“…For clarity, the contact formulation is briefly presented here based on the methodology previously published for CoC bearings (Liu et al, ). The IMPACT function in Adams was used for both the edge loading and the articular bearing contact of the cup and head (MSC, ), which can be expressed as follows where F is contact force generated at the contact interface either of the cups and head articular bearing surfaces or between the cup rim and the head bearing surface, k is a generalized stiffness, e is nonlinear force exponent, x 1 is the distance calculated by Adams based on the contacting geometry above which there is no contact force, x is the approaching distance between the two contacting objects, d is the penetration at which to apply the maximum damping coefficient c max , the STEP function takes 1 for x = x 1 − d , 0 for x = x 1 , and a cubic polynomial interpolation for ( x 1 − d ) < x < x 1 , and is penetration velocity.…”