Determination of Location and Size of a Through-Thickness Part-Width Crack in Cantilever Beams

Abstract

With advancements in sensor technology and structural health monitoring systems, the application of modal response measurements for online damage detection and assessment appears more promising than ever. This paper examines the use of natural frequency measurements of the structure for detection of cracks. A method to assess the crack location as well as crack size in elastic beams with through thickness-crack is formulated. Here, crack is modelled as a torsional spring whose stiffness is proportional to the size of the crack. Changes in modal frequencies depend on both location and size of crack. With three or more measured natural frequencies, the location and size of the crack are determined. The theory is first validated with frequency data generated by Finite Element Modelling (FEM) of through-thickness, partial-width cracks in cantilever beams. Experimental Modal Analysis (EMA) is performed on beams with simulated through thickness partial width cracks and the measured frequency changes are used to determine the damage location and size. Good agreement between predicted and actual location of crack is obtained for experimental frequency data.