Modelling the joint rotational compliance of stud-pocket type flight inter-section joint

Joint rotational compliance (JRC) of a flight intersection joint (FIJ) is an important parameter in the structural design and analysis of a launch vehicle. The JRC is always quantified through extensive experiments due to the non-availability of a reliable theoretical or numerical model. This paper attempts to bring out an analytical model based on the modelling of localised component joint stiffness. The local component joint stiffness is modelled and quantified through numerical methods and verified through experiments. The analytically predicted JRC for a typical FIJ is compared with that obtained from independent numerical modelling of the full FIJ based on finite element analysis, where a very good agreement is observed between analytical and FEA results. Further, the effect of pre-tightening of studs and variations in size and number of studs and their combinations on the JRC of a FIJ is investigated. It has been demonstrated that (1) the pre-tightening of studs enhances the JRC to an extent of 30% to 10% when loading is increased from no load to the first yield moment; and (2) the increase in the number of studs for a given stud size results in significantly enhanced JRC as compared to the increase in the size of studs. •Joint rotational compliance (JRC) of a flight intersection joint (FIJ) is a vital parameter in launch vehicle's structural design and analysis.•JRC quantification relies mostly on extensive experiments due to the non-availability of a predictive model.•An analytical model is developed for JRC which relies on local component joint stiffness determined from numerical and experimental methods.•Analytically predicted JRC for a typical FIJ closely matches with numerical simulations.•Effect of pre-tightening and variations in size and the number of studs and their combinations on JRC of FIJ are investigated.