Online Function Monitoring of Faulty Beam

Abstract

Early detection of damage is of special concern for engineering structures. The traditional methods of damage detection include visual inspection or instrumental evaluation. A comparatively recent development for the diagnosis of structural crack location and size by using
the finite element method and Fuzzy logics techniques. A method based on measurement of natural frequencies is presented for detection of the location and size of a crack in a cantilever beam. Numerical and programming in MATLAB is done for solving the eular equation for uncrack beam to obtain first three natural frequencies of different modes of vibration considering various boundary conditions for the beam. Here ALGOR software package is used for finite
element analysis of both crack and un-crack cantilever beam taking input file as a CAD design developed in AUTOCAD 2006. Experiments is done for total 21 models of crack beam having different crack location and crack depth and it generates natural frequency for 5 modes of vibration. Fuzzy controller here used comprises of three input variables (fnf, snf, tnf) with Gaussian MF and two output variables (rcl, rcd) are generated with Triangular MF. Fuzzy
analysis is done based on some set of fuzzy rules obtained from the information supplemented by finite element analysis and numerical analysis. The proposed approach has been verified by comparing results obtained from fuzzy logic technique and finite element analysis. The results show the successful detection of the undamaged and damaged states of structural part with very good accuracy and repeatability.