Study of the interference contribution on the performance of an adhesive bonded press-fitted cylindrical joint

The adhesive bonding technology can be used in combination with other traditional joining methods, such as mechanical fastening techniques (e.g. rivets or bolts) or welding techniques, generating a hybrid joint. Hybrid adhesive joints are designed to exploit the advantages of the different techniques and, if possible, overcome their drawbacks. This study focuses on the interference fitted/adhesive bonded joining technique. This method consists in two cylindrical components coupled together by inserting one into the other, after having placed an adhesive on the mating surfaces. This hybrid joint, generally realized by exploiting acrylic anaerobic systems, has been studied to evaluate the interaction between the tensile field of the components (at the interference level) and the adhesive strength under both static and dynamic loading conditions. Notwithstanding this, the contributions of the adhesive and the interference on the performance of the final joint are still not completely clear. The aim of this research is then to further study the factors affecting the resistance of this hybrid joint. Hub-shaft samples, joined by means of a press fit, were tested under an axial push out load. Hybrid joints were compared to both adhesive joints in clearance conditions and interference joints. In particular, different levels of interference were analyzed in order to clarify the role played by the tensile field between the hub and the shaft, and the influence of the friction effects between them. Numerical simulations were also employed to support the experimental data in the evaluation of the behavior of the adhesive and its relation with all the phenomena influencing the hybrid system. It was found that tribological phenomena played an important role in governing the mechanical behavior of the unbonded samples, while they can be considered negligible in presence of the adhesive. The correlation between bonded and unbonded press-fitted joints was investigated pointing out that the maximum strength of the hybrid joint is mainly related to the resistance of the epoxy adhesive.