Showing papers on "Inertia published in 1979"

Seismic Behavior of Gravity Retaining Walls

Abstract: First, the paper shows that in order to use the quasi-static Mononobe-Okabe analysis for the prediction of earthquake dynamic forces on a gravity retaining wall, wall inertia effects must be included. Second, a design procedure is developed in which the designer chooses an acceptable level of wall displacement: he then computes the design wall weight which will restrict displacement in an earthquake to the predetermined level. Wall inertia effects are shown to be of the same order as the dynamic soil thrust, and to be sensitive to vertical acceleration and to base and wall friction. Design recommendations are given which relate to proposed American provisions for seismic zoning.

The Theory of Ship Motions

Abstract: Publisher Summary This chapter highlights that the oceangoing ships are designed to operate in a wave environment that is frequently uncomfortable and sometimes hostile Unsteady motions and structural loading of the ship hull are two of the principal engineering problems that result Ships generally move with a mean forward velocity and their oscillatory motions in waves are superposed upon a steady flow field The solution of the steady-state problem is itself of interest, particularly with regard to the calculation of wave resistance in calm water The problem of ship motions in waves can be regarded as a superposition of these two special cases, but interactions between the steady and oscillatory flow fields complicate the more general problem The chapter also discusses the dynamics of ship motions that are governed by the equations of motion that balance the external forces and moments acting upon the ship, with the internal force and moment because of gravity and inertia Assuming the ship to be in stable equilibrium in calm water, its weight is balanced by the force of hydrostatic pressure Similarly, the steady drag and propulsive force are balanced These steady forces may be neglected and attention is focused on the unsteady perturbations

Theory of Minimum Rate of Energy Dissipation

Abstract: A general theory of minimum rate of energy dissipation for a class of open channel flows with or without the movement of sediment is proposed in this paper. This theory states that the rate of energy dissipation is a minimum under steady equilibrium or gradually varied flow conditions. The theory is derived from the Navier-Stoke's equations of motion for gradually varied open channel flow without sediment transport. It applies to turbulent and laminar flows as long as the inertia forces due to the time-averaged velocity distribution is small compared with the forces due to gravity and shear. The theory in different degrees of generality can be used to explain the fluvial processes from the movement of sediment to the change of velocity, slope, roughness, channel geometry, pattern, and profile of a river under an eqiulibrium condition or during the process of self-adjustment to reach an equilibrium condition.

Multiport representation of inertia properties of kinematic mechanisms

Abstract: The practical simplicity of obtaining equations of motion using the methods of Lagrange and Hamilton is lost in the algebra of the Euler-Lagrange equation when many nonlinear constraints exist among the physical coordinates in the energy state functions. Such is the case for mechanical systems containing kinematic mechanisms. This paper presents a technique which produces explicit Lagrange or Hamilton equations for mechanism dynamics suitable for computer solution. A general matrix description of mechanism kinematics and inertial properties permits the algebra of the reduction from physical to generalized coordinates to be performed symbolically or numerically by a digital computer. The physical inertia transformed into properties associated with the generalized coordinates of the mechanism displays both physical and artificial behavior to account for conservation of momentum, kinetic co-energy and energy. The method produces equations efficient for numerical calculation and provides insight into the complex inertial dynamics of mechanisms. Vector bond graphs provide a conceptual basis for the technique and describe the energetic structure of the equations. A numerical example illustrates the procedure and results.

Dynamic Frictional Effects as Measured from the Split Hopkinson Pressure Bar

Abstract: This paper presents the results of a simplified theoretical analysis to estimate both the effects of friction and inertia durting fast compression of a cylinder. The solution enables to eliminate stress errors developed in experiment due to presence of friction and inertia. Using this analysis it was attempted to estimate the static and dynamic coefficient of friction by compression of aluminum specimens of ten height-to-diameter ratios in the range from 0.1 to 1.0. It is concluded that the dynamic coefficient of friction, as estimated from experiments with the split Hopkinson bar /lubrication by the MoS2 powder/, is a bit larger than that estimated from the quasi-static experiments.

Optical strapdown inertia system

Abstract: An optical strapdown inertial system using passive laser gyros and passive laser accelerometers and a computer. These components may be disposed on "chips" in integrated optics format to provide an all solid-state system having no moving parts.

Nonlinear Inertia Forces on Bodies

Abstract: The theoretical influence of convective acceleration terms on the inertia force on a body is considered. The assumptions involved in using the inertia force are reviewed and an expression is derived for the inertia force acting on a body subjected to an unsteady and nonuniform flow of an inviscid fluid. Applications to a submerged sphere and to horizontal and vertical cylinders in waves are considered and differences between alternative predictions of the nonlinear inertia forces are compared. It is reassuring to find that the predicted forces are generally less than those calculated when convective acceleration terms are neglected.

The influence of fluid inertia, viscosity and extra stress on the load bearing capacity of a squeeze film of oil

Abstract: Equations are derived giving the force required to cause squeeze-film motion of flat plates separated by a liquid. Two geometries are considered, discs and flat strips, and the forces calculated are those arising from fluid viscosity (Newtonian and power-law fluids), fluid inertia and from normal stresses which may be present in the liquid. The assumptions made are carefully described. These include the additive nature of the various contributions to load bearing capacity, the existence of a “power law” relationship between normal stress and shear rate and the existence of relationships between the components of normal stress. It is shown that the force developed due to the presence of normal stresses is not strongly dependent on the relationship chosen between the components of normal stress. The influence of different variables on the contributions to load bearing is examined in a realistic squeeze film situation by using experimental data for hot, polymer-thickened oils in conjunction with the derived equations. It is shown that both fluid inertia and normal stress effects assist the load bearing process if the approach velocity of the surfaces is sufficiently high. This important conclusion has not been reached in most theoretical approaches to the problem, though it has been demonstrated experimentally.

An Introduction to the Variable Inertia Flywheel (VIF)

Abstract: A flywheel with variable moment of inertia, combining the functions of energy storage and power control is introduced. Potential designs are presented and the basic physical governing equations developed. Examples of the flywheel system powering a constant angular rate, frictional load, and an accelerating automobile are presented. Limitations of and potential for future development which become evident in the examples are discussed.

Bi-directional rotary impact tool for applying a torque force

Abstract: A rotary impact tool of the type for applying a torque force and having an input, output and spring-accelerated inertia members and journaled on each other for rotative movement relative to each other and a cam connected for conjoined rotation with the input member and for actuating juxtaposed pawls carried by the inertia member into and out impact engagement with circumferentially spaced teeth on the output member for driving the latter, the cam being so shaped and positioned relative to the input inertia and output members to coact with the pawls so as to provide impact engagement of the pawls with the spaced teeth of the output member in both directions of rotation. In another aspect of the invention, the cam is capable of angular adjustment relative to the input and inertia members to predetermined positions to achieve impact driving forces of different magnitude or to apply impact driving force in one direction or the opposite direction of rotation.

A Numerical Procedure for the Dynamic Plastic Response of Beams with Rotatory Inertia and Transverse Shear Effects

Abstract: A numerical procedure is used to examine the influence of transverse shear forces in the yield criterion and rotatory inertia on the dynamic plastic response of beams. Various results are presented for a long beam impacted by a mass and a simply supported beam loaded impulsively, both of which are made from a rigid perfectly plastic material with yielding controlled by the Ilyushin-Shapiro ield criterion. Transverse shear effects lead to a dramatic reduction in the slopes of the deformed profiles for both beam problems. Moreover, the slope of the deformed profile underneath the striker in the impact problem is quite sensitive to the actual shape of a yield curve, while the maximum transverse displacement is less sensitive. The retention of rotatory inertia in the basic equations leads to further reductions up to 17 and 10% in the slopes and maximum transverse displacements, respectively.

Analysis of Step Journal Bearings—Infinite Length, Inertia Effects

Abstract: This paper analyzes infinitely long centered and eccentric step journal bearings using finite elements. Step inertia and turbulence effects are included. The analysis is verified by comparison with other theoretical and experimental results for centered step bearings. Results of a parametric study for the centered case considering both turbulence and step inertia effects predict optimum step geometrics similar to those predicted by pure laminar theory. Neglecting the pressure drop due to inertia forces at the step, but including the effects of turbulence around the bearing, produces errors less than 10 percent in both load capacity and dynamic coefficients for Reynolds numbers less than 1500. This analysis concludes that finite length step bearings with oil lubricants may be adequately analyzed without taking into account step inertia effects. Presented at the 33rd Annual Meeting in Dearborn, Michigan, April 17–20, 1978

Hydrodynamic reactions to propeller vibrations

Abstract: The unsteady dynamic loads resulting from a propeller running in a non-uniform wake induce propeller vibrations, and, depending on the magnitude of these vibrations, reactions of the surrounding water will occur. These reactions are effects of added masses and added monents of inertia, and of damping, and the Authors, of the Netherlands Ship Model Basin, have here used unsteady lifting-surface theory to calculate them for a number of propellers from the Wageningen B series. The study is presented in some detail, and it is shown that, for the propellers investigated, the added masses and moments of inertia have an important, more or less linear, relationship with the blade area ratio and a weaker relationship with the pitch. For the axial transitory vibrations, a simple expression for the added mass, and for the damping, has been derived; the general validity has to be investigated further. More work is also required on the other hydrodynamic reaction effects. It is also found that the relationships between added masses and moments of inertia, with respect to the corresponding propeller values, are neither linear nor constant. The added masses and moments of inertia have such values that they essentially influence the natural frequencies. The effect of the hydrodynamic reactions in relation to damping is smallest for the longitudinal vibrations (about 3%) of the critical damping and the largest for the transverse vibrations (about 9%). An accurate determination of these hydrodynamic reactions is essential in modern vibration analysis. Order form BSRA as No. 51,909.

Arrangement for the compensation of inertia forces in the reciprocating driving of a machine element

Abstract: When a machine element having a large mass is given a reciprocating movement, the recurring changes in speed as well as direction of movement require that very great driving forces must be applied, which cause varying stresses on the driving unit. In case the movement path of the machine element is more or less vertical the force of gravity causes extra stresses on the machine element. These difficulties are overcome in accordance with the invention by providing a spring system which on the one hand equalizes the effect of the force of gravity on the machine element and, on the other hand compensates the arising mass forces by absorbing, storing and emitting energy following the movement of the machine element. Hereby the amount of applied driving force is reduced, so that shocks and vibrations occurring during the driving are effectively reduced.

Inertia Calculation Procedure for Preliminary Design

Abstract: : This report explains the methods involved in estimating aircraft moments of inertia for preliminary design purposes Assumptions that were made for this procedure and the derivation of equations that evolved from these assumptions are included An example using the method on the C-5A aircraft is shown This procedure requires a knowledge of the major aircraft group weights, the location of major components (landing gear, avionics bay, etc), geometry information, and inertias of some major subsystem items Using this data, the moments of inertia about the roll, pitch, and yaw axes are calculated as well as the roll-yaw cross-product of inertia

Power Requirement of Horizontal Cylindrical Mixer

Abstract: Power requirement of horizontal cylindrical mixers has been measured with a variety of solid powders.A dimensional analysis of the basic force balance equations including gravity, inertia and friction forces has been made to obtain useful correlation of the power data in terms of the operating conditions and the dimensions of the mixers and the properties of the powders (specifically, the bulk density and the friction factor between the vessel wall and the powders bed).The Newton number and the Froude number, both non-dimensional terms have been found important for the estimatioil of power requirement for this type of mixer. They can be correlated by the following equation:[Newton No.]=A+B [Froude No.]where, A and B are constant. These are functions of the charge ratio, the angle of repose and the friction coefficient of wall. The values of the above constants, A and B, have been calculated for the various conditions, and power requirement has been estimated. An agreement between the measured power and the one predicted by the correlations is within an accuracy of ±20%.

The role of inertial effects in macroparticle diffusion

Abstract: The influence of macroparticle and solvent inertia on diffusion of interacting spherical Brownian particles is studied. Results are applied to the determination of the spectrum of light and neutrons scattered quasielastically from solutions of macroparticles.

Inertia dependent sensor - has cardanically mounted inertia body with pivotally mounted release arm for release and/or blocking of safety members

Abstract: The inertia-dependent sensor has a second inertia body (15) with an at most equal mass moment of inertia as the first inertia body on which the second body is mounted movably. The second inertia body has at its lower end on the outside a sharp edge (38) which fits movably into a sharp groove (37) at the top in the first inertia body (9). A frame (10) is used as cardanic suspension of the first inertia body. The second inertia body is positioned tight up against a curved face of the release arm.

A cylindrical pulsar magnetosphere model with particle inertia

Abstract: An investigation is made of the equations to a steadily rotating nonaxisymmetric pulsar magnetosphere model, with the effects of particle inertia fully incorporated but with no dissipative forces. As an illustrative example the basic theory is applied to a 'cylindrical pulsar' model, in which quantities do not vary parallel to the rotation axis. It is shown that Endean's Bernoulli-type integral imposes severe constraints on particle motion, indicating that, in a realistic model, dissipation (e.g. by radiation damping) may play an essential role.

Seismic design of gravity retaining walls

Abstract: Starting from the Mononobe-Okabe analysis, the seismic behaviour of gravity retaining walls is investigated. The importance of including wall inertia effects is demonstrated. The sensitivity of the results to changes in various parameters is explored: care must be taken in some ranges. For a moderately severe earthquake, it is shown that most walls will move, but that the movement is finite, and calculable. An approximate expression is given for the expected displacement. From this, a design approach is developed in which the designer chooses an allowable displacement, uses it to compute a design acceleration coefficient, and then computes the wall mass required.

Dynamics of a Nuclear-Reactor Shell Structure in an Incompressible Fluid

Abstract: In this paper, a numerical model of dynamical interactions of structures with fluids in a pressurized water reactor (PWR) vessel is described. The present investigation forms part of a more extended experimental and theoretical program in which the former HDR-reactor is used as a test facility [1, 2]. Similar fluid-solid interaction simulations are described in [3, 4]. The goal of the computation is to determine the stresses which are induced in the core barrel during a blowdown accident which is assumed to be initiated by break of one of the cold legs of the primary coolant circuits, see Fig. 1. It has been argued [1, 2] that the computed stresses are significantly reduced if the elasticity of the (rather thin) core barrel is taken into account (the vessel itself is assumed to be rigid). The calculation of the fluid motion during a blow-down is a hard problem on its own because of the complicated three-dimensional (3D) geometry and diversity of physical effects involved (inertia, friction, evaporation, compressibility etc.).