Bolted joints: Eigenfrequencies from non-linear FE-models and experimental modal analysis

This paper focuses on the finite element modeling of bolted joints for structural dynamic analysis to achieve a reasonable accuracy in simulation results. Non-linear numerical models have a high computational cost, this makes it desirable to merely introduce local non-linearities to an otherwise linear FE-model. Here, only the joints are modeled non-linearly, while the remaining structure is assumed to behave in a linear way. Two beams connected by seven bolts are numerically and experimentally analyzed. Specifically, a tie constraint, interactions to simulate contact and the bolt's threads, a static load case with the corresponding pre-load, as well as the bolt's and beams' geometry are used to model a non-linear joint in Abaqus. The numerical results for the system's eigenfrequencies are compared to data from an experimental modal analysis via laser Doppler vibrometer. For bending modes, simple linear models prove sufficient, while the comprehensive non-linear model is required for an accurate analysis of torsional modes.