,what you said in last paragraph, its amusing and fascinating that the ANSYS has this implemented within its alogrithm. I was thinking that distance is the same between the nodes of contact to nodes of target, so frictional contact should get detected no matter what the Shell face is being used (TOP or BOTTOM). But the contact and target faces must face each other otherwise the contact will not get detected, thats very impressive by ANSYS. It implies that ANSYS has extremely sophisticated codes and algorithm implemented within it, because what I was saying was simple. ANSYS could had just done that, but they modified the code such that the contact will not at all be tracked if the target and contact faces are chosen so that they not facing each other. They didn't leave any room for the Analyst Engineer to make any mistake by choosing the wrong face and conduct the analysis (since the contact will not at all be tracked) because the results would be wrong, and Analyst might not even bat an eye on it . IMPRESSIVE.
I wonder how does the ANSYS get to know if the faces are actually facing each other or not, I couldn't think of any way. I mean its code. Maybe surface normal, maybe something else, don't know.