A physical theory of snow gliding

1981 ◽  
Vol 18 (1) ◽  
pp. 86-94 ◽  
Author(s):  
David M. McClung
Keyword(s):  
Rigid Body ◽  
Constitutive Equations ◽  
Slip Velocity ◽  
Physical Theory ◽  
Water Film ◽  
Point Of View ◽  
Slip Condition ◽  
Realistic Case ◽  
Viscous Deformation ◽  
Snow Gliding

Snow glide, slip of the entire snowpack over the ground, is not observed unless water reaches the ground interface. In this paper, snow gliding is approached from the point of view that a perfect slip condition is attained at the glide interface whereby a thin continuous water film is envisioned to exist between the snowpack and the ground. Two mechanisms are described by which the snowpack may move forward: (i) creep (defined as slow, viscous deformation) over roughness asperities under the condition that the snowpack conforms to the interface and (ii) rigid body sliding of the snowpack over the interface when it does not conform to the interface. Constitutive equations relating tangential drag on the snowpack to slip velocity are derived for these idealized cases, and the extension to the more realistic case where the processes compete is discussed.

Prediction of Tread Pattern Wear by an Explicit Finite Element Model3

2007 ◽  
Vol 35 (4) ◽  
pp. 276-299 ◽  
Author(s):  
J. C. Cho ◽  
B. C. Jung
Keyword(s):  
Finite Element ◽  
Wear Rate ◽  
Tangential Stress ◽  
Rate Equation ◽  
Constitutive Equations ◽  
Slip Velocity ◽  
Test Results ◽  
Explicit Finite Element ◽  
Driving Condition ◽  
Driving Conditions

Abstract Tread pattern wear is predicted by using an explicit finite element model (FEM) and compared with the indoor drum test results under a set of actual driving conditions. One pattern is used to determine the wear rate equation, which is composed of slip velocity and tangential stress under a single driving condition. Two other patterns with the same size (225/45ZR17) and profile are used to be simulated and compared with the indoor wear test results under the actual driving conditions. As a study on the rubber wear rate equation, trial wear rates are assumed by several constitutive equations and each trial wear rate is integrated along time to yield the total accumulated wear under a selected single cornering condition. The trial constitutive equations are defined by independently varying each exponent of slip velocity and tangential stress. The integrated results are compared with the indoor test results, and the best matching constitutive equation for wear is selected for the following wear simulation of two other patterns under actual driving conditions. Tens of thousands of driving conditions of a tire are categorized into a small number of simplified conditions by a suggested simplification procedure which considers the driving condition frequency and weighting function. Both of these simplified conditions and the original actual conditions are tested on the indoor drum test machines. The two results can be regarded to be in good agreement if the deviation that exists in the data is mainly due to the difference in the test velocity. Therefore, the simplification procedure is justified. By applying the selected wear rate equation and the simplified driving conditions to the explicit FEM simulation, the simulated wear results for the two patterns show good match with the actual indoor wear results.

scholarly journals Thin-film-induced morphological instabilities over calcite surfaces

2015 ◽  
Vol 471 (2176) ◽  
pp. 20150031 ◽  
Author(s):  
R. Vesipa ◽  
C. Camporeale ◽  
L. Ridolfi
Keyword(s):  
Morphological Evolution ◽  
Water Film ◽  
Environmental Parameters ◽  
Climatic Conditions ◽  
Point Of View ◽  
Theoretical Point ◽  
Carbon Dioxide Transport ◽  
Physical Mechanisms ◽  
Water Films ◽  
Dissolved Ions

Precipitation of calcium carbonate from water films generates fascinating calcite morphologies that have attracted scientific interest over past centuries. Nowadays, speleothems are no longer known only for their beauty but they are also recognized to be precious records of past climatic conditions, and research aims to unveil and understand the mechanisms responsible for their morphological evolution. In this paper, we focus on crenulations, a widely observed ripple-like instability of the the calcite–water interface that develops orthogonally to the film flow. We expand a previous work providing new insights about the chemical and physical mechanisms that drive the formation of crenulations. In particular, we demonstrate the marginal role played by carbon dioxide transport in generating crenulation patterns, which are indeed induced by the hydrodynamic response of the free surface of the water film. Furthermore, we investigate the role of different environmental parameters, such as temperature, concentration of dissolved ions and wall slope. We also assess the convective/absolute nature of the crenulation instability. Finally, the possibility of using crenulation wavelength as a proxy of past flows is briefly discussed from a theoretical point of view.

scholarly journals A teaching proposal for the study of Eigenvectors and Eigenvalues

2017 ◽  
Vol 7 (1) ◽  
pp. 100 ◽  
Author(s):  
María José Beltrán Meneu ◽  
Marina Murillo Arcila ◽  
Enrique Jordá Mora
Keyword(s):  
Rigid Body ◽  
Mathematical Thinking ◽  
Point Of View ◽  
Moment Of Inertia ◽  
Geometric Point ◽  
The Moment ◽  
Eigenvectors And Eigenvalues

In this work, we present a teaching proposal which emphasizes on visualization and physical applications in the study of eigenvectors and eigenvalues. These concepts are introduced using the notion of the moment of inertia of a rigid body and the GeoGebra software. The proposal was motivated after observing students’ difficulties when treating eigenvectors and eigenvalues from a geometric point of view. It was designed following a particular sequence of activities with the schema: exploration, introduction of concepts, structuring of knowledge and application, and considering the three worlds of mathematical thinking provided by Tall: embodied, symbolic and formal.

scholarly journals Pose Changes From a Different Point of View

2018 ◽  
Vol 10 (2) ◽  
Author(s):  
Gregory S. Chirikjian ◽  
Robert Mahony ◽  
Sipu Ruan ◽  
Jochen Trumpf
Keyword(s):  
Rigid Body ◽  
Reference Frame ◽  
Semidirect Product ◽  
Group Structure ◽  
Linear Part ◽  
Point Of View ◽  
Affine Transformations ◽  
Fixed Reference ◽  
New Perspective ◽  
Direct Product Group

For more than a century, rigid-body displacements have been viewed as affine transformations described as homogeneous transformation matrices wherein the linear part is a rotation matrix. In group-theoretic terms, this classical description makes rigid-body motions a semidirect product. The distinction between a rigid-body displacement of Euclidean space and a change in pose from one reference frame to another is usually not articulated well in the literature. Here, we show that, remarkably, when changes in pose are viewed from a space-fixed reference frame, the space of pose changes can be endowed with a direct product group structure, which is different from the semidirect product structure of the space of motions. We then show how this new perspective can be applied more naturally to problems such as monitoring the state of aerial vehicles from the ground, or the cameras in a humanoid robot observing pose changes of its hands.

scholarly journals LIVING BEINGS AS INFORMED SYSTEMS: TOWARDS A PHYSICAL THEORY OF INFORMATION

1996 ◽  
Vol 04 (04) ◽  
pp. 565-584
Author(s):  
ANTONIO LEÓN
Keyword(s):  
Physical Theory ◽  
Point Of View ◽  
Physical Point ◽  
Absolute Measure ◽  
Functional Measure ◽  
Physical Information ◽  
Physical Effects ◽  
Theory Of Information ◽  
Concept Of Information ◽  
Physical Laws

I propose here a new concept of information based on two relevant aspects of its expression. The first refers to the undeniable fact that the expression of information modifies the physical state of its receiver. The second, to that the said changes are arbitrary, not deducible from physical laws but from a code established arbitrarily. Thus, physical information is proposed here as the capacity of producing arbitrary changes. Once defined information from this physical point of view, I deduce some basic physical properties of informed systems. These properties (renewal, self-reproducing, evolution, diversification) are immediately recognisable as the attributes most characteristic of living beings, the only natural informed systems we know. Although no new attribute of living beings has been discovered here, the formal way used to obtain them is a significant novelty. I also propose here a double evaluation of information. The former is an absolute measure of the physical effects of its expression based on Einstein’s probability. The latter is a functional measure based on the probability that an informed system attain a given objective as consequence of the expression of its information.

scholarly journals The theory on homogeneous micro-fluid mixtures

1979 ◽  
Vol 1 (3-4) ◽  
pp. 38-48
Author(s):  
Nguyen Van Diep ◽  
Truong Minh Chanh
Keyword(s):  
Rigid Body ◽  
Relative Motion ◽  
Constitutive Equations ◽  
Fluid Mixtures ◽  
Rigid Body Motions ◽  
Thermodynamic Restrictions

This paper deals with the construction x of a generalized- diffusive theory of simple micro-fluid mixtures composed of a reactive constituents in the relative motion to one another and treated as a single simple micro-fluid. The basic laws of balance are given by postulating the balance law of energy together with invariant requirement under superposed rigid body motions or the mixture as a whole. The linear or nonlinear constitutive equations and full thermodynamic restrictions are given.

scholarly journals Kinematic support modeling in Sage

2020 ◽  
Vol 28 (2) ◽  
pp. 141-153
Author(s):  
Oleg K. Kroytor ◽  
Mikhail D. Malykh ◽  
Sergei P. Karnilovich
Keyword(s):  
Rigid Body ◽  
Computer Algebra ◽  
Computer Algebra System ◽  
Seismic Isolation ◽  
Equations Of Motion ◽  
Classical Mechanics ◽  
Vertical Plane ◽  
Base Plate ◽  
Euler Method ◽  
Point Of View

The article discusses the kinematic support, which allows reducing the horizontal dynamic effects on the building during earthquakes. The model of a seismic isolation support is considered from the point of view of classical mechanics, that is, we assume that the support is absolutely solid, oscillating in a vertical plane above a fixed horizontal solid plate. This approach allows a more adequate description of the interaction of the support with the soil and the base plate of the building. The paper describes the procedure for reducing the complete system of equations of motion of a massive rigid body on a fixed horizontal perfectly smooth plane to a form suitable for applying the finite difference method and its implementation in the Sage computer algebra system. The numerical calculations by the Euler method for grids with different number of elements are carried out and a mathematical model of the support as a perfectly rigid body in the Sage computer algebra system is implemented. The article presents the intermediate results of numerical experiments performed in Sage and gives a brief analysis (description) of the results.

Practical Introduction to Rigid Body Linear Complementary Problem (LCP) Constraint Solvers

2012 ◽  
pp. 159-201 ◽  
Author(s):  
Ben Kenwright ◽  
Graham Morgan
Keyword(s):  
Rigid Body ◽  
Real Time ◽  
Point Of View ◽  
Test Cases ◽  
Practical Point ◽  
Linear Complementary Problem ◽  
Real Test

This chapter introduces Linear Complementary Problem (LCP) Solvers as a method for implementing real-time physics for games. This chapter explains principles and algorithms with practical examples and reasoning. When first investigating and writing a solver, one can easily become overwhelmed by the number of different methods and lack of implementation details, so this chapter will demonstrate the various methods from a practical point of view rather than a theoretical one; using code samples and real test cases to help understanding.

A new experimental set-up to study the shear strength of snow-mortar interfaces

2021 ◽  
Author(s):  
Gianmarco Vallero ◽  
Monica Barbero ◽  
Fabrizio Barpi ◽  
Mauro Borri-Brunetto ◽  
Valerio De Biagi
Keyword(s):  
Shear Strength ◽  
Progressive Failure ◽  
Failure Process ◽  
Construction Materials ◽  
Water Film ◽  
Video Camera ◽  
Point Of View ◽  
High Definition ◽  
Snow Layer ◽  
Particle Image Velocimetry Technique

<p>The progressive failure of a snow layer deposited on a stiff substrate is at the base of the comprehension of several physical processes that can be found both in natural and artificial conditions. For instance, glide avalanches often originate from the reduction of the basal friction between the snowpack and the underlying ground due to the presence of liquid water film or depth hoar at the snow-ground interface. Moreover, the interaction between snow and construction materials relates to many other applications such as the study of new and more efficient snow removal techniques, the safety of travelers along snow covered roads, the snow redistribution from roofs and buildings, etc. </p><p>Despite this large number of application fields, laboratory investigations are still limited. We performed cold room tests on artificially made snow-mortar interface specimens through a direct shear test device. The effects of confinement pressure, temperature and dry snow hardness (due to sintering times) were taken into account. The tests were carried out in displacement-controlled conditions in order to study the entire failure process at the interface and the following irreversible sliding. The results show some interesting and encouraging aspects for understanding the shear strength of the interface. From a micromechanical point of view we recorded the tests with a high-definition video camera and analyzed the data with the Particle Image Velocimetry technique to obtain the motion fields on the external side of the specimens. Here, we present and discuss some preliminary results of the experimental activity and suggest some future implementations and further developments of the studied topic.       </p>

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