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Showing papers on "Bearing (mechanical) published in 2006"


Journal ArticleDOI
TL;DR: In this paper, an experimental investigation reported in this paper was centred on the application of the acoustic emission (AE) technique for identifying the presence and size of a defect on a radially loaded bearing.

403 citations


Book
09 Oct 2006
TL;DR: In this paper, the authors introduce the concept of rolling bearing and apply it to a variety of applications, including industrial, national, and international standards, such as interference fitting and clearance.
Abstract: ROLLING BEARING TYPES AND APPLICATIONS Introduction to Rolling Bearings Ball Bearings Roller Bearings Linear Motion Bearings Bearings for Special Applications Closure References ROLLING BEARING MACROGEOMETRY General Ball Bearings Spherical Roller Bearings Radial Cylindrical Roller Bearings Tapered Roller Bearings Closure References INTERFERENCE FITTING AND CLEARANCE General Industrial, National, and International Standards Effect of Interference Fitting on Clearance Press Force Differential Expansion Effect of Surface Finish Closure References BEARING LOADS AND SPEEDS General Concentrated Radial Loading Concentrated Radial and Moment Loading Shaft Speeds Distributed Load Systems Closure References BALL AND ROLLER LOADS DUE TO BEARING APPLIED LOADING General Ball-Raceway Loading Symmetrical Spherical Roller-Raceway Loading Tapered and Asymmetrical Spherical Roller-Raceway and Roller-Flange Loading Cylindrical Roller-Raceway Loading Closure CONTACT STRESS AND DEFORMATION General Theory of Elasticity Surface Stresses and Deformations Subsurface Stresses Effect of Surface Shear Stress Types of Contacts Roller End-Flange Contact Stress Closure References DISTRIBUTION OF INTERNAL LOADING IN STATICALLY LOADED BEARING General Load-Deflection Relationships Bearings under Radial Load Bearings under Thrust Load Bearings under Combined Radial and Thrust Load Closure References BEARING DEFLECTION AND PRELOADING General Deflections of Bearings with Rigidly Supported Rings Preloading Limiting Ball Bearing Thrust Load Closure References PERMANENT DEFORMATION AND BEARING STATIC CAPACITY General Calculation of Permanent Deformation Static Load Rating of Bearings Static Equivalent Load Fracture of Bearing Components Permissible Static Load Closure References KINEMATIC SPEEDS, FRICTION TORQUE, AND POWER LOSS General Cage Speed Rolling Element Speed Rolling Bearing Friction Rolling Bearing Friction Torque Bearing Power Loss Thermal Speed Ratings Closure References FATIGUE LIFE: BASIC THEORY AND RATING STANDARDS General Rolling Contact Fatigue Fatigue Life Dispersion Weibull Distribution Dynamic Capacity and Life of a Rolling Contact Fatigue Life of a Rolling Bearing Load Rating Standards Effect of Variable Loading on Fatigue Life Fatigue Life of Oscillating Bearings Reliability and Fatigue Life Closure References LUBRICANTS AND LUBRICATION TECHNIQUES General Types of Lubricants Liquid Lubricants Grease Solid Lubricants Lubricant Delivery Systems Seals Closure References STRUCTURAL MATERIALS OF BEARINGS General Rolling Bearing Steels Steel Manufacture Effects of Processing Methods on Steel Components Heat Treatment of Steel Materials for Special Bearings Cage Materials Seal Materials Tribological Coatings for Bearing Components Closure References VIBRATION, NOISE, AND CONDITION MONITORING General Vibration- and Noise-Sensitive Applications The Role of Bearings in Machine Vibration Measurement of Nonroundness and Vibration Detection of Failing Bearings in Machines Condition-Based Maintenance Closure References APPENDIX INDEX

327 citations


BookDOI
09 Oct 2006
TL;DR: For the last four decades, Tedric Harris' Rolling Bearing Analysis has been the "bible" for engineers involved in rolling bearing technology as mentioned in this paper, which is why so many students and practicing engineers rely on this book.
Abstract: For the last four decades, Tedric Harris' Rolling Bearing Analysis has been the "bible" for engineers involved in rolling bearing technology Why do so many students and practicing engineers rely on this book? The answer is simple: because of its complete coverage from low- to high-speed applications and full derivations of the underlying mathemati

314 citations


Journal ArticleDOI
TL;DR: The double concave friction pendulum (DCFP) bearing as mentioned in this paper is an adaptation of the single concave force pendulum bearing, which has the capacity to accommodate substantially larger displacements compared to a traditional FP bearing of identical plan dimensions.
Abstract: The double concave Friction Pendulum (DCFP) bearing is an adaptation of the well-known single concave Friction Pendulum bearing. The principal benefit of the DCFP bearing is its capacity to accommodate substantially larger displacements compared to a traditional FP bearing of identical plan dimensions. Moreover, there is the capability to use sliding surfaces with varying radii of curvature and coefficients of friction, offering the designer greater flexibility to optimize performance. This paper describes the principles of operation of the bearing and presents the development of the force–displacement relationship based on considerations of equilibrium. The theoretical force–displacement relationship is then verified through characterization testing of bearings with sliding surfaces having the same and then different radii of curvature and coefficients of friction. Lastly, some practical considerations for analysis and design of DCFP bearings are presented. Copyright © 2006 John Wiley & Sons, Ltd.

284 citations


Journal ArticleDOI
Abstract: This paper presents a practical approach to eliminating both bearing current and ground leakage current from an inverter-driven motor rated at 400 V and 3.7 kW. When the shaft voltage with respect to the motor frame exceeds the dielectric breakdown voltage of thin lubricating grease films in two metal bearings at the drive and non-drive ends, an electrical discharge machining (EDM) current flows through the bearings. A passive electromagnetic interference (EMI) filter can keep the shaft voltage in check, as a result of having eliminated high-frequency common-mode voltage from the motor terminals. Hence, no dielectric breakdown occurs in the grease films, so that no EDM current flows in the bearings. Experimental results verify the viability and effectiveness of the passive EMI filter designed in this paper

254 citations


Journal ArticleDOI
TL;DR: In this article, a theoretical model has been developed to obtain the vibration response due to a localized defect in various bearing elements in a rotor-bearing system under radial load conditions, and the results of vibration measurements on roller bearings with simulated local defects have also been presented to experimentally validate the theoretical model.
Abstract: In the present investigation, a theoretical model has been developed to obtain the vibration response due to a localized defect in various bearing elements in a rotor-bearing system under radial load conditions. The rotor-bearing system has been modeled as a three degrees-of-freedom system. The model predicts significant components at the harmonics of characteristic defect frequency for a defect on the particular bearing element. In the case of a defect on the inner race or a rolling element, the model predicts sidebands about the peaks at defect frequencies, at multiples of shaft and cage frequencies, respectively. The model has also predicted some additional components at harmonics of shaft and cage frequencies due to a local defect on the inner race and a rolling element, respectively. The expressions for all these spectral components have also been derived. Typical numerical results for an NJ 204 bearing have been obtained and plotted. The amplitude of the component at defect frequency, for an outer race defect, is found to be much higher as compared to those due to inner race defect or a rolling element defect of the same size and under similar conditions of load and speed. The results of vibration measurements on roller bearings with simulated local defects have also been presented to experimentally validate the theoretical model proposed. It can be observed from the results that the spectral components predicted by the theoretical model find significant presence in the experimental spectra. Comparison of the normalized analytical values of the spectral components with their experimental values shows fair agreement for most of the cases considered. Probable area of the generated excitation pulses has been calculated and the effects of pulse area variation on the experimental results have been studied.

127 citations


Journal ArticleDOI
TL;DR: In this paper, a method based on the finite element vibration analysis is presented for defect detection in rolling element bearings with single or multiple defects on different components of the bearing structure using the time and frequency domain parameters.

121 citations


Journal ArticleDOI
TL;DR: In this article, the effect of the recessed shape of the bearing on the performance analysis through numerical method was studied, and the results showed that the average loading capacity reduces as the following sequence: rectangular recessed bearing, spherical recessed and non-recessed bearing.

113 citations


Journal ArticleDOI
TL;DR: In this paper, a fault-signature model and a faultdetection scheme for using machine vibration to detect inner-race defects were developed, where the authors examined machine-vibration spectra for peaks with phase-coupled sidebands occurring at a spacing predicted by the model.
Abstract: This paper develops a fault-signature model and a fault-detection scheme for using machine vibration to detect inner-race defects. To motivate this research, it is explained and illustrated with experimental results why fault signatures from nonouter-race defects (e.g., inner-race defects) can be less salient than those from outer-race defects. Then, a signal model is presented for the production and propagation of an inner-race fault signature; this model is then used to design an inner-race fault-detection scheme. This scheme examines machine-vibration spectra for peaks with phase-coupled sidebands occurring at a spacing predicted by the model. The proficiency of this fault-detection scheme at detecting inner-race bearing faults is then experimentally verified with results from 12 bearings representing varying degrees of fault severity.

112 citations


Journal ArticleDOI
TL;DR: In this paper, a method of calculating the deformation characteristics of roller slewing bearings is presented, where the type and the parameters of the roller generator correction have the largest influence on the analysed deformation.

110 citations


Journal ArticleDOI
TL;DR: In this article, a low load bearing is constructed and the influence of surface roughness and the wetting properties of the surfaces on friction are investigated over a wide range of sliding speeds.
Abstract: In recent years it has been shown experimentally by a number of workers that simple, Newtonian liquids can slip against solid surfaces when the latter are both very smooth and lyophobic. It has also been shown theoretically how, based on a half-wetted bearing principle, this phenomenon may be used to significantly reduce friction in lubricated sliding contacts and thus make possible the hydrodynamic lubrication of very low load contacts. This paper describes the experimental validation of this concept. A low load bearing is constructed and the influence of surface roughness and the wetting properties of the surfaces on friction are investigated over a wide range of sliding speeds. It is shown that liquid slip can be used to considerably reduce friction in full film, hydrodynamic conditions.

Journal ArticleDOI
01 Feb 2006
TL;DR: In this article, it was shown that a simple parallel pad bearing containing a closed pocket can support load if it operates in an ambient pressure that is appreciably in excess of the cavitation pressure of the lubricating fluid.
Abstract: It is shown that a simple parallel pad bearing containing a closed pocket can support load if it operates in an ambient pressure that is appreciably in excess of the cavitation pressure of the lubricating fluid. This arises due to fluid flow driven by subambient pressures in the inlet region of the pad (‘inlet suction’).Maximum load capacity occurs when the pocket is located near the inlet to the bearing and under conditions such that cavitation is just provoked.

Patent
31 Oct 2006
TL;DR: A knee prosthetic system includes a femoral component, a fixed tibial bearing component, an integrated or common Tibial base component, and a mobile bearing component.
Abstract: A knee prosthetic system includes a femoral component, a fixed tibial bearing component, a mobile tibial bearing component and an integrated or common tibial base component. The same tibial base component can be used with either the fixed tibial bearing component or the mobile tibial bearing component. The fixed bearing component and tibial base component have mating anti-rotation features. One embodiment of the mobile bearing component does not engage the anti-rotation feature of the tibial base component. Another embodiment engages the anti-rotation feature to allow for limited rotation.

Patent
02 Nov 2006
TL;DR: In this paper, a thrust bearing assembly is described, which consists of a seat including a generally spherical surface at least partially defining a recess, and a bearing support is positioned within the recess.
Abstract: Thrust-bearing assemblies, and thrust-bearing apparatuses and downhole motors incorporating such thrust-bearing assemblies are disclosed. In one aspect of the present invention, a thrust-bearing assembly is disclosed. The thrust-bearing assembly comprises a seat including a generally spherical surface at least partially defining a recess. A bearing support is positioned within the recess. The bearing support includes a generally spherical surface configured so that the bearing support is capable of movement with the recess of the seat. At least one bearing element may be mounted to the bearing support. The thrust-bearing assembly further includes a motion-limiting structure configured to limit relative movement between the bearing support and the seat. The motion-limiting structure does not extend between the generally spherical surface of the seat and the generally spherical surface of the bearing support.

Journal ArticleDOI
TL;DR: In this article, a thermohydrodynamic model is developed for predicting the three-dimensional (3D) temperature field in an air-lubricated, compliant foil journal bearing, which accounts for the compressibility and the viscosity-temperature characteristic of air and the compliance of the bearing surface.
Abstract: A thermohydrodynamic model is developed for predicting the three-dimensional (3D) temperature field in an air-lubricated, compliant foil journal bearing. The model accounts for the compressibility and the viscosity-temperature characteristic of air and the compliance of the bearing surface. The results of numerical solutions are compared to published experimental measurements and reasonable agreement has been attained. Parametric studies covering a fairly wide range of operating speeds and load conditions were carried out to illustrate the usefulness of the model in terms of predicting the thermal performance of foil journal bearings.

Journal ArticleDOI
TL;DR: In this article, a model for investigating structural vibrations in rolling element bearings due to radial internal clearance is presented, where the contacts between rollers and races are treated as nonlinear springs and the springs act only in compression.

Patent
10 Nov 2006
TL;DR: In this article, an interbody distracter is inserted within the intervertebral space between adjacent vertebrae, the vertebra are distracted and are supported by the distracter.
Abstract: A method and a distracter for replacing a removed, intervertebral disc with a prosthesis. An inter-body distracter is inserted within the intervertebral space between adjacent vertebrae, the vertebrae are distracted and are supported by the distracter. A fluid, curable polymer is injected into the intervertebral space and around the distracter and then the polymer is cured to a semi-rigid, pliable, elastically deformable state. The distracter is then disabled from supporting compressive forces applied by the vertebrae and remains in place. The preferred distracter is a scissors jack having intermediate bearings joined by links to support feet. One of the bearings has a threaded lateral bore and the second bearing has a lateral bore. A rod extends through the bores and has a threaded portion extending from a first end of the rod and threadedly engaging the threaded bearing. The inside diameter of the second bore is greater than the outside diameter of the threaded portion of the rod so the rod is axially slidable through the second bore. A thrust bearing is fixed on the threaded rod and positioned laterally outwardly of the second bearing for forcing the second bearing laterally toward the first bearing upon rotation of the rod in one direction and for permitting the rod to be withdrawn from the bearing by rotating the rod in the opposite direction and disengaging it from the first bearing. Alternative distracters are also disclosed.

Proceedings ArticleDOI
24 Jul 2006
TL;DR: In this article, a physics-based model for bearing spall propagation is presented. But the model is not suitable for all bearing applications and it is readily adaptable to most bearing applications, and a reduced order version has also been developed which is efficient enough to run on board with little or no loss in accuracy.
Abstract: Diagnostic technologies for rolling element bearings are relatively well developed, but accurate prediction of remaining life once an incipient fault has been detected is considerably more difficult. This paper describes a comprehensive experimental study of bearing spall progression and a physics-based model being developed for bearing prognostics. The model computes the spall growth trajectory and time to failure based on operating conditions, and uses diagnostic feedback to self-adjust and reduce prediction uncertainty. The predictions compare very well to fault progression tests on both subscale bearings and full-scale turbine engine bearings. The experimental data has demonstrated that spall propagation is better behaved than once thought and can be predicted with high confidence. For turbine engine core thrust bearings with a typical mission mix, the prognostic window (first detection to failure) is on the order of 100 flight hours, which provides ample opportunity to plan future missions and maintenance activities with considerable safety margin. Since the model is physics-based, it is readily adaptable to most bearing applications, and a reduced order version has also been developed which is efficient enough to run on-board with little or no loss in accuracy.

Journal ArticleDOI
TL;DR: In this paper, a hydraulic axial piston motor with an annular orifice damper was investigated, where the effects of various geometric parameters (e.g., damping length, supporting length, and clearance between the piston and the cylinder bore) are reflected.

01 Jan 2006
TL;DR: In this paper, both linear and non-linear features are extracted using Multi-Scale Fractal Dimension (MFD), Mel frequency Cepstral Coefficients and kurtosis.
Abstract: . Most rotating-machine failures are often linked to bearing failures. Propercondition monitoring on bearings is therefore essential to reduce the duration of machinedown-times. This paper introduces feature extraction methodologies that can facilitateearly detection of bearing faults. The time-domain vibration signals of a rotating ma-chine with normal and defective bearings are processed for feature extraction. Both lin-ear and non-linear features are extracted using Multi-Scale Fractal Dimension (MFD),Mel frequency Cepstral Coefficients and kurtosis. The extracted features are then usedto classify faults using Gaussian Mixture Models (GMM) and hidden Markov Models(HMM). Results demonstrate that HMM outperforms GMM in classification of bearingfaults. However, the disadvantage of HMM is that it is computationally expensive totrain compared to GMM.Keywords: Multi-scale fractal dimension, Hidden Markov models, Gaussian mixturemodels 1. Introduction. Rotating machines are the most widely used components in variousindustrial applications ranging from system maintenance to process automation. Mostmachine failures are linked to bearing failures [1],whichoftenresultinlengthyindustrialdowntime that has economic consequences. Bearing faults induce high vibrations whichgenerate noise and lead to malfunctions in the rotating machinery. There is therefore ahigh demand for a cost effective and automated condition monitoring system that candetect faults as early as possible. The early identification of defects in a machine canreduce offline time, maintenance periods, avoid accidents and catastrophic break-down.An automated condition monitoring of bearings is necessary as manual checks may takean unacceptably long duration resulting in money losses. Vibration-based condition mon-itoring is the most popular approach and hasbeenusedextensivelyinvariousbearingcondition monitoring techniques [1, 2]. Vibrations can also be used to detect existence offaults such as mass imbalance, shaft misalignment and gear failures by simply comparingthe vibration signals of a machine operating in faulty conditions and in normal, un-faultedconditions. There are several causes of bearing failure such as incorrect design, acid corro-sion, poor lubrication and plastic deformation [3]. Damage in bearings is typically on therolling element, inner race or outer race[1]. The difficulty of fault detection in bearings

Journal ArticleDOI
TL;DR: In this paper, the authors evaluated the bearing capacity of shallow foundations on a bed of well-graded sand and found that the bearing stratum thickness is not infinite and that the presence of a hard layer within a certain depth below the foundation can significantly influence the unit load supported by the soil.
Abstract: Traditional bearing capacity theories for the ultimate capacity of shallow foundations assume that the thickness of the bearing stratum is infinite. The presence of a hard layer within a certain depth below the foundation can significantly influence the unit load supported by the soil. Therefore the original bearing capacity equations should be modified to account for this condition in determining the ultimate bearing capacity. In order to evaluate this phenomenon further, model square and circular footing tests were performed on a bed of well-graded sand. Test beds were prepared at three different relative densities corresponding to loose, medium, and dense conditions: Dr =24 , 57, and 87%, using five different sand layer thicknesses, H ; H∕B values of 0.5, 1, 2, 3, and 4, where B is the footing width. Results of the model scale footing tests show that the bearing capacity factor, Nγ , should be modified up to H∕B=3 , instead of H∕B=1 , as previously suggested. The footing shape factor, sγ , should accou...

Journal ArticleDOI
TL;DR: In this paper, the authors show that for a given cylindrical construction volume, an optimized repulsive bearing design with respect to a maximal radial stiffness can be found, independent of the aspect ratio of the bearing, but is determined by the width of the air gap between rotor and stator.
Abstract: Passive magnetic bearings are an attractive alternative to conventional ball bearings in applications where wear and tear must be minimal and cost or construction restrictions ban the use of active magnetic bearings. They also find applications as miniaturized high-speed bearings where no other low-friction solutions are available. We show that, for a given cylindrical construction volume, an optimized repulsive bearing design with respect to a maximal radial stiffness can be found. This optimal configuration is independent of the aspect ratio of the bearing, but is determined by the width of the air gap between rotor and stator. Our method can determine the optimal configuration for any bearing geometry. We develop a design for a miniaturized high-speed bearing as an example.

Patent
Jay Dittmer1
18 May 2006
TL;DR: In this paper, a self-balancing adjustable mounting system for a flat panel display is presented, where a display interface having a hollow, frusto-spherical shell portion is attached to the display.
Abstract: A self-balancing adjustable mounting system for a flat panel display. A display interface having a hollow, frusto-spherical shell portion is attached to the flat panel display. The display interface is received in a guide structure that has a bearing portion engaging the outer surface of the frusto-spherical shell, and a second bearing portion engaging the inner surface of the frusto-spherical shell. The frusto-spherical shell is guided between the first and second bearing portions so that the flat panel display and device interface are generally rotatable about the center of the radius of curvature of the semi-spherical shell. A friction adjustment mechanism enables selective adjustment of the amount of friction between the first and second bearing portions and the frusto-spherical shell so as to enable the flat panel display to be fixed in a position to inhibit undesired movement of the display due to contact or other cause.


Proceedings ArticleDOI
TL;DR: In this paper, a new foil gas bearing with spring bumps was constructed, analyzed, and tested, and load capacity, structural stiffness, and equivalent viscous damping were measured to demonstrate the feasibility of the new foil bearing.
Abstract: A new foil gas bearing with spring bumps was constructed, analyzed, and tested. The new foil gas bearing uses a series of compression springs as compliant underlying structures instead of corrugated bump foils. Experiments on the stiffness of the spring bumps show an excellent agreement with an analytical model developed for the spring bumps. Load capacity, structural stiffness, and equivalent viscous damping (and structural loss factor) were measured to demonstrate the feasibility of the new foil bearing. Orbit and coast-down simulations using the calculated stiffness and measured structural loss factor indicate that the damping of underlying structure can suppress the maximum peak at the critical speed very effectively but not the onset of hydrodynamic rotor-bearing instability. However, the damping plays an important role in suppressing the subsynchronous vibrations under limit cycles. The observation is believed to be true with any air foil bearings with different types of elastic foundations.

Journal ArticleDOI
TL;DR: A comparative study of four representative time-frequency analysis techniques commonly employed for non-stationary signal processing demonstrates that selecting appropriate signal processing technique can significantly affect defect identification and consequently, improve the reliability of bearing health monitoring.
Abstract: Signals generated by transient vibrations in rolling bearings due to structural defects are non-stationary in nature, and reflect upon the operation condition of the bearing. Consequently, effective processing of non-stationary signals is critical to bearing health monitoring. This paper presents a comparative study of four representative time-frequency analysis techniques commonly employed for non-stationary signal processing. The analytical framework of the short-time Fourier transform, wavelet transform, wavelet packet transform, and Hilbert-Huang transform are first presented. The effectiveness of each technique in detecting transient features from a time-varying signal is then examined, using an analytically formulated test signal. Subsequently, the performance of each technique is experimentally evaluated, using realistic vibration signals measured from a bearing test system. The results demonstrate that selecting appropriate signal processing technique can significantly affect defect identification and consequently, improve the reliability of bearing health monitoring.

Journal ArticleDOI
TL;DR: In this article, a finite element foil bearing model that incorporates radial and circumferential deflections of a corrugated sub-foil into the prediction of rotor dynamic coefficients is presented.
Abstract: A finite element foil bearing model that incorporates radial and circumferential deflections of a corrugated sub-foil into the prediction of rotor dynamic coefficients is presented. The corrugated sub-foil is treated as a continuous structure that supports the top-foil. Radial and circumferential deflections are coupled in the sub-foil model. The Coulomb friction between the top-foil, sub-foil, and the bearing shell is modeled as an equivalent viscous friction. The foil deflections, the film thickness, and gas pressure are then perturbed to calculate the rotor dynamic coefficients. The results are presented demonstrating the effects of frequency, orbit size, and friction coefficient on the rotor dynamic coefficients and the energy dissipation rate.

Journal ArticleDOI
TL;DR: In this article, a high-firequency (50 MHz) ultrasonic transducer is mounted on the static outer raceway of a bearing to measure the reflection coefficient of the lubricant in the "contact" ellipse between bearing components.
Abstract: A lubricant-film monitoring system for a conventional deep groove ball bearing (type 6016, shaft diameter 80 mm, ball diameter 12.7 mm) is described. A high-firequency (50 MHz) ultrasonic transducer is mounted on the static outer raceway of the bearing. The transducer is focused on the ball-raceway interface and used to measure the reflection coefficient of the lubricant in the "contact" ellipse between bearing components. The reflection coefficient characterizes the lubricant film and can be used to calculate its thickness. An accurate triggering system enables multiple reflection measurements to be made as each lubricated contact moves past the measurement location. Experiments are described in which bearings were deliberately caused to fail by the addition of acetone, water and sand to the lubricant. The ultrasonic reflection coefficient was monitored as a function of time as the failure occurred. Also monitored were the more standard parameters, temperature and vibration. The results indicate that the ultrasonic measurements are able to detect the failures before seizure. It is also observed that, when us,ed in parallel, these monitoring techniques offer the potential to diagnose the failure mechanism and hence improve predictions of remaining life.

Journal ArticleDOI
TL;DR: In this article, a method based on modal superposition and regularization technique is developed to identify moving loads on an elastically supported multi-span continuous bridge deck. But the method is limited to the case of a single bridge and the number of vibration modes used in the identification should exceed the highest frequency of the excitation forces.

Patent
Thomas Ganz1
14 Dec 2006
TL;DR: A bearing element for a rotary, earth boring drag bit effectively reduces an exposure of at least one adjacent cutting element by a readily predictable amount, as well as a depth-of-cut (DOC) of the cutter as discussed by the authors.
Abstract: A bearing element for a rotary, earth boring drag bit effectively reduces an exposure of at least one adjacent cutting element by a readily predictable amount, as well as a depth-of-cut (DOC) of the cutter. The bearing element has a substantially uniform thickness across substantially an entire area thereof. The bearing element also limits the amount of unit force applied to a formation so that the formation does not fail. The bearing element may prevent damage to cutters associated therewith, as well as possibly limit problems associated with bit balling, motor stalling and related drilling difficulties. Bits including the bearing elements, molds for forming the bearing elements and portions of bodies of bits that carry the bearing elements, methods for designing and fabricating the bearing elements and bits including the same, and methods for drilling subterranean formations are also disclosed.