Abaqus 6.10

12 August 2010

Al Dean looks at the latest updates to Abaqus, the Finite Element Analysis software from Simulia, and finds enhancements to existing tools and some exciting new additions

Product Abaqus 6.10
Company name Simulia
Price On application

Abaqus is well-respected in the simulation world. It offers a huge range of tools to those looking to conduct in-depth and complex simulations of products, where advanced structural simulations with multiple factors, including non-linearity, large deformation and static analyses are common.

Since the acquisition by Dassault Systèmes (DS), the product and the organisation behind it have been incorporated into the Simulia brand, which now handles the simulation efforts across the entire DS empire.

Modelling and meshing

Pre-processing is currently a big focus in all simulation software and Abaqus 6.10 is no exception. It’s an extremely important stage of the simulation process and the accuracy of the task appropriate mesh, plus the boundary and loading conditions, directly impact the quality of the simulation. Get it right and the rest is relatively easy; get it wrong and you’ll end up with inaccurate results - the old adage of “rubbish in, rubbish out” still holds true.

In Abaqus 6.10 there’s a good spread of new pre-processing functionality. This includes the ability to create a 3D sweep based on an arbitrary 3D path or a solid shell or cut from a spline connected by discrete points. There are new tools for sectioning or view cutting 3D data, which helps users gain a greater understanding of what’s going on internally within a product. They work both with solid/surface data as well as mesh geometry and can also be used across the whole system and not just at the pre-processing stage.

Also on the geometry-modelling front, there are new tools for mid-surface modelling. These allow mid-surface or mid-plane geometry to be extracted from solid geometry, which saves a great deal of processing time. There are also tools for offsetting and extending/blending faces to ensure the model is robust. It can also render out the model with the thickness of the resulting shell element mesh being displayed.

There are also enhancements to the associative links between Abaqus and workhorse modelling tools. In addition to the existing links to Catia V5, SolidWorks and Pro/Engineer, there’s now one for Siemens PLM NX. This link can only be purchased through data translation specialist, Elysium.

Finally for pre-processing, Abaqus 6.10 offers greater control over mesh seeding. It allows users to double bias the seeding, so that the mesh density varies from the centre of the edge towards each end of an edge. This helps provide greater control over the mesh in general, including it being editable at an assembly, allowing for the renumbering of nodes or specifying a numerical range for node numbers and even manual entry. The latter is going to be particularly useful for those integrating Abaqus with in-house codes or automation tasks that require specific node references to be in position.

Mechanics and solver enhancements

In terms of solver-related updates, the last major release saw the introduction of general (automatic) contact, which means that the user does not have to discretely define potentially contacting surfaces at the pre-processing stage.

For 6.10 this has been updated to allow user-specified interference and clearance values, greater diagnostics (to find those contact conditions), a new output variable to aid the visualisation of any strain free adjustments made to the contact surfaces and step dependency control over local stabilisation where damping can be added between contact surfaces to allow the solution to converge more quickly.

The next update involves a common problem within Abaqus/Standard. While it was possible to solve standard dynamics problems if the study involved intermittent contact, the solver would often fail or not converge.  To solve this, implicit dynamics can now be applied to a wider range of problems where intermittent contact is present and it should see users through those types of studies more easily.

Extending the reach

Alongside the core tools there has also been work done on several, what might be considered, specialist areas of Abaqus’ functionality. These are the areas where there’s not quite the broad appeal of the headline updates, but may become more applicable to a larger proportion of the engineering sector as things progress.

There’s a new high-speed dynamics material model for the simulation of impact when acting on highly brittle materials, such as ceramics.

This is intended for those that work on ballistics or explosion-related simulations where traditionally you would need to model the blast source - the impacted material and the fluid between them (it’s often used for subsea applications as well as on land).

Based on an interpretation of ConWep (which stands for Conventional Weapons) formulation, this removes some unnecessary steps (such as the fluid modelling step) and gives a more accurate solution, more quickly.

Next is the addition of a material model for “viscoelasticity with anisotropy elasticity.” For those normal humans reading that mouthful, it’s basically been developed in partnership with Bentley and Engenuity as an add-on material for simulating the crushing of composite materials and is found in the CZone Abaqus modules.

Finally, the XFEM (Extended Finite Element Modelling) method of simulating crack propagation, which was introduced in the last release, has been extended.

As a reminder, it differs from many similar technologies in that it’s not dependent on the underlying mesh to create the initial crack and further damage. Abaqus 6.10 allows the simulation of crack propagation within multi-layer composite materials - with each layer having a different growth path.

This is all backed up with tools to visualise both the complete structure and each individual layer separately. For those with a serious interest in crack propagation, contour integral output variables, such as J-Integal and stress intensity factors, can now be extracted without the need for a focussed mesh.

Abaqus/CFD

While the updates we’ve discussed so far are updates or extensions of existing functionality, there’s a brand spanking new technology available with Abaqus 6.10 and it relates to Computational Fluid Dynamics (CFD). Yes, CFD within Abaqus, the structural analysis tool. Let’s explore Abaqus/CFD further.

The first thing to understand is that this is not aiming to compete with the likes of Fluent and StarCD as a fully-fledged CFD code. Abaqus/CFD is aimed fairly and squarely at the structural engineer who needs to carry out structural analyses but also needs to factor in fluid and heat transfer - or to put it another way, those looking to conduct Fluid Structure Interaction (FSI) related simulations. 

FSI is the study of the complex interactions that occur when a structure is placed within a fluid. Traditionally, you either simulate the action of a fluid on the structure of a product or the flow of fluid around or within that structure.

With FSI, you can correlate the two, so the action of the fluid has an effect on the structure (and hence its shape or mechanical properties) and vice versa. It works in a much more holistic manner and as a result, helps users gain a much better understanding of such a product.

FSI is a growing field of development, and a common problem is that the user is not only trying to transfer data between the Fluid mesh and the Structural mesh, but also trying to couple together disparate solvers, often from different vendors.

To solve this and to bring FSI capabilities directly within the Abaqus product range, the Simulia group has developed its own CFD solver from scratch so that it can be directly integrated into the Abaqus environment and used as a native tool to couple with the existing structural analysis tools. For something usually quite complex, it’s much easier to use than you may think.

The user creates a new CFD model and existing tools are used to create the fluid volume (either externally or internally) and define the material. The next step is to define the fluid structural co-simulation boundary (where the surfaces defining the fluid and structural geometry meets), then the conditions and any inlets/outlets. The final step is to define the wall conditions within the simulation.

Once this is in place, along with the structural analysis set-up, a co-execution is defined which creates two jobs - the fluid simulation and the structural siulation. The end result is two results sets and Abaqus now allows these to be opened simultaneously, creating two layers within a single post processing session.

The CFD-specific post processing tools include all the functionality one would expect: contour plots for experienced FEA users, and for those with CFD experience a vector display. View Cuts will be very handy, particularly when combining multiple cuts through the results. There’s no support for particle tracing, but this is a first release and something that will come in the next revision.

Performance

Of course, alongside all of these functional updates, every software release always talks about performance enhancements and for Abaqus 6.10, the team has done a lot of work to make the multi-core processing capabilities more efficient and more intelligent.

Conclusion

Abaqus has always been an impressive chunk of technology and while it can be used to carry out routine simulations it’s most impressive when applied to more challenging structural simulation tasks, both in terms of scale and complexity.

It’s here that the experienced analyst comes into his or her own in order to get the most out of the application and effectively transfer an engineering problem into a digital simulation environment. That’s not to say that Abaqus is an analyst-only tool, far from it.

The user interface and the language used make it perfectly usable for anyone with a solid understanding of FEA as well as their own product’s behaviour and characteristics.

The biggest news for this release is the introduction of the CFD tools. For me, that changes things for Abaqus greatly. While Simulia is not the only vendor to have both fluid and structural solver technology in house, it’s perhaps the first to start building a set of tools specifically aimed at solving Fluid Structure Interaction (FSI) problems and this area of functionality can only get better as things develop.

In short, Abaqus provides a huge range of general purpose and specialist CAE technology, but presents in it a way that’s approachable without dumbing down on the finer points of simulation. A good solid release.

Simulia

Comments on this article:

i am a student ..i wanna do fluid structure interaction studies of hyperbolic cooling tower.As you said simula launched its own cfd tool ..but i donno how to proceed with it..do you have any tutorial to use abaqus\cfd…?? if so can you please send the link to my mail…thank you…

Posted by rajendra prasad on Friday 16 2011 at 06:05 AM

in abaqus documentation has been mentioned a “unified finite element method”, but i have a question if is the abaqus/CFD finite element based or is it finite volume method based like fluent?

Posted by goshtasb on Wednesday 19 2011 at 10:03 AM

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