Abstract: A method for characterizing a threaded coupling such as between two tubular members is disclosed. In one embodiment, a threaded connection between a first tubular and a second tubular is considered, where the first tubular has a internally-threaded box structure and the second tubular has outer threads defining a pin structure. A mathematical model of the connection between the two tubulars is generated, and the mathematical model is permuted to reflect application of at least one flexing force to the joint. From the permuted model, a stress/strain distribution of the box and pin structures is derived. A connection fatigue index value is calculated based on the stress/strain distribution. In one embodiment, connection fatigue indices are computed for a variety of connection combinations, such that a user can compare the relative suitability of multiple box/pin combinations to select one that is deemed desirable for a particular use.