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You searched for +publisher:"Georgia Tech" +contributor:("Miller, Brad"). Showing records 1 – 2 of 2 total matches.

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Georgia Tech

1. Varney, Philip. Analysis of simultaneous rotordynamic faults using coupled mechanical face seal vibration.

Degree: PhD, Mechanical Engineering, 2016, Georgia Tech

Rotating machines are inherently vulnerable to many different faults; detecting these faults in real time can reduce costs and improve safety. A prerequisite for a successful condition monitoring system is an accurate characterization of the system and associated faults. Furthermore, the pursuit to increase efficiency has heightened susceptibility to coexisting fault situations; comprehensive condition monitoring systems should consider the possibility of multiple simultaneous faults. Previous studies have primarily considered the rotor and associated triboelements (e.g., mechanical face seals) as separate machine components. This work hypothesizes that rotor vibration transmitted to the mechanical face seal could serve as a convenient surrogate for analyzing rotor fault signatures. A comprehensive dynamic model is developed to study the dynamics of a mechanical face seal with two flexibly mounted elements, including axial, eccentric, and angular degrees-of-freedom. In addition, and for the first time, the model developed herein includes coupled rotordynamics, inertial maneuver loads, and transient dynamic excitation (i.e., start-up and shut-down). The faults investigated here include intermittent rotor-housing contact, a breathing shaft crack, and seal face contact. A novel model for intermittent contact is developed using a realistic surface roughness model founded on elastoplastic asperity contact. Exhaustive simulation is then used to identify and characterize hallmark dynamic fault signatures. Finally, the multiple fault scenario is studied using a synthesis of stationary and non-stationary signal processing techniques. Advisors/Committee Members: Green, Itzhak (advisor), Ferri, Aldo (committee member), Leamy, Michael (committee member), Streator, Jeffrey (committee member), Miller, Brad (committee member).

Subjects/Keywords: Rotordynamics; Tribology; Mechanical seals; Vibration monitoring; Dynamics; Vibrations

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Varney, P. (2016). Analysis of simultaneous rotordynamic faults using coupled mechanical face seal vibration. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/56320

Chicago Manual of Style (16th Edition):

Varney, Philip. “Analysis of simultaneous rotordynamic faults using coupled mechanical face seal vibration.” 2016. Doctoral Dissertation, Georgia Tech. Accessed November 13, 2019. http://hdl.handle.net/1853/56320.

MLA Handbook (7th Edition):

Varney, Philip. “Analysis of simultaneous rotordynamic faults using coupled mechanical face seal vibration.” 2016. Web. 13 Nov 2019.

Vancouver:

Varney P. Analysis of simultaneous rotordynamic faults using coupled mechanical face seal vibration. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2019 Nov 13]. Available from: http://hdl.handle.net/1853/56320.

Council of Science Editors:

Varney P. Analysis of simultaneous rotordynamic faults using coupled mechanical face seal vibration. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/56320

2. Varney, Philip A. Transverse fatigue crack diagnosis in a rotordynamic system using vibration monitoring.

Degree: MS, Mechanical Engineering, 2013, Georgia Tech

To increase efficiency, shafts are made lighter and more flexible, and are designed to rotate faster to increase the system's power-to-weight ratio. The demand for higher efficiency in rotordynamic systems has led to increased susceptibility to transverse fatigue cracking of the shaft. Shaft cracks are often detected and repaired during scheduled periods of off-line maintenance. Off-line maintenance can be expensive and time consuming; on-line condition monitoring allows maintenance to be performed as-needed. However, inadequate (or a lack of) monitoring can allow rapidly propagating cracks to result in catastrophic shaft failure. It is therefore imperative to develop on-line condition monitoring techniques to detect a crack and diagnose its severity. A particularly useful method for transverse shaft crack detection/diagnosis is vibration monitoring. Detection, and especially diagnosis, of transverse fatigue cracks in rotordynamic systems has proven difficult. Whereas detection assesses only the presence of a crack, diagnosis estimates important crack parameters, such as crack depth and location. Diagnosis can provide the operator with quantitative information to assess further machinery operation. Furthermore, diagnosis provides initial conditions and predictive parameters on which to base prognostic calculations. There is a two-fold challenge for on-line diagnosis of transverse fatigue crack parameters. First, crack characterization involves specifying two important parameters: the crack's depth and location. Second, the nature of rotating machinery permits response measurement at only specific locations. Cracks are typically categorized as breathing or gaping; breathing cracks open and close with shaft rotation, while gaping cracks remain open. This work concerns the diagnosis of gaping crack parameters; the goal is to provide metrics to diagnose a crack's depth and location. To this end, a comprehensive approach is presented for modeling an overhung cracked shaft. Two linear gaping crack models are developed: a notch and a gaping fatigue crack. The notch model best approximates experimentally manufactured cracks, whereas the gaping fatigue crack model is likely more suited for real fatigue cracks. Crack diagnosis routines are established using free and forced response characteristics. Equations of motion are derived for both crack models, including excitation due to gravity and imbalance. Transfer matrix techniques are established to expediently obtain the steady-state system response. A novel transfer matrix technique, the Complex Transfer Matrix, is developed to distinguish forward and backward whirl components. The rotor's angular response is primarily employed in this work for crack detection and diagnosis. The overhung shaft induces an increased sensitivity to variations in crack depth and location. In addition, an available overhung rotordynamic experimental test rig allows for comparison of the current analytic results to previously obtained experimental results. Under the… Advisors/Committee Members: Green, Itzhak (Committee Chair), Ferri, Aldo (Committee Member), Leamy, Michael (Committee Member), Miller, Brad (Committee Member).

Subjects/Keywords: Diagnostics; Condition monitoring; Crack detection; Dynamics; Vibration monitoring; Rotordynamics; Structural health monitoring; Vibration; Rotors Dynamics; Rotors Fatigue

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Varney, P. A. (2013). Transverse fatigue crack diagnosis in a rotordynamic system using vibration monitoring. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/47655

Chicago Manual of Style (16th Edition):

Varney, Philip A. “Transverse fatigue crack diagnosis in a rotordynamic system using vibration monitoring.” 2013. Masters Thesis, Georgia Tech. Accessed November 13, 2019. http://hdl.handle.net/1853/47655.

MLA Handbook (7th Edition):

Varney, Philip A. “Transverse fatigue crack diagnosis in a rotordynamic system using vibration monitoring.” 2013. Web. 13 Nov 2019.

Vancouver:

Varney PA. Transverse fatigue crack diagnosis in a rotordynamic system using vibration monitoring. [Internet] [Masters thesis]. Georgia Tech; 2013. [cited 2019 Nov 13]. Available from: http://hdl.handle.net/1853/47655.

Council of Science Editors:

Varney PA. Transverse fatigue crack diagnosis in a rotordynamic system using vibration monitoring. [Masters Thesis]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/47655

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