# Define gap with contact element CONTA178

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• Last Post 12 June 2018
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saraahf1 posted this 12 June 2018

Hi!

I'm trying to create a contact between 2 nodes and I would like to define a initial gap between this two elements because initially they are separated with 5mm and the contact only can occurs if the force is sufficient to move both elements more than the defined gap. Does anybody know how to define the dimensions of the gap?

This is the part of code where I've created the contact.

ET,8,CONTA178

type,8

e,NODE(xpos1,ypos1,zbsuk+0.1),1

peteroznewman posted this 12 June 2018

Hi saraahf1,

You should read this thread for info on COMBIN40 element which allows you to easily define a gap between two nodes.

Regards,
Peter

saraahf1 posted this 12 June 2018

Is it the same way to use it with CONTA178?

peteroznewman posted this 12 June 2018

Both CONTA178 and COMBIN40 will use the initial locations of the two nodes as the initial gap.

CONTA178 keeps track of 3 DOF for the contact and supports sliding friction when the gap closes.

COMBIN40 keeps track of 1 DOF for the contact and requires a spring rate for the contact.

What version of ANSYS are you using?

saraahf1 posted this 12 June 2018

I'm using ANSYS APDL 15.0 and also have the same version of Workbench.

peteroznewman posted this 12 June 2018

So build a 2 beam, 4 node model with a gap between the end points the beams as I did in this post, and try each element to see what works for you.

saraahf1 posted this 12 June 2018

I'll keep in mind the building of the proposed model.

I was reading about the options for the initial gap for the CONTA178 and I've seen that you can define them by the keyopt(4)=1, but then it is necessary to define the gap with the real constant (real constan 2 I think). Maybe my question is very basic but I don't know how to define this in the code. Would it be like this (the real constant parameter is defined in this way)?

ET,8,CONTA178

keyopt(4)=1

r,8,2,GAP

type,8

e,NODE(xpos1,ypos1,zbsuk+0.1),1