Dynamic Force and Torque Analysis of Mechanisms Using Dual Vectors and 3 × 3 Screw Matrix

1972 ◽  
Vol 94 (2) ◽  
pp. 738-745 ◽  
Author(s):  
Cemil Bagci
Keyword(s):  
Rate Of Change ◽  
Inertia Force ◽  
Dynamic Force ◽  
Equilibrium Equations ◽  
Force Vector ◽  
Time Rate ◽  
Output Force ◽  
Dynamic Analyses ◽  
Torque Analysis ◽  
Space Mechanisms

The method of determining dynamic force and torque distributions in mechanisms by using dual vectors and 3 × 3 screw matrix is presented. The dual equilibrium equations for each moving link of a mechanism are written as a null resultant dual force vector in a reference system located on the link. The resulting 6 × (n – 1) equilibrium equations for an n-link mechanism are solved for the unknown force and torque components at the pair locations, and for the input force or torque required to drive the mechanism to produce the specified dual output force. The dynamics of the mechanism is governed by introducing the dual inertia force acting on a link, which is determined as the negative of the time rate of change in the dual momentum of the link due to its own mass and mass moments of inertia, in the dual equilibrium equation for that link. Dynamic analyses of the 4R plane and the RCCC space mechanisms are performed. Dynamic transmissivities are defined. The RCCC mechanism is analyzed in a numerical example and the results of the dynamic distributions are compared with those of static distributions.

Dynamic Force and Torque Analysis of a Spherical Four-Bar Mechanism

1995 ◽  
Author(s):  
J. R. Dooley
Keyword(s):  
Dynamic Analysis ◽  
Dynamic Force ◽  
Accurate Model ◽  
Dynamic Analyses ◽  
Torque Analysis

Abstract Spherical four-bar linkages are compact mechanisms capable of motion outside the plane and transmission between intersecting shafts. Dynamic analyses of spherical four-bar linkages are complicated by the fact that they are statically indeterminate. Previous solutions have used an RCCC approximation to model the 4R linkage. This paper extends previous results to include the material elasticity in the dynamic analysis. The results of this more accurate model are compared to those obtained from the RCCC model and it is shown that the RCCC approximation yields significant errors.

Static Force and Torque Analysis Using 3 × 3 Screw Matrix, and Transmission Criteria for Space Mechanisms

1971 ◽  
Vol 93 (1) ◽  
pp. 90-101 ◽  
Author(s):  
C. Bagci
Keyword(s):  
Static Force ◽  
Equilibrium Equations ◽  
Torque Distribution ◽  
Dual Vector ◽  
Output Torque ◽  
Transmission Angle ◽  
Torque Analysis ◽  
Force Components ◽  
Space Mechanisms ◽  
Input Torque

The method of determining the static force and torque distributions in space mechanisms by use of the 3 × 3 screw matrix is presented. Transmissivities in favor of rotation and translation, and angles of transmission in space mechanisms are defined. Transmissivities are used to show why some space mechanisms have no dead center positions. In the process, the dual equilibrium equations, one for each link, are written in dual vector form, then they are solved simultaneously for the dual force components. Explicit expressions for forces and torques in the RCCC and RSSR space mechanisms are obtained. Torque distribution in the spherical four-bar mechanism is reduced from the results for the RCCC space mechanism. The numerical example considers a symmetrical crank-rocker RSSR space mechanism, where the output torque is due to the load inertia. Variations in the input torque, output torque, mechanical advantage, and transmission angle for one cycle are given for both geometric inversions.

Dynamic Force and Torque Analysis of Spherical Four Link Mechanisms

1983 ◽  
Vol 105 (3) ◽  
pp. 492-497 ◽  
Author(s):  
A. T. Yang ◽  
Sun Zhishang
Keyword(s):  
Dynamic Analysis ◽  
Optimum Design ◽  
Mass Distribution ◽  
High Speed ◽  
Dynamic Force ◽  
Arbitrary Mass ◽  
Link Mechanism ◽  
Torque Analysis ◽  
Analytical Expressions

In this paper we present a dynamic analysis of a general spherical four-link mechanism whose links have arbitrary mass distribution. Results, which are in explicit analytical expressions in terms of inertia-induced forces and moments in links, are useful for optimum design of the mechanism under high-speed operation.

STUDY OF PHASE PROPAGATION IN SUPERCONDUCTING ALUMINUM BY ULTRASONIC ATTENUATION MEASUREMENTS

1959 ◽  
Vol 37 (5) ◽  
pp. 614-618 ◽  
Author(s):  
K. L. Chopra ◽  
T. S. Hutchison
Keyword(s):  
Magnetic Field ◽  
Eddy Current ◽  
Ultrasonic Attenuation ◽  
Cylindrical Specimen ◽  
Current Theory ◽  
Superconducting Phase ◽  
Rate Of Change ◽  
Time Rate ◽  
Phase Propagation ◽  
The Magnetic Field

The phase propagation in superconducting aluminum has been studied by measuring the time rate of change of ultrasonic attenuation. The time taken for the destruction of the superconducting phase in a cylindrical specimen, by means of a magnetic field, H, greater than the critical field, Hc, is approximately proportional to{H/(H–Hc)} in agreement with eddy-current theory. In the converse case, where the superconducting phase is restored by switching off the magnetic field H (>Hc), the total time taken is nearly independent of the temperature (or Hc) as well as H. The superconducting phase grows at a non-uniform volume rate which is considerably less than the uniform rate of collapse.

Contractile force of canine airway smooth muscle during cyclical length changes

1983 ◽  
Vol 55 (3) ◽  
pp. 759-769 ◽  
Author(s):  
S. J. Gunst
Keyword(s):  
Muscle Force ◽  
Isometric Force ◽  
Smooth Muscles ◽  
Rate Of Change ◽  
Dynamic Force ◽  
Airway Caliber ◽  
Length Changes ◽  
Isometric Muscle ◽  
Isometric Muscle Force

Strips of tonically contracted canine tracheal and bronchial airway smooth muscles (AWSM) were studied in vitro to compare dynamic muscle force during stretch-retraction cycles with static isometric muscle force at various length points within the cycling range. At any particular rate, a characteristic force-length loop was obtained by cycling over a given range of lengths. Dynamic muscle force dropped well below static isometric muscle force at lengths short of the peak length at all rates of cycling. When stretch or retraction of the muscle was stopped at any point along either path of the cycle, muscle force rose to approach the isometric force at that length. Dynamic force at the peak length of the cycle remained close to, or slightly greater than, the static isometric force. The results suggest that the velocity of shortening of tonically contracted AWSM is very slow relative to the rates of cycling employed. A slow rate of shortening of AWSM relative to the rate of change in airway caliber during breathing could account for well-known effects of volume history on airway tone.

Cosmic-Ray Energy Changes

1974 ◽  
Vol 2 (5) ◽  
pp. 297-299 ◽  
Author(s):  
L. J. Gleeson ◽  
G. M. Webb
Keyword(s):  
Cosmic Rays ◽  
Current Density ◽  
Cosmic Ray ◽  
Rate Of Change ◽  
Time Rate ◽  
Differential Current

The purpose of this paper is to provide a new expression for < ṗ > the average time-rate-of-change of momentum of cosmic-ray particles propagating in the interplanetary region. The expression derived replaces the previously used adiabatic deceleration formula and it is arrived at by a rearrangement and reinterpretation of the well known equation of transport for cosmic-rays. Thus, although we provide a new expression for < ṗ > we maintain the equation of transport and do not render invalid results for differential intensity and differential current density of cosmic-ray particles obtained by its solution (Jokipii 1971; Gleeson 1972).

Sound and turbulence modulation by particles in high-speed shear flows

2019 ◽  
Vol 875 ◽  
pp. 254-285 ◽  
Author(s):  
David A. Buchta ◽  
Gregory Shallcross ◽  
Jesse Capecelatro
Keyword(s):  
Gas Phase ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Sound Radiation ◽  
Rate Of Change ◽  
Intensity Increase ◽  
Mass Loading ◽  
Local Pressure ◽  
Time Rate ◽  
Particle Laden Flows

High-speed free-shear-flow turbulence, laden with droplets or particles, can radiate weaker pressure fluctuations than its unladen counterpart. In this study, Eulerian–Lagrangian simulations of high-speed temporally evolving shear layers laden with monodisperse, adiabatic, inertial particles are used to examine particle–turbulence interactions and their effect on radiated pressure fluctuations. An evolution equation for gas-phase pressure intensity is formulated for particle-laden flows, and local mechanisms of pressure changes are quantified over a range of Mach numbers and particle mass loadings. Particle–turbulence interactions alter the local pressure intensity directly via volume displacement (due to the flow of finite-size particles) and drag coupling (due to local slip velocity between phases), and indirectly through significant turbulence changes. The sound radiation intensity near subsonic mixing layers increases with mass loading, consistent with existing low Mach number theory. For supersonic flows, sound levels decrease with mass loading, consistent with trends observed in previous experiments. Particle-laden cases exhibit reduced turbulent kinetic energy compared to single-phase flow, providing one source of their sound changes; however, the subsonic flow does not support such an obvious source-to-sound decomposition to explain its sound intensity increase. Despite its decrease in turbulence intensity, the louder particle-laden subsonic flows show an increase in the magnitude and time-rate-of-change of fluid dilatation, providing a mechanism for its increased sound radiation. Contrasting this, the quieter supersonic particle-laden flows exhibit decreased gas-phase dilatation yet its time-rate-of-change is relatively insensitive to mass loading, supporting such a connection.

A PC-Based Modeling Tool for Creep, Fatigue, and Creep-Fatigue Interactions Using a Viscoplasticity Theory

1991 ◽  
Vol 113 (2) ◽  
pp. 174-179 ◽  
Author(s):  
J. T. Fong ◽  
B. Bernstein
Keyword(s):  
Elevated Temperatures ◽  
Helmholtz Free Energy ◽  
Thermodynamic Theory ◽  
Rate Of Change ◽  
Free Energy Function ◽  
Explicit Dependence ◽  
Time Rate ◽  
Modeling Tools ◽  
One Dimensional ◽  
Creep Fatigue

Computational results for modeling one-dimensional stress relaxation, creep, fatigue, and creep-fatigue interaction phenomena of metals at elevated temperatures using a unifying thermodynamic theory of viscoplasticity are presented. The theory incorporates in a nonequilibrium formulation the idea of a “concealed” parameter α, originally due to Bridgman (1950), where the constitutive equations are governed by 1) a thermodynamic potential such as the Helmholtz free energy function F with an explicit dependence on α, and 2) a prescription for α˙, the time rate of change of α, such that α˙ is proportional to −Fα, the negative of the partial derivative of F with respect to α. Significance of the results and a comparison with other modeling tools in the literature are discussed.

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