Condition Monitoring of Multi-Bolted Joints with Combination of Preload Measurement and Extended Evaluation from FEA

This paper shows an approach developed to cover in detail different behaviour of threaded fasteners with a robust test setup for multibolted joints and numerical simulations by means of finite element analysis (FEA). Resulting from this combination, it is possible to monitor the axial, torsion and bending stress in fasteners themselves. Importance is given to interpretation of the measurement signals of strain gauge bolts. Integrity of the complete structure can be better interpreted with this approach. This depends on the modelling of bolts for FEA and the quality of the measured signals from experiments. For FE modelling the general purpose non-linear solver Abaqus is used, for preload measurement strain gauges are integrated into metric bolts. Simulation and experimental results from this unique test setup with several bolts are shown. This test-setup allows investigation of not only the preload distribution but also the resulting behaviour of the structure with regards to external loading and bolt stressing in detail. Typical preload deviations from tightening procedure are considered. With this combination of preload measurement at several bolts and transfer of data obtained from FEA, a detailed monitoring of the structure′s status is possible. Investigations are performed on previously unexplored influences on self-loosening for example from number of bolts and geometry of the clamped part.