Department of Mechanical Engineering

Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

The stability threshold of a rotor-bearing system having a transverse crack has been studied by using FEM and considering the various crack parameters and shaft internal damping (viscous and hysteretic damping) and geometric parameters. It has been observed that the instability speed has reduced considerably with increase in crack depth and influenced more with hysteretic damping compared to viscous damping. The stability of the rotor system including shaft with two open cracks has also been carried out and observed the influence of one crack over the other for threshold speed limits.

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Mechanism and Machine Theory

Effects of cracks on rotor system instability

The dynamic response of structures, in particular that of a rotor containing cracks, is a subject of considerable current interest. Several researchers have developed models of cracked rotor systems considering mainly a single transverse surface crack. In the present study, finite element analysis of a rotor system with two open cracks is carried out, and the influence of one crack over the other with regard to eigenfrequencies, mode shapes, and threshold speed limits is observed.

Shock and Vibration Digest

Vibration characteristics of a cracked rotor with two open cracks

The dynamic behaviour of structures, in particular, that of a rotor, containing cracks is a subject of considerable current interest. Several researchers have developed models of cracked rotor systems considering mainly a single transverse surface crack. In the present study Finite Element (FEM) analysis of a rotor system for flexural vibrations has been considered by including two transverse open cracks The eigenvalue analysis and stability study of a rotor system including a shaft with two open cracks have been carried out and the influence of one crack over the other for eigenfrequencies, mode shapes and for threshold speed limits has been observed. © 1999 Academic Press.

Journal of Sound and Vibration

In this investigation the unbalance response and stability of a flexible rotor supported on hydrodynamic journal bearings with rough surfaces have been studied. The influence of the surface roughness patterns on the unbalance response and the stability of a rotor have been evaluated. In this investigation the unbalance response and stability of a flexible rotor supported on hydrodynamic journal bearings with rough surfaces have been studied. The influence of the surface roughness patterns on the unbalance response and the stability of a rotor have been evaluated.

Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology

Unbalance response and stability analysis of a rotor supported on hydrodynamic journal bearings with rough surfaces

The subsynchronous whirl stability limit of a rigid rotor supported on two symmetrical finite journal bearings has been studied using the linearised perturbation method and the nonlinear transient analysis technique. A quantitative comparison for journal bearings with different l/d ratios has been provided. © 1999 ASME.

Journal of Tribology

Comparison between linear and nonlinear transient analysis techniques to find the stability of a rigid rotor

The influence of the roughness parameter (C) and the roughness patterns (longitudinal, transverse and isotropic) on the steady state and dynamic characteristics of hydrodynamic journal bearings with rough surfaces has been studied using the model of Christensen and Tonder. Reynolds-type equations have been solved using the stochastic finite method. It is seen that the transverse roughness tends to increase significantly load carrying capacity and stability with roughness values, whereas in the case of other roughness patterns the effect as seen to be very small.

Tribology International

Effect of roughness parameter on the performance of hydrodynamic journal bearings with rough surfaces

Detection and condition monitoring of a rotor system having a slant crack which occurs because of the fatigue of the shaft due to the torsional moment has been studied. Finite Element (FEM) analysis has been done for flexural vibrations by developing the stiffness matrix of a slant cracked element. Parametric study for eigen values and response has been performed with crack parameters VIZ, crack depth & location and operating and torsional frequencies. The frequency spectra of the steady state responses of the cracked rotor were found to have sub harmonic frequency components at an interval frequency corresponding to torsional frequency, which can be used for crack detection and monitoring.

Noise and Vibration Worldwide

Conditioning monitoring of a rotor system having a slant crack in the shaft

This study deals with the stability characteristics of journal bearings using the finite element method. Two different elements, a 3-node linear triangle and a 6-node quadratic triangle, have been used. The results show a significant difference in (]) stiffness and damping coefficients and (2) stability characteristics at high eccentricity ratios due to the use of the two different elements. © 1998 by ASME.

On the choice of element for solving lubrication problems

Identification of crack location and magnitude through measurement in changes in system characteristics, such as modal measurements, has been studied by various researchers. In the present work based on the new method proposed by Gounaris et al. (1996) for crack detection through coupled response measurements, experiments were carried out on a cracked cantilever beam for eigenfrequencies, bending, and axial response measurements. It has been observed that the rate of change of direct response (bending) is much less at small cracks, while that of the coupled response (axial) changes substantially, which allows for diagnoses of smaller cracks. © 1998 by ASME.

Journal of Engineering for Gas Turbines and Power

Crack identification in a cantilever beam using coupled response measurements

In the present study a simple Laval rotor with a transverse crack is considered. The analysis assumes that the vibrations remain small in comparison to the sag of the rotor under its own weight. If a cracked shaft rotates slowly under the load of its own weight, then the crack will open and close once per revolution, i.e. it breathes. Considering a simple hinge model which is a very good model for small cracks with the breathing action of crack, the transient vibration response of a cracked rotor passing through its critical speed is analysed, as an attempt for crack detection and monitoring. Effects of different factors such as crack depth, unbalance eccentricity with phase and acceleration influencing vibration are investigated. © 1998 Elsevier Science Ltd. All rights reserved.