Finite element modeling of single shear fastener joint specimens: A comparison of simplified joint modeling techniques

Abstract

Simplified finite element joint models were compared to a detailed three-dimensional model at coupon level to study their performance. Simplification of bolted joints is warranted by the element size limitation present when using explicit time integration methods for studying large scale finite element models. Two simplified models which are the rigid beam element bolt model with hole (configuration 1) and the mesh independent spotweld beam model (configuration 2), and extensions to these models which are the mesh independent spotweld beam with an elastic patch model (configuration 3) and the rigid beam element bolt model with no hole (configuration 4) were explored in this study. The load transfer, failure modes, stresses and strains, energy levels and bolt loads were evaluated for each simplified technique using a single shear lap joint specimen and compared to the detailed model. In addition, the effect of friction (0 to 0.4), preload (0 to 2300 N) and material rate sensitivity (loading rate, 20 in/s, 50 in/s and 100 in/s) was also studied. In comparison to the detailed model, the load transfer was up to 10% higher for configuration 1, 9% higher to 17% lower for configuration 2, 11% higher to 8% lower for configuration 3 and 3% higher to 10% lower for configuration 4. The simplified models captured load transfer but due to the joining methods and absence of fastener hole (weak point in a joint), the joint was in fact stiffer and resulted in large load carrying capability. Higher loading rates did not affect the load transfer but increased the load carrying capacity of the detailed model by 26% and simplified model by 5%. Preload affected the load transfer in detailed model but not in simplified models. Friction affected the detailed model by 4% and the simplified model by 1%. The detailed finite element model used for comparison was successfully validated using experimental test data and can be used as a baseline for further studies.