Development of linearization methods for contact non-linearities

The nonlinear nature of contacts has consistently posed a significant challenge in Finite Element Analysis, requiring nonlinear solutions to accurately describe the static and dynamic behavior of structures. This project aims to investigate contact linearization models by examining various configurations of fasteners on bolted plates, the most common type of mechanical joint in industrial applications. Linear analysis offers numerous advantages, including reduced computational costs and, above all, the ability to implement solutions provided by the MSC Nastran solver, widely used in the Aerospace & Defense field. The study initially focuses on static and dynamic analyses of discretization methods for two bolted plates. These models were created by combining three types of fastener discretization (using CBAR and CBUSH elements) and two types of mesh for the plates (2D and 3D). As the results favor the use of CBUSH elements, six semi-empirical formulas were studied to predict their stiffness, providing additional insights into their advantages and limitations. The analyses were then repeated on different models representing a joint of three bolted plates, to identify the 3D models that best approximate the ideal 2D case. Finally, to provide a comprehensive overview of the dynamic response of the structure, a modal frequency response analysis was performed on selected models for each structure.