## General Mechanical

#### How to apply DOF in the radial and tangential directions on a half circle?

• safiana
Subscriber

Hi everyone,

I am modeling a 2D plain strain bearing model in ANSYS APDL. I have created 5 roller in the bottom half of the bearing, and to simplify applying pressure on these rollers, I made them by half circle to apply surface pressure on their top lines (SFL). The contact type is rough in my model however I prefer to put it on frictionless. But the solution doesn't converge which is logical due to the rigid body motion of the rollers. For example for the middle half circle if I constrain the KP 9 and 10 in X direction, that solves my problem. But, for other four rollers, the top surface is not in X or Y direction and is angular which makes it hard for me to understand how to apply DOF. When I was creating these rollers, I first made the middle one, and for other rollers, I rotated my workplane. If I apply DOF on the KP while the coordinate system is rotated, that doesn't solve the issue. This is why I mean:

CYL4,0,0,30.782, ,27
CYL4,0,-22,5,180, ,360
save
BLC5,0,-27,1,2.5
DK,9,Ux,0
DK,10,Ux,0

csys,4
wpcsys,-1,0
WPROTA, -32.72
CYL4,0,-22,5,180, ,360
BLC5,0,-27,1,2.5
DK,16,Ux,0
DK,17,Ux,0
csys,4
wpcsys,-1,0

So, does anyone know how to constrain the tangential direction of the half circles (top lines) and have free DOF on the radial direction? In this way, I am sure the rollers won't slide and move. As a note, using bonded contact solves the issue and that's why I am suspicious to the boundary conditions.

Thank you
Ali

• Chandra Sekaran
Ansys Employee

To constrain in tangential direction you should rotate the nodes into the local cylindrical coordinate system of that half cylinder. Something like:

local,11,1,x,y,z,    ! where x,y,z is the center of that half cylinder

nsel,s,....           ! select the nodes of that half cylinder or just the top line node

nrotate,all         ! rotate into local cylindrical coordinate system

d,nodeid,uy,0    ! fix tangential motion

• safiana
Subscriber

Awesome, thank you!