Abstract
This paper represents the dynamic response of a steel shaft which is fixed at both ends by bearing. The shaft is subjected to both axial and bending loads. The behavior of the shaft in the presence of two transverse cracks subjected to the same angular position along longitudinal direction is observed by taking basic parameters such as nondimensional depth (bi/D), nondimensional length (Li/L), and three relative natural frequencies with their relative mode shapes. The compliance matrix is calculated from the stress intensity factor for two degrees of freedom. The dynamic nature of the cracked shaft at two cracked locations at a different depth is observed. The compliance matrix is a function of crack parameters such as depth and location of crack from any one of the bearings. The three relative natural frequencies and their mode shapes at a different location and depth obtained analytical and experimental method. Multiple adaptive neurofuzzy inference system (MANFIS) methodology (an inverse technique) is used for locating the cracks at any depth and location. The input of the MANFIS is provided with the first three natural frequencies and the first three mode shapes obtained from analytical method. The predicted result of the MANFIS (relative crack location and depth) has been validated using the results from the developed experimental setup.
Highlights
Generation and propagation of transverse crack in a shaft or rotor is a common phenomenon for every machine
The proposed multiple adaptive neurofuzzy evolutionary systems (MANFIS) for multiple crack diagnosis and the detailed showing the different layers of the adaptive neuro fuzzy interface system (ANFIS) system for crack detection have been presented in Figures 6 and 7, respectively
A methodology based on measurement of natural frequencies and mode shapes of the system has been presented for identification of crack locations and their severities in a shaft using MANFIS having one input layer, four hidden layers, and one output layer
Summary
Generation and propagation of transverse crack in a shaft or rotor is a common phenomenon for every machine. Bachschmid et al [2] have analyzed the vibration response of a shaft line used in a turbo generator unit They have used the quasilinear approach and finite element method to obtain the vibration signature (modal frequencies and amplitude of vibration). They have found out the effect of a crack along the shaft line on the dynamic response of the system at different speed of the shaft. They have simulated the crack as a notch or a wedge with a unilateral Signorini contact model They have compared the dynamic response of the damage structure with the finite element model using the least square approach and claimed that the GA-based algorithm can detect the damage parameter in the structure system effectively. The present shaft consists of two cracks at different locations and depths
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