Scholars@Duke
Josiah D. Knight

Josiah D. Knight

Associate Professor of the Thomas Lord Department of Mechanical Engineering and Materials Science
Thomas Lord Department of Mechanical Engineering and Materials Science
jknight@duke.edu
175 Engineering Bldg, Box 90300, Durham, NC 27708-0300
175 Hudson Hall, Box 90300, Durham, NC 27708
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Selected Publications

Predicting critical speeds in various rotordynamics problems

Journal Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science · November 1, 2017 Rotating shafts often experience undesirable large-amplitude whirling oscillations associated with resonance at critical speeds. This paper further develops a nondestructive technique in which measured information about the growing nature of the response i ... Full text Cite

Predicting Critical Speeds in Rotordynamics: A New Method

Conference Journal of Physics: Conference Series · October 3, 2016 In rotordynamics, it is often important to be able to predict critical speeds. The passage through resonance is generally difficult to model. Rotating shafts with a disk are analyzed in this study, and experiments are conducted with one and two disks on a ... Full text Cite

A New Method for Predicting Critical Speeds in Rotordynamics

Journal Article Journal of Engineering for Gas Turbines and Power · February 1, 2016 The prediction of critical speeds of a rotating shaft is a crucial issue in a variety of industrial applications ranging from turbomachinery to disk storage systems. The modeling and analysis of rotordynamic systems is subject to a number of complications, ... Full text Cite

Resource policy. Wood energy in America.

Journal Article Science (New York, N.Y.) · March 2009 Full text Cite

Welcome from the technical program chair

Journal Article Proceedings of the ASME/STLE International Joint Tribology Conference, IJTC 2004 · December 1, 2004 Cite

Analysis and observation of cavities in a journal bearing considering flow continuity

Journal Article Tribology Transactions · 2001 Steady-state cavities in a journal bearing are analyzed in two contexts: first, an approximate thermohydrodynamic theory developed earlier is applied to additional cases, and comparisons are made between temperatures predicted by the theory and measured te ... Cite

Nonlinear dynamic simulation of an active magnetic bearing system with non-symmetric coordinate coupling forces

Conference American Society of Mechanical Engineers (Paper) · December 1, 1997 Equations of motion are presented for a two degree of freedom system representing a rotor suspended with an active magnetic bearing. The rotor is subjected to both a rotating unbalance force and a steady load, which is balanced by differential bias in the ... Cite

Nonlinear dynamic simulation of an active magnetic bearing system with non-symmetric coordinate coupling forces

Journal Article Proceedings of the ASME Turbo Expo · January 1, 1997 Equations of motion are presented for a two degree of freedom system representing a rotor suspended with an active magnetic bearing. The rotor is subjected to both a rotating unbalance force and a steady load, which is balanced by differential bias in the ... Full text Cite

Nonlinear behavior of a magnetic bearing system

Journal Article Trans. ASME, J. Eng. Gas Turbines Power (USA) · 1995 This paper describes the results of a study into the dynamic behavior of a magnetic bearing system. The research focuses attention on the influence of nonlinearities on the forced response of a two-degree-of-freedom rotating mass suspended by magnetic bear ... Cite

Nonlinear behavior of a magnetic bearing system

Journal Article American Society of Mechanical Engineers (Paper) · January 1, 1994 This paper describes the results of a study into the dynamic behavior of a magnetic bearing system. The research focuses attention on the influence of nonlinearities on the forced response of a two-degree-of-freedom rotating mass suspended by magnetic bear ... Cite

Nonlinear behavior of a magnetic bearing system

Journal Article Proceedings of the ASME Turbo Expo · January 1, 1994 This paper describes the results of a study into the dynamic behavior of a magnetic bearing system. The research focuses attention on the influence of nonlinearities on the forced response of a two-degree-of-freedom rotating mass suspended by magnetic bear ... Full text Cite

Effects of modified effective length models of the rupture zone on the analysis of a fluid journal bearing

Journal Article Tribology Transactions · January 1, 1992 Two versions of a model for the thermal behavior of the lubricant film in the cavitation region of a journal bearing are presented and incorporated into a solution algorithm for the operating characteristics of an axially grooved bearing. The model is base ... Full text Cite

Determination of forces in a magnetic bearing actuator: Numerical computation with comparison to experiment computation with comparison to experiment

Journal Article Journal of Tribology, Transactions of the ASME · 1992 Calculations of the forces exerted on a journal by a magnetic bearing actuator are presented, along with comparisons to experimentally measured forces. The calculations are based on two-dimensional solutions for the flux distribution in the metal parts and ... Cite

Observation and prediction of cavities in a lubricant between non-parallel disks in relative rotation

Journal Article Tribology Transactions · January 1, 1992 Observed and predicted cavity shapes in a lubricant between two disks are presented. The geometry is similar to that of a thrust bearing or a face seal having non-parallel rotating surfaces. Photographs of cavitated regions are shown and compared with pred ... Full text Cite

Performance characteristics of shrouded Rayleigh-step and spiral groove viscous pumps

Journal Article Journal of Tribology, Transactions of the ASME · 1992 In this paper the optimum geometrical configurations of a shrouded Rayleigh-step and a spiral groove viscous pump are analyzed. Then their performance characteristics are compared. The geometries and film shapes of these viscous pumps are optimized with re ... Cite

Performance characteristics of shrouded Rayleigh-step and spiral groove viscous pumps

Journal Article American Society of Mechanical Engineers (Paper) · December 1, 1991 In this paper the optimum geometrical configurations of a shrouded Rayleigh-step and a spiral groove viscous pump are analyzed. Then their performance characteristics are compared. The geometries and film shapes of these viscous pumps are optimized with re ... Cite

Prediction of temperatures in tilting pad journal bearings

Journal Article Tribology Transactions · January 1, 1990 A solution technique for tilting pad journal bearings is presented that includes two dimensional heat conduction in the individual pads and applies a heat convection boundary condition to the pad ends. The method makes use of approximations to the axial pr ... Full text Cite

Predicting critical speeds in various rotordynamics problems

Journal Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science · November 1, 2017 Rotating shafts often experience undesirable large-amplitude whirling oscillations associated with resonance at critical speeds. This paper further develops a nondestructive technique in which measured information about the growing nature of the response i ... Full text Cite

Predicting Critical Speeds in Rotordynamics: A New Method

Conference Journal of Physics: Conference Series · October 3, 2016 In rotordynamics, it is often important to be able to predict critical speeds. The passage through resonance is generally difficult to model. Rotating shafts with a disk are analyzed in this study, and experiments are conducted with one and two disks on a ... Full text Cite

A New Method for Predicting Critical Speeds in Rotordynamics

Journal Article Journal of Engineering for Gas Turbines and Power · February 1, 2016 The prediction of critical speeds of a rotating shaft is a crucial issue in a variety of industrial applications ranging from turbomachinery to disk storage systems. The modeling and analysis of rotordynamic systems is subject to a number of complications, ... Full text Cite

Resource policy. Wood energy in America.

Journal Article Science (New York, N.Y.) · March 2009 Full text Cite

Welcome from the technical program chair

Journal Article Proceedings of the ASME/STLE International Joint Tribology Conference, IJTC 2004 · December 1, 2004 Cite

Analysis and observation of cavities in a journal bearing considering flow continuity

Journal Article Tribology Transactions · 2001 Steady-state cavities in a journal bearing are analyzed in two contexts: first, an approximate thermohydrodynamic theory developed earlier is applied to additional cases, and comparisons are made between temperatures predicted by the theory and measured te ... Cite

Nonlinear dynamic simulation of an active magnetic bearing system with non-symmetric coordinate coupling forces

Conference American Society of Mechanical Engineers (Paper) · December 1, 1997 Equations of motion are presented for a two degree of freedom system representing a rotor suspended with an active magnetic bearing. The rotor is subjected to both a rotating unbalance force and a steady load, which is balanced by differential bias in the ... Cite

Nonlinear dynamic simulation of an active magnetic bearing system with non-symmetric coordinate coupling forces

Journal Article Proceedings of the ASME Turbo Expo · January 1, 1997 Equations of motion are presented for a two degree of freedom system representing a rotor suspended with an active magnetic bearing. The rotor is subjected to both a rotating unbalance force and a steady load, which is balanced by differential bias in the ... Full text Cite

Nonlinear behavior of a magnetic bearing system

Journal Article Trans. ASME, J. Eng. Gas Turbines Power (USA) · 1995 This paper describes the results of a study into the dynamic behavior of a magnetic bearing system. The research focuses attention on the influence of nonlinearities on the forced response of a two-degree-of-freedom rotating mass suspended by magnetic bear ... Cite

Nonlinear behavior of a magnetic bearing system

Journal Article American Society of Mechanical Engineers (Paper) · January 1, 1994 This paper describes the results of a study into the dynamic behavior of a magnetic bearing system. The research focuses attention on the influence of nonlinearities on the forced response of a two-degree-of-freedom rotating mass suspended by magnetic bear ... Cite

Nonlinear behavior of a magnetic bearing system

Journal Article Proceedings of the ASME Turbo Expo · January 1, 1994 This paper describes the results of a study into the dynamic behavior of a magnetic bearing system. The research focuses attention on the influence of nonlinearities on the forced response of a two-degree-of-freedom rotating mass suspended by magnetic bear ... Full text Cite

Effects of modified effective length models of the rupture zone on the analysis of a fluid journal bearing

Journal Article Tribology Transactions · January 1, 1992 Two versions of a model for the thermal behavior of the lubricant film in the cavitation region of a journal bearing are presented and incorporated into a solution algorithm for the operating characteristics of an axially grooved bearing. The model is base ... Full text Cite

Determination of forces in a magnetic bearing actuator: Numerical computation with comparison to experiment computation with comparison to experiment

Journal Article Journal of Tribology, Transactions of the ASME · 1992 Calculations of the forces exerted on a journal by a magnetic bearing actuator are presented, along with comparisons to experimentally measured forces. The calculations are based on two-dimensional solutions for the flux distribution in the metal parts and ... Cite

Observation and prediction of cavities in a lubricant between non-parallel disks in relative rotation

Journal Article Tribology Transactions · January 1, 1992 Observed and predicted cavity shapes in a lubricant between two disks are presented. The geometry is similar to that of a thrust bearing or a face seal having non-parallel rotating surfaces. Photographs of cavitated regions are shown and compared with pred ... Full text Cite

Performance characteristics of shrouded Rayleigh-step and spiral groove viscous pumps

Journal Article Journal of Tribology, Transactions of the ASME · 1992 In this paper the optimum geometrical configurations of a shrouded Rayleigh-step and a spiral groove viscous pump are analyzed. Then their performance characteristics are compared. The geometries and film shapes of these viscous pumps are optimized with re ... Cite

Performance characteristics of shrouded Rayleigh-step and spiral groove viscous pumps

Journal Article American Society of Mechanical Engineers (Paper) · December 1, 1991 In this paper the optimum geometrical configurations of a shrouded Rayleigh-step and a spiral groove viscous pump are analyzed. Then their performance characteristics are compared. The geometries and film shapes of these viscous pumps are optimized with re ... Cite

Prediction of temperatures in tilting pad journal bearings

Journal Article Tribology Transactions · January 1, 1990 A solution technique for tilting pad journal bearings is presented that includes two dimensional heat conduction in the individual pads and applies a heat convection boundary condition to the pad ends. The method makes use of approximations to the axial pr ... Full text Cite

Effects of two film rupture models on the thermal analysis of a journal bearing

Journal Article Journal of Tribology, Transactions of the ASME · 1990 A model for the thermal behavior of lubricant in the cavitated regions of a journal bearing is presented. The model assumes a bubbly mixture of liquid and air and includes the calculation of local mixture properties for the fluid film. Temperature in the f ... Cite

Effects of two film rupture models on the thermal analysis of a journal bearing

Journal Article American Society of Mechanical Engineers (Paper) · December 1, 1989 A model for the thermal behavior of lubricant in the cavitated regions of a journal bearing is presented. The model assumes a bubbly mixture of liquid and air and includes the calculation of local mixture properties of the fluid film. Temperature in the fi ... Cite

Experiments and stability predictions of two sets of tilting pad bearings on an overhung rotor

Journal Article Tribology Transactions · January 1, 1988 An overhung rotor was experimentally tested in two sets of five shoe tilting pad bearings. The preload factors of the two sets were 0.1 and 0.5, respectively. The rotor had critical speeds at 3000 and 6800 rpm. When mounted on the first set of bearings, th ... Full text Cite

ANALYSIS OF TILTING PAD JOURNAL BEARINGS WITH HEAT TRANSFER EFFECTS.

Journal Article Journal of Tribology, Transactions of the ASME · 1988 An approximate solution technique for tilting pad journal bearings is presented. The method makes use of approximations to the axial pressure profile and the temperature profiles and includes heat transfer between the film and its boundaries. A second orde ... Cite

Experiments and stability predictions of two sets of tilting pad bearings on an overhung rotor.

Journal Article STLE TRIBOLOGY TRANS. · 1988 An overhung motor with critical speeds of 3000 and 6800 rpm was experimentally tested in two sets of five shoe tilting pad bearings with preload factors of 0.1 and 0.5 respectively. Mounted on the first set the rotor remained stable to over 11,000 rpm but ... Cite

Analysis of tilting pad journal bearings with heat transfer effects.

Journal Article · January 1, 1987 An approximate solution technique for tilting pad journal bearings is presented. The method makes use of approximations to the axial pressure profile and the temperature profiles and includes heat transfer between the film and its boundaries. A second orde ... Cite

ANALYSIS OF AXIALLY GROOVED JOURNAL BEARINGS WITH HEAT TRANSFER EFFECTS.

Journal Article ASLE Transactions · 1987 An approximate solution technique for axially grooved fluid film journal bearings is presented. The method makes use of earlier approximations for the axial pressure distribution and the circumferential temperature variation and extends the theory to inclu ... Cite

Analysis of axially grooved journal bearings with heat transfer effects

Journal Article ASLE Transactions · January 1, 1987 An approximate solution technique for axially grooved fluid film journal bearings is presented. The method makes use of earlier approximations for the axial pressure distribution and the circumferential temperature variation and extends the theory to inclu ... Full text Cite

Analysis of tilting pad journal bearings with heat transfer effects.

Journal Article · January 1, 1987 An approximate solution technique for tilting pad journal bearings is presented. The method makes use of approximations to the axial pressure profile and the temperature profiles and includes heat transfer between the film and its boundaries. A second orde ... Cite

ANALYSIS OF AXIALLY GROOVED JOURNAL BEARINGS WITH HEAT TRANSFER EFFECTS.

Journal Article ASLE Preprints · December 1, 1986 An approximate solutions technique for axially grooved fluid film journal bearings is presented. The method makes use of earlier approximations for the axial pressure distribution and the circumferential temperature variation and extends the theory to incl ... Cite

The effects of supply pressure on the operating characteristics of two-axial-groove journal bearings

Journal Article ASLE Transactions · January 1, 1985 The effects of variations in lubricant supply pressure on the characteristics of two-lobe non-preloaded bearings are examined. The bearing solutions are obtained by an approximate method developed earlier that includes viscosity variation due to thermal ef ... Full text Cite

ROTOR DYNAMIC ANALYSIS OF A NUCLEAR HEAT TRANSPORT PUMP UNDER NORMAL AND PART VOID CONDITIONS.

Journal Article I Mech E Conference Publications (Institution of Mechanical Engineers) · December 1, 1984 The model includes the motor, coupling, pump, casing and external supports with the associated bearings. Predicted forces on the impeller are obtained from scaled test results for somewhat similar impellers. Two types of analysis are considered: vibration ... Cite

Rotor dynamic analysis of nuclear heat transport pump under normal and part void conditions.

Journal Article · January 1, 1984 A rotor dynamic analysis of a heat transport pump for nuclear power applications is carried out for normal, part void and full operating conditions. The model includes the motor, coupling, pump, casing and external supports with the associated bearings. Pr ... Cite

Rotor dynamic analysis of nuclear heat transport pump under normal and part void conditions.

Journal Article · January 1, 1984 A rotor dynamic analysis of a heat transport pump for nuclear power applications is carried out for normal, part void and full operating conditions. The model includes the motor, coupling, pump, casing and external supports with the associated bearings. Pr ... Cite

Active Vibration Control of a Single Mass Rotor on Flexible Supports

Journal Article Journal of the Franklin Institute · January 1, 1983 This paper considers vibration control of a single mass flexible rotor on damped flexible supports with active feedback control. Both proportional and derivative feedback control are utilized. Free vibrations and unbalance response of the rotor-control sys ... Full text Cite

An approximate solution technique for multilobe journal bearings including thermal effects, with comparison to experiment

Journal Article ASLE Transactions · January 1, 1983 An approximate solution method for multilobe journal bearings that includes thermal effect is presented. The method is based on the assumption of an axial pressure distribution in the form of a polynomial, which allows the solution of Reynolds' equation by ... Full text Cite

APPROXIMATE SOLUTION TECHNIQUE FOR MULTILOBE JOURNAL BEARINGS INCLUDING THERMAL EFFECTS, WITH COMPARISON TO EXPERIMENT.

Journal Article ASLE Preprints · December 1, 1982 An approximate solution method for multilobe journal bearings that includes thermal effects is presented. The method is based on the assumption of an axial pressure distribution in the form of a polynomial, which allows the solution of Reynolds' equation b ... Cite