Image

Many of our Abaqus customers don’t know that the Computational Fluid Dynamics approach (CFD) is not the only method of modeling fluids in Abaqus. There are many other possibilities and the right approach depends on the physics of the problem. This blog post discusses the multi physics methods of modeling fluids in Abaqus.

  • CFD method: This is the well-known and traditional method for fluids modeling. It’s based on Eulerian formulation, in which material flows through the mesh and can be accessed through the Abaqus/CFD solver. Application example: Flow through exhaust systems.
  • CEL method: This is a coupled Eulerian Lagrangian method primarily used in problems involving unbounded fluids where fluids free surface visualization is required. It’s also possible to simulate interaction between multiple materials, either fluids or solids. This method is accessible through Abaqus/explicit solver. Application example: Fluid motion in washing machine.
  • SPH method: This is a smooth particle hydrodynamics approach primarily used to model unbounded fluids that undergo severe deformation or disintegrate into individual particles. This method uses a Lagrangain approach in which material moves with the nodes or particles and can be accessed through the Abaqus/explicit solver. This method can be used for fluids as well as for solids. Application example: bird strike on an aero structure.

We can compare these three methods against multiple parameters such as materials, contact, computation speed, etc. to understand their applications and limitations:

  • Material considerations:

SPH method is most versatile in terms of material support. SPH supports fluids, isotropic solids as well as anisotropic solids.

CFD is the only technique that can model fluid turbulence

CFD is the only technique to model porous media

CFD and CEL allows material flow through the mesh: Eulerian

  • Contact considerations:

[…]

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. […]

Product development companies need to manage a wide variety of documents in different formats and types as they design, manufacture and support their products. Gone are the days when paper documents used to run businesses. Today everything is digital, but very often these digital documents related to product and product development are created in siloed environments disconnected from product development processes. Document authors often recreate or reenter information from product development into their documents.

If the document authors don’t have visibility into the latest product changes, documents become out of sync with product updates. This impacts critical business processes due to inaccuracies or lack of current data. For organizations working globally, another challenge is the high cost and time involved in building complex documents that have multiple language/regional and regulatory requirements.

Teamcenter addresses this challenge by enabling documents that relate to and support product development to be stored alongside product data and processes. When documents are managed in the context of product data related to parts, or to other documents, companies have a single version control, access control and process control system for the entire enterprise, including product data and documents.

Source material from product data can be accessed and used to create documents like parts catalogs, work instructions, service material, specifications for suppliers, trade studies, or even regulatory filings. The documents can then be delivered  as appropriate to the end user in the required format, whether as a PDF or HTML web page, an interactive web tool, or exchanged with customers or suppliers using an industry standard.

The Teamcenter document management solution is focused on improving the document quality while streamlining the process of document creation and delivery. One of the central themes to this is “Transparent PLM.”

In a transparent PLM approach, users continue to do all their document work in their existing document authoring tools, the like Microsoft Office product suite.  They can also do the PLM activities – including review, approval or version or effectivity tracking, etc – directly from the same Office products.   With users continuing to work with document tools in which they are already proficient, they become more productive and the learning curve involved with a new PLM tool is eliminated. This helps with easy user adoption of the solution without any formal training requirements. […]

There is an excellent story in leadership consulting lore. I’m not sure how true it is, but the lessons derived from it are incredibly valuable.

There was once a detachment of Hungarian soldiers that struck out on a reconnaissance mission from their platoon in the Alps. While they were out, there was a massive snowstorm and the soldiers lost their way – returning was impossible.  The team was worried; they were not prepared for an extended stay out in these harsh conditions, and even if they had been, how would they get back with no knowledge of their location? They had all but given up hope when one soldier, while rummaging through his uniform, found a map. He showed it to the group and a new =found sense of hope came over them. They rallied together, found shelter, and waited out the storm.

After a couple of days, the blizzard finally let up. Wearily, the soldiers set about returning to their platoon. Using the map, they identified various features of the land, and made their way back. Their commander was elated to see them alive and well. When he asked the team how they did it, the soldier showed the commander the map that had not only guided them back, but had also given them the hope to persevere.  Confused, the commander asked this soldier, “How on earth did you find your way using a map of the Pyrenees?”

This story teaches us many things; here are two:

  • Fear and anxiety can lead people to inaction, even to their own detriment (and the effect usually intensifies in groups)
  • Even with the wrong strategy or plan, the chances of success are higher than if there were no plan at all

The second point has many application in the business world.  One I think of most, in terms of our manufacturing customers, is that of their shop floors.  Often manufacturers, especially small and medium sized ones, don’t have a chance to get deep into process planning.  Stations are haphazardly placed, too many or not enough activities are scheduled at stations, new machinery is placed wherever it fits, etc.  All of this causes bottlenecks and a slower time getting things out the door.  As we all know, time is money – especially in manufacturing, where every lost minute, hour, or day translates into lost revenue.

Tata Technologies has an amazing team of technical experts and works with many solution providers that can help manufacturers find their own map. One of the maturity benchmarks we offer is for the “Digital Factory;” contact us to schedule yours.

 

This post was originally written in January of 2017.

With all the buzz about Additive Manufacturing, or 3D Printing, in the manufacturing world today, there is a lot of mystery and confusion surrounding common practices and techniques. This week’s blog post will address a common type of 3D printing known as Electron Beam Freeform Fabrication (EBF³) .

What is Electron Beam Freeform Fabrication?

It is actually part of a broader category, commonly referred to as a Filament Extrusion Techniques. Filament extrusion techniques all utilize a thin filament or wire of material. The material, typically a thermoplastic polymer, is forced through a heating element, and is extruded out in a 2D cross-section on a platform. The platform is lowered and the process is repeated until a part is completed. In most commercial machines, and higher-end consumer grade machines, the build area is typically kept at an elevated temperature to prevent part defects. The most common, and the first, technology of this type to be developed is Fused Deposition Modeling.

The Fused Deposition Modeling Technique was developed by S. Scott Crump, co-founder of Stratasys, Ltd. in the late 1980s. The technology was then patented in 1989. The patent for FDM expired in the early 2000s. This helped to give rise to the Maker movement by allowing other companies to commercialize the technology.

Electron Beam Freeform Fabrication, or EBF³ is one of the newest forms of rapid prototyping. This technique is performed with a focused electron beam and a metal wire or filament. The wire is fed through the electron beam to create a molten pool of metal. The material solidifies instantaneously once the electron beam passes through, and is able to support itself (meaning support structures generally aren’t required). This entire process must be executed under a high vacuum.

Pioneered by NASA Langley Research Center, this process is capable of producing incredibly accurate parts at full density (other additive manufacturing techniques have trouble achieving, or require secondary operations to achieve similar results). This is also one of the only techniques that can be successfully performed in zero gravity environments.

What Are the Advantages of this Process? […]

Abaqus has always been first choice of analysts for modeling any form of non-linearity in the model: geometric non-linearity, material non-linearity, or boundary condition non-linearity which is large sliding contact. Within material non-linearity, the most popular model is piecewise linear plasticity used to model plastic deformations in alloys or metals beyond their yield point. This blog post primarily discusses another powerful but somewhat less known non-linear material model of Abaqus used to model elastomers or rubbers.

Before getting into Abaqus’ functionalities for rubbers, let’s see what types of rubbers primarily exist, along with their mechanical characteristics:

Solid Rubbers

They exist almost everywhere: tires, weather seals, oil seals, civil engineering equipment, etc. Their main mechanical characteristics are

  • Nearly incompressible: While it is easy to stretch these materials, it is very difficult to compress them volumetrically. It’s a common observation that a rubber band can be stretched easily but a piece of pencil eraser cannot be compressed so easily. This behavior is particularly important in elastomer modeling.
  • Progressive loading and unloading cycles show hysteresis as well as damage. As cycles continue, damage progresses.

Thermoplastics

They are a physical combination of rubber materials and thermal plastics. They can be easily molded or extruded. They are not physically as strong as solid rubbers, neither resistant to heat and chemicals. They are more prone to creep and permanent set.

Elastomeric foams

Commercially, they are referred to as porous rubbers or just foams.

  • They can undergo very large strain, as large as 500% that is still recoverable. Their counterparts, crushable foams, can exhibit inelastic strains.
  • They exhibit cellular structure that may be open or closed type. Typical examples are cushions, paddings, etc.
  • The compressive stress strain curve is as follows:

Foams exhibit a linear behavior in a compressive strain range of 0% to 5%. Subsequently, there is a plateau of severe deformation at almost constant stress. In this region, the walls and plates of cells buckle under compression thereby forming a denser structure. Post buckling, the cellular walls and plates start interacting with each other, causing a gradual increase in compressive stress.

  • Due to high porosity, foams exhibit very large axial compressive strain without any lateral strain. Due to this, the Poisson’s ratio of foams is nearly zero. This behavior is critical for material modeling of foams in Abaqus.

Material models in Abaqus for rubbers

Abaqus uses the “hyperelastic materials” terminology for its material libraries that support rubbers. This is primarily because rubbers are elastic in nature even at very high strains. The basic assumptions in modeling solid rubbers are: elastic, isotropic and nearly incompressible. Foam material libraries in Abaqus are referred as “hyperfoam” and are highly incompressible. None of the rubber material models can be represented by a single coefficient such as modulus. It rather requires a strain energy density function that can have an infinite number of terms. Therefore, in Abaqus, strain energy functions have specific forms with certain numbers of parameters to be determined. Each of these function is associated with a separate material model, as shown below. […]

Are you faced with a complex data migration or translation? Do you have years of legacy data that needs to be migrated to a new system? Have you got old CAD data from a outdated system that is still being used?

If you have answered yes to any of these questions, you are facing the prospect of performing a migration or translation project. Here are 10 potential problems that you must look out for before starting:

  1.  Underestimation of effort – too many projects are underestimated, primarily because the use cases for the translation are thought to be simpler then they actually are. For example, assemblies only need translation until someone remembers that drawings need to be included.
  2.  “Everything” syndrome – Looking at a project, most organizations default to attempting to translate or migrate everything. In all cases, this is not necessary, as only a subset of the data is really relevant. Making this mistake can drive up both cost and complexity dramatically.
  3.  Duplicate data – of everything that needs to be moved, how much of it is duplicate data (or same data in slightly different forms)? Experience shows that duplicate data percentages can be as high as 20 to 30 %. Unfortunately, identifing these duplicates can be difficult, but there are techniques to overcome this problem
  4.  Accuracy of CAD translation – When looking at 3D CAD translations, how accurate a copy do the translated models need to be relative to the originals? Again, a blanket requirement of “identical” can drive up cost and complexity hugely. Some lesser target (say +- 2 mm) can improve success.
  5.  Data already exists in Target – Some level of informal manual migration may have already occurred. So, when a formal migration is performed, data “clashes” can occur and result in failures or troublesome duplicates.
  6.  Automatic is not always best – Developing an automated migration or translation tool can be costly, if the requirements are multiple. Sometimes, a manual approach is more cost-effective for smaller and simpler cases.
  7.  Data Enrichment – Because the source data was created in an older system, it may not have all the properties and data that the target system requires. In this case, these have to be added during the migration or translation process. Forgetting about this step will prevent users from accurately finding data later.
  8.  Loss of Data – For large data volumes, is it possible that some of the data is missed and deleted during the project? Very possible – to prevent this requires exhaustive testing and planning.
  9.  Archive Solution – Once the translation or migration is complete, what happens to the original data? In some cases it is possible to delete it. However, in some environments (e.g. regulatory situations) this may not be allowed. In such a case, has an archive solution been put in place?
  10.  Security – Legacy data may be subject to security (ITAR, competitive data, etc.). Does the migration or translation process expose sensitive information to unauthorized users? Often a process will take the data out of its protected environment. This problem has to be considered and managed.

Ask these questions before translations and migrations begin!

This post was originally created in January 2017.

With all the buzz about Additive Manufacturing, or 3D Printing, in the manufacturing world today, there is a lot of mystery and confusion surrounding the common practices and techniques. So, this week’s blog post will address a common type of 3D printing known as Electron Beam Melting (EBM).

What is Electron Beam Melting?

It is actually part of a broader category, commonly referred to as a Granular Based Technique. All granular based additive manufacturing techniques start with a bed of powdered material. A laser beam or bonding agent joins the material in a cross section of the part. Then the platform beneath the bed of material is lowered, and a fresh layer of material is brushed over the top of the cross section. The process is then repeated until a complete part is produced. The first commercialized technique of this category is known as Selective Laser Sintering.

The Selective Laser Sintering Technique was developed in the mid-1980s by Dr. Carl Deckard and Dr. Joseph Beaman and the University of Texas at Austin, under DARPA sponsorship. As a result of this, Deckard and Beaman established the DTM Corporation with the explicit purpose of manufacturing SLS machines, and in 2001 DTM was purchased by their largest competitor, 3D systems.

Electron Beam Melting is very similar to Selective Laser Melting, though there are a few distinct differences. EBM uses an electron beam to create a molten pool of material, to create cross-sections of a part. The material solidifies instantaneously once the electron beam passes through it. In addition, this technique must be performed in a vacuum. This is one of the few additive manufacturing techniques that can create full density parts.

What Are the Advantages of this Process?

EBM is quick; it’s one of the fastest rapid prototyping techniques (though, relatively speaking, most techniques are fast). In addition, it can potentially be one of the most accurate rapid prototyping processes, the major limiting factor being the particle size of the powdered material.

As mentioned previously, this is one of the only additive manufacturing techniques that yields full-density parts; this means parts created with EBM will have similar properties to parts created using traditional manufacturing processes.

Another advantage of the material bed is the ability to stack multiple parts into the build envelope. This can greatly increase the throughput of an EBM machine.

What Are the Disadvantages of this Process? […]

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. […]

© Tata Technologies 2009-2015. All rights reserved.