Zero-length Element VS Two Node Link Element

[confidentyou]

Hi everyone:
Could you tell me the difference between the Zero-length Element and the Two Node Link Element in modeling bearings and impact ? I am a little confuse about the two element, especially for modeling impact effect between two beams. Can I use the Two Node Link Element to model the impact ? And which one is better for modeling impact if I use the Impact Material. I am looking forward your reply.

[fmk]

they are very similar if the element has 0 length .. with Length the twoNodeLink couples rotation-displacement and can add some PDelta effects.

for impact you probably just want the zeroLengh.

[confidentyou]

Dear Dr. Frank
Thanks for your reply. I have another question about the Zerolength Element. What is the exact meaning of “zerolength”？ According to the  instruction of this element，the zeroLength element object is defined by two nodes at the same location. But for the pounding in my model, the two nodes are not at the same location. Is it right for this case to use zero length element to modeling pounding？

[Fameh]

yes, i think so.

[fmk]

even if the 2 nodes are not at the same location you can use the zeroLength element (ignore the warning) .. the element just passes the change in displacements to the material as the strain .. there is no length factor involved in modifying these displacements as there is for example in a truss element.

[confidentyou]

Dear Dr. Frank
Thank you very much. I learn a lot from you.