Showing papers on "Deformation (meteorology) published in 1981"

Speckle Displacement and Decorrelation in the Diffraction and Image Fields for Small Object Deformation

Abstract: Laser-speckles show displacement accompanied by structure change when diffuse objects generating them undergo displacement and/or deformation. This behaviour is theoretically investigated by calculating the cross-correlation functions of speckle intensities before and after the deformation. The dependences of speckle displacement on geometries of object illumination and speckle observation as well as on deformation parameters are clarified. The relations derived are interpreted physically by introducing the shift in diffraction rays due to displacement and deformation of a grating. Distributions of speckle displacement are calculated numerically and shown graphically.

Ultradrawing of high-molecular-weight polyethylene cast from solution. II.Influence of initial polymer concentration

Abstract: Ultradrawing of films of high-molecular-weight polyethylene (Mw = 15 × 106) produced by gelation crystallization from solution is discussed The influence of the initial polymer volume fraction (ϕ) on the maximum draw ratio (λmax) of the dried films is examined in the temperature region from 90–130°C The results can be described very well by the relation λmax = λ ϕ−1/2 where λ is the (temperature-dependent) maximum draw ratio of the melt-crystallized film An attempt is made to discuss the marked influence of the initial polymer volume fraction on λmax in terms of the deformation of a network with entanglements acting as semipermanent crosslinks

Surface Tension Driven Instability in a Horizontal Liquid Layer with a Deformable Free Surface. I. Stationary Convection

Abstract: The effect of a free surface deformation on the onset of surface tension driven instability in a horizontal thin liquid layer subjected to a vertical temperature gradient is examined using linear stability theory. Assuming that the neutral state is a stationary one, the conditions under which instability sets in are determined in detail. It is shown that when the upside of the liquid layer is a free surface the free surface deformation is important only for unusually thin layers of very viscous liquids. It is also shown that when the underside of the liquid layer is a free surface the free surface deformation plays an essentially important role and the presence of a vertical temperature gradient can stabilize the layer which, in case of no temperature gradient, is always unstable.

Finite deformation by mechanical twinning

Abstract: 1. The phenomenon of twinning . . . . . . . . . . . . . . . . . . . . . . 143 2. The definition of a twin . . . . . . . . . . . . . . . . . . . . . . . . 146 3. Kinematics of twinning, trilling, etc . . . . . . . . . . . . . . . . . . . . 156 4. Static theory of piecewise homogeneous deformations in finite elasticity . . . . 165 a) Equilibria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 b) Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

Painlevé Property of Monodromy Preserving Deformation Equations and the Analyticity of τ Functions

Abstract: Painleve's six equations were discovered in his classification of second order ordinary differential equations whose general solutions have no movable singularities other than poles. We call this property the Painleve property. It is now well-known [3], [4], [5] that all the Painleve equations are obtained as monodromy preserving deformation equations. Thus in [i] the authors naturally conjectured that the general monodromy preserving deformation equations have the Painleve property. Ablowitz, Ramani and Segur [6] posed a similar conjecture: Every non linear ordinary differential equation obtained by an exact reduction of a non linear partial differential equation of inverse scattering class enjoy the Painleve property. If we understand the meaning of an exact reduction as the reduction of a spectrum preserving deformation equation to a monodromy preserving deformation equation [5], their conjecture follows from our Theorem 1 below. They also showed in some special examples that the Painleve property can be proved by exploiting the Fredholm determinant. Oishi [7] obtained similar

Theory of optical-phonon deformation potentials in tetrahedral semiconductors

Abstract: A nonlocal pseudopotential theory of the optical-phonon deformation potentials in 11 diamond and zinc-blende semiconductors is presented. The one-phonon deformation potentials associated with the major conduction- and valence-band states at the $\ensuremath{\Gamma}$, $L$, and $X$ point are calculated. The effect of the spin-orbit interaction on the optical deformation potentials is examined in detail. The published experimental data are compared both to one another and to the present theory. In addition, an analytical linear combination of atomic orbitals (LCAO) model is developed which predicts the optical deformation potentials for any tetrahedral semiconductor in a simple yet accurate way. The optical deformation potentials are presented for 37 semiconductors. The LCAO model also yields an analytical expression for the optical deformation potentials in terms of the observed optical gaps of the semiconductors.

Voltage-Induced large amplitude bending device-PVF2 Bimorph-its properties and applications

Abstract: Status is reviewed of various applications of bimorphs composed of PVF2 piezoelectric films. Fundamental properties of different device structures were discussed with respect to the voltage-induced bending motion, generated force, frequency response, gravity deformation, and the influence of temperature. The applications discussed were displays, a light shutter, deformable mirrors, an optical fiber switch, and an air-flow generating fan.

Creep rupture of copper and aluminium under non-proportional loading

Abstract: The development of existing constitutive equations is described for high temperature creep deformation and rupture under proportional loading. The validity of these equations has been assessed for non-proportional loading of copper and aluminium alloy test specimens. It is shown that these equations adequately describe the rupture and deformation behaviour of the aluminium alloy. The rupture behaviour of copper is closely described by the theory for proportional loading but the deformation behaviour is only approximately described by the same constitutive equations.

Creep and failure of slopes in clays

Abstract: The accumulated experience on slope stability is reviewed with due consideration to the time-dependent behaviour of natural clays prior to failure. A consistent picture of the behaviour of both man...

Characterization and modeling for forging deformation of Ti-6Ai-2Sn-4Zr-2Mo-0.1 Si

Abstract: The deformation behavior during upset forging has been determined for Ti-6242 in both the (α + β) and β starting microstructures. For (α + β), flow softening attributed to deformation heating was observed. Deformation heating accounted for only a fraction of the extensive flow softening of the β microstructure. The dependence of log σ on 1/T was linear for (α + β) and bilinear for the β microstructure, with an approximate transition temperature of 930 °C. The two temperature regimes for β corresponded to distinct deformed microstructures which were manifestations of different softening mechanisms, all promoting the flow-induced transformation of metastable β microstructure to the equilibrium (α + β) microstructure. Based on the experimental data, flow stress equations for both microstructures, and empirical equations describing the flow softening behavior of β have been developed. WithT and ġe as the only input variables, these equations can accurately predict the σ - e relationships for process modeling of this alloy.

Plane stress deformation zones at crack tips in polycarbonate

Abstract: The plastic deformation produced crack tips in polycarbonate (PC) films stretched in tension, has been characterized by optical and transmission electron microscopy. An extensive and diffuse region of deformation is formed in unannealed specimens. Within this zone the ratio (vf) of local film thickness to the (undeformed) thickness far away from the crack varies gradually both along and across the zone. The minimum ratio of ∼ 0.5 occurs at the crack tip. In contrast to this behaviour, films annealed for a short time just below the glass transition temperature Tg showed a highly localized response, the plastic strain being confined to a well-defined flame shaped deformation zone (DZ) ahead of the crack. Within most of this DZ, vf is constant at ∼ 0.7, rising to 1 over a distance of 10 μm at the zone tip, and falling to ∼ 0.5 over a distance of ∼ 4 μm around the crack tip. Bi-refringence measurements show that a high degree of molecular orientation occurs within the zone. These experiments support the idea that an increase in the localization of the plastic strain response upon annealing below Tg is responsible for the embrittlement of PC by such heat treatment.