Calculation Services

Nonlinear analysis that you can trust

Impetus Afea Solver

We leverage unique partnerships and years of experience with IMPETUS Afea Solver, a non-linear explicit finite element tool, to offer highly detailed and accurate structural analysis.

Impetus is a modern finite element platform apt for large deformations, dynamic analyses, thin-wall structures, contact problems, and large, complex structures. The key technologies that drive precision are:

  • Unique higher-order solid element technology.

  • Uncompromised integration in the explicit scheme (time-domain).

  • True surface-to-surface contact appreciating the smooth surfaces of the higher order elements.

  • Node splitting at fracture allows for realistic prediction of cracks and preserves energy and mass in dynamic events.

  • Material library with test-verified non-linear materials including hardening curves and fracture mechanics. Hyndla has also developed own models including models for pipeline steels and high-strength concrete.

  • Massive parallelization in workstation format with GPU acceleration.

 

Some examples of what we can do with Impetus

In this project our simulations showed that a 20 ft shipping container impacting a subsea gas export pipe did not cause a critical breach in the structural integrity of the pipe, saving millions of dollars in potential risk reducing measures.

A scaled model for realistic material and geometry interactions in a fiber net using Impetus Solver.

Why Impetus Afea Solver instead of Abaqus or Ansys?

For highly non-linear and/or very dynamic simulations, explicit finite element analysis is often most suitable. Commonly used general purpose solvers such as Abaqus and Ansys (Mechanical or LS-Dyna) offer the explicit formulation, like Impetus Afea Solver. But very different element types are available. When it comes to hex-mesh, full or reduced integration linear elements are available in Ansys and Abaqus. Abaqus also offers improved “Incompatible Modes” elements that reduce shear locking and hourglass effects. Impetus Afea Solver, on the other hand, offers unique higher order elements for explicit analysis, with both quadratic (27 nodes) and cubic (64 nodes) elements available.

To show the power of the Impetus elements, we challenged the Abaqus elements in a simple beam bending problem. A simple 10mm x 10mm x 100mm elastic beam with a 200 GPa modulus was loaded at the tip with 1 kN. The analytical solution predicts a tip deflection of 2 mm. With this set-up, we achieved the same accuracy as 16000 of the best Abaqus elements with only 6 Impetus elements. With only one element Impetus Solver has less than 5% error. Using 40 full or reduced linear integration elements (not the more expensive “incompatible modes” elements) give errors of more than 30%.

A simple beam bending simulation shows the unrivalled accuracy of Impetus Afea Solver elements for explicit analysis.

Uncompromised nonlinear solutions

Most finite element solvers try to linearize as much as possible to make matrix inversion simpler and run-times faster. In the last 50 years of finite element analysis, countless schemes have been proposed and implemented to account for the fact that nature is not linear and invertible, all with caveats and pitfalls that the engineer should be aware of (but most often isn’t). This concerns contact interfaces, material behavior post-yield, dynamic events, fracture, geometric changes, and many more.

One known solution to the inversion problem is to solve the system in the time domain and solve the system as it evolves in time (explicit finite element analysis). Even though this method offers unique robustness, it has been disfavored because it is computationally expensive and typically limited to simpler discretization techniques (see element test above!). Impetus Afea Solver goes a long way in solving this by offering massive GPU parallelization and unique, higher order elements.

At Hyndla, we have doubled down on the explicit scheme and adopt a brute-force, robust, and accurate approach to solving nonlinear systems. This may be computationally expensive at times—we often run simulations that take 100 hours to execute!—but in our experience this is much cheaper and quicker than the endless pondering and evaluation of the validity of linear assumptions.

And for truly dynamic events, such as dropped objects, ship impact, electrical short circuits, blasts, crashes, etc., where no inversion scheme will work, Impetus Afea Solver opens up a new world of accuracy and efficiency that Hyndla takes maximum advantage of.

This video shows a contact problem that would not be possible to solve with an iterative solver.

This video shows a deformation problem that would not be possible to solve with an iterative solver.

 

Product Development

Both internally in our tranmission tower and offshore wind ventures and for external customers, Hyndla use Impetus Afea Solver for product development. Our designs are the product of a holistic approach to geometry, production, and process. The design process is not confined to a linear progression. In practice this means an iterative process based around a digital twin that we power with our in-house, cloud based algorithms for a streamlined CAD to FEM process. This drastically reduces the cost of the first iteration of trustworthy FEM calculations, which is often the barrier that keeps designers from making better use of FEM calculations.

In this way we build useful digital twins that influence the real product. With smart CAD to FEM models, we can test many iterations of the design without any production and guide design, material, and production decision making.

Structural Analysis with Correct Stiffness

A traditional Eurocode approach leaves many open questions with regards to plate connections, bolted connections, and buckling of members subject to eccentric and complex boundary conditions. This makes it near to impossible to find the optimal solution, particularly for aluminium structures, resulting in heavier, costlier, and more polluting projects.

The challenge lies in having a model that is able to accurately predict all relevant failure modes based on the true stiffnesses in the system. This is especially difficult with thin-walled structures where the geometry changes quite significantly before failure. Impetus is the only commercially available software today that can accurately predict correct failure modes without unphysical material properties using volume elements. A 25% weight reduction or more compared to the Eurocode 9 approach is in principle achievable for almost any larger aluminium structure using Impetus Solver.

Models by Tore Tryland, SINTEF Manufacturing. Reproduced with permission.

Risk assessment

The many benefits of Impetus Afea Solver makes it ideal for risk assessment of accidental events such as short circuit events, dropped objects, ship impacts, etc. These are typically dynamic events where large deformations or even fractures are expected. Hyndla has carried out several such projects for large offshore operators and contractors with a proven track record of trustworthiness and delivery assurance. Check out our reference projects by following the link below.

Video credits: Impetus Afea

This video shows a deformable container model impacting an offshore platform deck structure.

By using correct description of the dynamic short circuit loads, we optimize the design and give a realistic risk assessment. Here we show a simulation of a short-circuit event in a trefoil formation, with a FRP profile mounted to a surface with two neodymium magnets.