Failure mechanisms of bolted flanges in aero-engine casings subjected to impact loading

In this paper, a failure evaluation criterion was proposed for the bolted casing-flange structure under impact loading. Subsequently, ballistic tests with eighteen bolted casing-flange structure specimens were conducted to validate the failure evaluation criterion. Parameter studies were then carried out using the validated FE models. Both the experimental and numerical results demonstrated the accuracy of the failure evaluation criterion. The failure evaluation criterion provided a quick and easy way to determine the failure mode of the casing connection area by using the materials and dimensions of the structure. Based on the failure evaluation criterion, designing the structural failure mode of the bolted casing-flange structure to be between flange failure and bolt failure can improve the impact resistance of the connection area of the aero-engine casings. This investigation revealed that the impact failure is not the unique criterion in evaluating the containment of the casing connection area, structural failure should also be involved in the evaluation criteria.