Modeling of the response of a seated passenger to vibrations and impulsive forces

2021 ◽  
Author(s):  
Riccardo Conti
Keyword(s):  
Impulsive Forces

Dominance of Shear Stresses in Early Stages of Impulsive Motion of Beams

1960 ◽  
Vol 27 (1) ◽  
pp. 132-138 ◽  
Author(s):  
H. H. Bleich ◽  
R. Shaw
Keyword(s):  
Differential Equations ◽  
Timoshenko Beam ◽  
Shear Stresses ◽  
Impulsive Motion ◽  
Early Stages ◽  
Plastic Analysis ◽  
Bending Stresses ◽  
Impulsive Forces

In order to compare the magnitude of bending stresses and shear stresses in beams under the action of impulsive forces, the values of these stresses are determined from the known differential equations for the Timoshenko beam. It is found that in the early stages, soon after the initiation of the motion, the shear stresses are of much larger magnitude than the bending stresses. This result indicates that for sufficiently large initial velocities first yielding will be in shear, a matter of consequence in plastic analysis.

POD Analysis of the Impact Dynamics of the Olive Tree Branch: Nature’s Paradigm of a Complex Soft-Stiff Structural System in Biomechanics

2017 ◽  
Author(s):  
Ioannis T. Georgiou
Keyword(s):  
Nonlinear Vibrations ◽  
Field Measurements ◽  
Olive Tree ◽  
Structural System ◽  
Impulsive Forces ◽  
Spatio Temporal ◽  
Pod Analysis ◽  
Complete Detachment ◽  
Tree Branch ◽  
The Impact

Geometry consistent spatio-temporal measurements of the experimental acceleration of olive tree branches were analyzed with advanced POD tools in an effort to gain knowledge on the mechanics-dynamics of this bio-mechanical structure. To pave the way for understanding the dynamics of this system, both the typical olive tree as a whole and its typical branch are approached as interacting soft-stiff continuum mechanical systems. The POD analysis reveals that the impact response is a nonlinear vibration with very fast dissipation. The POD modal amplitudes are nonlinear vibrations of continuous, broadband frequency spectrum. Initially they exhibit regular phases of nonlinear slow dissipation-and-amplification followed by irregular, fast dissipation-and-amplification phases. Sequentially applied impacts at the branch soft area results in a complete detachment of the fruit. The POD analysis reveals that this occurs because the response is highly localized in the soft area where the impact is applied and thus it transfers its momentum to the fruits. The work is supplemented with analysis of field measurements of the acceleration dynamics of orchard olive tree branches excited by harvesting devices generating combing clouds of impulsive forces aimed at detaching the olive fruit by momentum transfer.

Length to diameter ratio of extrudates in catalyst technology I. Modeling catalyst breakage by impulsive forces

AIChE Journal ◽  
2015 ◽  
Vol 62 (3) ◽  
pp. 639-647 ◽  
Author(s):  
Jean W. L. Beeckman ◽  
Natalie A. Fassbender ◽  
Theodore E. Datz
Keyword(s):  
Diameter Ratio ◽  
Impulsive Forces ◽  
Length To Diameter Ratio

A Note on the Computation of the Euler Parameters

2000 ◽  
Vol 123 (4) ◽  
pp. 719-722 ◽  
Author(s):  
Lars Johansson
Keyword(s):  
Computational Algorithm ◽  
Closed Form Solution ◽  
Form Solution ◽  
Constant Angular Velocity ◽  
Euler Parameters ◽  
Order Accuracy ◽  
Order Continuity ◽  
Piecewise Constant ◽  
Angular Velocities ◽  
Impulsive Forces

This paper is concerned with the integration of the differential equations for the Euler parameters, for the purpose of describing the orientation of a rigid body. This can be done using standard methods, but in some cases, such as in the presence of impulsive forces, the angular velocities are not continuous and methods based on high order continuity are not appropriate. In this paper, the use of the closed-form solution for piecewise constant angular velocity as the basis for a computational algorithm is studied. It is seen that if this solution is implemented in a leapfrog manner a method with second-order accuracy is obtained in the smooth case, while this method also makes sense in the discontinuous case.

scholarly journals Elastic waves in a prestressed Mooney material

1972 ◽  
Vol 7 (1) ◽  
pp. 135-160 ◽  
Author(s):  
J.A. Belward
Keyword(s):  
Simple Form ◽  
Fourier Transforms ◽  
Secular Equation ◽  
Sufficient Conditions ◽  
Axially Symmetric ◽  
Transverse Waves ◽  
Wave Speeds ◽  
Impulsive Forces ◽  
Plane Wavefront ◽  
Necessary And Sufficient

The dynamic response of a prestressed incompressible Mooney material is studied by investigating plane wave propagation and the response of the material to impulsive lines of force. The choice of an initial deformation which is axially symmetric gives a particularly simple form for the secular equation for the plane wavefront velocities. The speeds of propagation and the amplitudes of the two permissible transverse waves are found and necessary and sufficient conditions for there to exist two real wave speeds in all directions are established. The simple form of the secular equation enables the response of the material to concentrated disturbances to be readily solved using Fourier transforms. The motions caused by a line of impulsive forces is examined in some detail.

The determinants of impulsive forces at heel strike of women walking at a naturally selected walking speed

1992 ◽  
Vol 25 (7) ◽  
pp. 741
Author(s):  
David G. Lloyd ◽  
Jacqui Raymond ◽  
Stephen R. Lord ◽  
Noel L. Svensson
Keyword(s):  
Walking Speed ◽  
Heel Strike ◽  
Impulsive Forces

Dynamic Analysis of Mechanical Systems With Intermittent Motion

1982 ◽  
Vol 104 (4) ◽  
pp. 778-784 ◽  
Author(s):  
R. A. Wehage ◽  
E. J. Haug
Keyword(s):  
Dynamic Analysis ◽  
Numerical Integration ◽  
Large Scale ◽  
Mechanical Systems ◽  
Integration Algorithm ◽  
Large Scale Systems ◽  
Jump Discontinuities ◽  
Impulsive Forces ◽  
Computer Generation ◽  
Intermittent Motion

A method is presented for dynamic analysis of systems with impulsive forces, impact, discontinuous constraints, and discontinuous velocities. A method of computer generation of the equations of planar motion and impulse-momentum relations that define jump discontinuities in system velocity for large scale systems is presented. An event predictor, working in conjunction with a new numerical integration algorithm, efficiently controls the numerical integration and allows for automatic equation reformulation. A weapon mechanism and a trip plow are simulated using the method to illustrate its capabilities.

Recovering the Timing of Impulsive Forces From Noisy Vibration Transients

1995 ◽  
Author(s):  
Daniel J. McCarthy ◽  
Richard H. Lyon
Keyword(s):  
Phase Behavior ◽  
Vibration Signal ◽  
Transient Vibration ◽  
Nonminimum Phase ◽  
Impact Forces ◽  
Impulsive Forces ◽  
Exponential Window ◽  
Pure Delay ◽  
Group Delays ◽  
Impulsive Source

Abstract A transient vibration signal can be processed to extract information about impulsive forces within a machine, by removing the effects of dispersion and reverberation. These source waveform signatures, like the timing and strength of valve impact forces within a reciprocating air compressor, can then be used to diagnose machine faults. Stable and causal inverse filters are guaranteed through the use of minimum-phase processing. Unfortunately, the timing of the impulsive source waveform is lost in this manner. A technique to accurately recover the timing is highly desirable. The time of occurrence of the force input can be robustly obtained from the frequency-averaged group delays of the transfer function and vibration response once the nonminimum-phase behavior of the signals, except that due to pure delay, has been removed. This is best done with the allpass components of the signals because, in addition to the nonminimum-phase inherently present in a structure due to reverberation, additional nonminimum-phase zeros can be artificially introduced by data truncation. Since only the phase is of interest, the nonminimum-phase behavior can be removed by electronically damping the signals with exponential windows, effectively de-reverberating them. In some instances the timing of the impulsive source events that we aim to recover will change as faults develop; also, in any machine there will be some normal random variation in the timing of internal events like valve impacts. The correct timing can be determined in the presence of this inherent variability through the use of a sliding exponential window and statistical curve fitting.

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