Indice (mathématiques)Le mot indice a en mathématiques des significations multiples. Certaines n'ont rien à voir entre elles, d'autres touchent des sujets si voisins qu'il y a parfois des confusions. Il y a néanmoins un point commun : l'indice en mathématiques est très souvent (mais pas toujours) un nombre entier. Un indice est un symbole placé souvent à droite et au-dessous d’un autre symbole, qu’il caractérise ou numérote. Par exemple, 1 est l’indice de dans l’écriture , qui se lit x indice 1.
Ion trackIon tracks are damage-trails created by swift heavy ions penetrating through solids, which may be sufficiently-contiguous for chemical etching in a variety of crystalline, glassy, and/or polymeric solids. They are associated with cylindrical damage-regions several nanometers in diameter and can be studied by Rutherford backscattering spectrometry (RBS), transmission electron microscopy (TEM), small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS) or gas permeation.
OrthotropieL’orthotropie désigne des caractéristiques de symétrie d'un corps, d'une grandeur ou d'un phénomène. Ce terme est utilisé dans plusieurs domaines avec des définitions différentes. L’orthotropie désigne des caractéristiques de symétrie d'un matériau. C’est un cas particulier d’anisotropie. On distingue deux types d'orthotropie : un matériau est orthotrope s'il possède trois plans de symétrie orthogonaux entre eux. Son comportement élastique est alors défini par neuf modules d'élasticité, son comportement thermique par trois constantes thermiques.
Critical resolved shear stressIn materials science, critical resolved shear stress (CRSS) is the component of shear stress, resolved in the direction of slip, necessary to initiate slip in a grain. Resolved shear stress (RSS) is the shear component of an applied tensile or compressive stress resolved along a slip plane that is other than perpendicular or parallel to the stress axis.
Slip (materials science)In materials science, slip is the large displacement of one part of a crystal relative to another part along crystallographic planes and directions. Slip occurs by the passage of dislocations on close/packed planes, which are planes containing the greatest number of atoms per area and in close-packed directions (most atoms per length). Close-packed planes are known as slip or glide planes. A slip system describes the set of symmetrically identical slip planes and associated family of slip directions for which dislocation motion can easily occur and lead to plastic deformation.
Flow stressIn materials science the flow stress, typically denoted as Yf (or ), is defined as the instantaneous value of stress required to continue plastically deforming a material - to keep it flowing. It is most commonly, though not exclusively, used in reference to metals. On a stress-strain curve, the flow stress can be found anywhere within the plastic regime; more explicitly, a flow stress can be found for any value of strain between and including yield point () and excluding fracture (): .
Relaxation de contrainteLa relaxation de contrainte est une des trois méthodes expérimentales d’analyse de la viscoélasticité linéaire, avec le fluage et les techniques dynamiques. Dans un essai en quasi statique de relaxation, à partir d’un instant initial , une déformation (sollicitation) instantanée maintenue constante ou est appliquée à un échantillon, et la contrainte résultante (réponse), ou , est suivie en fonction du temps.
Cross slipIn materials science, cross slip is the process by which a screw dislocation moves from one slip plane to another due to local stresses. It allows non-planar movement of screw dislocations. Non-planar movement of edge dislocations is achieved through climb. Since the Burgers vector of a perfect screw dislocation is parallel to the dislocation line, it has an infinite number of possible slip planes (planes containing the dislocation line and the Burgers vector), unlike an edge or mixed dislocation, which has a unique slip plane.
Thermal stressIn mechanics and thermodynamics, thermal stress is mechanical stress created by any change in temperature of a material. These stresses can lead to fracturing or plastic deformation depending on the other variables of heating, which include material types and constraints. Temperature gradients, thermal expansion or contraction and thermal shocks are things that can lead to thermal stress. This type of stress is highly dependent on the thermal expansion coefficient which varies from material to material.
Vector notationIn mathematics and physics, vector notation is a commonly used notation for representing vectors, which may be Euclidean vectors, or more generally, members of a vector space. For representing a vector, the common typographic convention is lower case, upright boldface type, as in v. The International Organization for Standardization (ISO) recommends either bold italic serif, as in v, or non-bold italic serif accented by a right arrow, as in . In advanced mathematics, vectors are often represented in a simple italic type, like any variable.
