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Hydrostatic stress

About: Hydrostatic stress is a research topic. Over the lifetime, 1568 publications have been published within this topic receiving 37773 citations.


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TL;DR: A comprehensive theoretical study of short-period strained-layer superlattices (SLS's) on Si and Ge [001] substrates, and the ``free-standing'' case, based on ab initio calculations.
Abstract: We present a comprehensive theoretical study of short-period (Ge${)}_{\mathit{n}}$/(Si${)}_{\mathit{m}}$ strained-layer superlattices (SLS's) on Si and Ge [001] substrates, and the ``free-standing'' case, based on ab initio calculations. In order to compensate for the error in the excitation energies inherent to the local-density approximation, we add ad hoc potentials on the atomic sites. With this correction the calculated transition energies compare favorably with quasiparticle calculations and experiment. Special emphasis is placed on the orthorhombic nature of the SLS's with both n and m even, as reflected in both the energy-band structure and the dielectric response ${\mathit{varepsilon}}_{2}$(\ensuremath{\omega}), which is different for all three polarizations along the main axes. The effects of various substrates is examined for the occurring interband transitions, and in some cases reduced to a simple deformation-potential ansatz. A similar approach is taken for the splitting of the top of the valence band due to the internal uniaxial strain, which obeys a simple Vegard-type law; it is shown that confinement effects are negligible up to the values considered, i.e., n+m=12. The SLS's with a period of n+m=10 and sufficiently large strain in the Si layers have a direct gap; the transition from the top of the valence band to the lowest zone-folded conduction band at k=0, however, is only dipole allowed for special cases, such as the superlattices with n,m odd, i.e., for systems with no inversion symmetry. The (Ge${)}_{5}$/(Si${)}_{5}$ SLS is predicted to be a good candidate for optoelectronic devices. A reversal of the two lowest folded conduction states (dipole allowed and forbidden, respectively) is obtained when going from the n=4 to the n=6 case. Recent experiments on 10-monolayer SLS's are discussed in the light of our results.

67 citations

Journal ArticleDOI
TL;DR: In this article, a flywheel was modified to carry out compression tests at high strain rates, and a hydrostatic chamber designed to obtain the variation of stress with volumetric strain, as a function of density and deformation rate.

66 citations

Journal ArticleDOI
TL;DR: In this paper, the propagation of plane waves in fiber-reinforced, anisotropic thermoelastic half-space under hydrostatic initial stress is discussed and the problem has been solved numerically using a finite element method.
Abstract: The propagation of plane waves in fiber-reinforced, anisotropic thermoelastic half-space proposed by Lord-Shulman under hydrostatic initial stress is discussed. The problem has been solved numerically using a finite element method. Numerical results for the temperature distribution, the displacement components and the thermal stress are given and illustrated graphically. Comparisons are made with the results predicted by the theory of generalized thermoelasticity with one relaxation time for different values of pressure. It is found that the hydrostatic initial stress has a great effect on the distribution of field quantities.

66 citations

Journal ArticleDOI
TL;DR: In this paper, a new version of a hypoplastic constitutive equation is presented which is characterized by the introduction of a stress-like internal parameter called back stress, which is a function of the void ratio and of the hydrostatic stress.
Abstract: A new version of a hypoplastic constitutive equation is presented which is characterized by the introduction of a stress-like internal parameter called back stress. The back stress is a function of the void ratio and of the hydrostatic stress. Using a unique set of material constants, the new constitutive equation describes many aspects of the behaviour of cohesionless soils including the influence of density and stress level. This is demonstrated by a series of verification tests. The determination of the material constants from laboratory tests is described analytically.

65 citations

Journal ArticleDOI
TL;DR: In this article, a new methodology to investigate the failure of elastomers in a confined geometry has been developed and applied to model end-linked polyurethane elastomer.
Abstract: A new methodology to investigate the failure of elastomers in a confined geometry has been developed and applied to model end-linked polyurethane elastomers. The experimental in situ observations show that the elastomers fail by the growth of a single cavity nucleated in the region of maximum hydrostatic stress. Tests carried out at different temperatures for the same elastomer show that the critical stress at which this crack grows is not proportional to the Young's modulus E but depends mainly on the ratio between the mode I fracture energy G IC and E. A reasonable fit of the data can be obtained with a model of cavity expansion by irreversible fracture calculating the energy release rate by finite elements with a strain hardening constitutive equation. Comparison between different elastomers shows that the material containing both entanglements and crosslinks is both tougher in mode I and more resistant to cavitation relative to its elastic modulus.

64 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202318
202246
202134
202047
201948
201839