Generalization of the Energetic Coefficient of Restitution for Contacts in Multibody Systems

2008 ◽  
Vol 3 (4) ◽  
Author(s):  
Seyed Ali Modarres Najafabadi ◽  
József Kövecses ◽  
Jorge Angeles
Keyword(s):  
Kinetic Energy ◽  
Energy Absorption ◽  
Multibody Systems ◽  
Point Contact ◽  
Coefficient Of Restitution ◽  
Multiple Point ◽  
Decomposition Technique ◽  
Potential Applications ◽  
New Interpretation ◽  
Tangential Directions

This paper introduces a new interpretation of the energetic coefficient of restitution, especially applicable to contact involving multibody systems. This interpretation generalizes the concept of the energetic coefficient of restitution and allows for consideration of simultaneous multiple-point contact scenarios. Such a generalization is obtained by an analysis of energy absorption and restitution during impact, using a decomposition technique, which exactly decouples the kinetic energy associated with the normal and tangential directions of the contact pairs. The main advantages of the new definition and its potential applications are highlighted.

An Energy-Based Approach to the Dynamics of Impacts in Unilaterally-Constrained Multibody Systems

2007 ◽  
Author(s):  
Seyed Ali Modarres Najafabadi ◽  
Jo´zsef Ko¨vecses ◽  
Jorge Angeles
Keyword(s):  
Multibody Systems ◽  
Point Contact ◽  
Coefficient Of Restitution ◽  
Multiple Point ◽  
Dynamics Analysis ◽  
Constrained Multibody Systems ◽  
Novel Approach ◽  
Potential Applications ◽  
Definition Of ◽  
Tangential Directions

This paper introduces a novel approach to dynamics analysis of contacts involving multibody systems, and particularly the case of simultaneous multiple-point impact. This approach is based on an analysis of energy absorption and restitution during impact, using a decomposition technique, which exactly decouples the kinetic energy associated with the normal and tangential directions of the contact pairs. Such decomposition leads to a generalized definition of the energetic coefficient of restitution, which allows for consideration of simultaneous multiple-point contact scenarios. The main advantages of this new definition and the potential applications of the said technique are highlighted.

Energy Analysis and Decoupling in Three-Dimensional Impacts of Multibody Systems

2006 ◽  
Vol 74 (5) ◽  
pp. 845-851 ◽  
Author(s):  
Seyed Ali Modarres Najafabadi ◽  
József Kövecses ◽  
Jorge Angeles
Keyword(s):  
Kinetic Energy ◽  
Energy Absorption ◽  
Multibody Systems ◽  
Energy Analysis ◽  
Multibody System ◽  
Energy Content ◽  
Three Dimensional ◽  
Unilateral Contacts ◽  
Potential Applications

This paper discusses an exact decomposition of the kinetic energy to determine the energy content that influences the dynamics of unilateral contacts in multibody systems. This decomposition essentially divides the kinetic energy of the whole multibody system into two completely decoupled parts associated with the constrained and admissible directions of unilateral contacts. This will provide a picture of how the energy absorption/dissipation during impacts is related to the variation of the generalized velocities and the configuration of multibody systems. Potential applications of such a decoupling are highlighted.

A Comparative Study of Approaches to Dynamics Modeling of Contact Transitions in Multibody Systems

2005 ◽  
Author(s):  
Seyed Ali Modarres Najafabadi ◽  
Jo´zsef Ko¨vecses ◽  
Jorge Angeles
Keyword(s):  
Comparative Study ◽  
Dynamic Analysis ◽  
Multibody Systems ◽  
Multibody System ◽  
Point Contact ◽  
Transition Phase ◽  
Multiple Point ◽  
Dynamics Modeling ◽  
Modeling Techniques ◽  
Two Bodies

This paper presents detailed discussions and a potential grouping of various approaches to the dynamic analysis of the transition phase in multibody contacts. The methods considered are able to address the general case of multiple-point contact. The main grouping principle relies on the fundamental unilateral nature of the contact between two bodies in a multibody system. Based on this, three main classes of modeling techniques are considered.

scholarly journals Multiple point contact wear prediction and source identification scheme using a single channel blended airborne acoustic signature

2020 ◽  
Vol 53 (3) ◽  
pp. 283-288
Author(s):  
Muhammad Atayyab Shahid ◽  
Tariq Mairaj Khan ◽  
Kevin Lontin ◽  
Kanza Basit ◽  
Muhammad Khan
Keyword(s):  
Source Identification ◽  
Single Channel ◽  
Point Contact ◽  
Multiple Point ◽  
Wear Prediction ◽  
Identification Scheme ◽  
Contact Wear ◽  
Acoustic Signature

scholarly journals Quantum conductance staircase of holes in silicon nanosandwiches

2019 ◽  
Vol 20 (2) ◽  
pp. 81-98
Author(s):  
N. T. Bagraev ◽  
L. E. Klyachkin ◽  
A. M. Malyarenko ◽  
V. S. Khromov
Keyword(s):  
Kinetic Energy ◽  
Quantum Wells ◽  
Quantum Wires ◽  
Energy Gap ◽  
Point Contact ◽  
Quantum Conductance ◽  
One Dimensional ◽  
Drastic Increase ◽  
Quantum Point ◽  
The One

The results of studying the quantum conductance staircase of holes in one−dimensional channels obtained by the split−gate method inside silicon nanosandwiches that are the ultra−narrow quantum well confined by the delta barriers heavily doped with boron on the n−type Si (100) surface are reported. Since the silicon quantum wells studied are ultra−narrow (~2 nm) and confined by the delta barriers that consist of the negative−U dipole boron centers, the quantized conductance of one−dimensional channels is observed at relatively high temperatures (T > 77 K). Further, the current−voltage characteristic of the quantum conductance staircase is studied in relation to the kinetic energy of holes and their sheet density in the quantum wells. The results show that the quantum conductance staircase of holes in p−Si quantum wires is caused by independent contributions of the one−dimensional (1D) subbands of the heavy and light holes; these contributions manifest themselves in the study of square−section quantum wires in the doubling of the quantum−step height (G0 = 4e2/h), except for the first step (G0 = 2e2/h) due to the absence of degeneracy of the lower 1D subband. An analysis of the heights of the first and second quantum steps indicates that there is a spontaneous spin polarization of the heavy and light holes, which emphasizes the very important role of exchange interaction in the processes of 1D transport of individual charge carriers. In addition, the field−related inhibition of the quantum conductance staircase is demonstrated in the situation when the energy of the field−induced heating of the carriers become comparable to the energy gap between the 1D subbands. The use of the split−gate method made it possible to detect the effect of a drastic increase in the height of the quantum conductance steps when the kinetic energy of holes is increased; this effect is most profound for quantum wires of finite length, which are not described under conditions of a quantum point contact. In the concluding section of this paper we present the findings for the quantum conductance staircase of holes that is caused by the edge channels in the silicon nanosandwiches prepared within frameworks of the Hall. This longitudinal quantum conductance staircase, Gxx, is revealed by the voltage applied to the Hall contacts, Vxy, to a maximum of 4e2/h. In addition to the standard plateau, 2e2/h, the variations of the Vxy voltage appear to exhibit the fractional forms of the quantum conductance staircase with the plateaus and steps that bring into correlation respectively with the odd and even fractional values.

scholarly journals The influence of surface charge on the coalescence of ice and dust particles in the mesosphere

2020 ◽  
Author(s):  
Joshua Baptiste ◽  
Connor Williamson ◽  
John Fox ◽  
Anthony J. Stace ◽  
Muhammad Hassan ◽  
...  
Keyword(s):  
Particle Size ◽  
Dielectric Constant ◽  
Kinetic Energy ◽  
Surface Charge ◽  
Coefficient Of Restitution ◽  
Dust Particles ◽  
Energy Collision ◽  
Opposite Charge ◽  
Relative Kinetic ◽  
Small Separation

Abstract. Agglomeration of charged ice and dust particles in the mesosphere is studied using a classical electrostatic approach, which is extended to capture the induced polarisation of surface charge. Collision outcomes are predicted whilst varying particle size, charge, dielectric constant, relative kinetic energy, collision geometry and the coefficient of restitution. In addition to attractive Coulomb forces acting on particles of opposite charge, instances of strong attraction between particles of the same sign of charge are predicted, which take place at small separation distances and also lead to the formation of stable aggregates. These attractive forces are governed by the polarisation of surface charge.

Enhanced Photocatalytic Degradation Activity of 2-D Graphitic Carbon Nitride-SnO2 Nanohybrids

2019 ◽  
Vol 19 (6) ◽  
pp. 3576-3582 ◽  
Author(s):  
Kiran Preethi Kirubakaran ◽  
Sakthivel Thangavel ◽  
Gouthami Nallamuthu ◽  
Vinesh Vasudevan ◽  
Priya Arul Selvi Ramasubramanian ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Environmental Remediation ◽  
Carbon Nitride ◽  
Waste Water Treatment ◽  
Sol Gel ◽  
Point Contact ◽  
Order Rate Constant ◽  
Graphitic Carbon ◽  
Graphitic Carbon Nitride ◽  
Potential Applications

In this paper, we report on the facile synthesis of graphitic carbon nitride (g-C3N4)-tin oxide (SnO2) nanohybrid as an efficient photocatalyst prepared via sol–gel method. SnO2 nanoparticles are pointcontacted with g-C3N4. The results of physio-chemical characterizations such as SEM-EDAX, XRD, BET, FT-IR and UV-DRS spectra reveal the successful formation and integration of nanohybrid. The photocatalytic activity has been studied by using methylene-blue as a model dye for degradation. It has been observed that the pseudo-first order rate constant was increased up to 1.78 times compared with pure SnO2. The enhanced photocatalytic activity was ascribed from the inhibition of electron–hole recombination where g-C3N4 nanosheets acts as an electron receiver from SnO2 via point contact. This mechanism is further verified via photoluminescence spectra. Our results prominently show new insights and potential applications of g-C3N4-SnO2 nanohybrids in the waste water treatment and environmental remediation sectors.

Viscoplastic Effects Occurring in Impacts of Aluminum and Steel Bodies and Their Influence on the Coefficient of Restitution

2010 ◽  
Vol 77 (4) ◽  
Author(s):  
Robert Seifried ◽  
Hirofumi Minamoto ◽  
Peter Eberhard
Keyword(s):  
Kinetic Energy ◽  
Strain Rate ◽  
Yield Stress ◽  
Split Hopkinson Pressure Bar ◽  
Material Model ◽  
Coefficient Of Restitution ◽  
Material Behavior ◽  
Steel Sphere ◽  
Elastic Plastic ◽  
The Impact

Generally speaking, impacts are events of very short duration and a common problem in machine dynamics. During impact, kinetic energy is lost due to plastic deformation near the contact area and excitation of waves. Macromechanically, these kinetic energy losses are often summarized and expressed by a coefficient of restitution, which is then used for impact treatment in the analysis of the overall motion of machines. Traditionally, the coefficient of restitution has to be roughly estimated or measured by experiments. However, more recently finite element (FE) simulations have been used for its evaluation. Thereby, the micromechanical plastic effects and wave propagation effects must be understood in detail and included in the simulations. The plastic flow, and thus the yield stress of a material, might be independent or dependent of the strain-rate. The first material type is called elastic-plastic and the second type is called elastic-viscoplastic. In this paper, the influence of viscoplasticity of aluminum and steel on the impact process and the consequences for the coefficient of restitution is analyzed. Therefore, longitudinal impacts of an elastic, hardened steel sphere on aluminum AL6060 rods and steel S235 rods are investigated numerically and experimentally. The dynamic material behavior of the specimens is evaluated by split Hopkinson pressure bar tests and a Perzyna-like material model is identified. Then, FE impact simulations and impact experiments with laser-doppler-vibrometers are performed. From these investigations it is shown that strain-rate effects of the yield stress are extremely small for impacts on aluminum but are significant in impacts on steel. In addition, it is demonstrated that it is possible to evaluate for both impact systems the coefficient of restitution numerically, whereas for the aluminum body a simple elastic-plastic material model is sufficient. However, for the steel body an elastic-viscoplastic material model must be included.

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