Finite Element Analyses of Bolted Joints Using Different Thread Modelling Techniques

Abstract

Intensive finite element analyses (FEA) were carried out to investigate the effects of thread modelling techniques on torque-force relation in threaded joints. The bolt thread was modelled by solid revolving the ISO thread profile and it was meshed using hexahedral elements. The nut thread was modelled either by solid/cut revolving the ISO thread profile, with/without root fillet or by using hexahedral/tetrahedral elements. Excellent agreement was found between torque-force relationship obtained using the FEA, the experimental result and the theoretical analyses. The FEA results showed the torque-force relationship is independent of both the modelling techniques and the mesh size but highly dependent on coefficient of friction between surfaces in contact. The study outputs support the simplified approach to use the tetrahedral elements to model threaded joints. The value of the equivalent coefficient of friction to be used is approximately the sum of the coefficients of friction at the threads and that at the bearing area.

Keywords

• finite element thread modelling
• nut-bolt friction
• threaded joint
• tightening force
• tightening torque