On the Role of Elastic Constants in Multiphase Contact Problems

1992 ◽  
Vol 59 (2) ◽  
pp. 328-334 ◽  
Author(s):  
J. M. Neumeister
Keyword(s):  
Stress Field ◽  
Elastic Constants ◽  
Plane Stress ◽  
Arbitrary Number ◽  
Plane Deformation ◽  
Contact Problems ◽  
Composite Body ◽  
State Of Stress ◽  
Minimum Number

For a plane composite body consisting of an arbitrary number of different linearly elastic constituents under conditions of plane deformation or plane stress, the minimum number of required elastic constants describing the stress field is determined. For conditions in accordance with the assumptions of Michell and Dundurs, i.e., for prescribed surface tractions and no net forces on internal boundaries, the state of stress in a body involving N different phases is found to be determined by only 2N-2 combinations of the elastic constants. This result holds for conditions of complete adhesion and frictionless slip at the interfaces of the materials.

Role of Elastic Constants in Certain Contact Problems

1970 ◽  
Vol 37 (4) ◽  
pp. 965-970 ◽  
Author(s):  
J. Dundurs ◽  
M. Stippes
Keyword(s):  
Elastic Constants ◽  
Poisson’S Ratio ◽  
Contact Problems ◽  
Poisson's Ratio ◽  
Two Dimensional ◽  
Frictionless Contact ◽  
Plane Contact

The dependence of stresses on the elastic constants is explored in frictionless contact problems principally for the case when the contacting bodies are made of the same material and the deformations are induced by prescribed surface tractions. The strongest results can be obtained for problems with contacts that either recede or remain stationary upon loading. In such problems, the stresses are proportional to the applied tractions and the extent of contact is independent of the level of loading. Furthermore, it is shown that the Michell result regarding the dependence of stresses on Poisson’s ratio carries over to plane contact problems with receding and stationary contacts. In three and two-dimensional problems with advancing contacts, it is possible to establish certain rules for scaling displacements and stresses.

Cavities vis-a`-vis Rigid Inclusions and Some Related General Results in Plane Elasticity

1989 ◽  
Vol 56 (4) ◽  
pp. 786-790 ◽  
Author(s):  
John Dundurs
Keyword(s):  
Stress Field ◽  
Plane Strain ◽  
Elastic Constants ◽  
Plane Stress ◽  
Poisson Ratio ◽  
Plane Elasticity ◽  
By Products

There is a strange feature of plane elasticity that seems to have gone unnoticed: The stresses in a body that contains rigid inclusions and is loaded by specified surface tractions depend on the Poisson ratio of the material. If the Poisson ratio in this stress field is set equal to +1 for plane strain, or +∞ for plane stress, the rigid inclusions become cavities for elastic constants within the physical range. The paper pursues this circumstance, and in doing so also produces several useful by-products that are connected with the stretching and curvature change of a boundary.

scholarly journals Higher spins from exotic dualisations

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Nicolas Boulanger ◽  
Victor Lekeu
Keyword(s):  
Infinite Number ◽  
Arbitrary Number ◽  
Degrees Of Freedom ◽  
Young Tableaux ◽  
Spacetime Dimension ◽  
Massless Field ◽  
Free Level ◽  
Higher Spins

Abstract At the free level, a given massless field can be described by an infinite number of different potentials related to each other by dualities. In terms of Young tableaux, dualities replace any number of columns of height hi by columns of height D − 2 − hi, where D is the spacetime dimension: in particular, applying this operation to empty columns gives rise to potentials containing an arbitrary number of groups of D − 2 extra antisymmetric indices. Using the method of parent actions, action principles including these potentials, but also extra fields, can be derived from the usual ones. In this paper, we revisit this off-shell duality and clarify the counting of degrees of freedom and the role of the extra fields. Among others, we consider the examples of the double dual graviton in D = 5 and two cases, one topological and one dynamical, of exotic dualities leading to spin three fields in D = 3.

Experimental Determination of the Two-Dimensional State of Stress and the Orthotropic Elasticity Coefficients for Coatings

1990 ◽  
Vol 203 ◽  
Author(s):  
Richard J. Farris ◽  
M. A. Maden ◽  
K. Tong
Keyword(s):  
Elastic Constants ◽  
Physical Property ◽  
The State ◽  
Normal Stresses ◽  
Free Standing ◽  
Vibrationally Excited ◽  
Plane Shear ◽  
Plane Normal ◽  
State Of Stress ◽  
The One

ABSTRACTThe state of stress for a uniform coating away from the edges reduces to that of plane stress, two in-plane normal stresses, and an in-plane shear stress. For this state, the interface between the coating and the substrate is totally stress free. Since the substrate and the coating are not interacting mechanically, an internal section of the substrate can be removed creating a tensioned drum-like membrane without altering the stress state. Holographic interferometry of vibrationally excited membranes is used to evaluate the stress. Using this technique, up to thirty vibrational modes can be obtained. This high degree of redundancy enables one to determine the one shear and two normal stresses that act in the plane of the coating. The only physical property requires is the coating density. The density is obtained from commonly reported literature values. Simple variations on the membrane vibration scheme, e.g., cutting the membrane to create a uniaxially tensioned ribbon, enables one to determine the in-plane Poisson's ratio and shearmodulus.In separate but related experiments on commercially made free-standing films with residual orientation, the above techniques, combined with special free and axially constrainedcompressibility experiments should enable all of the Poisson's ratios and elasticmoduli for an orthotropic material (nine elastic constants) to be determined. Methods for measuring the state of stress and the elastic constants are required to predict the state of stress in complex coating geometries.

scholarly journals Role of temperature in the numerical analysis of CaO under high pressure

2010 ◽  
Vol 8 (1) ◽  
pp. 126-133 ◽  
Author(s):  
Purvee Bhardwaj ◽  
Sadhna Singh
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Numerical Analysis ◽  
Thermodynamic Properties ◽  
Elastic Constants ◽  
Volume Change ◽  
Thermodynamical Properties ◽  
Phase Transition Pressure ◽  
Different Temperatures

AbstractIn this paper we focus on the elastic and thermodynamic properties of the B1 phase of CaO by using the modified TBP model, including the role of temperature. We have successfully obtained the phase transition pressure and volume change at different temperatures. In addition elastic constants and bulk modulus of B1 phase of CaO at different temperatures are discussed. Our results are comparable with the previous ones at high temperatures and pressures. The thermodynamical properties of the B1 phase of CaO are also predicted.

scholarly journals Iridescent structural colour production in male blue-black grassquit feather barbules: the role of keratin and melanin

2009 ◽  
Vol 6 (suppl_2) ◽  
Author(s):  
Rafael Maia ◽  
João Victor O Caetano ◽  
Sônia N Báo ◽  
Regina H Macedo
Keyword(s):  
Thin Film ◽  
Natural Variation ◽  
Single Layer ◽  
Coherent Scattering ◽  
Interspecific Variation ◽  
Stray Light ◽  
Main Role ◽  
Minimum Number ◽  
Keratin Layer

Iridescent coloration plays an important role in the visual communication system of many animal taxa. It is known that iridescent structural colours result from layers of materials with different refractive indexes, which in feathers usually are keratin, melanin and air. However, the role of these materials in the production of structural iridescent coloration is still poorly documented. Despite the great interspecific variation in the organization of such structures in bird plumage, melanin layers are usually considered too opaque, suggesting its main role is to delineate the outermost keratin layer and absorb incoherently scattered stray light. We combined spectrometry, electron microscopy and thin-film optical modelling to describe the UV-reflecting iridescent colour of feather barbules of male blue-black grassquits ( Volatinia jacarina ), characterized by a keratin layer overlying a single melanin layer. Our models indicate that both the keratin and the melanin layers are essential for production of the observed colour, influencing the coherent scattering of light. The melanin layer in some barbules may be thin enough to allow interaction with the underlying keratin; however, individuals usually have, on an average, the minimum number of granules that optimizes absorbance by this layer. Also, we show that altering optical properties of the materials resulted in better-fitting models relative to the empirically measured spectra. These results add to previous findings concerning the influence of melanin in single-layer iridescence, and stress the importance of considering natural variation when characterizing such photonic structures.

scholarly journals Near Complete Protection Against Covid-19 in a Section of Population: Implication of Lockdown on Development of Passive Vaccination to Counter SARS-CoV-2 Attack

2021 ◽  
pp. 8-15
Author(s):  
Prabir Chakravarty Ph.D
Keyword(s):  
Immune Response ◽  
Infectious Virus ◽  
Marked Decrease ◽  
Early Stage ◽  
Passive Immunization ◽  
Early Introduction ◽  
Fast Spreading ◽  
Minimum Number ◽  
Passive Vaccination

COVID-19 is fast spreading around the globe in a highly contagious manner. Until date there are no therapeutic agents/vaccines developed which could control this highly infectious virus from spreading among human population. During early stage of COVID-19, stringent Lockdown was implemented throughout India on 25 March, 2020. Our earlier findings reflected that early introduction of complete Lockdown significantly controlled the spread of COVID-19 in the population immediately after Lockdown. It was hypothesized that immune response was responsible for the control of the spread of COVID-19. To further evaluate the role of immune response/passive vaccination, data from COVID-19 positive/recovered individuals in eight states were assessed for the month of December, 2020. The results from our study reflect that in all the eight states, there was marked decrease in the number of confirmed COVID-19 cases after Lockdown, with one region recording no COVID-19 cases. All the states studied had very low number of active cases; the minimum number being two even after such a long period from the start of this disease. A negative correlation between number of recovered individuals and number of active cases of COVID-19 was noted. Here we hypothesize that passive immunization may have played a significant role in controlling SARS-CoV-2. It could be inferred from this study that implementation of prolonged Lockdown was able attenuate the virus and create an environment for the development of passive immunity in the section of population studied.

scholarly journals From Point to Filament Defects in Hybrid Nematic Films

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Cesare Chiccoli ◽  
Paolo Pasini ◽  
Claudio Zannoni ◽  
Gregor Skačej ◽  
Hiroyuki Yoshida ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Point Defects ◽  
Elastic Constants ◽  
3D Structure ◽  
Support Surface ◽  
Hybrid Films ◽  
Surface Ordering ◽  
Polarized Microscopy ◽  
Homeotropic Alignment

AbstractWe have studied nematic hybrid films with homeotropic alignment at the top surface and various controlled degrees of in plane ordering, going from a random degenerate organization to a completely uniform alignment along one direction, at the bottom one. We show, by Monte Carlo (MC) computer simulations and experiments on photopatterned films with the bottom support surface fabricated with in-plane order similar to the simulated ones, that the point defects observed in the case of random planar orientations at the bottom tend to arrange along a filament as the surface ordering is sufficiently increased. MC simulations complement the polarized microscopy texture observations allowing to inspect the 3D structure of the defects and examine the role of elastic constants.

Kinking of a Crack out of an Interface: Role of In-Plane Stress

1991 ◽  
Vol 74 (4) ◽  
pp. 767-771 ◽  
Author(s):  
Ming-Yuan He ◽  
Andrew Bartlett ◽  
Anthony G. Evans ◽  
John W. Hutchinson
Keyword(s):  
Plane Stress
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