Loosening of steel threaded connection subjected to axial compressive impact loading

•This paper investigated the loosening of threaded connection similar to fuse-projectile structure under impact loading using a modified SHPB apparatus. The high speed camera was used to capture the loosening process and the correlation between the preload variation and the loosening rotation angle was established by using the digital image correlation technique.•A 3D finite element model was developed to analyze the loosening mechanism of threaded connection. The transient behavior of threaded connection under single shock wave shows a tightening-loosening alternation process.•The loosening of threaded connection under impact loading is the result of multiple impact pulses with dispersion effects. When the amplitude of shock wave is approximately 10 times of the initial axial stress, the rotation increases rapidly. The loosening process of each individual shock loading could be accumulated to result in a final loosening of the threaded connection. Loosening of threaded connection under impact loading is important in engineering structures such as the fuze on a projectile. It is difficult to predict the loosening behavior of threaded connection under impact loading due to their high nonlinearities introduced by friction and discontinuity. This paper investigated the loosening response of a threaded connection under a series of impact loadings using Hopkinson bar experiments. The loosening phase diagram was constructed by measuring the preload variation. The correlation between the preload variation and the loosening rotation angle was established by using high speed camera and digital image correlation technique. A 3D finite element model was developed to analyze the loosening mechanism of threaded connection. The transient behavior of threaded connection shows a tightening-loosening alternation process. This study provides an understanding of the loosening process of threaded connection under impact loading and is helpful for optimizing structural design under extreme conditions.