Detection of crack location and size in structures using improved damaged finite element

Abstract

In this paper two-dimensional finite element with an embedded edge crack proposed by Potirniche et al [1] is improved further for crack depth ratios ranging up to 0.9 h (h is the element depth) and for predicting natural frequency of a cracked beam more accurately. The element is implemented in the commercial finite element code ABAQUS as user element (UEL) subroutine. The accuracy of the UEL is verified by comparing the first natural frequency for the bending mode for several beam cases with different damage locations with available experimental data. Subsequently a methodology to detect crack location and size in conjunction the proposed improved cracked element with is presented for singularity problems like a cracked beam. The frequency response functions, function of crack location and size, are approximated by means of surface-fitting techniques. Measured natural frequencies are used in a crack detection process and the crack location and size can be identified by finding the point of intersection of three frequency contour lines. The experimental data from beams studied by other researchers is employed to verify the accuracy of the proposed methodology in the diagnosis of structural crack faults.