Tightening performance analysis of bolted connection considering non-parallel contact

Bolted connection is one of the most widely used connection forms in various mechanical structures. However, the discretization of preload during tightening will be aggravated by the presence of geometric error caused by manufacturing. In this work, the geometric error transmitted by all parts of the bolted joint is equated to the existence of a certain wedge angle between the nut and the bearing surface of the connected part, that is, the nut and the bearing surface are in non-parallel contact. A torque-preload mathematical equation is theoretically established to account for non-parallel contact. On this basis, the relation between torque and preload deviation is considered to analyze the formation mechanism of preload deviation according to non-parallel contact. Subsequently, the influence of non-parallel contact on tightening performance was quantitatively analyzed by experiments and finite element. The analysis results showed that the tightening process under non-parallel contact can be divided into two stages: nonlinear increase stage and linear increase stage. Among them, the deviation mainly appears in the first stage. Tightening performance analysis herein is helpful to reduce the influence of geometric error on the preload control and further improve its reliability.