FAQ 002400 EN-US 02/12/2019

Markus Baumgärtel Modeling | Structure RFEM

Which joint conditions should I choose for a line joint or line release in order to flexibly couple surfaces?


The easiest way to explain the differences is to use an example (see Download -> Example file). This contains the result of the comparison of non-linear calculation to linear calculation (see also Figure 1).

The left model and the middle model have linear line joints. The left model defines a compliance in u_x and u_y. At the middle model "only" in u_x direction. On the right model, the compliance is defined in u_x and u_y. However, a pressure contact between the surfaces is defined here. These surfaces can not penetrate to pressure.

If you look at the results, you can see that the left model is too soft, because the surfaces penetrate in the u_y direction because of the softness. The middle and right models, on the other hand, give identical results.

Often it makes sense to stay as linear as possible, so the middle model is probably the most appropriate for numerical investigations. Even if the right nonlinear model represents reality even better. However, the example is only a small comparison model. In reality, one probably does not use the spring in u_y / u_z, but assigns this force to a tie rod. That's why it's better to use the middle model without u_y.

The consideration of the flexibility between surfaces is also discussed in the following technical contribution of our knowledgebase:



Line joint line release compliance between surfaces


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