Modal stress parameters-based methods for defect localization on the propeller blade edges

Abstract

The stress mode shapes are highly sensitive to the local state of the structure, e.g., holes, cracks, and grooves. In this paper, two new defect indices based on stress mode shapes are developed to locate single or multiple local structural defects with different severity levels on the marine propeller blade edge. A stress modal analysis was performed on the intact model of the blade and the different models of the defective blade. The first four stress mode shapes along the propeller blade edge were calculated for every model of the blade. The new defect indices called modal stress flexibility change and defect index based on stress modal energy were calculated for each stress mode shape. Firstly, the ability of the two new defect indices calculated for each mode to locate a single defect was investigated. Secondly, the effectiveness of the defect indices calculated from the combination of the first four stress mode shapes is investigated for single and multiple defect localization considering different severity levels. Through the numerical investigation, the modal stress flexibility and defect index based on stress modal energy are promising to locate single or multiple defects in real structures such as marine propeller blades.