Showing papers on "Inertia published in 1984"

Structural Inertia and Organizational Change

Abstract: Considers structural inertia in organizational populations as an outcome of an ecological-evolutionary process. Structural inertia is considered to be a consequence of selection as opposed to a precondition. The focus of this analysis is on the timing of organizational change. Structural inertia is defined to be a correspondence between a class of organizations and their environments. Reliably producing collective action and accounting rationally for their activities are identified as important organizational competencies. This reliability and accountability are achieved when the organization has the capacity to reproduce structure with high fidelity. Organizations are composed of various hierarchical layers that vary in their ability to respond and change. Organizational goals, forms of authority, core technology, and marketing strategy are the four organizational properties used to classify organizations in the proposed theory. Older organizations are found to have more inertia than younger ones. The effect of size on inertia is more difficult to determine. The variance in inertia with respect to the complexity of organizational arrangements is also explored. (SRD)

Analysis and Design of a Direct-Drive Arm With a Five-Bar-Link Parallel Drive Mechanism

Abstract: The direct-drive arm that has no gears between motors and their loads have several important advantages including no backlash, small friction, and high mechanical stiffness. The arm mechanism, however, becomes extremely massive, when each motor is directly attached to its joint along a serial linkage mechanism. The complicated dynamics resulting from varying inertia, interactions, and nonlinearities, is also more prominent than that of a robot with gears. This paper describes a lightweight arm mechanism with invariant and decoupled inertia characteristics. Instead of having motors at serial joints, a parallel drive mechanism with a closed-loop five bar linkage is utilized. The dynamic behavior of this mechanism is analyzed and the condition for the elimination of the interactions and nonlinearities in the mass properties is derived. The decoupled and invariant arm dynamics significantly reduces the complexity of controlling the direct-drive arm. In the latter half of the paper, a prototype robot developed on this basis is described. By using high torque brushless motors which were specially designed for the direct-drive robot, top speed and maximum acceleration were increased by an order-of-magnitude to about 10 m/s and 5 G, respectively.

The rate of coagulation of a dilute polydisperse system of sedimenting spheres

Abstract: We consider a dilute dispersion containing small rigid particles in a Newtonian fluid. These spherical particles are of different size and density, and they settle relative to one another under the action of gravity. When the particles become close, they exert an attractive van der Waals force on each other, and doublets are formed when two particles come into contact as a result of this force. The rate at which doublets are formed is calculated using a trajectory analysis to follow the relative motion of pairs of particles.We restrict our attention to dispersions where the Peclet number is large (negligible Brownian motion) and where the Reynolds number is small (negligible fluid inertia). However, the effects of the inertia of the particles on their trajectories are included, and these are measured by the Stokes number. A key dimensionless parameter is identified, denoted by Qij which provides a measure of the relative importance of gravity and the van der Waals force. An asymptotic solution to the trajectory equations is presented for large values of this parameter in the case of zero Stokes number. This asymptotic solution is then complemented by numerical computations of the particle trajectories. Application to typical hydrosol and aerosol dispersions is presented, and, in particular, a comparison is made between the effects of van der Waals forces and Maxwell slip in promoting collisions between aerosol particles.

A new approach to evaluate instantaneous friction and its components in internal combustion engines

Abstract: A new approach has been developed at Wayne State University to determine the instantaneous friction and its components in internal combustion engines. The method is based on the fact that the instantaneous cylinder gas forces and the instantaneous frictional, inertia and load forces cause the instantaneous variation in the flywheel angular velocity. The instantaneous total friction forces have been computed for a single diesel engine, under idling conditions. A breakdown of the friction into its components and a formulation for each component has been made. By applying linear regression, correlations between the individual components of the friction losses and the different parameters have been developed. The components are classified into two categories: piston assembly losses and crankcase assembly losses. The correlations have been applied to a multi-cylinder and a single cylinder diesel engine to compute frictional losses under operating and motoring conditions. The computed results have been found to be in a fairly good agreement with the experimental results. The correlations were also applied to the gasoline engine and compared with published experimental results in the literature.

Dynamic analysis and design of robot manipulators using inertia ellipsoids

Abstract: An analysis of robot arm dynamics and a graphical method of representing these dynamics suitable for computer aided design is presented. The inertia ellipsoid, which is used for graphically representing the mass properties of a single rigid body, is extended to a generalized ellipsoid for a series of rigid bodies such as a robot arm. By drawing the Generalized Inertia Ellipsoid (GIE) on a computer display, one can visualize the mass properties and dynamic behaviour of a robot manipulator. This method is applied to aid the design of a mechanical arm; the dimensions of the arm structure and its mass distribution are optimized on the basis of the evaluation of the arm dynamics displayed on a graphics terminal.

An Analysis of the Hydrodynamics of Aluminum Reduction Cells

Abstract: An investigation of the flow of the two superposed liquids (the electrolyte and the molten aluminum) and of the interface shape has been carried out with the intention of revealing the main mechanisms and to clarify the hydrodynamic behavior of Hall-Heroult cells. The wide channels present around the anodes and between the two anodes rows in modern cells appear responsible, in the final analysis, for the electrolyte motion. The horizontal component of the current density in the aluminum layer largely determines the interface shape. It can also drive an organized motion when it is not a pure gradient. Two main ideas are at the source of this theory: (1) the shallow depth of the fluid layers (compared with their horizontal dimensions) justifies an approximation of zero inertia, and (2) a linear approximation is proposed for the horizontal shear stresses. This almost explicit theory results in predictions that are not completely realistic, but it is shown how certain features of actual cell behavior can be revealed.

A Finite Element Method for Nonlinear Forced Vibrations of Beams

Abstract: Techniques for defining a finite element model (FEM) for analysis of nonlinear vibrations in beam structures subjected to harmonic excitation are presented. The resulting model covers longitudinal deformation and inertial effects. The nonlinear oscillations of a beam element under forced excitation are modeled by a harmonic force matrix based on first order approximations of the Jacobian elliptic forcing function. Harmonic force and nonlinear stiffness matrices are derived and the nonlinear forced responses of beams are calculated under various boundary conditions. The results of FEM computations for simply-supported and clamped beams show that midplane stretching caused by large deflections increases the nonlinearity. Axially-restrained beams experience only hardening nonlinearity, while axially-free beams have reduced nonlinearity in deformation and inertia and an increase in linearity due to large deflection.

Vibration and Flutter of Mistuned Bladed-Disk Assemblies

Abstract: An analytical model for investigating vibration and flutter of mistuned bladed disk assemblies is presented. This model accounts for elastic, inertial and aerodynamic coupling between bending and torsional motions of each individual blade, elastic and inertial couplings between the blades and the disk, and aerodynamic coupling among the blades. The disk was modeled as a circular plate with constant thickness and each blade was represented by a twisted, slender, straight, nonuniform, elastic beam with a symmetric cross section. The elastic axis, inertia axis, and the tension axis were taken to be noncoincident and the structural warping of the section was explicitly considered. The blade aerodynamic loading in the subsonic and supersonic flow regimes was obtained from two-dimensional unsteady, cascade theories. All the possible standing wave modes of the disk and traveling wave modes of the blades were included. The equations of motion were derived by using the energy method in conjunction with the assumed mode shapes for the disk and the blades. Continuities of displacement and slope at the blade-disk junction were maintained. The equations were solved to investigate the effects of blade-disk coupling and blade frequency mistuning on vibration and flutter. Results showed that the flexibility of practical disks such as those used for current generation turbofans did not have a significant influence on either the tuned or mistuned flutter characteristics. However, the disk flexibility may have a strong influence on some of the system frequencies and on forced response.

Component inertial effects on transmission design

Abstract: The placement of components within a manual transmission influences gear rattle and shiftability. This is due to changes in the effective inertia of the transmission. Gear rattle can be reduced and shiftability can be improved by positioning components to optimize the transmission's effective inertia. In this report, the effect of inertia on shiftability is discussed. The causes and types of gear rattle are then discussed. A theory is developed for the threshold of rattle within a transmission. A transmission arrangement is then presented that reduces gear rattle and improves shiftability by optimizing the placement of components by taking into account component inertial effects.

Hydrodynamic Forces on Flexible Offshore Structures

Abstract: The extension of Morison's equation to allow for structural motion in predicting the hydrodynamic force on offshore steel jacket platforms may be based on two different hypotheses: (1) The relative velocity model which replaces the fluid velocity by the relative velocity between the fluid and the structure; and (2) the independent flow fields model which considers the flow to be a superposition of two unrelated flows, one due to the wave‐current action on a rigid cylinder, and the other due to the structural motion in still water. An iterative computational procedure that combines time domain and frequency domain analysis techniques is developed to solve the nonlinear governing equations for both models. Comparison studies are carried out for seastates ranging from the drag dominant through the inertia dominant regimes. Results indicate that the independent flow fields model always predicts a higher structural velocity response, the difference increasing with wave height. There is negligible difference fo...

Wave force tests on vertical and inclined cylinders

Abstract: A wave tank test was performed on fixed vertical and inclined cylinders in which forces on the cylinder in regular waves were measured. The hydrodynamic coefficients are computed based on the measured local forces on the cylinder, Morison equation and stream function theory. The inertia and drag forces are shown as functions of the Keulegan‐Carpenter number. The lift coefficients and lift force frequencies are presented as functions of the Keulegan‐Carpenter number. The coefficients obtained locally are shown to generally apply to the entire cylinder based on the respective local KC values.

Inertia rope grab

Abstract: A safety device is provided for removably fastening to a safety line a rope grab which contains both inertia and positive locking features. A roller is provided in angled guide tracks to provide an inertia locking effect while a pivot arm can bear against the roller to provide positive locking as well.

A new matrix development of the potential and attraction at exterior points as a function of the inertia tensors

Abstract: In this work a novel tensor-matrix notation is first introduced and later applied to develop a new general expression to compute the potential of a body at exterior points as a function of the full tensors of inertia. As a corollary the general matrix development of the gravitational attraction in function of the inertia tensors is also established. For clarity the first terms in both expansions are given explicitly in a simplified matrix form. Some classical particular cases still used in geophysical and geodetic literature are pointed out and discussed.

Influence of Hydro Units' Generator-to-Turbine Inertia Ratio on Damping of Subsynchronous Oscillations

Abstract: The torsional data of hydro generators are examined and it is found that the inertia ratio between the generator and the turbine lies in the range of 10 to 40 and that the torsional frequency lies between 10 Hz and 24 Hz. It is shown that the high inherent generator to turbine inertia ratio of a hydro unit increases the modal damping at the torsional frequency significantly. This is substantiated by digital simulations for a generator connected to a series compensated AC network and by simulations on an HVDC-simulator for a generator feeding an HVDC-link. It is shown that with reasonable values of the turbine damping no torsional interactions problem would occur for the cases studied.

Hydrodynamic impeller stiffness, damping, and inertia in the rotordynamics of centrifugal flow pumps

Abstract: The lateral hydrodynamic forces experienced by a centrifugal pump impeller performing circular whirl motions within several volute geometries were measured. The lateral forces were decomposed into: (1) time averaged lateral forces and (2) hydrodynamic force matrices representing the variation of the lateral forces with position of the impeller center. It is found that these force matrices essentially consist of equal diagonal terms and skew symmetric off diagonal terms. One consequence of this is that during its whirl motion the impeller experiences forces acting normal and tangential to the locus of whirl. Data on these normal and tangential forces are presented; it is shown that there exists a region of positive reduced whirl frequencies, within which the hydrodynamic forces can be destablizing with respect to whirl.

Measurements of Squeeze Film Bearing Forces to Demonstrate the Effect of Fluid Inertia

Abstract: Squeeze film dampers are commonly applied to high speed rotating machinery, such as aircraft engines, to reduce vibration problems. The theory of hydrodynamic lubrication has been used for the design and modeling of dampers in rotor dynamic systems despite typical modified Reynolds numbers in applications between ten and fifty. Lubrication theory is strictly valid for Reynolds numbers much less than one, which means that fluid viscous forces are much greater than inertia forces. Theoretical papers which account for fluid inertia in squeeze films have predicted large discrepancies from lubrication theory, but these results have not found wide acceptance by workers in the gas turbine industry. Recently, experimental results on the behavior of rotor dynamic systems have been reported which strongly support the existence of large fluid inertia forces. In the present paper direct measurements of damper forces are presented for the first time. Reynolds numbers up to ten are obtained at eccentricity ratios 0.2 and 0.5. Lubrication theory underpredicts the measured forces by up to a factor of two (100% error). Qualitative agreement is found with predictions of earlier improved theories which include fluid inertia forces.Copyright © 1984 by ASME

Control constant setting method for speed controller

Abstract: PURPOSE:To optimally set a control gain by integrating to be hardly affected by the influence of a noise, and presuming an accurate inertia moment considered for the influence of a load torque. CONSTITUTION:The inertial moments J of a rotor of an induction motor 3 and a load unit 4 coupled with the rotor are calculated by a calculator B. Then, a torque T is calculated by an i*m/theta converter 13, an integrator 14 for integrating a torque current command signal i*8, and a torque calculator 16, and a signal DELTAomegar proportional to the rotating speed is obtained by the change width detector 15 of the speed omegar. They are input to an inertia moment calculator 17, the inertial moment of the machine system is calculated, and the gain of a speed regulator ASR10 is regulated by the output.

Relativistic Mechanics, Time and Inertia

Abstract: A Aspects of Relativistic Mechanics- AI General remarks- AII Remarks on the theory of relativity- AII1 Special relativity- AII11 Synchronization of clocks- AII12 The Lorentz-Einstein relations- AII13 The invariant of Lorentz-Einstein transformations- AII14 Classification of space-time intervals- AII15 Minkowski space- AII16 Transformation of velocity components- AII17 The velocity and acceleration 4-vectors- AII18 The momentum 4-vector- AII19 The 4-force- AII110 The fundamental law of dynamics and the energy of a particle in relativistic dynamics- AII111 The momentum-energy vector and the properties of its components- AII112 The conservative case Potential energy- AII113 The mass defect- AII114 The relativistic study of collisions- AII115 Some physical interpretations and other remarks on relativistic mechanics- AII2 Some aspects of general relativity- AIII The main aims of this work- B Time- BI The concept of time- BI1 The evolution of the concept of time- BI2 Time as measure and consequence of motion- BI21 Motion- BI22 The clock- BI23 Examples of mechanical motion- BI24 Time as an abstraction of general motion- BI3 The properties of time- BI31 The irreversibility of time- BI32 The velocities and accelerations in various equivalence classes- BI33 The transport of information- BI34 Information transport as a timing motion- BI35 The character of the unique constant velocity of light in all inertial frames- BI36 Relativity of time and the problem of several information carriers- BII Examples- BII1 The irreversibility and continuity of time- BII11 The probabilistic irreversibility- BII12 The continuity of the time variable- BII2 The forced open curves in Minkowski space- C Inertia- CI Use of time in defining some elements of space- CI1 The definition of the straight line- CI11 Inertial spaces- CI12 The straight line- CI13 Non-inertial spaces- CI14 The rigid line- CI2 Reference frames- CI21 Inertial frames- CI22 Non-inertial frames- CII The inertia- CII1 Aspects related to motion of particles in inertial and non-inertial spaces- CII11 General aspects of the study of motion in non-inertial spaces- CII12 Mescerski-Levi-Civita equation in the relativistic case- CII13 The effect of percussion force in the relativistic case- CII2 Manifestation of inertia- CII21 The inertial spaces- CII22 Non-inertial spaces- CII3 Some aspects of the motion of a particle in a non-inertial situation- CII31 Accelerated translation- CII32 A particular gravitational field- CII33 The case of relative motion of the frame- CIII Some aspects of classical mechanics- CIII1 Grounding mechanics on a single axiom- CIII11 The single axiom of mechanics- CIII12 Definition of force and derivation of the fundamental laws of mechanics- CIII2 The inertial or non-inertial character of frames- CIII21 Inertial frames- CIII22 Non-inertial frames