Dassault Systèmes

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When it comes to Abaqus structural solver, picture is clear. There is a standard (implicit) solver as well as an explicit solver. Each of these has its own merits and demerits that we have discussed in previous blog articles. However, in CFD there appears to be only one solver. So…

Is it implicit or explicit!!

Well, if you look at the underlying parameters of the solver, it appears to be hybrid. The solver talks about inner loop and outer loop convergence. That makes user feel that solver is implicit and it requires matrix based calculations. This is true for both steady state as well as transient flows. But then when we talk about transient flow parameters, solver mentions CFL number that primarily governs the step size of transient flow. Higher CFL number results in larger step sizes but beyond a certain value of CFL, the flow may become unstable. This looks more like an explicit scheme where stability plays a role. But then, the transient flow also requires convergence that is not an explicit property. So where do we stand.

The answer is somewhat mixed. The CFD solver of Abaqus is implicit by nature. However, it does not follow all the traits of structural implicit solver. One big difference is that CFD implicit solver is not unconditionally stable. While the explicit structural solver just exits if time increment exceeds its critical value, the CFD solver continues at larger than desired CFL numbers but it may give non-realistic flow results. The other big difference is the physical quantities involved. The structural implicit solver looks at force and displacement residuals for convergence. The CFD solver looks at momentum, pressure and velocity residuals.

SIMULIA has made good efforts in 2018x release of CFD solution on the 3D Experience platform in terms of making the solver fully implicit so that it can handle large time increments. There have been other solver enhancements to improve accuracy and reduce solution time. Wish to know more about SIMULIA CFD techniques! Please get in touch.

In recent blog article on friction, I discussed about a new Abaqus functionality that allows user to define friction as surface property and Abaqus computes contact pair friction coefficients from corresponding surface friction properties. In this blog article we discuss yet another nice and recent functionality in Abaqus explicit called anisotropic friction.

The anisotropic behavior may arise from number of scenarios the most common of which is composite material that has longitudinal and transverse fiber directions. In such a scenario, the coefficient of friction between contact pair depends on the relative direction of sliding between the contact surfaces. Looking for a real-life example!!!

“The interaction of seat belt with the occupant body is an example of anisotropic friction”

he above figure shows the concept pictorially. Blue arrows indicate the direction of relative sliding. Hence these arrows are always at an angle of 180 degrees. The red lines show the direction of primary material axis. Theta is the angle between blue arrows and red lines per surface. The directional friction stress is computes as:

Both anisotropic friction as well as estimation of friction interaction from surface property are in the category of “combinatorial rules” and both are controlled by same keyword entry as follows in the .inp file.

If both the nominal friction and directional preferences are to be determined from surface property, it is not necessary to define *friction keyword.

 

In this article we are going to discuss an advanced friction modeling technique in Abaqus. It is based on combination rules that allows solver to compute effective friction interaction based on two contacting surfaces with different coefficients of friction. As an example, look at the following table:

If someone asks: “what is the coefficient of friction of steel?” There really is no answer to this question. The answer really depends on the other object with which steel interacts. The table shows two different values, one for steel-steel interaction and other with steel-teflon interaction. If the user has NXM matrix of materials interacting with each other and each cell of that matrix has a friction coefficient assigned to it, then modeling in Abaqus is trivial. Define surface interaction with friction coefficient for each cell and use it with corresponding surface pair in the contact property assignment. The example below highlights it.

 

But this straightforward approach is possible only if friction values for all cells are available. However, at times only the diagonal values are available. That means all the non-diagonal cell values are unknown. In that case contact property assignment is not possible.

Abaqus now allows users to define friction as surface property as well. For two different surfaces (A,B) with individual coefficient of friction, the effective friction for pair is computed as follows:

The default value of alpha is 0.3. In case of mixed problems, where surface property and contact property methods co-exist, either method can take precedence. Look at following example.

The approach is an approximation but its worth in situations where user has no access to friction coefficients values for all the contact material pairs. This friction algorithm is available in Abaqus explicit 2018 release and beyond.

 

This topic has always been very popular and this problem has always been very complicated in FEA user community since the inception of Abaqus, or any non-linear FEA code in general. In this brief article, I will highlight few simulation situations where Abaqus standard may not be a good candidate from convergence perspective. Identifying these situations early during pre-processing and working in Explicit right away may save lots of time and efforts that otherwise would be wasted in trying Abaqus Standard.

  • Look at the motion aspect: We always say that simulation is not the complete replacement of physical testing right away. In the beginning physical tests play a critical role in identifying right approach for simulation as well as in data correlation between physical and virtual tests. Look closely at the physical test. Is there a large relative motion between different parts involved? If yes, then Standard is very likely to face convergence problems, even if problem is static by nature. Standard has an option of “small sliding” and “finite sliding”. But user should remember the difference between “finite sliding” and “large sliding”. Attached is the video of wire crimping simulation that ideally is a static problem but numerically not a good candidate for Standard, primarily because of motion.
  • Clock time matters: Apart from magnitude of motion, the duration of motion matters as well. While looking at physical test, closely look at the time in which motion is completed. If too much of motion is covered in too less time, problem is indeed dynamic instead of static as inertia effects cannot be ignored. In such a situation either Standard dynamics or Explicit would be the right way to go. Which one to choose really depends on event duration. If a lot of dynamic phenomenon happens in the order of milliseconds or microseconds, Explicit is only option for this candidate.
  • Is there a severe discontinuous contact: In the status file of Abaqus Standard, there is an undesirable column called SDI’s. It’s called severe discontinuous iterations and too many of these often always leads to convergence nightmare. The reason of SDI’s is discontinuous contact, also known as “chattering”. It’s a phenomenon in which nodes between two bodies in contact continuously change their contact status from OPEN to CLOSE from one iteration to the other as analysis proceeds. If chattering occurs due to modeling errors, it can be corrected but at times discontinuous contact is the nature of problem itself. In such a situation, explicit is the only approach to be taken, even for long duration events with respect to physical time. The attached video is an example of a dynamic event that would only solve in explicit or multi body dynamics, primarily because of severe discontinuous contact.
  • Is there too much Plasticity: Abaqus has material models to capture plasticity but there is a limit on the magnitude of Plasticity Abaqus Standard can handle. If the permanent deformation becomes so high that underlying part completely loses its load carrying capacity then Newton Raphson method of Abaqus Standard would not be able to establish equilibrium and further leading to non-convergence. Ideally, there is no further need to perform simulation as it’s a classic situation of part failure but if further simulation is needed, it should be continued in Explicit using Restart options.

In previous blog articles on 3D Experience simulation roles, we primarily discussed platform configurations, concept of personas and roles as well as simulation capacity of the platform. In this blog article contains detailed information about three primary structural simulation roles: MDS, DRD and SMU.

To begin with, lets recapitulate that simulation roles are categorized in groups based on personas of users working on such roles. In terms of complexity and functionality, offerings range from based to intermediate to advanced.

 

Engineer profile: The is the simplest and easiest to use simulation offering primarily meant for designers with low to intermediate simulation knowledge. Their primary job is product design and they perform simulations very occasionally. Roles for this profile are CAD centric and are associated with a guided workflow. Simulation tokens are embedded in the role.

Analysis engineer profile: This profile is one level above the engineer profile and is suitable for structural analysis engineers associated with product engineering. Their simulation knowledge is of intermediate level which means they understand simulation process in terms of meshing, BC, Loads, result visualization etc. but don’t have any hands-on experience of advanced simulation tools. Usually there is no guided workflow. Simulation tokens are embedded in the role.

Analyst profile: This role is for full time analysts who primarily perform intermediate to advanced level simulations. They have in depth expertise in at-least one simulation domain and often hold Masters or Doctorate level credentials. This role requires extensive knowledge of pre-processing, solver terminologies such as statics, dynamics, non-linearity, convergence schemes, as well as post processing etc. There is no guided workflow. Simulation tokens are procured separately.

 Research Specialist profile: This is a complex simulation offering primarily for experts who develop novel simulation workflows and processes. The simulation requirements often span across multiple physical domains and involves advanced Physics such as vibrations and noise. The pre-processing aspect may include complex meshing of assemblies and assemblies of meshes.

Let’s look at one role from each of first three profiles:

Stress Engineer role (MDS)

 

It’s a role from engineer profile and has a guided workflow. The snapshot shows apps available in MDS role. It performs routine strength and deflection calculations under static loading conditions. It can also compute product fatigue life for very simple loads. The CATIA and SOLIDWORKS associativity is well maintained. Local solver execution up to 4 cores is included.

Structural analysis Engineer role (DRD)

 

It’s a role from analysis engineer profile that has no guided workflow. It is used to access the structural integrity of products subjected to wide range of loading conditions. The snapshot above shows available apps in this role. It works on MSR concept available in advanced simulation tools i.e.  Model-Scenario-Results. Many advanced settings are exposed to the user. This role can perform multi step simulations. Local job execution of up to 8 cores is available.

Mechanical Analyst role (SMU)

 

It’s a role from analyst profile and it does not include a guided workflow. The snapshot above shows available apps in this role.  It uses advanced finite element techniques to simulate and validate complex engineering problems. It offers multiple advanced meshing techniques such as Octree, surface, sweep and RBM. Both single step as well as multi step scenarios are included. Supported analysis steps include static perturbation, non-linear static, frequency, buckling, implicit dynamics, explicit dynamics, steady state heat transfer, transient heat transfer etc. Most of the non-linear materials and complex engineering connections are included.

While we discussed one prominent role from each profile, the south quadrant of 3D Experience platform offers numerous simulation roles. To know more, please contact us.

One thing common between SIMULIA roles of 3DExperience platform and the standalone Abaqus products is that both require an Abaqus solver to perform computations. It further means that both solutions require Abaqus tokens to complete or speed up the computation part of the simulation. For standalone abaqus product, we know that the calculation is straight forward. Abaqus requires a minimum of five tokens to execute a single core non-linear job. Large models require more number of cores to solve in real time and more number of cores require more tokens as follows:

The computation capacity of 3D Experience platform, however, cannot be defined by a single equation. Unlike Abaqus solver, that is available as an integrated all-in-one license for all types of simulations such as standard, CFD, explicit etc., 3D Experience offerings are in form of roles. Each role is a sellable license that includes either some or all Abaqus solver capabilities. Offers are made further flexible by on premise vs. on cloud offerings. Let’s have a look at solver offerings in different configurations and roles.

    Engineer role vs. Analyst role

While most of design engineer roles have embedded Abaqus tokens, most of the analyst roles do not have any compute capacity at all. The number of tokens embedded in designer role depends on the level of simulation complexity a role can accommodate. For example

Stress Engineer role has 8 embedded tokens to accommodate up-to 4 cores job

Structural analysis engineer role has 12 embedded tokens to accommodate up-to 8 cores job

It is possible to submit jobs on more number of cores than what embedded solver permits but in that situation external tokens need to be utilized and embedded solver takes no credit at all.

                Tokens vs. Credits

In case of analyst roles such as stress analyst, fluid mechanics analyst etc., the role itself does not have any compute capacity which should be procured either in the form of tokens or credits. Tokens are renewable form of compute capacity which means they can be used over and over. 3D Experience uses tokens in a very similar fashion as does standalone Abaqus. The token consumption with respect to number of cores is the same for Abaqus as for 3D Experience platform. On the contrary credits are a non-renewable form of compute power. It means that credits, just like the talk time over phone, can be consumed only once.

               Why credits at all!!!

In general credits is an expensive preposition for customer but there are exceptions. Credits are utilized to meet unexpected and rare increase in peak usage. This is somewhat more common in engineering consulting firms that can face high demand of simulation capacity due to influx of many short duration simulation projects at any time. To meet this sudden spike in demand, one-time credit bundle offering makes more sense than increase in perpetual tokens. Once peak demand is over and credits are consumed, simulation capacity is returned to normal levels.

On premise vs. on cloud

Design engineer as well as analyst roles are available in on premise as well as on cloud formats. There are three ways of utilizing cloud resources: store the models on cloud, stores the results on cloud and solve on cloud. The first two offerings require only cloud storage and are available at no additional charge with cloud based license. However, the third offering requires cloud compute resources that consumes compute credits in addition to cloud based license.

Need to know more about SIMULIA 3D Experience platform compute capacity! Please approach us and we are ready to help.

 

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.

You have probably heard about 3D EXPERIENCE. Or you may have heard about “The Platform”. But what does it actually do? How is it made? This article will explain, from the very beginning, what the 3D EXPERIENCE Platform is all about.

The Platform is created by Dassault Systemes and is their central product for the future. Here is a quote from the 3DS website:

“Dassault Systemes, the 3DEXPERIENCE Company, provides business and people with virtual universes to imagine sustainable innovations”

3D EXPERIENCE Platform is primarily a Product Lifecycle Management (PLM) system and is aimed at supporting the digital design and development of products that subsequently get manufactured. This explains the references to “virtual” and “innovations” in the quote. As a platform, it houses multiple capabilities (apps) in a single seamless piece of software. A user logs into one interface and is able to access all the installed and licensed capabilities of their 3D EXPERIENCE from there. The platform is based on a database, allowing for storage and indexing of data.

Dassault Systemes explain their platform in terms of a 3D compass illustrated below:

 

Let us look at the four quadrants, starting at the top and work around the quadrant in a clockwise direction:

  1. Collaboration apps include functionality that foster informal collaboration across extended teams (SWYM) and structured collaboration such as formal change management (ENOVIA)
  2. Information intelligence apps are designed to handle Big Data and drawing from multiple sources, present the user with concise summaries of the information they need (NETVIBES)
  3. Simulation apps are aimed at virtual digital validation and testing of designs. Traditionally this is known as CAE or FEA (SIMULIA). It can also be extended to virtual simulation of factories or retail store layouts.
  4. 3D Modeling apps are perhaps what Dassault Systemes is best known for and include CATIA and Solidworks

Finally, because all this functionality is in a single platform, this allows the user a realistic and immediate experience in a virtual world (Real time Experience).

A few more pertinent point regarding the 3D EXPERIENCE Platform:

  1. The platform is scalable to suit the requirements of each organization using the technology. Adopters can chose to start with basic functionality and then move to more advanced capabilities.
  2. The concept of a design platform grew out of the necessity to store and maintain all the digital data generated during product development after widespread adoption of CAD applications. It now has extensive capabilities beyond that.
  3. Dassault Systemes are constantly added new apps and functions to the platform, so the range of capability is expanding.
  4. More and more of the platform is moving to the cloud. Dassauly Systemes now offer a complete SAAS model for a lot of apps within the platform. This dramatically reduces implementation complexity.

Obviously, each application included in the platform is comprehensive enough to warrant a complete subject in and of itself, but I hope this breakdown has given you a useful high-level overview of what 3D EXPERIENCE can do for an organization, not just at initial implementation but in terms of adapting to its changing needs over time

 

 

“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.

 

Perhaps one of the biggest surprises for Abaqus user community in 2018 is that the two most popular licensing schemes of Abaqus would gradually go away for new customers. These schemes are Abaqus analysis pack and Abaqus portfolio pack. It’s worth mentioning that many of our Abaqus customers are still using either of these two licensing schemes. While our current customers who have perpetual or lease licenses may be able to continue with these schemes, our future customers will have to migrate to something that is available as a replacement. Instead of putting this news as a surprise to each customer individually, I thought a common piece of information well in advance through a blog article would keep the anxiety under control.

THE MIGRATION PATH

The migration path eventually leads to a token configuration that has been available since couple of years now. It is called the extended tokens configuration. While many of our customers have already migrated to this licensing scheme by choice, others are still using one of the traditional licensing schemes. Let’s look at the logic behind this high-level decision. If we look at the history of acquisitions that Dassault Systemes has made in past few years, it looks like this:

 

The inception of extended tokens is related to acquisition of three companies in above chart: FE-Design, Safe Tech and Engineous. The product offerings from these companies, if coupled with Abaqus can greatly enhance its simulation portfolio. Following acquisition, these products were offered as point tools for a long time with their individual licensing and pricing schemes. As a result, existing Abaqus customers who wished to use either one or more of these products had to go through a complicated purchase and IT process. Dassault Systemes has been looking for a consolidated licensing scheme that would enable users to procure these products along with Abaqus in a single license file that works on a single token scheme and on a single license server. This token scheme is now called the extended tokens. At this point of time Dassault Syetemes believes it makes sense to migrate all existing Abaqus users to extended tokens through a migration path that would enhance the simulation portfolio of users in a cost-effective way.

           COMPARISON BETWEEN DIFFERENT TOKEN SCHEMES

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