Analysis of friction‐related acoustic emission in bolted joint structures

A bolted joint may be in a state of continuous fretting friction and wear under random oscillatory loading, which makes the bolted joint prone to loosening. Therefore, it is essential to find a way to monitor the contact state of a bolted joint on time and handle it adeptly. Acoustic emission (AE) signals will be generated during the reciprocating friction of the bolted joint interface. Exploring the relationship between the frictional slip features and the acoustic emission characteristics under different bolt preloads can lay the foundation for using the acoustic emission techniques to monitor the pretightening state of bolted joints. This paper experimentally investigates the acoustic emission signals of a bolted joint structure during friction under different preloads, three repeated tests are implemented. The relationship between friction behavior and acoustic emission characteristics under different preloads is studied. The evolution of classical acoustic emission parameters and kinematic parameters with bolt preload levels is also analyzed. The 3‐D topography of the specimens after parametric tests is analyzed. The results show that the characteristics of both burst‐type and continuous‐type acoustic emission can reflect different friction behavior under different bolt preloads. The evolution curves of acoustic emission parameters changed under the interaction of both frictional kinematic parameters and bolt preload levels. For the 3‐D surface topography, the reciprocating friction shears the peaks and fills the surface valleys, and the topography of the scratched surface areas is redistributed.