A study of the dissipation of energy in the helmet due to a blast on a helmet–skull–brain assembly

2021 ◽  
Vol 257 ◽  
pp. 113124
Author(s):  
P. Alagappan ◽  
A. Muliana ◽  
K.R. Rajagopal
Keyword(s):  
Dissipation Of Energy

Study On Energy Dissipation Mechanism of an Impact Damper System

2022 ◽  
Author(s):  
Vinayaravi R ◽  
Jayaraj Kochupillai ◽  
Kumaresan D ◽  
Asraff A. K
Keyword(s):  
Energy Dissipation ◽  
Numerical Simulations ◽  
Fundamental Frequency ◽  
Low Frequency ◽  
High Amplitude ◽  
Lagrangian Multiplier ◽  
Impact Damper ◽  
Contact Algorithm ◽  
Dissipation Of Energy ◽  
Excitation Time

Abstract The objective of this paper is to investigate how higher damping is achieved by energy dissipation as high-frequency vibration due to the addition of impact mass. In an impact damper system, collision between primary and impact masses cause an exchange of momentum resulting in dissipation of energy. A numerical model is developed to study the dynamic behaviour of an impact damper system using a MDOF system with Augmented Lagrangian Multiplier contact algorithm. Mathematical modelling and numerical simulations are carried out using ANSYS FEA package. Studies are carried out for various mass ratios subjecting the system to low-frequency high amplitude excitation. Time responses obtained from numerical simulations at fundamental mode when the system is excited in the vicinity of its fundamental frequency are validated by comparing with experimental results. Magnification factor evaluated from numerical simulation results is comparable with those obtained from experimental data. The transient response obtained from numerical simulations is used to study the behaviour of first three modes of the system excited in vicinity of its fundamental frequency. It is inferred that dissipation of energy is a main reason for achieving higher damping for an impact damper system in addition to being transformed to heat, sound, and/or those required to deform a body.

Damping in Unidirectional and Cross-Ply Ceramic Matrix Composites With Matrix Cracks

2001 ◽  
Author(s):  
Victor Birman ◽  
Larry W. Byrd
Keyword(s):  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Interfacial Friction ◽  
Matrix Composites ◽  
Matrix Interface ◽  
Unidirectional Composites ◽  
Matrix Cracks ◽  
Dissipation Of Energy ◽  
Fiber Matrix Interface ◽  
Fiber Matrix

Abstract The paper elucidates the methods of estimating damping in ceramic matrix composites (CMC) with matrix cracks. Unidirectional composites with bridging matrix cracks and cross-ply laminates with tunneling cracks in transverse layers and bridging cracks in longitudinal layers are considered. It is shown that bridging matrix cracks may dramatically increase damping in unidirectional CMC due to a dissipation of energy along damaged sections of the fiber-matrix interface (interfacial friction). Such friction is absent in the case of tunneling cracks in transverse layers of cross-ply laminates where the changes in damping due to a degradation of the stiffness remain small. However, damping in cross-ply laminates abruptly increases if bridging cracks appear in the longitudinal layers.

scholarly journals 2. On Vortex Motion

1872 ◽  
Vol 7 ◽  
pp. 576-577
Author(s):  
William Thomson
Keyword(s):  
Royal Society ◽  
Vortex Motion ◽  
Bounding Surface ◽  
Initial Shape ◽  
Liquid Mass ◽  
Dissipation Of Energy ◽  
Surrounding Liquid ◽  
Initial Motion

AbstractThis paper is a sequel to several communications which have already appeared in the Proceedings and Transactions of the Royal Society of Edinburgh. It commences with an investigation of the circumstances under which a portion of an incompressible frictionless liquid, supposed to extend through all space, or through space wholly or partially bounded by a rigid solid, can be projected so as to continue to move through the surrounding liquid without change of shape; and goes on to investigate vibrations executed by a portion of liquid so projected, and slightly disturbed from the condition that gives uniformity. The greatest and least quantities of energy which a finite liquid mass of any given initial shape and any given initial motion can possess, after any variations of its bounding surface ending in the initial shape, are next investigated; and the theory of the dissipation of energy in a finite or infinite frictionless liquid is deduced.

scholarly journals The atomic process in ferromagnetic Induction

1922 ◽  
Vol 100 (706) ◽  
pp. 449-460 ◽  
Keyword(s):  
Magnetic Particles ◽  
Strong Field ◽  
Molecular Magnets ◽  
Magnetic Element ◽  
Atomic Process ◽  
Dissipation Of Energy ◽  
Unstable Phase ◽  
Complete Alignment ◽  
The Stability ◽  
Ferromagnetic Substance

The object of this paper is to amend, in an important particular, the theory of ferromagnetic induction put forward by me more than 30 years ago, and to describe a new model. That theory was itself a modification of the earlier theory of Weber. To Weber is due the fundamental notion that a substance contains minute particles, each of which acts as a magnet, and that in the process of magnetising a ferromagnetic substance these are turned into more or less complete alignment. The ultimate magnetic particles use to be called “molecular magnets”: we now recognise them as attributes of the atom, not of the molecule, and (in all probability) they derive their magnetic moment from the circulation of electricity in electron orbits or in ring electrons. What turns is not the molecule nor the atom, but something within the atom. The characteristics which distinguish ferromagnetic substances from other paramagnetics are: (1) the much larger amount of magnetism they can acquire under the action of an impressed field; (2) the fact that the acquired magnetism tends towards a saturation limit when the field is progressively increased; (3) the fact that the acquired magnetism shows hysteresis with respect to variations of the field, except in certain small initial changes. Weber’s theory explained (1) and (2). My modification of it explained, in addition, (3) as an effect of the irreversible action which occurs when the equilibrium of a magnetic element becomes unstable through change in the externally impressed magnetic force, and it swings over, with dissipation of energy, into a new position of stability. The stability in both positions is sufficiently explained by magnetic forces only. In breaking away from one stable position it is deflected at first in a quasi­-elastic (reversible) manner until the external force reaches a certain value at which the equilibrium is upset. The essence of hysteresis is the turning from one position of stability to another, through a region of instability. If the conditions are such that there is no unstable phase in the turning, then there is no dissipation of energy, and consequently no hysteresis. This occurs in very feeble magnetisation, when the deflections are reversible; it also occurs if the piece be caused to rotate in a field of great strength. J. Swinburne pointed out that, as a consequence of my theory, hysteresis should vanish when a cylinder of ferromagnetic metal is rotated in a very strong field, and this curious result was confirmed experimentally by F. G. Baily.

scholarly journals DISSIPATION OF ENERGY OF A CIRCULAR JET SUBMERGED IN WATER

1960 ◽  
pp. 704-713
Author(s):  
N. S. GOVINDA RAO ◽  
K. SEETHARAMAIAH ◽  
N. V. CHANDRASEKHARA SWAMY
Keyword(s):  
Dissipation Of Energy

scholarly journals Dissipation of energy in the environment with turbulent viscosity and a Hill vortex

2019 ◽  
Vol 486 (6) ◽  
pp. 673-674
Author(s):  
G. F. Krymsky
Keyword(s):  
Shear Modulus ◽  
Mechanical Energy ◽  
Turbulent Viscosity ◽  
New Approach ◽  
Dissipation Of Energy

A new approach to calculation of the dissipation of mechanical energy in the environment with turbulent viscosity based on determination of the shear modulus of velocity is proposed. As an example the dynamics of Hill vortex moved in such environment is considered. The vortex radius extends linearly with the distance covered and makes up about 13% from it.

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