Browsing by Author "Suherman, Surjani"

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    Response of a cracked rotating shaft with a disk during passage through a critical speed
    Suherman, Surjani (Virginia Tech, 1992)
    Non-stationary motion of a cracked rotating shaft with accelerating or decelerating angular velocity Ω through a critical speed is studied. The shaft has a breathing transverse crack and a disk. There are two parts, which are the investigation of flexural response, neglecting the torsional vibrations, and the investigation of flexural-torsional response. In both studies the longitudinal vibration and the influence of shear deformation are neglected. The boundary conditions of the supports are simply supported for the transverse displacements and fixed-free in relation to torsion (for the flexural-torsional response only). The transverse surface crack, which causes a geometric discontinuity, is replaced by generalized moments at the crack location. The equations of motion follow the formulation of Wauer. Galerkin’s method and numerical integration are used to obtain approximate solutions. The maximum responses are determined. The effects of the acceleration and deceleration rate and the different parameters of the breathing cracked rotating shaft, such as crack depth, crack location, disk location, disk eccentricity, disk eccentricity angle, and disk mass, are studied. The influence of internal damping, external damping, and torsional external damping are investigated. Comparisons with an open cracked rotating shaft and an uncracked rotating shaft are also presented. The influence of torsional deformation is analyzed. The results are presented in tables and figures.
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    Transient analysis and vibration suppression of a cracked rotating shaft with ideal and nonideal motor passing through a critical speed
    Suherman, Surjani (Virginia Tech, 1996)
    In the first part of this study, the dynamic behavior of a cracked rotating shaft with a rigid disk is analyzed, with an ideal and a nonideal motor, passing through its critical speed. The shaft contains a single transverse crack that is assumed to be either completely open or completely closed at any given time, depending on the curvature of the shaft at the cross section containing the crack. Flexible, damped supports and overhangs with a mass at one end are included. The supports are modeled with elastic springs and dashpots. The influence of gyroscopic moments of the disk (with an ideal motor) is investigated. For a nonideal motor, there is an interaction between the shaft and the motor. Eccentricity of the disk, gravitational forces, and internal and external damping are included. The equations of motion and boundary conditions are derived by Hamilton's Principle. To eliminate the spatial dependence, the Extended Galerkin Method is applied. Longitudinal vibration, shear deformation and torsional vibration are neglected. In the second part of this study, the vibration suppression of a cracked, simply supported, rotating shaft with a rigid disk is discussed, with an ideal and a nonideal motor, passing through the critical speed. The use of a flexible internal constraint is introduced to suppress the vibration. By activating this additional internal support, the shaft is prevented from passing its critical speed. Transient motions occur at the time of activation or deactivation of the constraint. The maximum displacement of the shaft during acceleration (run-up) or deceleration (coast-down) can be reduced significantly by appropriate application of this flexible internal support.