Non-Destructive Evaluation of Preload Loss of Bolted Spherical Joints Based on Time Reversal Acoustics: A Numerical Simulation

Bolted spherical joints are widely used in space grid structures. However, the preload loss, which may arise from fabrication error, insufficient twist of the screw and some other unknown reasons can undermine the structural integrity and even lead to the collapse of the whole structure. Therefore, a method for evaluating the preload status of bolted spherical joints is vital to the structural health monitoring of the space grid structures. To this end, a non-destructive evaluation of the preload loss of bolted spherical joints based on time reversal acoustics (TRA) is presented. In this method, an excited signal generated by a lead zirconate titanate (PZT) patch at the bolted sphere is reconstructed after the signal recorded by another PZT patch at the bar is time-reversed and re-emitted. The deviation of the reconstructed signal from the initial signal allows identification of preload loss of the bolted spherical joint. This method is demonstrated to be effective by a finite element simulation. Furthermore, the effect of preload loss of the bolted spherical joint on its ultimate flexural capacity is studied, which highlights the necessity for the non-destructive evaluation.