As we saw, there is some penetration (0.01378 mm) in the contact as seen below. This is resolved during solution thus giving a reaction (parts are pushed away from each other to resolve the penetration)- try to move the cylinder away from the disc so they do not overlap and there is no penetration and there should not be any reaction (this is a quick test to show that it is the solution of the penetration that gives rise to the reaction force).
Erik
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