Category "Tips & Tricks"

Any complete FEA solution has at-least three mandatory components: Pre-Processor, solver and post-processor. If you compare it with an automobile, solver is the engine that has all the steps/solution sequences to solve the discretized model. It can be regarded as the main power source of a CAE system. The pre-processor is a graphical user interface that allows user to define all the inputs into the model such as geometry, material, loads and boundary scenarios etc. In our automobile analogy, pre-processor can be regarded as the ignition key without which it is not possible to utilize the engine (solver) efficiently. The post-processor is a visualization tool to make certain conclusion from requested output: either text or binary. A good CAE workflow is regarded as one that offers closed loop CAD to CAD data transfer.

The above workflow is not closed so there is no scope of model update. Any changes in design requires all the rework. This has been the traditional workflow in organizations that have completely disconnected design and analysis departments. Designers send the CAD data to analysts who perform FEA in specialized tools and submit the product virtual performance report back to designers. If a change is mandatory, FEA is performed manually all over again. Let’s look at a better workflow.

In this workflow, if the initial design does not meet the design requirements, it is updated and sent to the solver, not to the pre-processor. It means that all the pre-processing steps are mapped from old design to new design without any manual intervention. This is an effort to bridge the gap between design and analysis departments that has been embraced by the industry so far. The extent to which the GAP can be bridged depends on the chosen workflow but to some extent, almost every CAE company has taken an initiative to introduce products that bridge this GAP. Let’s discuss in context of Dassault Systemes and Siemens.

Dassault Systemes: After acquiring Abaqus Inc in 2005, Dassault Systemes rebranded it as SIMULIA with the objective of giving users access to simulation capabilities without requiring the steep learning curve of disparate, traditional simulation tools. They have been introducing new tools to meet this objective.

  • The first one in series was Associative interfaces for CATIA, Pro-E and Solidworks which is a plug-in to Abaqus CAE. With this plug-in it is possible to automatically transfer the updated data from above mentioned CAD platforms to Abaqus CAE with a single click. All the CAE parameters in Abaqus CAE are mapped from old design to updated design. It’s a nice way to reduce re-work but design and simulation teams are still separate in this workflow.
  • Next initiative was SIMULIA V5 in which Abaqus was introduced in CATIA V5 as a separate workbench. This workbench includes additional toolbars to define Abaqus model and generate Abaqus input file from within CATIA. Introduce Knowledge ware, and user has all the nice features to perform DOE’s and parametric studies. This approach brings designers and analysts with CATIA experience under one roof.
  • Next Dassault Systemes introduced SIMULIA on 3D Experience platform allowing analysts to utilize data management, process management and collaboration tools with Abaqus in the form of simulation apps and roles. The solution is now in a mature stage with incorporation of process optimization, light weight optimization, durability and advanced CFD tools. By merging SIMULIA with BIOVIA we are also talking about multi scale simulation from system to molecular level. It is further possible to perform the simulation and store the data on public or private cloud.

Siemens PLM solutions: Siemens traditional CAE tools include FEMAP user interface and NX Nastran solver. Both have been specialized tools primarily meant for analysts with little or no connectivity to CAD. More specialized and domain specific tools were added with the acquisition of LMS and Mentor Graphics.

  • In 2016 Siemens introduced its new Simulation solutions portfolio called as Simcenter that includes all Siemens simulation capabilities that can be integrated with NX environment. The popular pre-processor in Simcenter series is NX CAE that has bi-directional associativity with NX CAD. Though meant for specialists, NX CAE offers a closed loop workflow between NX CAD and NX Nastran thus making easier to evaluate re-designs and perform DOE’s.
  • Siemens also offers NX CAE add-on environments for Abaqus and Ansys thereby allowing analysis to efficiently incorporate these solvers in their NX design environment.
  • It is further possible to use Simcenter solutions with Siemens well known PLM solution Teamcenter for enterprise wide deployment of Siemens simulation tools.

This shift in approach is not limited to Dassault Systemes and Siemens. Every organization in this space be it Ansys, Autodesk or Altair are introducing such closed form solutions. One reason may be the recent acquisition of many CAE companies by bigger organizations such as Dassault, Siemens and Autodesk. Nevertheless, the change has been triggered and it will continue.

 

 

Autodesk University Session: 60 Tips in 60 Minutes – Autodesk Inventor 2018 Quick Tips

Whether new to Inventor software or a seasoned pro, you’ll learn something from this fast-paced course that will highlight 60 Inventor tips in 60 minutes. We’ll showcase some of the less obvious commands or features and their location within the Inventor environment. Along the way we’ll look at how some of the tips work and how they might help you in your daily designing. So buckle up—we’ve got a lot to cover and only 60 minutes to get it done.

Find out more about Tim’s Autodesk University Session:  Autodesk University Session Registration

With an i GET IT subscription, login at https://myigetit.com to view the upcoming live technical sessions and recordings, including Tim’s Autodesk 2018 Quick Tips session recording.

 

About i GET IT Online Training Management for Engineers

i GET IT is an online engineering knowledge development and sharing tool, which specifically addresses the engineering community with an extensive MCAD/PLM training library, powerful customization tools, learning management features and assessment capabilities.

Unlike other generic learning providers, i GET IT is created by dedicated resources from industry PLM leaders at Tata Technologies. This allows us to offer the most comprehensive training solution for the leading engineering design and manufacturing applications plus industry skills, providing a consistent and updated offering for each release. It also allows i GET IT to consult directly with customers, providing customized solutions that fit your exact training needs and beyond.

So how does your company handle the training and skill advancement needs of your engineers?  Realize your design potential at https://myigetit.com

 

There is an interesting news regarding CATIA to be shared by composites user community. While almost all the composites related functionalities such as composites design by zones/plies, ply drop offs, core sampling, ply producibility, ply flattening, ply cut outs, lay-up export etc. have been existing as native CATIA offerings in composites workbenches, one valuable piece has been missing. That piece is called Laser Projection, a tool that can assist manufacturing guys in placing cut plies at right location on the tool. Earlier this functionality was offered through one of Dassault Systemes software partner called Majestic. However, Majestic got acquired by Autodesk a while ago so Dassault Systemes decided to develop a similar functionality in-house.

Laser Projection functionality was introduced in V5-6R 2016 release of CATIA, both in classic as well as in Express configurations and has been refined in service packs such as V5-6R 2016 SP2 and SP3. In classic configuration license is named as CLA and in express configuration license is named as LPX. Either CATIA composites design or manufacturing workbenches are a pre-requisite in either of these configurations. This technology is most suitable for most hand-layup parts such as panels, hulls, wind blades etc.

Within the application, it is possible to define any number of lasers by coordinates and assign properties to them such as its dimensions and range in terms of distance, horizontal and vertical angles. It is also possible to optimize the resource allocation. The reach envelope can be visualized to make sure largest ply in the model can be displayed with given number of lasers in the model. If not, more lasers can be defined or their positions can be changed.

The Laser Projection module is compatible with most commercial available vendor machines such as Virtek, LAP, LPT etc. The core thickness as well as plies thickness is automatically taken into account during projection. It is also possible to change display properties such as laser color, length of normal vectors etc. It is further possible to include additional geometry or text as a part of the display from predefined CATIA sets.

For any further information regarding licensing or functionality of this module, including a demonstration, please approach us and we are ready to help. It is also possible to import the laser projection files such as .py and .cal extensions to review the laser projections data in CATIA laser projection.

In the FEA solver world, users come across multiple numerical schemes to solve the formulated stiffness matrix of the problem. The most popular ones among all are the implicit and explicit solvers. In Abaqus terminology they are called a standard solver and explicit solver respectively. Each of these schemes has its own merits and demerits and this blog post compares these two schemes based on several parameters.

For ease of understanding, I am avoiding the use of long and complicated mathematical equations in this post. 😉

        Implicit Scheme

From an application perspective, this scheme is primarily used for static problems that do not exhibit severe discontinuities. Let’s take an example of the simplest problem: Linear static in which any physical situation can be mathematically formulated as:

[K]{x}={F}

Here K is the stiffness matrix, x is the displacement vector and F is the load vector. The size of the matrix and vectors can vary depending on the dimensionality of the problem. For example, K can be a 6×6 matrix for a 3D continuum problem or a 3×3 matrix for a 2D structural problem. The composition of K is primarily governed by material properties. F primarily includes forces and moments at each node of the mesh. Now, to solve the above equation for x, matrix K should be inverted or inversed. After inversion, we get a displacement solution used to compute other variables, such as strains, stresses, and reaction forces.

[M]d2{x}/dt2+[C]d{x}/dt+[K]{x}={F}

The Implicit scheme is applicable to dynamic problems as well. In the above equation, M is mass matrix, C is damping matrix and the rest are as usual. This equation is defined in real time. Backward Euler time integration is used to discretize this equation in which the state of a system at a given time increment depends on the state of the system at later time increment. K matrix inversion takes place in a dynamic scenario as well because the objective is still to solve for x. Abaqus standard solver uses three different approaches to solve implicit dynamic problems: quasi static, moderate dissipation or transient fidelity. Each method is recommended for specific types of non-linear dynamic behavior. For example, the quasi static method works well in problems with severe damping.

Merits of this scheme

  • For linear problems, in which K is a constant, implicit scheme provides solution in a single increment.
  • For non-linear problems, in which K is a function of x, thereby making it necessary to solve problem in multiple increments for sake of accuracy, size of each increment can be considerably large as this scheme is unconditionally stable.

Due to these reasons, implicit scheme is preferred to simulate linear/non-linear static problems that are slow or moderate in nature with respect to time.

Demerits of this scheme […]

In today’s post, I would like to focus on Functional Modeling.

Plastic Part

I’ve always wondered why this workbench never really caught on. Speaking purely from an FM1 trigram standpoint, it comes with the MCE add-on that most people who have PLM Express have added on to their CAC (CAC+MCE).

CAC+MCE

FM1 gets you the Functional Modeling Part Workbench.

Functional Modeling Part Workbench

First let’s talk about what it was created for, which is plastic parts or parts with draft, because it could also be used for core-cavity type parts like castings. This workbench is very unique in that you do not necessarily model in a particular sequence order like you would in the Part Design workbench. Modeling in the Part Design workbench is what we would call traditional feature modeling, i.e. create a sketch then make a pad, then add some dress up features like draft, fillets, then shell it out, etc.

Feature Based Modeling

There is nothing at all wrong with modeling this way – in fact, it is how most of this work is done today! Now let’s look at what we call Functional modeling which looks at a shape and incorporates a behavior for a specific requirement. […]

Siemens PLM‘s robust FEA solver NX Nastran is offered in multiple flavors. At first, it is associated with multiple graphical user interfaces, and the right choice depends on the user’s existing inventory as well as technical resources available. There are three options to explore:

  • Basic designer-friendly solution: In this bundle, basic NX Nastran capabilities are embedded in the NX CAD environment. The environment also offers stress and frequency solution wizards that provide direction to the user throughout the workflow. This solution is primarily meant for designers who wish to perform initial FEA inquiry on simple models. Advanced solver and meshing functionalities are not available.
  • Advanced solution for analysts: This solution offers more features with more complexity, so it is not meant for novice users and requires prior understanding of FEA technology. There are two separate GUIs associated with this type of NX Nastran.
  • NX CAE based solver: This is a dedicated pre/post processor for FEA modeling that has its own look and feel. It looks different from NX CAD but it is tightly coupled with NX CAD in terms of associativity – hence any updates in the CAD model are quickly updated in the FEA model as well through synchronous technology. If required, it is possible to associate this solution with Siemens Teamcenter for simulation process management.
  • FEMAP based solver: This is yet another dedicated PC based pre/post processor from Siemens with its own look and feel. FEMAP offers a CAD neutral and solver neutral FEA environment. It is tightly coupled with the NX Nastran solver but it is also possible to generate input decks for Abaqus, ANSYS, LS-Dyna, Sinda, etc.

This explains all the possible GUI offerings for NX Nastran. Now let’s have a look at what functionalities are available within the NX Nastran solver. Veteran Nastran users know very well that various physics-based solver features of Nastran are called solution sequences and each one of those is associated with a number.

  • Solution sequence 101: This is the most popular sequence of Nastran family. It primarily offers linear static functionalities to model linear materials, including directional materials such as composites for small deformation problems. Basic contact features such as GAP elements are also included. This sequence is widely used in T&M and aerospace verticals.
  • Solution sequence 103: This is yet another popular solution sequence that extracts natural frequencies of parts and assemblies. Multiple algorithms are available for frequency extraction such as AMS and Lancoz. This sequence serves as a precursor for full-blown dynamics analysis in Nastran.
  • Solution sequence 105: This sequence offers linear buckling at the part and assembly level. A typical output is buckling factor as well as buckling eigen vector. The buckling factor is a single numerical value which is a measure of buckling force. Eigen vectors predicts the buckling shape of the structure.
  • Solution sequence 106: This sequence introduces basic non-linear static capabilities in the solution and Nastran 101 is a prerequisite for this sequence. It supports large deformations, metal plasticity as well as hyper elasticity. Large sliding contact is also available but it is preferable to limit the contact modeling to 2D models only; it is tedious to define contact between 3D surfaces in this sequence.
  • Solution sequences 108,109,111,112: All these solution sequences are used to model dynamic response of structure in which inertia as well as unbalanced forces and accelerations are taken into consideration. These solution sequences are very robust, which makes Nastran the first choice dynamic solver in the aerospace world. Sequences 108 and 111 are frequency-based, which means that inputs/outputs are provided in a frequency range specified by the user. The solution scheme can be either direct or modal. Sequences 109 and 112 are transient or time-based which means inputs/outputs are provided as a function of time and scheme can be either direct or modal.
  • Solution sequences 153, 159: These are thermal simulation sequences: 153 is steady state and 159 is transient. Each one of these takes thermal loads such as heat flux as inputs and provides temperature contours as outputs. They do not include fluid flow but can be used in conjunction with NX flow solver to simulate conjugate heat transfer flow problems.
  • Solution sequence 200: This is a structural optimizer that includes topology and shape optimization modules for linear models. An optimization solver is not an FEA solver, but works in parallel with the FEA solver at each optimization iteration, hence sequence 101 is a prerequisite for NX Nastran optimization. Topology and shape optimizations often have different objectives; topology optimization is primarily used in lightweight design saving material costs while shape optimization is used for stress homogenization and hot spot elimination.

Questions? Thoughts? Leave a comment and let me know.

Today we will continue our series on the hidden intelligence of CATIA V5.  It is important to note that I am using a standard Classic HD2 license for this series In my last post, we discussed building a catalog of parts based on a single part that has a spreadsheet that drives the parameters with part numbers.  What about features?  If CATIA V5 is powerful enough to generate entire parts based on parameters, shouldn’t it also be able to be able to generate repetitive features? For instance, take a boss feature that appears on the B-Side of a plastic part. As a leader, I would not be interested in paying my designer his rates to keep repeatedly modeling a feature that may only change slightly throughout the backside! Model smarter: make once, use many times.

To do this successfully, you must address a few things – the first being how it may change. Of course you may not anticipate all changes, but a good rule of thumb is to try to model with maximum flexibility (big slabs for surfaces, overbuild everything, pay close attention to design intent) and do not use B-reps for your design. Avoid creating and building off of features CATIA builds, meaning whenever possible build your own and pick only from the tree to link to them.  The second issue to address is – what are going to be the parametric numerical inputs to drive the design? See my first post in this series on how to set these up.  i.e. Draft Angle, Wall thickness, Outer Diameter, etc.

Finally, what are going to be the geometric inputs to drive the design?  i.e. Location point, Pull Line, Slide Line, Mating Surface, etc.  A good rule of thumb here is to limit these features to as few as possible that are needed to get the job done. Sometimes it may be beneficial to sketch all this out on paper before you build it; I suggest gathering input from all the possible parties to help you in your definition.

In the example below, I have constructed a boss. Let’s review what I did. […]

PDF Publishing

‘Nuff said.

*and there was much rejoicing*

Well, maybe I could add a little more detail. It has long been known that the PDF is the currency of visual data exchange. All too often, I work with users and organizations that have to print PDFs outside of Vault, creating an uncontrolled document. If you were using the item master (discussed by my colleague here), you could attach it to the item; however, keeping it up to date is still going to be a manual process.

Now, thanks to the #1 most requested feature being implemented, that will no longer be an issue. Vault will now publish PDFs as part of your release process (as part of a transition action in a lifecycle change). This file will be categorized differently than the native CAD file, or even the DWF visualization file. The new category is called “Design Representation,” which can then be assigned its own set of rules, properties, and lifecycles.

As of this release, we have the ability to publish 2D file formats: DWG and IDW; that means either AutoCAD based files or Inventor drawings can be published to PDF. At some point, Autodesk may need to add the 3D PDF generation that was added to Inventor recently – which, by the by, could be used to publish all of the new Model Based Definition (MBD) annotations Inventor 2018 has added. I suspect we could see 3D publishing in the next release, or even a mid-year “R2” release (if there is an “R2;” who knows at this point).

Questions, comments, and celebrations welcome.

This is Part 3 in my series on the hidden intelligence of CATIA V5. To quickly recap what we have already talked about, in my first post I discussed the importance of setting up and using parameters and formulas to capture your design intent and quickly modify things that you know are likely to change. We took those principles a bit farther in my second post and discussed the value of building a design table in those situations when you may have a design with parameters that will vary and that you want to use many times. In that case you could see that we had our rectangular tubing part and could modify its wall thickness, height, and width to make several iterations of basically any size of tubing one would ever need! You would simply keeping doing a Save as… and placing those parts in your working directory to be added into an assembly at some time (I assume).

This methodology would work fine, but today I want to focus on a very cool spin on this theory by building a catalog of your most commonly used parts which are similar enough to be captured in a single model. Using our tubing model, and picking up where we left off, we have a spreadsheet that defines the parameters that change. All we would need to do to build a catalog of each iteration of the design table is add a column to the spreadsheet named PartNumber just as I have it with no spaces in the name and then associate that to the ‘Part Number’ intrinsic parameter that is created automatically when you being a model.

Let’s get started.  I will open both the model and the spreadsheet, edit the spreadsheet with the column, and then add in some part numbers.

Part numbers added

When you save the file, the field should appear in CATIA when you click on the Associations tab. […]

When working with our customers, from time to time, we’ll get questions on why they see unexpected results in some of their searches. This typically happens when they search without wildcards (I’ll explain later). In this blog post, I hope to shed some light on what can be a confusing experience for some Vault users.

The search engine in Vault operates on a on a general computer science principle called general Tokenization. This process essentially chops up the indexed properties into chunks called tokens. When a user searches in Vault (either quick search or advanced find), the search engine will attempt to match the tokens in the search string to the tokens in the appropriate properties.  Before going further, I’ll explain how Vault does the slicing and dicing.

First, there are three categories of characters (for our purposes, at least); alpha [a-z, A-Z], numeric [0-9], and special [#^$, blank space, etc.].  Vault will parse the string and sniff out groups of characters belonging to a category.  For instance, ABC123$@# would be tokenized into 3 individual tokens:

  • ABC
  • 123
  • $@#

Again, what happened is that Vault saw the first character, A, and understood it to be an alpha character. Vault then asked “Is the next character an alpha, too?” to which the answer was yes, so the token became AB. C was then added to the initial token, as it too was an alpha character.  However, the answer was “No”, when it came to the character 1.  Vault finished its first token and began the next one, now that it sensed a different category of character. Vault continued this line of questioning with the subsequent characters.

Another example might be a file name like SS Bearing Plate-6×6.ipt. Here, we have 8 tokens:

  • SS
  • Bearing
  • Plate
  • 6
  • x
  • 6
  • ipt

Now, you may have caught the missing period. Vault will only tokenize six special characters – all others are ignored. These special special characters (sorry, had to do it) are:

  • $ (dollar sign)
  • – (dash)
  • _ (underscore)
  • @ (at symbol)
  • + (plus)
  • # (octothorpe, aka number sign)

So now where do the unexpected results come in? This usually happens when an incomplete token is used without wild cards. For example, a user wants to find a specific mounting bracket. This user then types in “mount,” expecting that to be enough. In our hypothetical Vault environment, the results would return “Fan mount.ipt” but not “Mounting bracket.ipt” like they intended. Why? Remember that Vault is trying to match exact tokens (again, without wild cards).

If the user had entered mount*, the results would return the expected “Mounting bracket.ipt” as the user intended.

Moral of the story?  Always use wild cards…always.  No, really, all the time.  For everything.

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