Question about contact problem
Question about contact problem
(OP)
Hi
I need to know wich element type is better to solve contact problems with FEA.
I think the better choice are linear elements, but I need any bibliographical reference to contrast this thought.
Thanks in advice
I need to know wich element type is better to solve contact problems with FEA.
I think the better choice are linear elements, but I need any bibliographical reference to contrast this thought.
Thanks in advice





RE: Question about contact problem
Chris
www.value-design-consulting.co.uk
RE: Question about contact problem
I've not seen any bibliographical references to this, and certainly not from the software producers.
Tata
RE: Question about contact problem
I'm writing a paper about the importance of precisión in geometry definition for contact problems FEA.
I've used type 'brick' linear elements because a recomendation of my supervisor, and i need to argue that decision in my paper.
So thank you very much, your answer has been very useful
RE: Question about contact problem
Cheers
Greg Locock
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RE: Question about contact problem
Tata
RE: Question about contact problem
Chris
www.value-design-consulting.co.uk
RE: Question about contact problem
Element choice for contact problems depends on ( amongst other factors) whether you are performing a 2D or 3D contact FEA. Also, FEA softwares have different and sometimes unique approach to element formulations for contacts analysis.
For example, in Abaqus you use tet10 modified (C3D10M)for contact problems and impact problems that involves contact
P.S: Corus could you clarify if you were referring to 'LINEAR' elements in terms of its interpolation order? i.e. (First Order) elements are these are sometimes called Linear Elements too.
RE: Question about contact problem
Ideally, if the contact pressure variation is smooth (when you have contact spanning multiple elements, with a smooth underlying geometry) then quadratic elements should be more accurate. In practice, the quadratic elements even in such cases sometimes give worse results. That is primarily due to issues with contact algorithms, and commercial FEA codes and academic researchers in this field have devised ways to improve results.
The most commonly used contact algorithm (in my opinion) is the master-slave algorithm with contact enforced at nodes. This algorithm does not work well with 20-node brick elements. That's because even a constant contact pressure produces tensile contact forces at the corner nodes. Using a 27-node element instead eliminates this problem. That's why Abaqus for example automatically converts 20-node bricks to 27 node bricks at slave contact surfaces. Master-slave algorithms that enforce contact at integration points do not have this issue with 20-node bricks (Ansys has this feature).
A similar problem happens with 10-node tets and that's why Abaqus recommends instead the "modified" 10-node tet for contact. This modified element is actually a patented Abaqus element which internally divides the 10-node tet into multiple 8-node bricks.
A newer generation of surface to surface master-slave contact algorithm enforcing contact more accurately than just at nodes or integration points is supposed to improve contact results with both linear and quadratic elements. Such algorithms are recently making their way to commercial codes. I know Abaqus has one (you activate it by choosing surface to surface discretization within a surface to surface contact interaction), and I believe other codes have something similar too. With these algorithms quadratic elements may finally be better for contact problems involving smoothly varying contact pressures.
Nagi Elabbasi
Veryst Engineering