered better! You can find the files on GrabCAD here.

 

Phoenix Business Journal: On 9/11, we’re reminded that the unthinkable can happen

Lots of things come to mind on September 11th. The bravery of the first responders, the way the country came together after the attacks, the changes in how we live our lives every day now because of what happened. The most important lesson that we learned was that “On 9/11, we’re reminded that the unthinkable can happen.

Introducing the 2017 ANSYS Arizona Innovation Conference

As the world of manufacturing continues to grow and change, engineers are being challenged to design, test, and evaluate products in increasingly complex environments. In such a time it is necessary to rely on an all-encompassing simulation platform that can handle a variety of physics efficiently, operating as a one stop shop for complete virtual prototyping. ANSYS is that platform!

Join us for this informative seminar including presentations from customers and ANSYS technical experts, focusing on how to effectively implement the ANSYS platform and productivity enhancement tools into your work-flow.

Through this free event we hope to inform you on how a single consolidated platform for complete virtual prototyping can help to drive efficiency across your company!

Date: October 4, 2017

Time: 9:00 AM – 4:30 PM MST AZ

Location: ASU SkySong – Building 3
1365 N. Scottsdale Rd.
Scottsdale, AZ 85257

Check out the full agenda, with presentations covering a plethora of topics including:

  • ANSYS Solutions for Additive Manufacturing
  • Wireless Connectivity with RF Engineering
  • Commercial Antenna Array Work Flow Using ANSYS Electromagnetic Tools

This event will include presentations from customers and ANSYS technical experts alike, focusing on how to effectively implement the ANSYS platform and productivity enhancement tools into your work-flow.

We look forward to seeing you there – Secure your spot today!

 

How to Simplify Aircraft Certification – Stratasys Webinar

The aerospace industry’s adoption of additive manufacturing is growing and predicted to revolutionize the manufacturing process. However, to meet stringent FAA and EASA requirements, AM-developed aerospace products must be certified that they can achieve the robust performance levels provided by traditional manufacturing methods. Current certification processes are complex and variable, and thus obstruct AM adoption in aerospace.

Thanks to a newly released aerospace package released by Stratasys for their Fortus 900mc printer and ULTEM 9085 resin, Aerospace Organizations are now able to simplify the aviation certification process for their manufactured parts.

Join PADT’s 3D Printing General Manager, Norman Stucker for a live webinar that will introduce you to the new Stratasys aerospace package that removes the complexity from FAA and EASA certification.

By attending this webinar, you will learn:

  • How Stratasys can help get more parts certified for flight quicker and easier.
  • The benefits of Aerospace Organizations using the Fortus 900mc and ULTEM 9085 resin
  • And much more!

Don’t miss your chance to attend this upcoming event,
click below to secure your spot today!

 

If this is your first time registering for one of our Bright Talk webinars, simply click the link and fill out the attached form. We promise that the information you provide will only be shared with those promoting the event (PADT).

You will only have to do this once! For all future webinars, you can simply click the link, add the reminder to your calendar and you’re good to go!

Working Wonders with ADPL Math Illustrated: Thermal Modal Analysis

Guest Blogger

We are pleased to publish this very useful post from Nicolas Jobert from Synchrotron SOLEIL in France. Nicolas is a Mechanical Engineer with more than 20 years of experience using ANSYS for engineering design and analysis in academia and industry. He currently is Senior Mechanical Engineer at Synchrotron SOLEIL, the French synchrotron radiation facility. He also teaches various courses on Design and Validation in the field of structural and optomechanics. He graduated from the Ecole Centrale Marseille, France, and is a EUSPEN member.

As Time Goes By

Do you remember the moment you first heard about ANSYS introducing APDL Math?

I, for one, do, and I have a vivid memory of thinking “Wow, that can be a powerful tool, I’m dead sure it won’t be long before an opportunity arises and I’ll start developing pretty useful procedures and tools”. Well, that was half a decade ago, and to my great shame, nothing quite like that has happened so far. Reasons for this are obvious and probably the same for most of us: lack of time and energy to learn yet another set of commands, fear of the ever present risk of developing procedures that are eventually rejected as nonstandard use of the software and therefore error-prone (those of you working under quality assurance, raise your hand!), anxiety of working directly under the hood on real projects with little means to double check your results, to name a few.

That said, finally an opportunity presented itself, and before I knew it, I was up and running with APDL Math. The objective of this article is to showcase some simple yet insightful applications and hopefully remove the prevention one can have regarding using these additional capabilities.

For the sake of demonstration, I will begin with a somewhat uncommon analysis tool that should nevertheless ring a bell for most of you, that is: modal analysis (and yes, the pun is intended). You may wonder what is the purpose of using APDL Math to perform a task that is a standard ANSYS capability since say revision 2.0, 40 years ago? But wait, did I mention that by modal analysis, I mean thermal modal Analysis?

Thermal Modal Analysis at a Glance

Although scarcely used, thermal modal analysis is both an analysis and a design validation tool, mostly used in the field of precision engineering and or optomechanics. Specifically, it can serve a number of purposes such as:

Q: Will my system settle fast enough to fulfill design requirements?
A: Compute the system Thermal Time Constants

Q: Where should I place sensors to get information rich / robust measurements?
A: Compute Thermal modes and place your sensors away for large thermal gradients

Q: Can I develop a reduced model to solve large transient thermal mechanical problems?
A: Modal basis allows for the construction of such reduced problem effectively converting a high-order coupled system to a low order, uncoupled set of equations.

Q: How to develop a reduced order state-space matrices representation of my thermal system (equivalent to SPMWRITE command)?
A: Modal analysis provides every result needed to build those matrices directly within ANSYS.

Although you might only be vaguely familiar with many or all of those topics, the idea behind this article is really to show that APDL Math does exactly what you need it to do: allow the user to efficiently address specific needs, with a minimal amount of additional work. Minimal? Let’s see what it looks like in reality, and you will soon enough be in a position to make your own opinion on the matter.

Thermal Modal Analysis using APDL Math

To begin with, it is worth underlining the similarities and differences between structural (vibration) modes and thermal modes.

Mathematically, both look very much the same, i.e. modes are solutions of the dynamics equation in the absence of forcing (external) term:

Domain

Equation solved

Terms Explained

Structural

[K] is the stiffness matrix
[M] is the mass matrix

Thermal

[K] is the conductivity matrix
[C] is the capacitance matrix

Now, the fundamental difference is that the eigenvalues have completely different physical interpretations (This is a direct consequence of the fact that dynamical systems are 2nd order systems, whereas thermal systems a 1st order systems. While after being disturbed the former will oscillate around equilibrium position, the latter will return to its initial state via exponential decay. Mind you, there is no such thing as thermal resonances!) :

  • Structural : λ=ω², i.e. the square of a circular frequency
  • Thermal: λ=1/τ, i.e. the inverse of time constant

No big deal, right? Hence, the APDL Math code for Thermal Modal Analysis should be a straightforward adaption of the original. As it turns out, the modifications are quite small. Below is a table comparing input codes to perform both type of analyses, using APDL Math.

 

Structural

Thermal

! Setup Model
 …

! Make ONE dummy transient solve 
! to write stiffness and mass
! matrices to .FULL file 
 /SOLU
 ANTYPE,TRANSIENT
 TIME,1
 WRFULL,1
 SOLVE


! Get Stiffness and Mass 
 *SMAT,MatK,D,IMPORT,FULL,,STIFF
 *SMAT,MatM,D,IMPORT,FULL,,MASS










! Eigenvalue Extraction
 Antype,MODAL
 modopt,Lanb,NRM,0,Fmax
 *EIGEN,MatK,MatM,,EiV,MatPhi

! No need to convert eigenvalues
! to frequencies, ANSYS does 
! it automatically



! Done !
! Setup Model
 …

! Make TWO dummy transient solve 
! to separately write conductivity
! and capacitances matrices to .FULL file
 /SOLU
 ANTYPE,TRANSIENT
 TIME,1
 NSUB,1,1,1
 TINTP,,,,1
 WRFULL,1

! Zero out capacitance terms
 …
 SOLVE
 ! Get Conductivity Matrice
 *SMAT,MatK,D,IMPORT,FULL, Jobname.full,STIFF
 ! Restore capacitance and zero out 
 ! conductivity terms
  …
 SOLVE
 ! Get Capacitance Matrice
 *SMAT,MatC,D,IMPORT,FULL,,STIFF

! Eigenvalue Extraction
 Antype,MODAL
 modopt,Lanb,NRM,,0,1/(2*PI*SQRT(Tmin))
 *EIGEN,MatK,MatC,,EiV,MatPhi

! Convert Eigenvalues for Frequency 
! to Thermal time Constants
!
 *do,i,1,EiV_rowDim
    Eiv(i)=1/(2*PI*Eiv(i))**2
 *enddo

! Done !

The only data requested from the users is the number of requested modes (NRM) as well as the upper frequency (or for that matter, the shortest time constant of interest). Also, note that in the thermal case, one needs to perform two separate dummy analyses to store the conductivity and capacitance matrices, since internally those are merged into an equivalent stiffness (conductivity) matrix:

If you are familiar with APDL, some important differences are apparent here:

  • Results from the eigenvalues are stored in a vector (EiV) and a matrix (MatPhi), which need not be declared but are created when executing the *EIGEN command (no *DIM required).
  • For each APDL Math entity, ANSYS automatically maintains variables named Param_rowDim and Param_colDim, hence removing the burden to keep track of dimensions.

But where on Earth is my eye candy?

Now that we have some procedure and results, we would like to be able to show this to the outside world (and to be honest, some graphical results would also help getting confidence in results).

The additional task to do so is really minimal. What we need to do is simply to put back those numerical results into the ANSYS database so that we can use all the conventional post-processing capabilities. This can be made using the appropriate POST1 commands, essentially: DNSOL. And, while we are at it, why not do a hardcopy to an image file? Here is the corresponding input.

 … User should place all nodes with non-prescribed temperatures in a component named MyNodeComponent

… First, convert Eigenvectors from solver to BCS ordering
 ! Conversion needed
 *SMAT,Nod2Bcs,D,IMPORT,FULL,Jobname.full,NOD2BCS
 *MULT,Nod2Bcs,TRAN,MatPhi,,MatPhi

! Then, read in mapping vector to convert to user ordering
 *VEC,MapForward,I,IMPORT,FULL,Jobname.full,FORWARD

! Put the results in ANSYS database
 /POST1
 *do,ind_mode,1,NRM
 cmsel,s,MyNodeComponent
 curr_node=0
 *do,i,1,ndinqr(0,13)
 curr_node=ndnext(curr_node)
 curr_temp=MatPhi(MapForward(curr_node),ind_mode)
 dnsol,curr_node,TEMP,,curr_temp
 *enddo
 Tau=1/(2*3.14*EiV(ind_mode))**2

To=NINT(Tau*10)/10 ! compress to 1 digit after comma
 /title,Mode #%ind_mode% - Tau=%To%s
 plnsol,temp
 ! Hardcopy to BMP file
 /image,SAVE,JobName_Mode%ind_mode%,bmp
 *enddo

This way, modes can be displayed, or even written to a conventional .RTH file (using RAPPND), and used as any regular ANSYS solver result.

Nice, but an actual example wouldn’t hurt, would it?

Now you may wonder what the results look like in reality. To remain within the field of precision engineering, let’s use a support structure typically designed for high-stability positioning. From a structural point of view, it must have a high dynamic stiffness and a low total mass so that a Delta shaped bracket is appropriate. Since we want the system to rapidly evacuate any heat load, we choose aluminum as candidate material. We do know from first principles that any applied disturbance will exponentially vanish and the system will go back to equilibrium state. Now, what will be the time constants of this decay?

For the sake of simplicity we restrict the analysis to a highly simplified, 2D model of such a support. PLANE55 elements are used to model the structural part while the heat sink is accounted for using SURF151. Boundary conditions are enforced using an extra node.

After applying boundary conditions, we execute the modal solution to obtain say – the first 8 modes.

Index Time Constant [s] Comment
1 535.9 Quasi-uniform temperature field (i.e. “rigid body” mode)
2 32.1 1st order (one wavelength along perimeter)
3 23.8 1st order (one wavelength along perimeter)
4 8.1 2nd order (two wavelengths  along perimeter)
5 6.8 2nd order (two wavelengths  along perimeter)
6 3.5 3rd order (three wavelengths  along perimeter)
7 3.1 3rd order (three wavelengths  along perimeter)
8 2.2 4th order (four wavelengths along perimeter)

The output is strictly the same as the one a standard modal analysis, except for the two additional lines at the end of the solving sequence.

Allocate a [8] Vector : EIV

Allocate a [227][8] Dense Matrix : MatPhi

Please note that the solution has 227 DOFs whereas the entire problem has 228 DOFs. This is the consequence of having introduced the boundary conditions as an enforced temperature on a node, which DOF is therefore removed from the DOF set to be obtained by the solver.

Also, we might want to use the modal shapes information to decide which locations are best suited to capture the entire temperature field on the structure. Without knowledge of the excitation source, one straightforward way to do so is to retain for each mode the node that has the largest amplitude. This is made even easier in this situation, since we have normalized each mode to have unit maximum amplitude we just need to select nodes having modal amplitude equal to 1 (or -1). On the figure below, each temperature sensor location is marked with a ‘TSm’ label where m is the mode index.

Doing so, we reach a pretty satisfactory distribution for the sensors locations, completely consistent with intuition. In numerical terms, we can also check that the modal matrix [Φ]_sensors, i.e. the original full matrix restricted to the selected DOF, has an excellent condition number. But there are many other things we could do starting from this. For example, with additional information, such as the location and the frequency content of the temperature fluctuations, one could further restrict the set of needed temperature sensors by running a dummy transient analysis and choosing locations where the correlation between sensors readings is as low as possible (using *MOPER,,,CORR). Even better, one can estimate the thermally induced displacements and select locations best suited to build an empirical model (typically using AR or ARMA), allowing one to predict structural displacements induced by temperature fluctuations using just a couple of sensors. This in turn can be used to select control strategies, check modal controllability… all within ANSYS.

Conclusion

APDL Math was presented as an alternate route for users who need to include specialized steps in an otherwise standard FE process, and in my opinion it does just that. The benefits can be immense and the learning curve is steep but short. As long as the user knows what he/she is doing, there is little possibility to get lost: after all, APDL Math only comprises 18 additional commands.

What hindered me so far was the necessity to account for internal, BCS and user ordering, but it really is not a big deal, as seen from the above example.

What is more, the possibility to store the created results in the Mechanical APDL database (DNSOL and RAPPND are your friends!) provides every means to control your results and finally to build confidence in your developments.

And for those of us who prefer to stay within Workbench environment, there is nothing preventing from including APDL Math procedures into Workbench command snippets.

This was just an introductory example, since many other applications could be found, to name a few just in the fields of precision engineering and/or opto-mechanics:

  • Speed up transient thermal mechanical analyses
  • Perform harmonic analysis of thermal models
  • Virtual testing of physical setup, including real-time control systems (model based)
  • Modal testing, error localization, automated model updating

Let us know your opinion on the matter, and if further introductory articles on APDL Math could be of use to the ANSYS users community.

All Things ANSYS Episode 004 – Fun fluid additions in ANSYS 18.2 and the disruptive nature of Discovery Live

Published on: September 11, 2017
With: Jim Peters, Tom Chadwick, Ted Harris, Eric Miller
Description: In this episode your host and Co-Founder of PADT, Eric Miller is joined by PADT’s Senior CFD Engineer Tom Chadwick, Senior Staff Technologist Jim Peters, and Simulation Support Manager Ted Harris for a look at the CFD updates available within ANSYS 18.2, along with a discussion on why they love the new disruptive simulation tool from ANSYS; Discovery Live.
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