Vibration Characteristics of Slotted Shafts

Sekhar, A. S.; Srinivas, B.N.

doi:10.1006/jsvi.2001.3643

Cited by 10 publications

(4 citation statements)

References 12 publications

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“…First of all, the 1× amplitudes increase or decrease with the increase of the transverse slot depth in both directions whereas the critical speed of the rotor system always decreases, as illustrated in Figure 8(a). The effect of slots on the critical speed of slotted rotors is consistent with the results reported by Sekhar and Srinivas [22], Pennacchi et al [12], and Darpe et al [13] From the analysis of the 2× and 3× amplitudes in Figures 8(b) and (c), it is observed that the horizontal and vertical maximum amplitudes of the 2× and 3× orders growth gradually with the non-dimensional open crack depth at the 1 2 and 1 3 sub-critical resonant speeds, respectively. Moreover, increasing the transverse slot depth decreases the rotating speed where the 2× and 3× maximum amplitudes are observed (at one-half and one-third of the first critical speed respectively).…”

Section: Slotted Rotor 321 N× Amplitudessupporting

confidence: 91%

Experimental response and vibrational characteristics of a slotted rotor

Sinou

2009

Communications in Nonlinear Science and Numerical Simulation

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This paper proposes to perform experimental tests on the vibrational characteristics of a slotted rotor. Changes in the responses of the n× amplitudes are examined for small and deep slots that can be considered as open cracks. The evolutions of the orbital patterns and the 2× harmonic components near one-half of the first critical speed are investigated in details to propose an efficient indicator of the presence of slots in rotor: a special attention is given to both the comparison of the horizontal and vertical maximum amplitudes of the 2× harmonic components, and changes in the size of the inside loop of orbits when the rotor is passing through one-half of the first critical speed. A huge experimental work considering the influences of the slot depth and the orientation of unbalance relative to the slot direction is investigated in order to examine the possibility of detecting the presence of a transverse slot in rotors.

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Section: Slotted Rotor 321 N× Amplitudessupporting

confidence: 91%

Experimental response and vibrational characteristics of a slotted rotor

Sinou

2009

Communications in Nonlinear Science and Numerical Simulation

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“…The cause of reduction in critical speed is due to decreased bending stiffness and anisotropy generated due to the crack. The results described in the transient test are consistent with the results presented by Adewusi and Al-Bedoor (2001), Darpe et al (2004), Sekhar and Srinivas (2002) and Sinou (2009).…”

Section: Transient Response Analysissupporting

confidence: 90%

Testing for detection of crack in rotor using vibration analysis: an experimental approach

Shah

Vakharia

2019

IJQRM

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Purpose Many incidents of rotor failures are reported due to the development and propagation of the crack. Condition monitoring is adopted for the identification of symptoms of the crack at very early stage in the rotating machinery. Identification requires a reliable and accurate vibration analysis technique for achieving the objective of the study. The purpose of this paper is to detect the crack in the rotating machinery by measuring vibration parameters at different measurement locations. Design/methodology/approach Two different types of cracks were simulated in these experiments. Experiments were conducted using healthy shaft, crack simulated shaft and glued shaft with and without added unbalance to observe the changes in vibration pattern, magnitude and phase. Deviation in vibration response allows the identification of crack and its location. Initial data were acquired in the form of time waveform. Run-up and coast-down measurements were taken to find the critical speed. The wavelet packet energy analysis technique was used to get better localization in time and frequency zone. Findings The presence of crack changes the dynamic behavior of the rotor. 1× and 2× harmonic components for steady-state test and critical speed for transient test are important parameters in condition monitoring to detect the crack. To separate the 1× and 2× harmonic component in the different wavelet packets, original signal is decomposed in nine levels. Wavelet packet energy analysis is carried out to find the intensity of the signal due to simulated crack. Originality/value Original signals obtained from the experiment test set up may contain noise component and dominant frequency components other than the crack. Wavelet packets contain the crack-related information that are identified and separated in this study. This technique develops the condition monitoring procedure more specific about the type of the fault and accurate due to the separation of specific fault features in different wavelet packets. From the experiment end results, it is found that there is significant rise in a 2× energy component due to crack in the shaft. The intensity of a 1× energy component depends upon the shaft crack and unbalance orientation angle.

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“…The critical speed of the shaft always decreases because of the presence of the transverse crack. The effect of transverse crack on the critical speed of the cracked rotor is consistent with the results presented by Darpe et al (2004); Sekhar and Srinivas (2002); and Sinou (2009), while critical speed of inverted cracked shaft increases (Figure 4) which is reverse in the case of cracked shaft (Figure 5). The cause of reduction in the resonant…”

Section: Transient Response Analysissupporting

confidence: 87%

Online condition monitoring for detection of crack in the shaft using vibration analysis method

Shah

Vakharia

2018

ILT

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Purpose The purpose of this study is to identify the crack in the shaft at incipient stage. Transverse crack is the most common type of crack found on the periphery of the shaft. The changes in dynamic behaviour of the rotor at high speed are enormous. The reliable operation of the machinery is paramount for the safety of individual and plant. Condition-based maintenance monitors the mechanical and operational condition of the machine. During such inspection, if any unhealthy symptoms are detected, then affected part is identified and taken out for the maintenance at most appropriate time. Design/methodology/approach Simulating the transverse crack of different depth and location is the most challenging part of the experimental analysis. To optimize the total experimental cost for simulation of crack in the shaft, inverted crack is proposed to be produced in shaft and investigation shall be carried out for of early crack detection in shaft using vibration analysis. The set of experiments has been conducted on healthy shaft, inverted cracked shaft and actual cracked shaft. Inverted crack methodology provides flexibility of simulating crack of any size and at any location, and it can be reconfigured for several times to obtain various set of results. Findings To derive objective of the study, steady state response analysis and transient response analysis are performed on the experiment test rig. Vibration signals are acquired from the bearing locations to detect the crack. The paper addresses the influence of the inverted crack on critical speed of the shaft and deviation of first and second harmonic component of the shaft because of introduction of inverted crack. The resultant Nyquist plots, orbit plots and frequency plots are compared with the baseline data (obtained with the healthy shaft) to identify the crack. Originality/value The present study focuses on methodology by which inverted crack is developed in the healthy shaft, which resembles the behaviour of actual crack, and it shall be used to study the changes in rotor stiffness caused by transverse crack. The experimental results obtained using the inverted crack shaft have same vibration characteristics but in reverse direction as it would have occurred with the cracked shaft.

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Vibration Characteristics of Slotted Shafts

Cited by 10 publications

References 12 publications

Experimental response and vibrational characteristics of a slotted rotor

Experimental response and vibrational characteristics of a slotted rotor

Testing for detection of crack in rotor using vibration analysis: an experimental approach

Online condition monitoring for detection of crack in the shaft using vibration analysis method

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