Showing papers on "Inertia published in 1989"
TL;DR: In this paper, a fully developed forced convection in a porous channel bounded by parallel plates is considered based on the general flow model, and exact solutions are obtained and presented for both the velocity and the temperature fields.
Abstract: In this paper fully developed forced convection in a porous channel bounded by parallel plates is considered based on the general flow model. Exact solutions are obtained and presented for both the velocity and the temperature fields. From these results the Nusselt number can be expressed in terms of the Darcy number and the inertia parameter. Finally, comparisons are made with the limiting case of no inertia and/or boundary effects. These results provide an in-depth insight into the underlying relationships between all of the pertinent variables. Furthermore, they can be used as strong candidates for bench marking of many numerical schemes.
232 citations
TL;DR: In this article, the Euler-Bernoulli theory for a slender beam is used to derive the governing non-linear partial differential equation for an arbitrary position of the lumped mass.
Abstract: The non-linear response of a slender cantilever beam carrying a lumped mass to a principal parametric base excitation is investigated theoretically and experimentally. The Euler-Bernoulli theory for a slender beam is used to derive the governing non-linear partial differential equation for an arbitrary position of the lumped mass. The non-linear terms arising from inertia, curvature and axial displacement caused by large transverse deflections are retained up to third order. The linear eigenvalues and eigenfunctions are determined. The governing equation is discretized by Galerkin's method, and the coefficients of the temporal equation—comprised of integral representations of the eigenfunctions and their derivatives—are computed using the linear eigenfunctions. The method of multiple scales is used to determine an approximate solution of the temporal equation for the case of a single mode. Experiments were performed on metallic beams and later on composite beams because all of the metallic beams failed prematurely due to the very large response amplitudes. The results of the experiment show very good qualitative agreement with the theory.
174 citations
TL;DR: In this article, a numerical model has been developed to estimate the inertial stress from this theory, and it was found that the new term can have the largest contribution to measured stress.
Abstract: Previous theories of the inertial contribution to measured stress in dynamic compression of cylindrical specimens have been extended to allow for anvil motion as well as specimen strain. A numerical model has been developed to estimate the inertial stress from this theory, and it was found that the new term can have the largest contribution. Because of the effects of wave propagation and dispersion found in experimental records, an estimate of the inertial errors from this numerical simulation is probably more reliable than an estimate derived directly from the experimental measurements.
126 citations
TL;DR: In this article, direct numerical simulations of decaying two-dimensional magnetohydrodynamic flows at Reynolds numbers of several thousand were performed, using resolutions of 10242 collocation points, with an inertial range extending to about one decade, with spectral properties depending on the velocity-magnetic field correlation.
Abstract: Direct numerical simulations of decaying two‐dimensional magnetohydrodynamic flows at Reynolds numbers of several thousand are performed, using resolutions of 10242 collocation points. An inertial range extending to about one decade is observed, with spectral properties depending on the velocity–magnetic field correlation. At very small scales, resistive tearing destabilizes current sheets generated by the inertial dynamics and leads to the formation of small‐scale magnetic islands, which may then grow and reach the size of inertial scales.
109 citations
TL;DR: The magnitude and distribution of the torques caused by inertial and aerodynamic forces on the wings of Diptera in flight are calculated and Wings are thicker nearer the base to resist bending, but thin and light near the tip to minimize inertial energy expenditure.
Abstract: Summary 1. The magnitude and distribution of the torques caused by inertial and aerodynamic forces on the wings of Diptera in flight are calculated. 2. The bending torque at stroke reversal due to the inertia of the virtual mass of air bound to the wing is only slightly less than the torque due to the inertia of the wing mass itself. The maximum inertial torque due to both wing mass and virtual mass is usually slightly greater than the maximum aerodynamic torque encountered by the wings. 3. Bending torques decrease rapidly away from the wing base. 4. Pitching torques are much smaller than bending torques at the wing base, but do not decrease much until near the tip. 5. The pattern of loading affects the wing design. Wings are thicker nearer the base to resist bending, but thin and light near the tip to minimize inertial energy expenditure. Their open, corrugated structure resists bending, while allowing them to be twisted as a result of the weak pitching moments.
102 citations
TL;DR: In this paper, the free vibration characteristics of laminated composite shells are presented using an isoparametric doubly curved quadrilateral shear flexible element and first-order shear deformation theory is accounted for using an extension of Sanders' shell theory.
95 citations
TL;DR: In this paper, the authors derived an equation for the potential-flow wave loading on a lattice-type offshore structure moving partially immersed in waves, which can be applied computationally by a simple stick model.
Abstract: This paper derives an equation for the potential-flow wave loading on a lattice-type offshore structure moving partially immersed in waves. It is for the limiting case of small lattice-member diameter, and deals entirely in member-centreline fluid properties, so that it can be applied computationally by a simple ‘stick model’ computer program. This field is currently served by a simple two-term semiempirical formula ‘Morison's equation’: the new equation is effectively a replacement for the Morison inertial term, allowing the Morison drag term (or some refinement of it) to describe exclusively the effects of vorticity, which can in principle be calculated to greater accuracy when isolated in this way.The new equation calculates the potential-flow wave load accurate to second order in wave height, which is a great improvement on ‘Morison's equation’: such results can currently only be sought by very much more complicated and computationally intensive methods, of currently uncertain repeatability. Moreover the third-order error is localized at the free-surface intersection, so the equation remains attractive for fully nonlinear problems involving intermittent immersion of lattice members, which are currently beyond even the most sophisticated of these computationally intensive methods. It is shown that the primary reason for this large contrast in computational efficiency is that the loads are derived from energy considerations rather than direct integration of surface pressures, which requires a lower level of flow detail for a given level of load-calculation accuracy.These improvements must of course be seen against the current levels of uncertainty over the calculation of vorticity-induced loads, which in many applications completely dwarf inaccuracies in potential-flow load calculation. The conditions are accordingly established under which the improvements are comparable to the total wave load predicted by the Morison drag and inertia terms in combination. They are that the lattice member diameter is greater than its length/10, or the relative fluid motion/5, or the structure's motion radius/20, or the wavelength/30: if any one of these conditions is satisfied, the new equation is worthwhile even when used in combination with simple vorticity-induced load calculations from a Morison drag term.
87 citations
TL;DR: In this paper, an algorithm based on a structural impedance approach has been developed to study the transient response of plates with arbitrary boundary conditions and subjected to moving loads, where thin plate theory is assumed for the plate model and the algorithm places no restrictions on the loading conditions.
43 citations
TL;DR: In this article, a dual-cavity coat-hanger die was designed to simulate polymeric fluid flow inside the die and the flow patterns in the outer cavity were computed by the finite element method so that the appearance of an undesirable vortex could be predicted.
Abstract: A method for the design and analysis of a dual-cavity coat-hanger die is presented in this paper. A macroscopic material balance and a microscopic flow analysis using the finite element method are combined to simulate polymeric fluid flow inside the die. Leonard's macroscopic procedure was adopted to include inertial, gravitational, and viscous effects, and the finite element method was then applied to estimate the contributions of inertial and viscous terms. In addition, the flow patterns in the outer cavity were computed by the finite element method so that the appearance of an undesirable vortex could be predicted. The residence time distributions for flow in the die were approximated by a simple, statistical approach. It was found through a case study that a dual-cavity coathanger die can effectively reduce the flow non-uniformities caused by fluid inertia and viscosity variations.
40 citations
TL;DR: In this paper, the effect of shear deformation upon the natural frequencies of a beam with classical boundary conditions can be estimated within the limits of practical accuracy by using a simple formula similar to the one used for simply supported beams.
36 citations
TL;DR: In this article, the authors discussed the instability of a gas cylinder in a moving infinite liquid under the action of capillary and inertia forces and showed that the motion of the liquid has always a destabilizing influence, which increases the region of instability.
Abstract: Instability of a gas cylinder in a moving infinite liquid under the action of capillary and inertia forces is discussed. The motion of the liquid has always a destabilizing influence, which increases the region of instability. But, the longitudinal wave number for the maximum instability does not change with the liquid velocity.
TL;DR: In this article, the authors present design equations and techniques for the complete shaking force and shaking moment balancing of four types of six-bar linkages due to both linear and rotary inertia, but excludes external loads.
TL;DR: In this article, the electrical field inside a uniformly charged, slowly accelerated spherical shell is calculated using the linearized gravitational field equations, and the relevance of this effect in connection with Mach's principle and the principle of relativity is discussed.
Abstract: The electrical field inside a uniformly charged, slowly accelerated spherical shell is calculated. The result is used to find the inertial translational dragging field inside a slowly accelerated spherical shell of dust particles, according to the linearized gravitational field equations. The relevance of this effect in connection with Mach's principle and the principle of relativity is discussed.
TL;DR: In this article, the authors generalize some matrix inertia theorems for the nonstationary case and generalize the Dichotomy Theorem for non-stationary matrix inertia.
Patent•
13 Nov 1989
TL;DR: In this article, a component which is installed for an absorption of energy with an ideal displacement-compressive force characteristic consists of a prismatic straight metal rod, which is long relative to its transverse dimensions and is adapted to inelastically buckle in the direction of the axis of its larger principal moment of inertia under an axially acting compressive load and is provided with spur teeth, which extend transversely to the longitudinal direction.
Abstract: A component which is to be installed for an absorption of energy with an ideal displacement-compressive force characteristic consists of a prismatic straight metal rod, which is long relative to its transverse dimensions and is adapted to inelastically buckle in the direction of the axis of its larger principal moment of inertia under an axially acting compressive load and is provided with spur teeth, which extend transversely to the longitudinal direction and are provided on at least one of the broadsides, which extend at right angles to the axis of the larger principal moment of inertia.
TL;DR: In this paper, the effects of the fluid film inertia forces on the performance of finite journal bearings were investigated using the finite difference method to determine the effect of the forces on loadcarrying capacity and attitude angle.
01 Sep 1989
TL;DR: A modeling scheme that uses the concepts of generalized and augmented links is proposed for computing joint-space inertia matrices of open-chain rigid body systems, and shows that the joint- space inertia-matrix of a six degree-of-freedom manipulator with revolute joints can be computed in approximately 420 multiplications and 339 additions.
Abstract: A modeling scheme that uses the concepts of generalized and augmented links is proposed for computing joint-space inertia matrices of open-chain rigid body systems. Expressions for evaluating these matrices are derived, utilizing orthogonal Cartesian tensors and the Newton-Euler equations of motion. The resulting recursive algorithm is applicable to all rigid-link manipulators having open-chain kinematic structures with revolute and/or prismatic joints. An efficient implementation of the algorithm shows that the joint-space inertia-matrix of a six degree-of-freedom manipulator with revolute joints can be computed in approximately 420 multiplications and 339 additions. For manipulators with 0 degrees to 90 degrees twist angles, the number of computations is reduced to 271 multiplications and 250 additions. >
TL;DR: In this article, the effect of temperature and pressure perturbations on the stability of a horizontal natural convection boundary flow in a saturated porous medium is examined by using the Forchheimer-extended Darcy equation of motion.
TL;DR: In this paper, an unconventional approach to teaching motion and inertia is presented and pupils' conceptual understanding has been carefully observed, where the concept of inertia is a difficult concept for young pupils.
Abstract: Inertia is a difficult concept for young pupils. An unconventional approach to teaching 'Motion and Inertia' is presented here and pupils' conceptual understanding has been carefully observed.
TL;DR: In this paper, an experimental investigation on regular wave induced forces on a smooth submarine pipeline fixed horizontally near a simulated seabed is carried out in the inertia dominated regime, where a simple poten...
Abstract: An experimental investigation on regular wave induced forces on a smooth submarine pipeline fixed horizontally near a simulated seabed is carried out in the inertia dominated regime. A simple poten...
14 May 1989
TL;DR: The results show that it is possible to estimate the parameters of a linearized or nonlinear rigid-body model with only a few percent error in spite of quantization effects, highly nonlinear friction and unmodeled elasticity and backslash.
Abstract: Several practical approaches to estimate the link inertia, gravity loading, and friction coefficients of a manipulator are discussed. All of the methods have been experimentally evaluated on a six-axis robot with conventional geared electric drives. The results show that it is possible to estimate the parameters of a linearized or nonlinear rigid-body model with only a few percent error in spite of quantization effects, highly nonlinear friction and unmodeled elasticity and backslash. Keys to successful parameter estimation in this case are careful choice of test motions, low-pass filtering of the data, and reduction of the model to the truly significant parameters. It has been demonstrated that a good match between measured torques and those predicted from the model for a certain test motion is a necessary but not sufficient condition for a good model. A model that has too many parameters with respect to the test motions considered may give a good match but perform poorly in regions of the workspace where no data were collected for the estimation. >
03 Apr 1989
TL;DR: In this paper, the authors proposed a generalization of Kane's equations for multibody codes to simulate the behavior of elastic structures undergoing large rotation and translation with small vibrations, which does not suffer from this defect and is valid for an arbifnary structure, and illustrative examples are given to demonstrate the validity and generality of the formulation.
Abstract: Conventional theories underlying my multibody codes used for simulating the behavior of elastic structures undergoing large rotation and translation with small vibrations fail to predict dynamic stiffening of the structures. This can lead to significantly incorrect simulations in many practical situations. A theory that does not suffer from this defect and is valid for an arbifnary structure is given here. The formulation is based on Kane's equations and consists of two steps: First, generalized inertia forces are written for an arbitrary structure for which one is forced to linearize prematurely in the modal coordinates; next, this defect in linearization is compensated for by the introduction of contributions to the generalized active forces from the "motion stiffness" of the stnrctwe. The stress associated with the motion stiffness is identified as due to 12 sets of inertia forces and 9 sets of inertia couples distributed throughout the body during ihe most general motion of its flying reference frame. An algorithm is set for a reader wishing to implement the theory, and illustrative examples are given to demonstrate tbe validity and generality of the formulation.
TL;DR: In this article, the sensitivities of the eigensystem of a manipulator's generalized inertia matrix with respect to kinematic (geometric and joint variable) parameters are used to form a set of indices as a measure of manipulator performance.
Abstract: The sensitivities of the eigensystem of a manipulator’s generalized inertia matrix with respect to kinematic (geometric and joint variable) parameters are used to form a set of indices as a measure of manipulator performance. The indices indicate the relative magnitude of the nonlinear forces (Coriolis and centripetal) and the effects due to the changes in geometric parameters. They also provide a new graphical means for delineating paths involving small nonlinear forces throughout the workspace. In addition, the inertia matrix is examined for invariance conditions. Finally, a design/path planning scenario is presented which utilizes the information provided by the indices.
TL;DR: In this paper, the effect of fluid inertia over the sill area on the rotordynamic coefficients of multirecess hybrid bearings has been investigated and it has been shown that only the direct stiffness coefficients amongst the various rotord dynamic coefficients are influenced by the inclusion of a fluid inertia effect over the sills.
14 May 1989
TL;DR: An efficient method of computation of the manipulator inertia matrix is presented, which leads to the definition of the composite rigid-body spatial inertia, which is a spatial representation of the notion of augmented body.
Abstract: An efficient method of computation of the manipulator inertia matrix is presented. Using spatial notations, the method leads to the definition of the composite rigid-body spatial inertia, which is a spatial representation of the notion of augmented body. The previously proposed methods, the physical interpretations leading to their derivation, and their redundancies are analyzed. The proposed method achieves a greater efficiency by eliminating the redundancy in the intrinsic equations as well as by a better choice of coordinate frame for their projection. In this case, removing the redundancy leads to greater efficiency of the computation in both serial and parallel senses. >
TL;DR: In this article, a microscopic study of slow collective dynamics of large scale and at finite intrinsic excitations is presented, where transport coefficients for average motion within linear response theory are computed.
31 Jan 1989
TL;DR: Modifications of the equations of motion from a direct drive system are developed and generalized to various cases encountered in robot manipulators.
Abstract: The effect of the joint drive system with gear reduction for a generic two-link system is studied. It is done by comparing the kinetic energy of such a system with that of a direct drive two-link system. The only difference are two terms involving the inertia of the motor rotor and gear ratio. Modifications of the equations of motion from a direct drive system are then developed and generalized to various cases encountered in robot manipulators.
21 Jun 1989
TL;DR: In this article, a learning controller for motion control of mechanical manipulators undergoing periodic tasks is developed, which does not require exact knowledge of the manipulator dynamical structure or its parameters, and is computationally efficient.
Abstract: A new learning controller for motion control of mechanical manipulators undergoing periodic tasks is developed. This controller does not require exact knowledge of the manipulator dynamical structure or its parameters, and is computationally efficient. In addition, no actual joint acceleration is needed in the control law, and the full nonlinear dynamics of the manipulator is fully accounted for in the convergence proof. Simulation results of this algorithm applied to a realistic Scara type manipulator [8], which includes friction, pay-load inertia variations, actuator/sensor noise, and unmodeled dynamics is also presented.
TL;DR: In this article, a mathematical framework is presented to handle an enlarged linear rotor-dynamics model which simultaneously includes both radial and misalignment motions, and a basis is developed for expanding physical insights by showing the individual interactive force and moment components into which this enlarged linear model decomposes the four inherent generalized forces.