Detection of Crack Location and Crack Depth by Using Fuzzy Logic Technique

Mechanical Engineering

Fault Diagnosis is one of the important aspect in structural engineering for safety reasons. A crack in structural components introduce the flexibility and it will influence the vibration parameters of that component. The presence of damage leads to alteration in natural frequencies and mode shapes. The conventional methods of fault diagnosis are available but main problem is to detect existence of crack with its location and depth. We used the changes in natural frequencies because of crack presence as a basic criteria. Theoretical calculations are done to find out first three natural frequencies by using Euler’s equation. ANSYS workbench 15.0 is used to find natural frequencies along with the experimentation on FFT Analyzer. Experimental analysis conduct on total ten beam models having square cross section. One beam is considered as uncracked beam and other nine beam are cracked beam. Cracks of 0.35mm width are produced on these nine beam by wire cutting machine. Fuzzy logic toolbox in Matlab 7.10.0(R2010a) is used as a solution for detection of crack location and crack depth. Gaussian membership function is used for input and Trapezoidal membership function is used for output. Fuzzy rules are formed from the information provided by the Finite element analysis and experimental analysis. Fuzzy controller use three input variables i.e. normalized frequencies of first, second and third mode of vibration and two output variables i.e. relative crack location and relative crack depth. The presented system is used to detect existence of a crack together with its location and depth in the structure.

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