Bolt clamping force versus torque relation (<i>F</i>-<i>T</i> relation) during tightening and untightening the nut having slight pitch difference
Xi Liu, Biao Wang, N. Noda, Yoshikazu Sano, Yuto Inui, Kosuke Tateishi, Yasushi TAKASE
Abstract
In this study, tightening and untightening experiments were conducted for pitch difference nuts toward realizing good anti-loosening performance. By applying the three-dimensional FEM, the relationship between the tightening force F and the tightening torque T was clarified by varying the pitch difference α during the whole nut tightening/untightening process. The well-known F-T formula available for tightening the normal nut (α = 0) agrees with the FEM results and the F-T formula for untightening the normal nut (α = 0) was newly proposed. Then, the loosening resistance ability of the pitch difference nut was clarified focusing on the untightening in comparison with the normal nut.