bluuebunny/crossref_metadata_2025 huggingface dataset:
Signature Analysis for Mechanical Systems via Dynamic Data System (DDS) Monitoring Technique
Authors: Wu S. M. , Tobin T. H. , Chow M. C.
Published: January 2010

A new modeling technique called Dynamic Data System (DDS) is introduced for signature analysis. A one-horsepower electric motor experiment is used to demonstrate the methodology. The ‘normal’ operation is simulated by idling runs and eccentric loads representing the ‘defective’ operations. A DDS Monitoring Technique, by employing statistical quality control theory, is developed to monitor the operations of imposed electric motor defects. It takes thirteen seconds for data processing and calculation of a control variable value from an On-line programmed microprocessor to provide the control justification. The DDS Monitoring Technique proves to be effective and sensitive in identifying the operational status of a mechanical system.
Loads Moving on Beam Supported by Layered Elastic Foundation
Authors: Shah V. N. , Cook R. D. , Huang T. C.
Published: January 2010

A finite element method is applied to analyze the dynamic response of a beam supported by layered inertial foundation and subjected to moving loads. The foundation is represented by the modified Pasternak model or by the Winkler model. The moving loads are simulated by a concentrated force, a point-mass or a spring-mass-damper system. The equations of motion are represented by a system of second-order ordinary differential equations with variable coefficients. Newmark’s method of constant average acceleration is used to integrate these equations. Two test cases are analyzed for numerical illustration. In the first case, the dynamic response of a beam supported by the modified Pasternak model and subjected to a moving concentrated force is analyzed. In the second, the dynamic response of a beam supported by the Winkler model and subjected to a moving spring-mass-damper system is analyzed. The results from these two cases are compared with those obtained by the transfer matrix method.
The Analysis of an Elastic Four-Bar Linkage on a Vibrating Foundation Using a Variational Method
Authors: Thompson B. S.
Published: January 2010

A variational method is employed to derive the equations of motion and the associated boundary conditions for a flexible crank-rocker linkage sited on a foundation which vibrates perpendicular to the plane of the mechanism. The links oscillate in axial, flexural and torsional modes, and the equations governing this behavior are systematically constructed using a variational theorem by permitting independent variations of the stress, strain, displacement and velocity parameters.
Application of Impact Damping to Rotary Printing Equipment
Authors: Skipor E. , Bain L. J.
Published: January 2010

This paper describes the theoretical and experimental work leading to the application of an impact damper to the image carrying cylinder of a web-fed printing press. The need for such a device arises from the desire to overcome a traditional limit on the operating speed of a press of this kind. This limit is the onset of an unacceptable anomaly in the finished print known as streaking. Streaking is caused by vibratory bending of the image carrying cylinders in a direction perpendicular to their axis of rotation. The selection of design parameters for an impact damper intended to reduce these vibrations was the objective of the study reported herein.
Experimental-Theoretical Comparison of Instability Onset Speeds for a Three Mass Rotor Supported by Step Journal Bearings
Authors: Nicholas J. C. , Barrett L. E. , Leader M. E.
Published: January 2010

Theoretically predicted instability onset speeds are compared to the experimental instability threshold speeds for a simple three mass flexible rotor supported by five geometrically different sets of step journal bearings and a set of two axial groove bearings. The near optimum step bearing designs increase the instability onset speed by around 109 percent in one case and 41 percent in another compared to two axial groove bearings. The off optimum designs increase the instability speed by 18, 30 and 35 percent. The theoretical stability analysis predicts the general trends in the experimental data.
Stability Analysis of Rotor-Bearing Systems Using Component Mode Synthesis
Authors: Glasgow D. A. , Nelson H. D.
Published: January 2010

A method of component mode synthesis is presented for the analysis of multishaft rotor-bearings systems. The motion of each component of the system is described as the superposition of constraint modes associated with boundary coordinates and constrained precessional modes associated with internal coordinates. The constrained precessional modes for each component are truncated and the reduced component equations are assembled to yield a set of system equations. The nonsymmetric nature of the general problem requires the utilization of biorthogonality relations between right and left vector sets in order to decouple the component precessional modes. The method is developed for damped whirl speed/stability analysis and comparative results are presented for various levels of mode truncation for two example systems.
Regional Monotonicity in Optimum Design
Authors: Papalambros P. , Wilde D. J.
Published: January 2010

Regional monotonicity is introduced to identify dominant constraints and simplify non-monotonic expressions in optimum design problems. The technique is applied to obtain a simple solution for the design of an explosive-actuated cylinder, a problem formulated and solved by various methods in the literature. The concept of regional monotonicity provides an extension to the method of monotonicity analysis. Computational work is reduced to a simple plotting over a narrow interval. The design rules developed assist in quick parametric analysis.
A Review of Ski Safety Technology
Authors: Roberts C. C.
Published: January 2010

Due to better ski equipment, instruction, slope management and increased safety awareness on the part of the skiing public, ski injuries appear to be declining. Ski equipment is incorporating computerized design procedures along with possible applications of microprocessor controlled hardware. Ski instruction has graduated from the maneuver oriented to skills development methods. Biomechanics researchers have obtained experimental loading data during skiing and are utilizing finite element methods to model the skier. Infrared thermography is being utilized on ski clothing design, environmental safety and rescue. Standards are being developed to assure consistent terminology, compatibility between ski equipment, and safety.
On The Design of Ductile Elastic Annular Diaphragms
Authors: Na T. Y. , Kurajian G. M.
Published: January 2010

This paper provides the designer with design formulations, tables and curve plots which may be employed in the design of uniformly loaded, ductile, elastic annular diaphragms clamped at the other edge and free at the inner edge. An exact solution of basic theoretical equations is employed along with the application of the well known and documented distortion energy theory of failure which results in a useful stress vs. strength relationship. An exact solution of the related deflections is also presented for concurrent stiffness (deflection) calculations.
Bending of Beams with Nonlinear Material Characteristics
Authors: Szuladzinski G.
Published: January 2010

When an expression is known for the curvature of a beam as a function of a bending moment, it is a simple matter to determine the deflected shape. It is a bigger problem to obtain such an explicit expression using a realistic stress-strain curve. This paper begins with a Ramberg-Osgood type of stress-strain formula, that is characterized by a continuous slope change typical of metals in elevated temperatures. A moment-curvature equation of a similar form is then developed and its accuracy is verified for several basic cross-sections. The advantage of this approach is to improve the accuracy and efficiency of deflection analysis compared with the existing manual methods.
Unit Load Method for Deflections of Planar, Nonlinear Structures
Authors: Szuladzinski G.
Published: January 2010

The unit load method, which is also known as a virtual work method, as well as by several other names, is a widely used tool for calculating deflections of linear structures. A procedure is developed here, which consists of similar steps and can be used when nonlinear material is involved. The formulae are developed based on the concept of complementary energy and the Castigliano theorem extended to nonlinear systems. A few simple examples are solved using this method and the results are compared with those obtained by a finite-element program. It appears that a blend of both types of analysis may be the optimal tool in many situations.
Optimization of Two Stage Evaporators for Minimizing Rad-Waste Entrainment
Authors: Holtz M. , Singh K. P.
Published: January 2010

Minimizing solute carry-over into the product is the central object in the design of Radioactive Waste Concentration Systems. Two Stage Evaporators are intrinsically superior to single stage designs in achieving this objective. An analysis of two stage system to optimize its performance is herein developed. A numerical example is employed to illustrate major conclusions.
Development of Pump Characteristics from Field Tests
Authors: Brown R. J. , Rogers D. C.
Published: January 2010

Field tests were conducted to determine the pump characteristics at four pumping plants on the Southern Nevada Water Project. Each pump tested was instrumented to measure speed, torque, and pressure head as functions of time. Records were obtained for pump startup, normal operation, and power failure. The Southern Nevada system was modeled for these same operations on a master computer program, TAHS. Using TAHS, the pump characteristics were adjusted by an iterative process until the computer results were in agreement with the field test records.
The Time of Frictionless Motion of a Swinging Compound Pendulum
Authors: Samson A.
Published: January 2010

The equations of motion of a free swinging compound (physical) pendulum were integrated to obtain a general solution for the elapsed time in the form of a trigonometric integral. The latter was reduced to Jacobian elliptic functions of the first kind, which were then solved by conventional techniques for complete and incomplete integrals. Applying the method developed to a generalized pendulum described by its degree of compounding, the period of its oscillation whilst in frictionless motion for any angle of launch was determined. The degree of compounding of the pendulum had a significant effect on its period of oscillation. This was shown graphically in the form of the variation of a dimensionless time ratio with change in angle of launch for various degrees of compounding. Five specific cases of the time intervals of motion of a compound pendulum were analyzed and solutions obtained. The general equation for the elapsed time of free swinging motion of a simple (mathematical) pendulun, launched from any position and its period of oscillation were also determined.
Influence of Flexible Connections on Response Characteristics of a Beam
Authors: Fossman R. , Sorensen A.
Published: January 2010

The natural frequencies and normal modes of a uniform beam depend upon support conditions. The effect of translation and rotation springs at the base is examined in this presentation. This is done in terms of non-dimensional variables and parameters to enhance the utility of the results. The paper also develops the mode participation and dynamic load factors for subsequent application.
An Experimental Investigation on the Response of a Flexible Rotor Mounted in Pressure Dam Bearings
Authors: Flack R. D. , Leader M. E. , Gunter E. J.
Published: January 2010

The response of a flexible rotor mounted in six bearing sets has been experimentally determined. One set of axial groove bearings and five sets of pressure dam bearings were tested. Conventional synchronous tracking was used in the analysis and other techniques utilizing an FFT analyzer were developed. The stability of the system was seen to strongly depend on the design of the step bearings. The dam bearings were also noted to lock into subsynchronous whip during deceleration after the system went unstable. The response of the system with varying degrees of unbalance is also analyzed and several structural resonances of the rotor system are discussed.
Ideal Spiral Bevel Gears—A New Approach to Surface Geometry
Authors: Huston R. L. , Coy J. J.
Published: January 2010

This paper discusses the fundamental geometrical characteristics of spiral bevel gear tooth surfaces. The parametric representation of an ideal spiral bevel tooth is developed. The development is based on the elements of involute geometry, differential geometry, and fundamental gearing kinematics. A foundation is provided for the study of nonideal gears and the effects of deviations from ideal geometry on the contact stresses, lubrication, wear, fatigue life, and gearing kinematics.
Effect of Molecular Weight Distribution of Mineral Oil on Tribofailure of Spur Gears
Authors: Hirano F. , Ichimaru K. , Kinoshita K. , Sakai T.
Published: January 2010

Using a series of straight mineral oils with a variety of molecular weight distributions failure loads of spur gears with gear ratios 27:25 and 1:1 were investigated. The failure loads in the case of the synchronous engagement 1:1 were considerably higher than those in the asynchronous engagement 27:25 as a result of imprinting of asperities of harder teeth on softer engaged teeth. The correlation among the results was found to be quite regular, showing the beneficial effect of wide-ranged oils in the molecular weight distribution. Summarizing the obtained results, it is concluded that the failure loads of narrow-ranged oils were conditioned by their viscosity grades, and that those of wide-ranged oils increased further with the aid of oxide film formation on teeth. Results of four-ball tests and two-disk tests previously carried out under mild conditions using the same narrow-ranged and wide-ranged oils show the similar feature to those of the gear tests.
Analytical and Experimental Spur Gear Tooth Temperature as Affected by Operating Variables
Authors: Townsend D. P. , Akin L. S.
Published: January 2010

A gear tooth temperature analysis was performed using a finite element method combined with a calculated heat input, calculated oil jet impingement depth, and estimated heat transfer coefficients. Experimental measurements of gear tooth average surface temperatures and instantaneous surface temperatures were made with a fast response infrared radiometric microscope. Increased oil jet pressure had a significant effect on both average and peak surface temperatures at both high load and speeds. Increasing the speed at constant load and increasing the load at constant speed causes a significant rise in average and peak surface temperatures of gear teeth. The oil jet pressure required for adequate cooling at high speed and load conditions must be high enough to get full depth penetration of the teeth. Calculated and experimental results were in good agreement with high oil jet penetration but showed poor agreement with low oil jet penetration depth.
A Direct Integration Technique for the Transient Analysis of Rotating Shafts
Authors: Chu F. H. , Pilkey W. D.
Published: January 2010

The Continuous Space Discrete Time Riccati Transfer Matrix Method is a new direct integration technique for transient analysis of structural members. This method is applied to rotating shafts with bearing systems containing masses. Numerical results are given for a rotor with isotropic bearings.
Study on Vibratory Feeders: Calculation of Natural Frequency of Bowl-Type Vibratory Feeders
Authors: Okabe S. , Yokoyama Y.
Published: January 2010

This paper treats a method of calculating natural frequency of vibratory feeders. In a bowl-type feeder, the deformation of the spring is complicated and the exact calculation of its constant is difficult. Therefore an approximate calculation is presented under some assumptions. The relations between spring constant and spring setting condition are clarified and shown in various diagrams. The equations of natural frequency for the fixed type and the semi-floating type feeder are represented briefly. The vibration direction of bowl-type feeder is also discussed. The theoretical results are confirmed by experimental studies.
Structural Confinement and Safety Design of a Fast Reactor Core
Authors: Ju F. D. , Bennett J. G.
Published: January 2010

In certain fast-reactor designs, the core is an assemblage of a large number of containers of long, hexagonal, hollow cylinders mounted vertically. These so-called “hex-cans” sit individually on coolant nozzles held down by their own weight, and are held as a group laterally at two levels by two constraint rings. At operating temperature, the rings bear on the hex-can assembly because of differences in thermal expansion. The compression of the rings on the hex-can assembly serves to prevent lifting of the can individually or in groups because of any accidental buildup of gas pressure. In the analysis, it is observed that the large number of hexcans and the distribution of the temperature field are such that the cross section of the reactor core can be treated as in a locally uniform dilatational field. An approximate equation was developed relating the plane deformation of a hollow hex cylinder to the global lateral pressure. The parameters are the material constitution and the thickness index (the ratio of the interior and the exterior cross-flat dimensions). The effective range of the equation covers the thickness ratio from zero to the stability limit when the wall becomes too thin resulting in buckling under the lateral pressure. The design equation is exact for zero thickness index. For hollow hex cylinders, numerical solutions were also obtained by the finite element method as a comparison. For a thickness index of 0.9 to 0.95, the difference is less than 0.1 percent. The cylinder constitutive equation is then used to determine an equivalent stiffness for a solid hex cylinder that is to have the same deformation as the given hex-can. The entire planar core region is then analyzed as a homogeneous medium of the equivalent stiffness. The method was applied to the core confinement design for a fast reactor. The thermoelastic solution was then applied to a relatively simpler configuration than the actual case to give a measure of the lateral pressure. The available friction forces for various lift configurations were then obtained. The gas pressure necessary to overcome the minimum friction force thus resulted. In addition, using the lateral pressure, the safety margin of the wall thickness of the hex-can for stability failures was determined.
International Technology Transfer—Who Should Learn the Second Language?
Authors: Eyre F. W.
Published: January 2010

The widening gap between Developed and Developing countries places a burden on Engineers to improve the quantity and quality of technology transfer to the developing countries. Language is an essential element of technology transfer in a two language situation, but receives inadequate attention. The objective of this paper is to show that although powerful arguments exist for using the language of origin of technology for technology transfer, and this usually means English, there are compelling arguments to the contrary. Examination of languages in use, the communication mechanism, cultural considerations, and experience in Quebec and elsewhere are used to support the proposition.
Effects of Case Depth and Relative Radius of Curvature on Surface Durability of Case-Hardened Chromium Molybdenum Steel Roller
Authors: Fujita K. , Yoshida A.
Published: January 2010

In this report, effects of case depth and relative radius of curvature on surface durability of case-hardened chromium molybdenum steel roller are experimentally clarified. The experimental results are discussed by amplitude of ratio of shear stress to Vickers hardness considering hardness and residual stress distributions of roller. Surface failure mode in this experiment was spalling due to the crack having the point of origin beneath the surface. Depth of spolling crack agreed well with depth of the maximum amplitude of the ratio of orthogonal shear stress to Vickers hardness. Surface durability of the roller tended to increase as the case depth increased, but in the case of too deep case depth it was not so high. And the surface durability tended to decrease as the relative radius of curvature increased.
Some Factors Influencing the Pitting, Micro-Pitting (Frosted Areas) and Slow Speed Wear of Surface Hardened Gears
Authors: Winter H. , Weiss T.
Published: January 2010

Surface hardness and hardening depth are the most important influence factors for the load capacity of surface hardened gears. Besides the structure of the hardening pattern, it’s carbon content, amount of retained austenite, residual stress and white layer (nitrided gears) have a considerable influence. Lubricant and material of the mating gear as well as roughness of the tooth flanks have a different influence on pitting, micro-pitting and wear.
Linkage Characteristic Polynomials: Definitions, Coefficients by Inspection
Authors: Yan H. S. , Hall A. S.
Published: January 2010

A linkage characteristic polynomial is defined as the characteristic polynomial of the adjacency matrix of the kinematic graph of the kinematic chain. Some terminology and definitions, needed for discussions to follow in a companion paper, are stated. A rule from which all coefficients of the characteristic polynomial of a kinematic chain can be identified by inspection, based on the interpretation of a graph determinant, is derived and presented. This inspection rule interprets the topological meanings behind each characteristic coefficient, and might have some interesting possible uses in studies of the structural analysis and synthesis of kinematic chains.
Kinematic Mappings. Part 1: Classification of Algebraic Motions in the Plane
Authors: De Sa S. , Roth B.
Published: January 2010

A classification scheme is developed for algebraic motions in the plane. The method is based upon the study of curves in a special three dimensional space into which the planar motions are mapped. As an example all possible cubic motions are classified. It is shown that this mapping, originally proposed by Blaschke, is based upon the rotation curves and the rotation angles of the planar motion.
A New Concept for Force Balancing Machines for Planar Linkages. Part 1: Theory
Authors: Tricamo S. J. , Lowen G. G.
Published: January 2010

A new theory for linkage force balancing machines is presented. These devices make it possible to remove the residual shaking forces of theoretically fully force balanced mechanisms. The required correction masses are obtained from the solution of a unique set of shaking force equations which contain experimentally determined values of the residual shaking force components as well as all relevant kinematic quantities. The essential ideas are first demonstrated for a four-bar linkage device. Subsequently, this theory is generalized to apply to machines for balanceable planar n-bar linkages containing both revolutes and sliders. Part 2 reports on the experimental development of such a machine for four-bar linkages.
On Predicting Vibrations in Realistically Proportioned Linkage Mechanisms
Authors: Haines R. S.
Published: January 2010

The paper explores the proposition that deflections in high-speed linkage mechanisms of ‘realistic’ proportions may be estimated as if the rigid-body inertial loads were applied statically. Some practical limitations are examined in detail, and the paper considers the circumstances in which the adoption of relatively more flexible links may become normal practice.
The Simultaneous Analytical Synthesis of Mass and Spring Elements in Planar Mechanisms
Authors: Griffin J. N. , Matthew G. K.
Published: January 2010

The potential energy storage of linear springs and the kinetic energy storage of a body in motion are associated with the nonlinear motion of planar mechanisms to provide precision point control of desired dynamic phenomena. The work is closely analogous to synthesis of constraint links for pure kinematics problems.
A New Solution to Coulomb Friction in Mechanism Bearings: Theory and Application
Authors: Imam I. , Skreiner M. , Sadler J. P.
Published: January 2010

A new approximate closed form solution is presented for analyzing Coulomb friction in mechanism bearings. This is accomplished by linearizing the nonlinear terms of the equilibrium equations by a novel approach. The method, based on the traditional friction circle concepts, is particularly well suited to computers and proceeds to the solution without the need for any numerical methods or iterative steps as has previously been required. Further, only a pair of simultaneous equations is solved at a time, thus eliminating the need for a complete matrix inversion. It is believed that this simplified approach will be more readily usable in actual design situations where consideration of bearing friction is of considerable importance. A number of analytical validity checks were applied that successfully verified the adequacy of this new approach. As an example, the theory is applied to various models of a class of circuit breaker mechanisms, consisting of five four-bar linkages in series under different operating conditions. In all cases, the analytical results compare very favorably with the test data, thus establishing the method as a valuable practical design tool.
Determination of Extreme Distances of a Robot Hand. Part 2: Robot Arms With Special Geometry
Authors: Sugimoto K. , Duffy J.
Published: January 2010

The algorithm developed in [1] for searching for extreme distance lines of robot arms with arbitrary skew joint axes can fail when applied to arms with special geometry. In this paper, procedures are developed to search for extreme distance lines of robot arms with intersecting or parallel axes. Such cases have important practical application. It is demonstrated that a robot arm with geometry common to industrial arms such as Cincinnati Milacron, Hitachi (Japan), Trallfa (Norway), Puma (Unimation), ASEA (Sweden), Volkswagen and Kuka (Germany) has a total of sixty-four extreme distances.
Assessment of the Dynamic Quality of a Class of Dwell-Rise-Dwell Cams
Authors: Chen F. Y.
Published: January 2010

A number of new cam profiles of the dwell-rise-dwell type have been proposed by different researchers in the past two decades. They were claimed as efficient cam curves suitable for high-speed applications. This paper re-examines these profiles with regard to the important vibrational response characteristics when they are applied as motion excitations to a cam-and-follower system. The severity of the dynamic response of the cam follower to the motion excitation of a cam will be measured by a dimensionless quantity known as the normalized acceleration amplification factor (NAAF). A simplified response envelop for the residual vibration of NAAF versus the fundamental period is constructed so that an assessment of the merit of any given cam profile can be made qualitatively and quantitatively.
The Balancing of Rotating Shafts by Quadratic Programming
Authors: Woomer E. , Pilkey W.
Published: January 2010

The application of quadratic programming methods to the computation of balance weights for rotating shafts is demonstrated. The use of the quadratic programming technique makes possible the minimization of the sum of the squares of the deflections of the balanced shaft when upper bounds have been placed on the magnitudes of the components of the correction weights. A simple shift of coordinates is employed to transform the constraint equations to the standard form necessary for the quadratic program.
On the Dynamic Simulation of Large Nonlinear Mechanical Systems. Part 1: An Overview of the Simulation Technique. Substructuring and Frequency Domain Considerations
Authors: Cipra R. J. , Uicker J. J.
Published: January 2010

In Part 1 an analytical technique is presented for determining the dynamic response of large complex nonlinear systems. The simulation technique is aimed at this class of problems having many describing coordinates, a complex model description, and nonlinear effects which need to be included for sufficient accuracy. The technique uses substructuring to look at complex systems, frequency reduction to handle large numbers of coordinates, and a numerical integration technique which includes the nonlinear effects. The method is seen to have much potential and can be applied to various problems including those having changing topology. The technique can be applied to any large nonlinear problem for which an appropriate model can be formulated.
A State Space Method for Kinematic Optimization of Mechanisms and Machines
Authors: Sohoni V. , Haug E. J.
Published: January 2010

Problems of optimal kinematic synthesis of mechanisms and machines are formulated in a state space setting that allows for treatment of large scale systems with general design objectives and constraints. An iterative kinematic analysis method is presented. An adjoint variable method of design sensitivity analysis is presented that uses the same matrices generated in kinematic analysis to efficiently calculate derivatives of cost and constraint functions with respect to design. A gradient projection optimization algorithm is presented, based on the state space kinematic and design sensitivity analysis formulation. Two mechanism synthesis problems are solved to illustrate the method and to evaluate its effectiveness.
MAPS-1: Computer-Aided Design System for Preliminary Material and Manufacturing Process Selection
Authors: Dargie P. P. , Parmeshwar K. , Wilson W. R. D.
Published: January 2010

A computer-aided design system for suggesting candidate manufacturing process and material combinations for a part is described. The system uses an interactively generated twelve-digit classification code to eliminate unsuitable combinations from consideration and rank the remainder. The ranking system is still under development.
Dynamic Response of an Electric Motor-Linkage System During Startup
Authors: Myklebust A.
Published: January 2010

The dynamic response of a d-c separately excited motor coupled to a general four-bar linkage is investigated. The analysis is formulated by the principles of analytical mechanics resulting in first order equations with first order constraints and undetermined multipliers with their derivatives. The constraint equations are based on the velocity ratio equations rather than the commonly used loop equations. An example is presented.
Dynamic Behavior of a Moving Belt Supported on Elastic Foundation
Authors: Bhat R. B. , Xistris G. D. , Sankar T. S.
Published: January 2010

The dynamic behavior of a belt moving on an elastic foundation and supported on two pulleys at the ends is investigated. The problem is formulated to include the nonlinear terms arising from large amplitude oscillations as well as material damping and the variation in tension along the belt. The differential equation of motion is solved employing numerical techniques, and the spatial response variations with time are presented graphically for different belt velocities. These results indicate that in the absence of damping, the system is unstable for any belt velocity larger than the wave velocity in the belt material. The results are useful in investigating the stability of large continuous conveyor systems supported on elastic foundations.
Member Initial Curvature Effects on the Elastic Slider-Crank Mechanism Response
Authors: Badlani M. , Midha A.
Published: January 2010

Parametric vibration of initially curved columns loaded by axial-periodic loads has received considerable attention, concluding that regions of instability exist and that excitation frequencies less than the natural frequency of the principal resonance may occur. Recent publications have cautioned against the use of curved members in machines designed for precise operation, suggesting a detrimental coupling of the longitudinal and transverse deformations. In this work, the dynamic behavior of a slider-crank mechanism with an initially curved connecting rod is investigated. Governing equations of motion are developed using the Euler-Bernoulli beam theory. Both steady-state and transient solutions are determined, and compared with those obtained for the mechanism possessing a geometrically perfect (straight) connecting rod. A very small initial curvature is shown to cause a significantly greater steady-state response. The magnification in its transient response is shown to be even greater than that due to a straight connecting rod. Additionally, an excitation frequency less than the natural frequency is also shown to occur.
Kinematic Synthesis of an Adjustable Six-Bar Angular-Motion Compensator
Authors: Tsai Lung-Wen
Published: January 2010

The synthesis of a six-bar Watt linkage for use as an angular motion compensator is presented. Functional requirements of an angular motion compensator for achieving a desired delay in the output motion were translated into the crank angle and crank velocity relationships of the mechanism. Design equations and procedures were derived for the synthesis of a special symmetrical six-bar Watt linkage. It has been shown that the synthesis of a symmetrical six-bar linkage can be decoupled into the synthesis of two identical four-bar linkages. This paper also illustrates how to adjust the phase of the mechanism to achieve various different delays in the output motion without changing the basic linkage proportions.
New Complex-Number Form of the Cubic of Stationary Curvature in a Computer-Oriented Treatment of Planar Path-Curvature Theory for Higher-Pair Rolling Contact
Authors: Sandor G. N. , Erdman A. G. , Hunt L. , Raghavacharyulu E.
Published: January 2010

New complex number forms of the Euler-Savary Equation (ESE) for higher-pair rolling contact planar mechanisms were derived in a former paper by the authors. The present work, based on the former, deals with the derivation of the cubic of stationary curvature (CSC) in complex-vector form, suitable for digital computation. The CSC or Burmester’s circlepoint curve and its conjugate, the centerpoint curve for four infinitesimally close positions of the moving plane requires taking into account not only the curvature but also the rate of change of curvature of the rolling centrodes in the immediate vicinity of the position considered. The analytical procedure based on the theory developed in the present paper, when programmed for digital computation using complex arithmetic, takes care of the algebraic signs automatically, without the need for observing traditional sign conventions. The analysis is applicable to both higher-pair and lower-pair planar mechanisms. An example using the complex-number approach illustrates this.
Improved Methods for the Fast Fourier Transform (FFT) Calculation of the Frequency Response Function
Authors: Mitchell L. D.
Published: January 2010

Most FFT machines today compute an estimate of the frequency response function, H(f), by the cross-spectral density of input to output divided by the power spectral density of the input. This estimator is contaminated by noise at the input. One uses the coherence function to help measure the level of contamination. However, the coherence function detects, among other things, noise at both the input and output. Several alternate methods are proposed for the computation of the frequency response function. One generates more accurate estimates at resonance, one has half or less of the contamination contained in the present methods, and the last one proposes to eliminate the biasing contamination all together.
Bearing Fault Detection Using Adaptive Noise Cancelling
Authors: Chaturvedi G. K. , Thomas D. W.
Published: January 2010

The ability to diagnose a mechanical fault is enhanced if the monitoring signal can be preprocessed to reduce the effect of unwanted noise. To this end, the adaptive noise cancelling technique (ANC) can substantially improve the signal to noise ratio where the required signal is contaminated by noise. ANC makes use of two inputs—a primary input which contains the corrupted signal, and a reference input containing noise correlated in some unknown way with the primary noise. A variation of ANC is also proposed and it is shown that this can be applied effectively in those situations where inputs contain correlated signals but uncorrelated or weakly correlated noises. Using vibrational data derived from a reasonably complex bearing rig and preprocessing the data by the ANC technique, this paper shows that the statistical and spectral analysis techniques can be made more effective in their diagnostic roles after the application of ANC.
Comparison of the Unbalance Responses of Jeffcott Rotors With Shaft Bow and Shaft Runout
Authors: Flack R. D. , Rooke J. H. , Bielk J. R. , Gunter E. J.
Published: January 2010

The unbalance response of a Jeffcott rotor with shaft bow and/or runout was theoretically and experimentally studied. Bow refers to a rotor which is warped; bow is a function of running speed. Runout refers to electrical or mechanical asymmetrics of the shaft and is not dynamical. Included in the theoretical model is the capability of low-speed response compensation, such that the response at low speed can be vectorially subtracted from the total response at any rotational speed. Responses of rotors with equal amounts of bow or runout are shown to be significantly different in both Bode and Nyquist forms. Using low speed compensation is shown to “correct” the unbalance response of a rotor with runout to an ideal (unbowed - no runout) case. The amplitude response plot of a bowed rotor is not corrected to the ideal response plot by the use of such compensation; however, the shape of the phase response plot closely resembles the ideal case for most cases. A small scale lightly damped Jeffcott rotor rig was also tested. The magnitude and angular position of the shaft bow were parametrically varied. The vibration data from the rotor tests were plotted using a synchronous tracking filter by two methods: both not using and using low speed compensation. Experimental data agree excellently with predictions for a bowed rotor for all cases and differences less than 8 percent were usually found.
Application of the Principle of Reciprocity to Flexible Rotor Balancing
Authors: Darlow M. S. , Smalley A. J.
Published: January 2010

The least desirable feature of most flexible rotor balancing procedures is the considerable number of trial mass runs required. This is of particular importance in the balancing of machines which require a substantial stabilization time during start-up. Using an adaptation of the principle of reciprocity, it is possible to significantly reduce the required number of trial mass runs for certain rotors when using either influence coefficient balancing or the Unified Balancing Approach. When applied to flexible rotor balancing, the principle of reciprocity states that, given two rotor axial locations, A and B (at which both balancing planes and vibration sensors are located), the influence coefficient relating the vibration level at A to the unbalance at B is identical to that relating the vibration level at B to the unbalance at A. This is true even in the presence of damping. This paper begins with a theoretical discussion of the principle of reciprocity and its application to flexible rotor balancing. The particular means by which reciprocity can be applied to improve the influence coefficient and Unified Balancing Approach procedures are then described in detail. A numerical study was conducted to verify this application of reciprocity, as well as to investigate any possible limitations. The results of this study are reported along with those of a similar experimental study using two substantially different test rotors.
Optimum Journal Bearing Parameters for Minimum Rotor Unbalance Response in Synchronous Whirl
Authors: Bhat R. B. , Rao J. S. , Sankar T. S.
Published: January 2010

Optimization techniques are employed to design hydrodynamic bearings for minimum unbalance response of rotors in synchronous whirl. The analysis for the unbalance response considers the effects of direct and cross coupled coefficients of stiffness and damping in the bearings. A parametric study of the unbalance response is carried out to show the influence of bearing parameters on the response and to demonstrate the merits of applying optimization techniques in bearing design. The bearing parameters optimized are the diameter, clearance, and the oil viscosity. In addition to setting upper and lower limits on the foregoing design variables, the Sommerfeld number is also constrained to be within a certain range for the operational speeds of the rotor. The quantity minimized is the maximum unbalance response of the rotor in the operational speed range. Plain cylindrical, grooved, elliptical, and four shoe tilting pad type bearings are considered in the optimal design of the rotor bearing system. The results indicate that an optimal design of hydrodynamic bearings can reduce the unbalance response of rotors.
Passage of a Rotor Through a Critical Speed
Authors: Tsuchiya K.
Published: January 2010

This paper deals with a nonstationary oscillation of a rotor passing through a critical speed. The analysis is based on the method of multiple scales and the method of matched asymptotic expansion. The peak amplitude of the response and the criteria for the onset of the stalling (inability to pass through the critical speed) are derived. These results are compared with those of digital computer simulation.
Analysis and Identification of Subsynchronous Vibration for a High Pressure Parallel Flow Centrifugal Compressor
Authors: Kirk R. G. , Nicholas J. C. , Donald G. H. , Murphy R. C.
Published: January 2010

The evaluation of turbomachinery designs prior to actual hardware test and field installation is now the rule rather than the exception for rotating machinery manufacturers. This requires the verification of the current state of the art analytical techniques for rotor-bearing-seal dynamics by development testing and/or controlled test stand or field vibration studies. This paper presents the summary of a complete analytical design evaluation of an existing parallel flow compressor and reviews a recent field vibration problem that manifested itself as a subsynchronous vibration that tracked at approximately 2/3 of compressor speed. The comparison of predicted and observed peak response speeds, frequency spectrum content, and the performance of the bearing-seal systems are presented as the events of the field problem are reviewed. Conclusions and recommendations are made based upon the results of this design review.
Vibrations of an Elastically Mounted Spinning Rotor Partially Filled With Liquid
Authors: Lichtenberg G.
Published: January 2010

The stability of a rotor with a cylindrical cavity, spinning with constant angular velocity and partially filled with an inviscid, incompressible fluid is studied. The rotor is elastically supported on a vertically mounted massless shaft in overhung position. A set of coupled linearized spatial equations of motion of the rotor and field equations, as well as boundary conditions of the liquid, is established and solved, leading to a characteristic equation. First numerical results predict a wide range of rotor speeds, where the system performs unstable motions caused by a two-dimensional surface wave of the liquid. The stability boundaries are calculated for a flat rotor in dependence on the mass of the contained liquid and agree extremely well with experimental data.
Vibration Analysis of a Flexible System Mounted on a Viscoelastic Sandwich Beam
Authors: Vikal R. C. Das , Gupta K. N. , Nakra B. C.
Published: January 2010

Vibration analysis of a simple flexible system mounted arbitrarily on a three-layer sandwich beam having a viscoelastic core and elastic faces is presented in this paper. The flexible system consists of a mass on rubber spring and is excited harmonically. The expressions for displacement response of mass and transmissibility provided by the whole system are obtained. The displacement response and transmissibility are studied for different geometrical and physical parameters of the sandwich beam. Some of the theoretical results are verified experimentally.
The Sensitivity Analysis of Cam Mechanism Dynamics
Authors: Young S.-S. D. , Shoup T. E.
Published: January 2010

In order to improve the dynamic performance of a cam mechanism, it is desired to have a method that does not require a trial-and-error procedure based on total system re-analysis or re-synthesis. In this paper a new sensitivity analysis method will be presented that allows the designer to make system modifications to move the design in the direction of the global optimum. To implement this method the output response of the system is first expressed in terms of the system eigendata. Then an efficient procedure for determining sensitivity of the system response to changes in individual system parameters is developed utilizing the eigenvalue and eigenvector derivatives with respect to the system design parameters. An example of a double lever cam mechanism with a four-degree-of-freedom dynamic system model is used to illustrate the technique.
A Mathematical Model Used in Conjunction With a Finite Element Analysis to Aid in the Design and Analysis of Bourdon Tubes
Authors: Weber R. C. , Davis R. L.
Published: January 2010

A mathematical model that describes a variety of Bourdon tube geometries has been used for the three-dimensional analysis of Bourdon tubes. The variation of the stresses and tip deflections with respect to the variables used in the mathematical model are then presented as an aid in the design and analysis of the Bourdon tube. The finite element program represents a user-orientated package for calculation of tip deflections and stresses. Stresses and deflections are compared to both strain gage data and instrumented tip deflections as well as published data to establish the credibility of both the model and computer program.
Approximate Design Analysis of Failure Within Composite Laminated Plates
Authors: Gallo R. L. , Palazotto A. N.
Published: January 2010

This paper is an analytical study of the effects of interlamina stresses near the free edge of a laminated plate due to axial and moment loading variations. A three-dimensional extension of the Tsai-Hill failure criterion is introduced to predict delamination. Results achieved by computer simulation show good agreement with experimental observations made by other sources. The distance from the free edge is decidedly important as is the effect of curing temperature because of the consequences these parameters have on the magnitude of the stress field. The failure estimations provide an approximate bound and are worthy of due consideration by the design engineer in the stress analysis of test specimens.