Experimental Investigations on Crack Detection Using Modal Analysis and Prediction of Properties for Multiple Cracks by
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Experimental Investigations on Crack Detection Using Modal Analysis and Prediction of Properties for Multiple Cracks by Neural Network P. R. Baviskar • V. B. Tungikar
Received: 1 August 2013 / Accepted: 18 October 2013 / Published online: 16 November 2013 Ó The Institution of Engineers (India) 2013
Abstract In the present study, a method is proposed for detection and prediction of properties of multiple transverse cracks on simply supported stepped rotor shaft. Two cases of cracks are considered. Initially, both cracks are perpendicular to axis. Later, both cracks are inclined to vertical plane and also inclined with each other. Modal analysis is performed to extract natural frequency and mode shapes. Finite element method (FEM) is treated as basis for numerical analysis. For validation, experimentation is performed using fast Fourier transform analyzer. Based on natural frequency, cracks are detected. The results of FEM and experimentation are found in agreement. Crack properties are predicted in forward technique using artificial neural networks (ANN). The database of natural frequencies is used to train the network of ANN to predict the crack properties. Applicability of the method is verified by comparing the predictions of ANN with FEM and experimentation. The predictions of ANN and results given by FEM and experimentation are found in agreement. It envisages that the method is competent, suitable and would be alternate to the existing methods. It enhances the performance of structural integrity assessment and online conditioning and monitoring. Keywords Bayesian statistics Crack configuration Modal analysis Natural frequency Neural network
P. R. Baviskar (&) Rajarshi Shahu College of Engineering, Tathwade, Pune 411033, Maharashtra, India e-mail: [email protected] V. B. Tungikar Shri Guru Gobind Singhji Institute of Engineering and Technology, Nanded 431606, Maharashtra, India
List a a1 a2 D L x M C K x€ x_ x h1 h2 c Lc1 Lc2 A
of symbols Crack depth Depth of first crack Depth of second crack Diameter of beam/shaft Length of beam Natural frequency Mass matrix Damping matrix Stiffness matrix Acceleration Velocity Displacement Angle made by plane of first crack Angle made by plane of second crack Angle between the two planes of cracks Location of first crack from support Location of second crack from support Cross-sectional area of the beam/shaft
Introduction Integrity assessment of structures and monitoring the health of machines comprising of rotating elements has always been very crucial. They are prone to catastrophic failure due to cracks. Early detection reduces machine down time and further consequences. It becomes necessary to predict the cracks by observing single parameter. A method is proposed which is competent to detect as well as predict the cracks with convenience and ease. It utilizes the natural frequency which is global parameter and susceptible to minor changes. Presently ultrasonic testing, magnetic particle testing, X-ray techniques, radiographic testin
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