One of the cool new features in CFX 18 is the ability to actively review results while the calculation is running. It is supported for steady state and transient calculations, and now includes support for rotating reference frames as well.
What follows are some tutorial-esque steps to get you started.
In a previous post, I laid out a structural classification of cellular structures in nature, proposing that they fall into 6 categories. I argued that it is not always apparent to a designer what the best unit cell choice for a given application is. While most mechanical engineers have a feel for what structure to use for high stiffness or energy absorption, we cannot easily address multi-objective problems or apply these to complex geometries with spatially varying requirements (and therefore locally optimum cellular designs). However, nature is full of examples where cellular structures possess multi-objective functionality: bone is one such well-known example. To be able to assign structure to a specific function requires us to connect the two, and to do that, we must identify all the functions in play. In this post, I attempt to do just that and develop a classification of the functions of cellular structures.
Any discussion of structure in nature has to contend with a range of drivers and constraints that are typically not part of an engineer’s concern. In my discussions with biologists (including my biochemist wife), I quickly run into justified skepticism about whether generalized models associating structure and function can address the diversity and nuance in nature – and I (tend to) agree. However, my attempt here is not to be biologically accurate – it is merely to construct something that is useful and relevant enough for an engineer to use in design. But we must begin with a few caveats to ensure our assessments consider the correct biological context.
1. Uniquely Biological Considerations
Before I attempt to propose a structure-function model, there are some legitimate concerns many have made in the literature that I wish to recap in the context of cellular structures. Three of these in particular are relevant to this discussion and I list them below.
1.1 Design for Growth
Engineers are familiar with “design for manufacturing” where design considers not just the final product but also aspects of its manufacturing, which often place constraints on said design. Nature’s “manufacturing” method involves (at the global level of structure), highly complex growth – these natural growth mechanisms have no parallel in most manufacturing processes. Take for example the flower stalk in Fig 1, which is from a Yucca tree that I found in a parking lot in Arizona.
At first glance, this looks like a good example of overlapping surfaces, one of the 6 categories of cellular structures I covered before. But when you pause for a moment and query the function of this packing of cells (WHY this shape, size, packing?), you realize there is a powerful growth motive for this design. A few weeks later when I returned to the parking lot, I found many of the Yucca stems simultaneously in various stages of bloom – and captured them in a collage shown in Fig 2. This is a staggering level of structural complexity, including integration with the environment (sunlight, temperature, pollinators) that is both wondrous and for an engineer, very humbling.
The lesson here is to recognize growth as a strong driver in every natural structure – the tricky part is determining when the design is constrained by growth as the primary force and when can growth be treated as incidental to achieving an optimum functional objective.
Even setting aside the growth driver mentioned previously, structure in nature is often serving multiple functions at once – and this is true of cellular structures as well. Consider the tessellation of “scutes” on the alligator. If you were tasked with designing armor for a structure, you may be tempted to mimic the alligator skin as shown in Fig. 3.
As you begin to study the skin, you see it is comprised of multiple scutes that have varying shape, size and cross-sections – see Fig 4 for a close-up.
The pattern varies spatially, but you notice some trends: there exists a pattern on the top but it is different from the sides and the bottom (not pictured here). The only way to make sense of this variation is to ask what functions do these scutes serve? Luckily for us, biologists have given this a great deal of thought and it turns out there are several: bio-protection, thermoregulation, fluid loss mitigation and unrestricted mobility are some of the functions discussed in the literature [1, 2]. So whereas you were initially concerned only with protection (armor), the alligator seeks to accomplish much more – this means the designer either needs to de-confound the various functional aspects spatially and/or expand the search to other examples of natural armor to develop a common principle that emerges independent of multi-functionality specific to each species.
1.3 Sub-Optimal Design
This is an aspect for which I have not found an example in the field of cellular structures (yet), so I will borrow a well-known (and somewhat controversial) example  to make this point, and that has to do with the giraffe’s Recurrent Laryngeal Nerve (RLN), which connects the Vagus Nerve to the larynx as shown in Figure 5, which it is argued, takes an unnecessarily long circuitous route to connect these two points.
We know that from a design standpoint, this is sub-optimal because we have an axiom that states the shortest distance between two points is a straight line. And therefore, the long detour the RLN makes in the giraffe’s neck must have some other evolutionary and/or developmental basis (fish do not have this detour) . However, in the case of other entities such as the cellular structures we are focusing on, the complexity of the underlying design principles makes it hard to identify cases where nature has found a sub-optimal design space for the function of interest to us, in favor of other pressing needs determined by selection. What is sufficient for the present moment is to appreciate that such cases may exist and to bear them in mind when studying structure in nature.
2. Classifying Functions
Given the above challenges, the engineer may well ask: why even consider natural form in making determinations involving the design of engineering structures? The biomimic responds by reminding us that nature has had 3.8 billion years to develop a “design guide” and we would be wise to learn from it. Importantly, natural and engineering structures both exist in the same environment and are subject to identical physics and further, are both often tasked with performing similar functions. In the context of cellular structures, we may thus ask: what are the functions of interest to engineers and designers that nature has addressed through cellular design? Through my reading [1-4], I have compiled the classification of functions in Figure 6, though this is likely to grow over time.
This broad classification into structural and transport may seem a little contrived, but it emerges from an analyst’s view of the world. There are two reasons why I propose this separation:
Structural functions involve the spatial allocation of materials in the construction of the cellular structures, while transport functions involve the structure AND some other entity and their interactions (fluid or light for example) – thus additional physics needs to be comprehended for transport functions
Secondly, structural performance needs to be comprehended independent of any transport function: a cellular structure must retain its integrity over the intended lifetime in addition to performing any additional function
Each of these functions is a fascinating case study in its own right and I highly recommend the site AskNature.org  as a way to learn more on a specific application, but this is beyond the scope of the current post. More relevant to our high-level discussion is that having listed the various reasons WHY cellular structures are found in nature, the next question is can we connect the structures described in the previous post to the functions tabulated above? This will be the attempt of my next post. Until then, as always, I welcome all inputs and comments, which you can send by messaging me on LinkedIn.
We here at PADT are proud to present the ease of use and productivity enhancements that have been added to ANSYS Mechanical in release 18.
With this new release, ANSYS Mechanical focuses on the introduction of a variety of improvements that help save the users time, such as smarter data organization and new hotkeys, along with additions that can help you to better visualize specific intricacies in your models.
Join PADT’s Simulation Support & Application Engineer Doug Oatis for an overview of the current user friendly interfaces within ANSYS Mechanical, along with the numerous additions in this new release that help to improve efficiency tenfold, such as:
Box Geometry Creation Within Mechanical
Free Standing Remote Points
Improved Status Bar Information
Pretension Beam Connection
Solver Scratch Directory Specification
Improved Probe Annotations
Register today to find out how you can use these enhancements to improve your throughput and stay ahead of the curve!
Occasionally when solid geometry is imported from CAD into ANSYS SpaceClaim the geometry will come in as solids, but when a mesh is generated on the solids the mesh will appear to “leak” into the surrounding space. Below is an assembly that was imported from CAD into SpaceClaim. In the SpaceClaim Structure Window all of the parts can be seen to be solid components.
When the mesh is generated in ANSYS Mechanical it appears like the assembly has been successfully meshed.
However, when you look at the mesh a little closer, the mesh can be missing from some of the surfaces and not displayed correctly on others.
Additionally, if you create a cross-section through the mesh, the mesh on some of the parts will “leak” outside of the part boundaries and will look like the image below.
Based on the mesh color, the mesh of the part in the center of the assembly has grown outside of the surfaces of the part.
To repair the part you need to go back to SpaceClaim and rebuild it. First you need to hide the rest of the parts.
Next, create a sketch plane that passes through the problem part.
In the sketch mode create a rectangle that surrounds the part. When you return to 3D mode in SpaceClaim, that rectangle will become a surface that passes through the part.
Now use the Pull tool in SpaceClaim to turn that surface into a part that completely surrounds the part to be repaired, making sure to turn on the “No Merge” option for the pull before you begin.
After you have pulled the surface into a solid, it should like the image below where the original part is completely buried inside the new part.
Now you will use the Combine tool to divide the box with the original part. Select Combine from the Tool Bar, then select the box that you created in the previous step. The cutter will be activated and you will move the cursor around until the original part is highlighted inside the box. Select it with the left mouse button. The Combine tool will then give you the option to select the part of the box that you want to remove. Select the part that surrounds the original part. After it is finished, close the combine tool and the Structure Tree and 3D window will now look like the following:
Now move the new solid that was created with the Combine tool into the location of the original part and turn off the original one and re-activate the other parts of the assembly. The assembly and Structure Tree should now look like the pictures below.
Now save the project, re-open the meshing tool, and re-generate the mesh. The mesh should now be correct and not “leaking” beyond the part boundaries.
What types of cellular designs do we find in nature?
Cellular structures are an important area of research in Additive Manufacturing (AM), including work we are doing here at PADT. As I described in a previous blog post, the research landscape can be broadly classified into four categories: application, design, modeling and manufacturing. In the context of design, most of the work today is primarily driven by software that represent complex cellular structures efficiently as well as analysis tools that enable optimization of these structures in response to environmental conditions and some desired objective. In most of these software, the designer is given a choice of selecting a specific unit cell to construct the entity being designed. However, it is not always apparent what the best unit cell choice is, and this is where I think a biomimetic approach can add much value. As with most biomimetic approaches, the first step is to frame a question and observe nature as a student. And the first question I asked is the one described at the start of this post: what types of cellular designs do we find in the natural world around us? In this post, I summarize my findings.
In a previous post, I classified cellular structures into 4 categories. However, this only addressed “volumetric”structures where the objective of the cellular structure is to fill three-dimensional space. Since then, I have decided to frame things a bit differently based on my studies of cellular structures in nature and the mechanics around these structures. First is the need to allow for the discretization of surfaces as well: nature does this often (animal armor or the wings of a dragonfly, for example). Secondly, a simple but important distinction from a modeling standpoint is whether the cellular structure in question uses beam- or shell-type elements in its construction (or a combination of the two). This has led me to expand my 4 categories into 6, which I now present in Figure 1 below.
Setting aside the “why” of these structures for a future post, here I wish to only present these 6 strategies from a structural design standpoint.
Volumetric – Beam: These are cellular structures that fill space predominantly with beam-like elements. Two sub-categories may be further defined:
Honeycomb: Honeycombs are prismatic, 2-dimensional cellular designs extruded in the 3rd dimension, like the well-known hexagonal honeycomb shown in Fig 1. All cross-sections through the 3rd dimension are thus identical. Though the hexagonal honeycomb is most well known, the term applies to all designs that have this prismatic property, including square and triangular honeycombs.
Lattice and Open Cell Foam: Freeing up the prismatic requirement on the honeycomb brings us to a fully 3-dimensionallattice or open-cell foam. Lattice designs tend to embody higher stiffness levels while open cell foams enable energy absorption, which is why these may be further separated, as I have argued before. Nature tends to employ both strategies at different levels. One example of a predominantly lattice based strategy is the Venus flower basket sea sponge shown in Fig 1, trabecular bone is another example.
Volumetric – Shell:
Closed Cell Foam: Closed cell foams are open-cell foams with enclosed cells. This typically involves a membrane like structure that may be of varying thickness from the strut-like structures. Plant sections often reveal a closed cell foam, such as the douglas fir wood structure shown in Fig 1.
Periodic Surface: Periodic surfaces are fascinating mathematical structures that often have multiple orders of symmetry similar to crystalline groups (but on a macro-scale) that make them strong candidates for design of stiff engineering structures and for packing high surface areas in a given volume while promoting flow or exchange. In nature, these are less commonly observed, but seen for example in sea urchin skeletal plates.
Tessellation: Tessellation describes covering a surface with non-overlapping cells (as we do with tiles on a floor). Examples of tessellation in nature include the armored shells of several animals including the extinct glyptodon shown in Fig 1 and the pineapple and turtle shell shown in Fig 2 below.
Overlapping Surface: Overlapping surfaces are a variation on tessellation where the cells are allowed to overlap (as we do with tiles on a roof). The most obvious example of this in nature is scales – including those of the pangolin shown in Fig 1.
What about Function then?
This separation into 6 categories is driven from a designer’s and an analyst’s perspective – designers tend to think in volumes and surfaces and the analyst investigates how these are modeled (beam- and shell-elements are at the first level of classification used here). However, this is not sufficient since it ignores the function of the cellular design, which both designer and analyst need to also consider. In the case of tessellation on the skin of an alligator for example as shown in Fig 3, was it selected for protection, easy of motion or for controlling temperature and fluid loss?
In a future post, I will attempt to develop an approach to classifying cellular structures that derives not from its structure or mechanics as I have here, but from its function, with the ultimate goal of attempting to reconcile the two approaches. This is not a trivial undertaking since it involves de-confounding multiple functional requirements, accounting for growth (nature’s “design for manufacturing”) and unwrapping what is often termed as “evolutionary baggage,” where the optimum solution may have been sidestepped by natural selection in favor of other, more pressing needs. Despite these challenges, I believe some first-order themes can be discerned that can in turn be of use to the designer in selecting a particular design strategy for a specific application.
This is by no means the first attempt at a classification of cellular structures in nature and while the specific 6 part separation proposed in this post was developed by me, it combines ideas from a lot of previous work, and three of the best that I strongly recommend as further reading on this subject are listed below.
As always, I welcome all inputs and comments – if you have an example that does not fit into any of the 6 categories mentioned above, please let me know by messaging me on LinkedIn and I shall include it in the discussion with due credit. Thanks!
We recently updated our slide presentation on PADT’s Medical Device product development capabilities that includes some examples of past work. Our team applies proven processes and deep industry experience across a wide spectrum of products. Please take a look to learn more about how we help companies engineer their medical devices.
Instant messaging has moved from a personal communication tool to an important part of business communication. But if we use it like email, it will loose its impact. “Intant messaging and business communication” looks at the topic.
Technology is an awesomely creative endeavor – innovation and inspiration is combined with science to create new products and tools for people and businesses. It is creative, but it’s not art. In “How can technology further art” I look at what technology can do to open new ways for people to express themselves and to make art more accesable.
We have a problem now in the Arizona Tech community – there is just too much going on. In “What the heck is happening? There is too much going on in Arizona tech” we look at how why this is a good thing and what we can to make it even better.
We here at PADT are excited to share with you the updates that ANSYS 18 brings to the table for AIM: The easy-to-use, upfront simulation tool for all design engineers.
ANSYS AIM is a single GUI, multiple physics tool with advanced ANSYS technology under the hood. It requires minimal training and is interoperable with a wide range of ANSYS simulation products.
Join PADT’s application engineer Tyler Smithas he covers the new features and capabilities available in this new release, including:
Magnetic frequency response
One-way FSI for shell structures
Model transfer to Fluent
One-way magnetic-thermal coupling
and many more!
ANSYS AIM is a perfect tool for companies performing simulation with a CAD embedded tool, design engineers at companies using high end simulation, and even companies who have yet to take the plunge into the world of simulation.
Register for this webinar today and learn how you can take advantage of the easy-to-use, yet highly beneficial capabilities of ANSYS AIM.
Remember the good old days of having to peruse through hundreds and thousands of lines of text in multiple files to see ANSYS license usage information? Trying to hit Ctrl+F and search for license names. Well those days were only about a couple months ago and they are over…well for the most part.
With the ANSYS License Manager Release 18.0, we have some pretty nifty built in license reporting tools that help to extract information from the log files so the administrator can see anything from current license usage to peak usage and even any license denials that occur. Let’s take a look at how to do this:
First thing is to open up the License Management Center:
In Windows you can find this by going to Start>Programs>ANSYS Inc License Manager>ANSYS License Management Center
On Linux you can find this in the ansys directory /ansys_inc/shared_files/licensing/start_lmcenter
This will open up your License Manager in your default browser as shown below. For the reporting just take a look at the Reporting Section. We’ll cover each of these 4 options below.
License Management Center at Release 18.0
License Reporting Options
VIEW CURRENT LICENSE USAGE
As the title says, this is where you’ll go to see a breakdown of the current license usage. What is great is that you can see all the licenses that you have on the server, how many licenses of each are being used and who is using them (through the color of the bars). Please note that PADT has access to several ANSYS Licenses. Your list will only include the licenses available for use on your server.
Scrolling page that shows Current License Usage and Color Coded Usernames
You can also click on Show Tabular Data to see a table view that you can then export to excel if you wanted to do your own manipulation of the data.
Tabular Data of Current License Usage – easy to export
VIEW LICENSE USAGE HISTORY
In this section you will be able to not only isolate the license usage to a specific time period, you can also filter by license type as well. You can use the first drop down to define a time range, whether that is the previous 1 month, 1 year, all available or even your own custom time range
Isolate License Usage to Specific Time Period
Once you hit Generate you will be able to then isolate by license name as shown below. I’ve outlined some examples below as well. The axis on the left shows number of licenses used.
Filter Time History by License Name
1 month history of ANSYS Mechanical Enterprise
1 month history of ANSYS CFD
Custom Date Range history of ANSYS SpaceClaim Direct Modeler
VIEW PEAK LICENSE USAGE
This section will allow you to see what the peak usage of a particular license during a particular time period and filter it based on data range. First step is to isolate to a date range as before, for example 1 month. Then you can select which month you want to look at data for.
Selecting specific month to look at Peak License Usage
Then you can isolate the data to whether or not you want to look at an operational period of 24/7, Monday to Friday 24/5 or even Monday to Friday 9am-5pm. This way you can isolate license usage between every day of the week, working week or normal working hours in a week. Again, axis on left shows number of licenses.
Isolating data to 24/7, Weekdays or Weekday Working Hours
Peak License Usage in March 2017 of ANSYS Mechanical Enterprise (24/7)
Peak License Usage in February 2017 of ANSYS CFD (Weekdays Only)
VIEW LICENSE DENIALS
If any of the users who are accessing the License Manager get license denials due to insufficient licenses or for any other reason, this will be displayed in this section. Since PADT rarely, if ever, gets License Denials, this section is blank for us. The procedure is identical to the above sections – it involves isolating the data to a time period and filtering the data to your interested quantities.
Isolate data with Time Period as other sections
Although these 4 options doesn’t include every conceivable filtering method, this should allow managers and administrators to filter through the license usage in many different ways without needing to manually go through all the log files. This is a very convenient and easy set of options to extract the information.
Please let us know if you have any questions on this or anything else with ANSYS.
Considered the “largest gathering of chip, board, and systems designers in the country,” with over 5,000 attendees this year and over 150 technical presentations and workshops, DesignCon exhibits state of the art trends in high-speed communications and semiconductor communities.
Here are the top 5 trends I noticed while attending DesignCon 2017:
1. Higher data rates and power efficiency.
This is of course a continuing trend and the most obvious. Still, I like to see this trend alive and well because I think this gets a bit trickier every year. Aiming towards 400 Gbps solutions, many vendors and papers were demonstrating 56 Gbps and 112 Gbps channels, with no less than 19 sessions with 56 Gbps or more in the title. While IC manufacturers continue to develop low-power chips, connector manufacturers are offering more vented housings as well as integrated sinks to address thermal challenges.
2. More conductor-based signaling.
PAM4 was everywhere on the exhibition floor and there were 11 sessions with PAM4 in the title. Shielded twinaxial cables was the predominant conductor-based technology such as Samtec’s Twinax Flyover and Molex’s BiPass.
A touted feature of twinax is the ability to route over components and free up PCB real estate (but there is still concern for enclosing the cabling). My DesignCon 2017 session, titled Replacing High-Speed Bottlenecks with PCB Superhighways, would also fall into this category. Instead of using twinax, I explored the idea of using rectangular waveguides (along with coax feeds), which you can read more about here. I also offered a modular concept that reflects similar routing and real estate advantages.
3. Less optical-based signaling.
Don’t get me wrong, optical-based signaling is still a strong solution for high-speed channels. Many of the twinax solutions are being designed to be compatible with fiber connections and, as Teledyne put it in their QPHY-56G-PAM4 option release at DesignCon, Optical Internetworking Forum (OIF) and IEEE are both rapidly standardizing PAM4-based interfaces. Still, the focus from the vendors was on lower cost conductor-based solutions. So, I think the question of when a full optical transition will be necessary still stands.
With that in mind, this trend is relative to what I saw only a couple years back. At DesignCon 2015, it looked as if the path forward was going to be fully embracing optical-based signaling. This year, I saw only one session on fiber and, as far as I could tell, none on photonic devices. That’s compared to DesignCon 2015 with at least 5 sessions on fiber and photonics, as well as a keynote session on silicon photonics from Intel Fellow Dr. Mario Paniccia.
4. More Physics-based Simulations.
As margins continue to shrink, the demand for accurate simulation grows. Dr. Zoltan Cendes, founder of Ansoft, shared the difficulties of electromagnetic simulation over the past 40+ years and how Ansoft (now ANSYS) has improved accuracy, simplified the simulation process, and significantly reduced simulation time. To my personal delight, he also had a rectangular waveguide in his presentation (and I think we were the only two). Dr. Cendes sees high-speed electrical design at a transition point, where engineers have been or will ultimately need to place physics-based simulations at the forefront of the design process, or as he put it, “turning signal integrity simulation inside out.” A closer look at Dr. Cendes’ keynote presentation can be found in DesignNews.
5. More Detailed IC Models.
This may or may not be a trend yet, but improving IC models (including improved data sheet details) was a popular topic among presenters and attendees alike; so if nothing else it was a trend of comradery. There were 12 sessions with IBIS-AMI in the title. In truth, I don’t typically attend these sessions, but since behavioral models (such as IBIS-AMI) impact everyone at DesignCon, this topic came up in several sessions that I did attend even though they weren’t focused on this topic. Perhaps with continued development of simulation solutions like ANSYS’ Chip-Package-System, Dr. Cende’s prediction will one day make a comprehensive physics-based design (to include IC models) a practical reality. Until then, I would like to share an interesting quote from George E. P. Box that was restated in one of the sessions: “Essentially all models are wrong, but some are useful.” I think this is good advice that I use for clarity in the moment and excitement for the future.
By the way, the visual notes shown above were created by Kelly Kingman from kingmanink.com on the spot during presentations. As an engineer, I was blown away by this. I have a tendency to obsess over details but she somehow captured all of the critical points on the fly with great graphics that clearly relay the message. Amazing!
1 x Intel® DC P3600 1.2TB, NVMe PCIe 3.0, MLC AIC 20nm
Windows 7 Ultimate Edition 64-bit
Step 1: Prepping
Check for and download the latest downloads for the Intel® Solid-State DC 3600 here: https://downloadcenter.intel.com/product/81000/Intel-SSD-DC-P3600-Series
You will need the latest downloads of the:
Intel® Solid State Drive Toolbox
Intel® SSD Data Center Tool
Intel® SSD Data Center Family for NVMe Drivers
Step 2: Installation
After instaling, the Intel® Solid State Drive Toolbox and the Intel® SSD Data Center Tool reboot the workstation and move on to the next step.
Step 3: Trust But Verify
Check the status of the 1.2TB NVMe card by running the INTEL SSD DATA Center Tool. Next, I will be using the Windows 7 Ultimate 64-bit version for the operating system. Running the INTEL DATA CENTER TOOLS within an elevated command line prompt.
Right-Click –> Run As…Administrator
Command Line Text: isdct show –intelssd
As the image indicates below the firmware for this 1.2TB NVMe card is happy and it’s firmware is up to date! Yay!
If you have more than one SSD take note of the Drive Number.
Pro Tip – In this example the INTEL DC P3600 is Drive number zero. You can gather this information from the output syntax. –> Index : 0
Below is what the command line output text looks like while the firmware process is running.
C:\isdct >isdct.exe load –intelssd 0 WARNING! You have selected to update the drives firmware! Proceed with the update? (Y|N): y Updating firmware…The selected Intel SSD contains current firmware as of this tool release.
isdct.exe load –intelssd 0 WARNING! You have selected to update the drives firmware! Proceed with the update? (Y|N): n Canceled.
isdct.exe load –f –intelssd 0 Updating firmware… The selected Intel SSD contains current firmware as of this tool release.
isdct.exe load –intelssd 0 WARNING! You have selected to update the drives firmware! Proceed with the update? (Y|N): y Updating firmware… Firmware update successful.
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. You can use the External Data tool to do just that. You can also create a table with a single variable and modify it in the Command Editor.
In the Presentation below, I show how to do all of this in a step-by-step description.