Experimental and numerical investigations into tensile and compressive behavior of radial countersunk screw lap joints

Radial countersunk screw lap joints are widely employed in aerospace vehicles to connect various cabin sections. These joints experience complex flight loads, leading to nonlinear deformation and strain behaviors due to the contact and friction mechanisms at the joint interfaces. To gain a deeper understanding of the nonlinear mechanical behavior of such joints, this study conducts static tension and compression tests, complemented by nonlinear finite element simulations. Initially, typical radial countersunk screw lap joint specimens are fabricated and tested under tension and compression loads using an MTS universal testing machine. A preliminary analysis of the load-deformation relationship is performed based on the experimental data. Subsequently, a numerical model is developed using the nonlinear finite element method. This model is validated against experimental results and utilized to predict the evolution of contact behavior and the distribution of stress/strain within the specimens. Furthermore, a parametric analysis is conducted to investigate the influence of key design parameters on the joint's mechanical behavior. The findings indicate that the nonlinear mechanical behavior primarily stems from changes in the contact state between different components, while the differences in tensile and compressive behaviors are driven by variations in contact stiffness. Additionally, the size of the screw-hole clearance and assembly clearance significantly impacts the slip behavior observed in the load-displacement curves. Variations in screw preload and lap length have an important effect on the initial stiffness of the joint. These insights provide a foundation for optimizing the design and performance of radial countersunk screw lap joints for aerospace applications.