A finite element method for calculating load distributions in bolted joint assemblies

Abstract: Bolted joints are often the most critical parts with respect to fatigue life of structures. Therefore, it is important to analyze these components and the forces they are subjected to. A one-dimensional nite element model of a bolted joint is created and implemented as a program module in the Saab software `DIM', together with a complete graphical user interface allowing the user to generate the structure freely, and to apply both mechanical and thermal loads. Available methods for calculating fastener exibility are reviewed. The ones derived by Grumman, Huth and Barrois are implemented in the module, and can thus be used when dening a geometry representing a bolted joint assembly. Investigations have shown that it cannot be said that either method is generally better than the other. Calculated properties of interest include the fastener forces, plate bearing and bypass loads, and - for simpler geometries without thermal loads - the load distribution between rows of fasteners. The program is fully functional and yields numerically accurate results for the most commonly used joints where fasteners connect two or three plates each. It has limited functionality on geometries with fasteners connecting four or more plates and for a certain loading combination also for three plates, due to the tilting of the fasteners not being accounted for in the model for these cases. Also, there is no explicit method available for nding an accurate value for the fastener exibility for these, less common, joint structures.