Investigation of Crack Effects on Isotropic Cantilever Beam

Abstract

The effect of an open edge crack on the parameters of an isotropic aluminum cantilever beam was investigated. The rotational stiffness and flexibility of the cantilever beam crack were analytically calculated for various crack depths. The results showed that as the depth of the crack increased, the rotational stiffness decreased and flexibility increased. For the intact cantilever beam, acceptable variation was validated by comparing the analytically estimated natural frequencies of the first three modes of bending vibration, and those obtained through modal analysis using the block Lanczos method of finite element analysis software ANSYS v16. The software was used to perform a structural, modal and harmonic analysis of the cracked cantilever beam under different scenarios. The results showed a reduction in the natural frequencies with the existence of the crack. The amount of the reduction varied based on the location and depth of the crack and the pattern of mode shapes. The calculated value of stiffness of the cantilever beam decreased with the presence of the crack. The amount of the decrease was dependent on the depth and location of the crack. The calculated values of the (SIF) stress intensity factor in mode I of the crack (opening edge crack) were proportional to the depth of the crack and inversely proportional to the distance of the crack from the fixed end of the cantilever beam. Based on these results, it is inferred that changes in the modal and structural parameters of the cracked cantilever beam were evidence which could be used to identify cracks.