SSA Blog

How to achieve convergence in advanced contact analysis for finite element modelling?...

Posted by Richard Cave-Penney

Performing Contact Analysis can be one of the more complex non-linear finite element challenges in the daily life of a structural engineer and in our opinion remains the single biggest challenge in simulation. As we have many involvements with people performing these non-linear contact analysis for their finite element model, we notice that there are a lot of challenges which often are not addressed well because a lack of convergence and ever reducing time-steps. This is where we see a lot of trial and error approaches with the hope on a possible solution.  Unfortunately many times the “hope” ends in a hugely stressful situation where you need to ask another company to do the analysis for you because you can’t seem to get it running properly.

Many engineers tend to forget that setting-up a contact analysis simulation takes quite some understanding of the actual physics and behavior behind this. The reason people tend to forget, probably exists due to easy and user-friendly CAD integrated Finite Element Software for which the user requires less knowledge and just applies the contact to their model. The downside of these CAD-Integrated simulation tools is that they focus on the average engineer performing slightly simple validations which most of the time are linear statics anyway. Using linear static analysis for contact behavior can produce nice colourful results, but can be completely off with respect to accuracy and the values like contact pressure or reaction forces. And even if the CAD-integrated FEA software would have the ability to perform non-linear analysis, often the solver capabilities are not powerful enough to provide the structural engineer with confidence and enough options to obtain convergence and get the job done to solve their contact challenge. Contact analysis finite element modelling

Structural Engineers who have ever used dedicated FEA software will already notice improvements with the robustness of the solvers compared to CAD-integrated FEA software. Most of the dedicated stand-alone high-end FEA software will claim that they can do more complex contact challenges, but this is where it all comes down to the internal algorithms and equations which should be robust and especially designed for non-linear purposes. Other types of contact challenges require the need to be able to switch between an Implicit and Explicit solver, which reduces the dedicated stand-alone high-end FEA software options available in the market. The Explicit solver for instance is used for high speed events such as impact or drop test. The option to be able to switch between Implicit and Explicit solver within the same interface is a very powerful capability and provides a highly flexible and efficient process.

For huge contact challenges, the accurate and powerful option, general contact, can be added to the equations, where all components can come into contact with each other and themselves and also applies for edge-to-edge contact. The general contact ability will spare you a whole lot of clicking and defining. And last but not least, a good dedicated stand-alone high-end FEA software has many options which you can influence in order to reach your convergence to solve the job.

Interested in the possibilities to achieve convergence for your contact analysis?

We have decided to run a series of free Contact workshops throughout the year, followed by an opportunity to try some modeling real world problems with Abaqus.Our first free Contact event of the year will be taking place on 12th February at SSA’s offices in Charlbury, Oxfordshire.

For further information and registration details for any of our free contact workshops, please follow the registration button.

Experience how you can perform contact analyse that do work!

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