Showing papers on "Discontinuity (geotechnical engineering) published in 1987"
TL;DR: In this paper, it was shown that mechanically weak zones (σ 1 − σ 3 <10 MPa) at upper-, mid-and lower crustal depths, inferred from geological and geophysical observations and interpretations, is supported by empirically-determined steady-state flow properties of some common crystalline rocks.
762 citations
TL;DR: In this article, the authors analyzed crack tip stress and deformation fields for tensile-loaded ideally plastic crystals and showed that the near-tip stress state is locally constant within angular sectors that are stressed to yield levels at a stationary crack tip and to change discontinuously from sector to sector.
314 citations
TL;DR: In this paper, a generalized Rayleigh wave is applied to a non-welded interface and a fast and a slow dispersive wave can propagate along the fracture even when the seismic properties of the rock on each side are identical.
Abstract: Non-welded interfaces can be treated as a displacement discontinuity characterized by elastic stiffnesses. Applying this boundary condition to a generalized Rayleigh wave, it is shown that a fast and a slow dispersive wave can propagate along the fracture, even when the seismic properties of the rock on each side are identical.
102 citations
TL;DR: In this article, the authors used waveform complexities similar to those observed in data sampling the D″ region beneath Alaska, the Caribbean, and Eurasia (Lay and Helmberger), which have been attributed to a 2.7% shear velocity discontinuity ∼ 280 km above the core-mantle boundary.
92 citations
TL;DR: In this paper, the splitting of a single pressure discontinuity into a propagating two-wave system is studied for the case of saturated-liquid expansion (liquid-evaporation wave splitting) and vapour compression (vapour-condensation wave splitting).
Abstract: The splitting of a single pressure discontinuity into a propagating two-wave system is studied for the case of saturated-liquid expansion (liquid-evaporation wave splitting) and vapour compression (vapour-condensation wave splitting). Experimental results from the Max-Planck-Institut fur Stromungsforschung and from Rensselaer Polytechnic Institute show that splitting occurs in test fluids of large molar heat capacity, such as iso-octane (Cv0/R ≈ 37). Each of the two forms of splitting results in a single-phase forerunner wave carrying a pressure discontinuity followed by a phase-change wave, also with a pressure discontinuity. The thermodynamic state between the forerunner wave and the phase-change wave is metastable (supersaturated liquid or vapour). The waves are quantitatively described by systems of adiabats, e.g. shock adiabats. It appears that nucleation processes are predominantly homogeneous.In vapour-compression shock-wave splitting, a combined wave (liquefaction shock) splits into discrete forerunner and condensation waves at a triple point, the intersection of a liquefaction shockfront, forerunner shock and condensation discontinuity: such a point occurs just at critical supersaturation (i.e. the Wilson-line state), where condensation is spontaneous and immediate. For shock waves that produce a metastable state of subcritical supersaturation, condensation is delayed, that is, the condensation discontinuity propagates more slowly; for a split-shock system, the condensation discontinuity propagates subsonically. The pressure amplitude of a real split-shock system is much larger than that predicted by an equilibrium model.In liquid-evaporation wave splitting, the forerunner wave is an acoustic expansion wave and the second wave an evaporation wave with a propagation velocity approximately determined by the Chapman-Jouguet condition for deflagration. Such evaporation wavefronts are increasingly distinct as the temperature approaches the critical-point value. The evaporation rates across the wavefront are comparable to those found in vapour explosions.
68 citations
TL;DR: In this article, the Moho discontinuity was modelled on the basis of the 6 DSS profiles across the Yugoslav area, by the use of regression analysis and expressed by fitting surfaces from the 1st up to the 4th degree.
Abstract: Summary. The Moho discontinuity was modelled on the basis of the 6 DSS profiles across the Yugoslav area, by the use of regression analysis and expressed by fitting surfaces from the 1st up to the 4th degree. Their characteristics were correlated to the geological structure of the Earth's crust, with intention to point out their connection with the deformations of the Moho discontinuity.
45 citations
01 Jan 1987
41 citations
Journal Article•
40 citations
Patent•
29 Oct 1987
TL;DR: In this paper, a tool positioning system comprises a discontinuity detection means, such as an eddy current system, for detecting the discontinuity within a workpiece resulting from a joint between a first piece of material relative to a second piece of materials.
Abstract: A tool positioning system comprises a discontinuity detection means, such as an eddy current system, for detecting a discontinuity within a workpiece resulting from a joint between a first piece of material relative to a second piece of material, the discontinuity being detected from the back side of the second piece of material. The discontinuity is detected at a plurality of points by translating an eddy current probe over the back side of the second piece of material, the individual points thereafter being utilized to compute line elements that define the joint between the first and second pieces of material in a continuous fashion over the surface of the second piece of material. Thereafter a tool, such as a laser welding tool, is guided along the computed position along the backside of the second piece of material such that the first and second pieces of material are welded together along the joint.
38 citations
TL;DR: In this paper, l'effet des zones aveugles sur l'identification des joints and des failles, en calculant la largeur des zones AVEUGLES en fonction des procedures d'investigation mises en œuvre (sondages, decouvrements de surfaces rocheuses)
26 citations
TL;DR: In this paper, a three-element analytical model for a free-free longitudinally vibrating uniform beam containing a symmetric discontinuity is presented, and an analytical expression is developed which relates the length of the section containing the damage to the depth of the discontinuity.
Abstract: A three-element analytical model for a free-free longitudinally vibrating uniform beam containing a symmetric discontinuity is presented. Based on this model, an analytical expression is developed which relates the length of the section containing the damage to the depth of the discontinuity. It thereby fixes the length of the element used to model this section of the beam. This expression was verified experimentally and shown to be material independent.
TL;DR: In this article, the deformation and stress fields near the tip of a crack under plane strain mode I conditions are studied. But the analysis is based on a direct asymptotic calculation.
Abstract: In this paper we study the deformation and stress fields near the tip of a crack under plane strain mode I conditions. A fully nonlinear theory of finite deformations is used and the material, which is assumed to be homogeneous, isotropic, incompressible and elastic, is characterized by its stress-strain behavior in simple shear. For the class of materials considered the governing system of differential equations may lose ellipticity at sufficiently severe strains. The analysis is based on a direct asymptotic calculation. The results involve two curves, issuing from each crack-tip, across which the deformation gradient, the ‘effective shear’ and the stresses are discontinuous.
Journal Article•
TL;DR: In this paper, a conservation law associated with non-equilibrium gas flow with chemical reaction is considered and some results on the growth of discontinuities and the occurrence of breakdown of the solution are pointed out.
Abstract: We shall consider a conservation law associated with a non-equilibrium gas flow with chemical reaction. Some results on the growth of discontinuities and the occurrence of breakdown of the solution are pointed out.
TL;DR: In this article, a risk model is presented in which both geometrical and shear strength parameters may be regarded as random variables, and the relevant equations and calculation procedures are outlined and typical results presented.
TL;DR: In this paper, the authors discuss the continuity and discontinuity in the history of optics: Kepler and the medieval tradition, and the Renaissance of a history of science and technology in general.
Abstract: (1987). Continuity and discontinuity in the history of optics: Kepler and the medieval tradition. History and Technology: Vol. 4, Science: The Renaissance of a History, pp. 431-448.
TL;DR: In this article, explicit expressions for some diffraction coefficients related to the diffraction from the impedance discontinuity on a cylindrically curved impedance surface are obtained, when the radius of the curvature becomes infinitely large.
Abstract: Explicit expressions for some diffraction coefficients related to the diffraction from the impedance discontinuity on a cylindrically curved impedance surface are obtained. When the radius of the curvature becomes infinitely large, the edge diffraction coefficient reduces to the known result related to the two-part impedance half-planes.
TL;DR: In this article, the authors measured the magnitude of the discontinuity in IPTS-68 at 6.74°C and found that it is 0.51 ± 0.10 percent.
Abstract: Although the IPTS-68 is meant to be a close approximation to thermodynamic temperatures, its definition makes no provision for continuity in dt/dt68 at 630.74°C. Any discontinuity in dt/dt68 at 630.74°C is directly related to the corresponding discontinuity in the first derivative with respect to t68 of sensor output, so the former can be obtained from measurement of the latter. The magnitude of the discontinuity has not previously been measured precisely; it has an important bearing on elucidating the behaviour of (t - t68) near 630.74°C. Over the temperature range from about 610°C to 645°C two calibrated platinum resistance thermometers, nine platinum - 10% rhodium/platinum thermocouples, and two other types of thermocouples have been intercompared in an experimental arrangement designed expressly to measure the discontinuity. The result for the relative discontinuity in dt/dt68 at 630.74°C was found to be 0.51 ± 0.10 percent.
TL;DR: In this paper, the critical pitch-angle for the trapping of a particle incident on the magnetopause is derived for the case when the magnetopsause is a tangential discontinuity.
01 Jan 1987
TL;DR: In this article, an attempt is made to investigate the properties of deep mantle discontinuities beneath the Kerguelen hot spot, where anomalous P to S converted waves are observed for some earthquakes recorded at the GEOSCOPE station; the characteristics of these phases are specified owing to a threedimensional polarization analysis of the signals.
TL;DR: The Stranski-Krastanov growth mode of Ga on the InP(100) surface is reexamined by electron-energy-loss spectroscopy and other surface-sensitive techniques, and the energy-band discontinuity between InP and GaP is estimated.
Abstract: The Stranski-Krastanov growth mode of Ga on the InP(100) surface is reexamined by electron-energy-loss spectroscopy and other surface-sensitive techniques. The formation of GaP on top of the InP surface as the result of the Ga-In exchange reaction is postulated from the experimental evidence, and the energy-band discontinuity between InP and GaP is estimated.
TL;DR: Using photoluminescence, this article investigated the properties of quasi-two-dimensional electron-hole plasmas in lattice-matched InGaAs/InP-multi-quantum well structures under quasi-stationary excitation.
TL;DR: In this article, the authors analyzed rigorously the problem of scattering from the discontinuity between two dielectric slabs by means of the Wiener-Hopf method and found that the scattering patterns agree well if the slabs are lossy (σ/ω ⩾ 1.0) and the thickness is more than the skin depth.
Abstract: A method often used for analyzing the problem of scattering by a lossy dielectric slab is an approximate one in which the dielectric slab is replaced with an impedance plane with an infinitesimal thickness. We analyzed rigorously the problem of scattering from the discontinuity between two dielectric slabs by means of the Wiener-Hopf method. The numerical calculations in such a method is quite complicated. If this problem can be replaced with that of two impedance planes, the analysis and computation can be simplified significantly.
In this paper, the scattered field of the E wave by the discontinuity of two impedance planes is analyzed by the Wiener-Hopf technique. The results are compared with the rigorous solution of the scattered E wave by the discontinuity of two dielectric slabs. From the numerical results of the two problems, it is found that the scattering patterns agree well if the slabs are lossy (σ/ω ⩾ 1.0) and the thickness is more than the skin depth. It is also found that the magnitude of the scattered wave almost agrees if the thickness is about one wavelength. Hence, if the slab thickness is more than a certain value for the E wave with the electric field component normal to the incident plane, the impedance plane approximation is effective for the lossy dielectric slab problem.