Category "Tips & Tricks"

Organizations invest huge sums of money in simulation software to avoid expensive and disruptive physical testing processes. But how long it really takes to make this transformation happen! One thing is sure; it does not happen in a day. The flow chart below explains the reason pictorially. The last two blocks “compare and improve model” and “compare and improve theory” make this transformation a longer process than expected.

 

Let’s explore the reasons behind it. Comparison is needed to make sure that simulation results mimic the physical testing results before latter can be discarded, partially or fully. The difference in results can be due to three main factors: lack of user competency, limitation of software used, lack of sufficient input data.

Lack of user competency: FEA analysts are not born in a day. The subject is complex to learn and so are the software associated with it. The ramp up time really depends on analyst background along with complexity of problem being simulated. Organizations usually make a choice between hiring expert and expensive analysts who can deliver the results right away or producing analysts of its own through class room and hands on trainings. First option saves time while the second saves money. CAE software development companies are also making big stories these days by introducing CAD embedded simulation tools that require nominal user competency. Nevertheless, the competency builds up over time.

Limitation of software used: Initial investment in simulation domain is usually small. It means two things: either number of users are less or software functionality is limited. With time, complexity of problems goes up but the software remains the same. A common example I have seen is of a customer starting with simple linear simulation workbench in CATIA and over period trying to simulate finite sliding contact problems with frictional interfaces in the same workbench. Users don’t realize that their problem complexity has exceeded the software capacity to handle and it’s time to upgrade. It’s always recommended that analysts get in touch with their software vendors whenever they anticipate an increase in simulation software capacity or functionality. A certified simulation software vendor is a trusted advisor who can really help.

Lack of sufficient input data: “Garbage in – Garbage out” is a very common phrase in simulation world. However, at times it is very difficult to get the right input for software in use. The complexity of input data can arise either from complex material behavior or from complex loading conditions. Example of complex material may be hyper-elasticity or visco-elasticity observed in elastomeric materials. Examples of complex loading may be real time multi block road load data to estimate fatigue life. Sometimes simple metallic structures exhibit complex behavior due to complex loading. Examples are high speed impact or creep loading. With time many material testing labs have come into existence that can perform in house testing to provide right input data for simulation.

Conclusion: You will come out of the vicious loop of physical and simulation results comparison after couple of iterations if you have three things in place: right people, right software product and right input data. If you need help in any of the three aspects, we are always available.

“What you buy makes a difference but from whom you buy makes a bigger difference”

Most often, I talk about greatness of our product offerings in my blog articles. Such kind of blogs assist prospective customers in choosing the right product. But the same product can be procured in multiple ways, either directly from the developer or through a value-added reseller also called as VAR. In this blog article, I would emphasize on how prospective customer should select the right VAR while purchasing a Dassault Systemes or Siemens simulation product.

The first thing a customer needs to verify is whether VAR is supplying just the product or the complete solution. The difference between the two is the “value added services” associated with product usage.

Without value added services, it’s not possible for a reseller to become a value-added reseller.” Please identify if you are doing business with just a reseller or a value-added reseller. Remember, simulation tools are not easy to use. There is a learning curve associated with these tools that can greatly impact the ROI and break-even timeline. The productivity of the user can be substantially enhanced if he is associated with a reseller who can provide whole bunch of services to shorten the learning curve and achieve break-even faster. Now let’s look at what type of services makes a difference in simulation space.

We are talking about software sales as well as consulting, training and support. Our software partners, Dassault Systemes, Siemens and Autodesk offer a bunch of certifications around these four components to distinguish between just “resellers” and “value added resellers.” Being certified means reseller has enough resources and knowledge to execute a given task of sales or service. Let’s talk about each component with respect to Simulation:

Software: To sell any DS SIMULIA product, the associated VAR should have “SIMULIA V6 design sight” certification as a minimum. There are further brand certifications available such as Mid-Market Articulate for product highlight and Mid-Market Demonstrate for product technical demonstration. To sell FEMAP product from Siemens, the VAR must have “FEMAP technical certification” as a minimum. All these certifications are associated with timed examinations.

Training: Training should be an integral part of simulation software sales. It gives users enough knowledge to use the software product in production environment. To offer technical training on any SIMULIA product, the VAR should have “finite element analysis with Abaqus specialist” certification as a minimum.

Support: Once users are in production environment, technical support is required on continuous basis. While many answers related to product usage are in documentation, it’s not a full source of information. Many queries are model specific that require attention of a dedicated support engineer. To offer technical support on any SIMULIA product, the VAR should have at-least one engineer who has “SIMULIA technical support specialist” certification.  This certification should be renewed every two years. It is associated with a lengthy and “hard to pass” support certification examination across all products of SIMULIA brand.

Consulting: Consulting service plays a big role when customer either does not have enough time or resources to execute projects in house in-spite of having software product. It happens during certain burst phases of demand. While there are no certification criteria for VAR’s related to consulting in simulation space, a dedicated consulting and delivery team is needed to offer the service when demand arises.

The above information should help you in ranking your VAR. Do you need to know our rank? Please contact us.

 

MESHING CAPABILITIES IN ABAQUS CAE

It is a well-known fact in the CAE community that the efficiency and accuracy of finite element models are directly dependent on the quality of the underlying meshes in the model. The various quality parameters associated with elements are element size, aspect ratio, skew angle, jacobian, warp, and many more. Yet another parameter of concern is element topology, which means triangular/quadrilateral elements in case of shell meshes and tetrahedral/hexahedral elements in case of solid meshes. Each of these element topologies has its own advantages and disadvantages; for example, tetrahedral elements are easy to create on complex geometries but they have slower convergence, while hexahedral elements are very much desired in computational expensive simulations such as crash due to better convergence and accuracy but cannot be created easily.

Due to specific meshing requirements arising from the increasing complexity of part geometries, meshing techniques are becoming more important across all industry verticals. Transportation & mobility is primarily concerned with hexahedral meshes of pre-defined quality for very complex geometries. This industry has more focus on using Hypermesh and Ansa as a dedicated meshing tools. However these tools are primarily known for good meshing capabilities only. When there is a need to create input decks for advanced non-linear simulations such as with Nastran solution sequences 600/700 or for Abaqus multiphysics or acoustics, many of the solver features are not supported by Hypermesh or Ansa and have to be entered manually into the deck. Aerospace industry has almost always a requirement for composites modeling. They prefer a user interface that can either create or import composite plies and layups. The need for high quality meshes on complex geometries is rather rare. Due to these reasons Aerospace industry has been relying on MSC Patran since many years due to its composites modeling capabilities. However industry is now looking at alternate tools as Patran is losing its competitive edge on CAD import, CAD repair as well as meshing techniques. The CAD repair features are very minimal, there is no CAD associative interface to propagate design changes on FE side and meshing techniques offered are still at very basic level as well.

The objective of this blog is to highlight the meshing techniques in Abaqus CAE that makes CAE a tool of choice in situations where a decent quality mesh, tight integration with multiple CAD platforms as well as tight integration with Abaqus solver are topics of concern for the analyst. It’s worth mentioning for Aerospace industry audience that Abaqus CAE has basic composite modeling capabilities. For advanced composite modeling and visualization capabilities, there is an add on module called composite modeler for Abaqus CAE and there is tight integration between CATIA composites workbench and Abaqus CAE for transfer of FE meshes as well as ply layup information.

THE MESHING TECHNIQUES

 There are primarily four meshing techniques available in Abaqus CAE, both for solid meshes as well as for shell meshes.

Free meshing: This is the easiest of all the techniques as it almost always works with a single click. It primarily generates quadrilateral or triangular elements on surfaces and tetrahedral elements on solids, even on very complex geometries. The downside is that user has very minimal control on elements quality except controlling the mesh density using global and local seeding options.

Sweep meshing: This technique is useful when hexahedral elements are needed on solids with minimal geometry editing though this technique is applicable on surfaces as well. The meshing algorithm automatically identifies a source side and a target side on the geometry, it creates a quadrilateral shell mesh on the source side and sweeps those elements to the target side thereby converting them to hexahedral or bricks. The underlying shell mesh is automatically deleted. The downside is some geometry restrictions with respect to source and target side.

Structured meshing: This meshing techniques is useful when high quality hexahedral or near to perfect shell elements are required on solids or surfaces. This technique offers a better mesh control to the user compared to sweep meshing technique. It works by partitioning the complex solids into smaller six or eight sided parametric solids that can be brick meshed. The nodes at the boundaries are automatically fused to ensure connectivity.

Bottom’s up meshing: This is the last approach when all the other meshing techniques fails. It works on the concept of divide and rule. To some extent it resembles sweep meshing but the underlying geometry restrictions are removed.

THE COLOR CODING FEATURE

This is one feature that sets Abaqus CAE apart from other meshing tools available in the market. While doing meshing, user can see either entire part or regions associated with part (in case of partitions) in pre-defined colors. These colors helps in determining which region of the part would be meshed with which meshing technique if the mesh algorithm is executed. The color cold is as follows:

untitled

 

 

 

 

 

 

 

 

 

The process is quite interactive. The orange color is most undesirable as these regions are non-meshable and require further partitions. Once the region is correctly partitioned and subdivided regions become meshable, the color code is updated instantly. What the user needs to see is the combination of greens, yellows and pinks with peach at certain times before executing meshing operation. During meshing, user has option to either mesh one region at a time or the entire part having multiple regions. In case of interfaces having different element topologies on each side such as green with pink or yellow with pink, tie constraints are automatically created at the boundary to ensure mesh connectivity.

Below is an example of a part that has been partitioned to create certain sweep meshable yellow regions where brick elements are needed. The other region is pink with tetrahedral elements associated to it.

untitled

EFFECTIVE PARTITIONING

Transition of orange region to either yellow, green or peach requires intelligent partitioning of surfaces or solids. While there are many such partitioning tools available, achieving desired results with minimum partitions requires some practice in using these tools. Let’s highlight few of these partitioning methods:

Solid partitions:  Six options are available.

untitled

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VIRTUAL TOPOLOGY

This is an optional process that may be needed before partitioning and prior to meshing. This is a way to fix bad CAD data. Many times CAD data has more details than needed by the meshing algorithm. This includes very short edges and very small surfaces. Virtual topology offers certain tools to combine such small faces and edges. There is also an option to suppress these small features so that meshing algorithm does not recognize them.

untitled

If you have been using Autodesk Inventor for a while you may already know this, but there is a process for migrating Inventor’s “Content Center” libraries.  This should be done to ensure you don’t end up with duplicate parts (file names) for the same fastener, pin or other common part.  When libraries are migrated, it allows the new software version and its updated libraries to recognize that a particular existing component is being placed.  The existing model will be utilized in this case.  If the libraries are not migrated, a whole new set of model files will get created when you start placing component from Content Center in a new version of Inventor.

Here is the general procedure:

  1. Determine where your current style library is located.  It may be in the default location for individual users, or may be in a common location.
  2. Launch the “Autodesk Inventor Style Library Manager”.  This is a separate program in Windows that isn’t started from within Inventor.
  3. In the “Style Library 1” area browse to your old style library that you located in step 1.  It should say that “some style collections need migration”.
  4. Select the Migrate button at the bottom

I also recommend backing up an previous style libraries before migrating them.  There have been various accounts of libraries failing to migrate and becoming corrupted.  Making a backup and testing the migration is imperative if you have extensive modifications in your existing style library.

Typically when new software releases come out, there are always a few really key improvements that really stand out.  Many times, it is a cool new modeling feature, or maybe an entirely new approach to design.  In Inventor, this might be like the addition of Freeform Modeling or Direct Editing as examples.  Unfortunately these are features or techniques that might not be applicable to many users.

If you are using both Autodesk Inventor and Vault together however, you should probably pay attention to this one:  The Vault status icons in the “recently used” area.  These icons now clearly identify the current Vault status of one of your recent files when in the Inventor “Open” dialog box.  Is the file checked out?  Is the file checked in, and up to date in my workspace? Has someone else modified the file since I last worked on it?  Have I checked in my latest development ideas or new parts yet?  All of these can be determined simply by noticing the Vault status bubbles in the “Open” dialog box.

Vault Status Icons

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. […]

© Tata Technologies 2009-2015. All rights reserved.