Browsing by Subject "Vibration"
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Item Analysis of downhole drilling vibrations : case studies of Manifa and Karan fields in Saudi Arabia(2011-08) Alabdullatif, Ziad Abdullrahman; Gray, Kenneth E., Ph. D.; Florence, FredDownhole vibrations lead to downhole failures and decrease the rate of penetration (ROP). The bottom hole assembly (BHA) static and dynamic design is a key factor in optimizing drilling operations. The BHA should be designed to minimize the vibration levels in the axial, lateral, and torsional directions. This would be achieved by avoiding rotating the drillstring in the speeds that are nearby the natural frequency of BHA. The complexity associated with current BHA components requires using advanced computational tools that are capable of solving complex and time-consuming equations. Finite Element Analysis (FEA) is the most used technique in analyzing vibration behavior of the drillstring by mesh discretizing of a continuous body into small elements. This thesis will study the dynamic behavior of different BHA designs for Manifa and Karan fields of Saudi Aramco to optimize the drilling operations. The FEA software that will be used to conduct these studies is called Vibrascope™, which was developed by NOV. The software will determine the critical speeds of the drillstring that should be avoided to prevent resonance of the BHA, which will lead to severe downhole vibration.Item Computer algorithm to detect and predict machine faults using cloud-based vibration data(2015-05) Olivares Villamediana, Ignacio Javier; Fernandez, Benito R.; Bukowitz, DavidIn this research a machine fault detection and diagnostic algorithm is presented. The algorithm uses time wave-form acceleration data stored in a server for cloud computing to calculate RMS and Peak values from it and give information to the user for maintenance schedule. Detection algorithm analyses the change in time of the acceleration signals and establish urgency and severity of the studied machines. Furthermore, the diagnosis sub-system studies also the change in time of the signals in frequency domain to give a forecast of the possible existing fault by discarding faults throughout a predetermined decision table. Simulated and real cases are performed to show the efficiency and results of using the algorithm as well.Item Diagonal plus low rank approximation of matrices for solving modal frequency response problems(2010-12) Vargas, David Antonio; Bennighof, Jeffrey Kent, 1960-; Sirohi, JayantIf a structure is composed mainly of one material but contains a small amount of a second material, and if these two materials have significantly different levels of structural damping, this can increase the cost of solving the modal frequency response problem substantially. Even if the rank of the contribution to the finite element structural damping matrix from the second material is very low, the matrix becomes fully populated when transformed to the modal representation. As a result, the complex-valued modal matrix that represents the structure’s stiffness and structural damping is both full rank, because of the diagonal part contributed by the stiffness, and fully populated, because of off-diagonal imaginary terms contributed by the second material’s structural damping. Solving the modal frequency response problem at many frequencies requires either the factorization of a coefficient matrix at every frequency, or the solution of a complex symmetric eigenvalue problem associated with the modal stiffness/structural damping matrix. The cost of both of these approaches is proportional to the cube of the number of modes included in the analysis. This cost could be reduced greatly if the damping properties of the structure were handled carefully in modeling the structure, but in practical computation of the modal frequency response, the information that could potentially reduce the computational cost is often unavailable. This thesis explores the possibilities of obtaining a representation of the complex modal stiffness/structural damping matrix as a diagonal matrix plus a matrix of minimal rank. An algorithm for computing a “diagonal plus low rank” (DPLR) representation is developed, along with an iterative algorithm for using an inexact DPLR approximation in the solution of the modal frequency response problem. The behavior of these algorithms is investigated on several example problems.Item Dynamic Modelling for Automobile Acceleration Response and Ride Quality Over Rough Roadways(Council for Advanced Transportation Studies, 1974-12) Healey, Anthony J.; Smith, Craig C.; Stearman, Ronald O.; Nathman, EdwardCurrent interest in dynamics and vibration of ground transportation vehicles arises from the fact that excessive levels can lead to unsafe operation and give an uncomfortable ride to passengers. Current work by the U.S. Department of Transportation in high-speed tracked air-cushion and magnetically levitated vehicles centers around suspension design (both active and passive) for isolating guideway roughness effects from the main body of the vehicle. The work described herein arose from a need to evaluate vibration acceptance criteria for use in both vehicle systems design and guideway specification. This report deals with the first part of a study of automobile riding quality. Three different models of an intermediate sedan together with two different models for roadway roughness are compared. Roadway models compared are, first, a random input single track model with statistics governed by a power spectral density proportional to the square of the wavelength and, second, a model using a data sequence with a zero order hold where the data sequence is obtained from measured evaluation profiles of actual roadway sections. Frequency weighted rms acceleration responses are compared with serviceability indices of roadway test sections. It is concluded that the commonly used roadway model is inadequate and that more complete roadway information regarding statistics of right and left wheel tracks, together with a vehicle model including body roll motions, is necessary to predict ride quality. Use of the ISO Standard on Whole Body Vibration Tolerances as a basis of frequency weighting provides a good correlation with subjective response measured in terms of the roadway servicability index.Item Evaluating vehicular-induced vibrations of typical highway bridges for energy harvesting applications(2012-05) Reichenbach, Matthew Craig; Wood, Sharon L.; Helwig, Todd A.Highway bridges are vital links in any transportation network. Identifying the possible safety problems in the approximately 600,000 bridges across the U.S. is generally accomplished through labor-intensive, visual inspections. Wireless monitoring technology seeks to improve current practices by supplementing the visual inspections with real-time evaluation of bridges. To be economically feasible, wireless sensor networks should be able to (a) operate independent of the power grid, and (b) achieve a service life of at least ten years. Novel energy harvesting approaches have been investigated to fulfill these two criteria. In particular, the feasibility of a vibration energy harvester as a long-term power source was assessed. The goal of the research was to process measured acceleration data and analyze the vibrational response of typical highway bridges under truck loads. The effects of ambient temperature, truck traffic patterns, and harvester position on the power content of the vibrations were explored, as well as the effects of linear and nonlinear harvesters. This thesis presents the results of evaluating the response of five steel bridges in Texas and Oregon for energy harvesting applications.Item Harvesting wind energy using a galloping piezoelectric beam(2011-05) Mahadik, Rohan Ram; Sirohi, Jayant; Bennighof, JeffreyGalloping of structures such as transmission lines and bridges is a classical aeroelastic instability that has been considered as harmful and destructive. However, there exists potential to harness useful energy from this phenomenon. The study presented in this paper focuses on harvesting wind energy that is being transferred to a galloping beam. The beam has a rigid prismatic tip body. Triangular and D-section are the two kinds of cross section of the tip body that are studied, developed and tested. Piezoelectric sheets are bonded on the top and bottom surface of elastic portion of the beam. During galloping, vibrational motion is input to the system due to aerodynamic forces acting on the tip body. This motion is converted into electrical energy by the piezoelectric (PZT) sheets. A potential application for this device is to power wireless sensor networks on outdoor structures such as bridges and buildings. The relative importance of various parameters of the system such as wind speed, material properties of the beam, electrical load, beam natural frequency and aerodynamic geometry of the tip body is discussed. A model is developed to predict the dynamic response, voltage and power results. Experimental investigations are performed on a representative device in order to verify the accuracy of the model as well as to study the feasibility of the device. A maximum output power of 1.14 mW was measured at a wind velocity of 10.5 mph.Item A hybrid-stress finite element approach for stress and vibration analysis in linear anisotropic elasticity(1987) Mahadevan, L. (Lakshminarayanan); Oden, J. Tinsley (John Tinsley), 1936-A hybrid-stress finite element method is developed for accurate stress and vibration analysis of problems in linear anisotropic elasticity. A modified form of the Hellinger-Reissner principle is formulated for dynamic analysis and an algorithm for the determination of the anisotropic elastic and compliance constants from experimental data is developed. These schemes have been implemented in a finite element program for static and dynamic analysis of linear anisotropic two-dimensional elasticity problems. Specific numerical examples are considered to verify the accuracy of the hybrid-stress approach and compare it with that of the standard displacement method, especially for highly anisotropic materials. It is that the hybrid-stress approach gives significantly better results than the displacement method. Preliminary work on extensions of this method to three-dimensional elasticity is discussed, and the stress shape functions necessary for this extension are includedItem Measurement of roadway roughness and automobile ride acceleration spectra(Council for Advanced Transportation Studies, 1974-07) Healey, Anthony J.; Stearman, Ronald O.The present study is designed to support an overall program for the evaluation and establishment of ride quality criteria in transportation systems. This report, which is restricted to the automobile, outlines the procedures and equipment employed to measure, record, and analyze automotive vibrations and highway or roadway roughness. Detailed automobile vibration responses and corresponding roadway roughness have been measured and recorded here for 20 different roadway sections which are typical of those found in the Austin - Travis County, Texas, area. Our highway roughness models are also compared to some of the roughness models found in the literature.Item Passenger Response to Random Vibration in Transportation Vehicles: Literature Review(Council for Advanced Transportation Studies, 1975-06) Healey, Anthony J.The design concepts used to implement a computer simulation of a land use decision model are described. Sources delineated by a literature search are examined for the statements made ("source postulates") concerning the interactions of leaders of dominant and subdominant social groups when making land use decisions. Specific attention is paid to the role of leader personalities and the power of the social groups represented in the final decision outcome. Source postulates are rewritten in a symbolic logic notation, and a set of "rules of behavior" is derived. Consistency among source postulates and correct implication procedures in deriving rules can be checked via theorem-proving methodology. The second phase of design entails replacing symbolic logic statements with "fuzzy logic" statements and algorithms. The set of rules in either notation constitutes a model, and both notations are programmable.Item Prediction of Passenger Riding Comfort From Acceleration Data(Council for Advanced Transportation Studies, 1976-03) Smith, Craig C.; McGehee, David; Healy, Anthony J.Various methods for evaluating ride quality in automobiles are investigated by means of a field study involving two different automobiles, seventy eight different passengers, and eighteen different roadway sections. Passenger rating panels were used to obtain subjective evaluation of the various rides, and measured vibration spectra were compared on the basis of various evaluation techniques to determine their ability to predict the subjective ratings. Included in the evaluation criteria considered are the ISO (International Standards Organization) Standard, the UTACV (Urban Tracked Air Cushion Vehicle) Specification, and the Absorbed Power method of Lee and Pradko. Excellent correlation was found to exist between the subjective ride ratings and simple root mean square acceleration measurements at either the vehicle floorboard or passenger/seat interface. Equations were developed to predict the subjective ride rating from measured vibration spectra.