Abstract
The principal aim of this work is the development of a specific experimental device used to identify the intrinsic characteristics of a thread and to characterize the influence of the tapping process. Two turns of thread engagement were only considered. The geometry of the tapping thread was visually inspected on a cross section of thread. Two tests of the screw-nut assembly were carried out. The first one that was used for analyzing the internal shear of thread consists in applying an axial displacement on the screw mounted on a fixed nut. In the second test, a tightening torque was applied on a pressure screw assembly to investigate principally the interface shear behavior of thread. Experiments revealed that the internal shear results in three-step spread over five distinct phases. The interface shear was quantified by the identification of the friction coefficient which was determined from the load-tightening torque relationship. The evolution of the friction coefficient versus the number of cycles of clamping/unclamping was also established. Therefore, the tribological behavior of each specimen was highlighted through thread wear analysis. The results and discussions are presented by comparing the cut and form triangular ISO thread and by studying the effect of the initial tap hole diameter.