3 research outputs found
Hashin-Shtrikman Bounds of Cubic Crystalline Aggregate Elasticity for poly-Si Solar Cells
In present work, the studies on the analytical determination of polycrystalline silicon effective mechanical propertiesfor solar cells based on a class of bounds are intensified while second-order estimates are introduced. Thereby the fundamentalaspects of the Hashin-Shtrikman bounds of linear elastic properties for a cubic crystal aggregate are surveyed. The aggregateis considered homogeneous and isotropic in a statistical sense. This framework is exploited to determine improved bounds incomparison to the classically applied first-order bounds. The results gained are related to previously published Voigt and Reussbounds and to experimental data. Improvements and problems are highlighted and discussed
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Capturing Evolving Size-Dependent Anisotropy from Brittle Fracture to Plasticity for Geological Materials
We present a computational framework for modeling geomaterials undergoing failure in the brittle and ductile regimes. This computational framework introduces anisotropic gradient regularization to replicate a wide spectrum of size-dependent anisotropic constitutive responses exhibited in layered and sedimentary rock. Relevant subsurface applications include oil/gas wellbore completions, caprock evaluation for carbon sequestration in saline aquifers, and geothermal energy recovery. Considered failure modes are mixed-mode fracture, shear band formation due to plastic strain localization, and rate-dependent frictional slip along the propagated fracture's rock surface, subsequent to fracture closure.
Our nonlocal modeling framework extends the state-of-the-art gradient-enhanced plasticity and damage mechanics for frictional materials with a special treatment that injects bias for the regularization for different orientations. A novel contribution is that the formulations not only contains a regularization, but that the regularization also provides a method to introduce size-dependent anisotropies. Consequently, this treatment provides a new means to create non-associative flow via a variational framework while introducing different anisotropic responses for specimens of different sizes (introduced in Chapter 1). These anisotropic regularization modeling techniques are then applied to three classes of common geomechanics problems: critical state plasticity of clay and shale rock (Chapter 2), brittle fracture of rock (Chapter 3), and the plastic slip of interfaces and cracks (Chapter 4).
This combination, of established rock physics, local anisotropy, and size-dependent anisotropy enfranchised with diffusive regularization, is investigated. For instance, experimentation on uniaxially compressed specimens failing in the brittle regime reveals a repeatable typology of wing- and coalescent-crack patterns, broadly taken to indicate a mixed-mode fracture phenomenon particular to rock-like materials. In the ductile regime, biaxially compressed shale rock displays orientation-dependence of the plastic deformation difficult to capture merely by attributing anisotropy to the elastic response, with localization at or near the critical state. We numerically capture both these phenomena. Verification and/or validation is provided for proposed constitutive relations
UvA-DARE (Digital Academic Repository) A test of QCD based on 3-jet events from Z ° decays L3 Collaboration
A test of QCD based on three jet events from Z0 decays Adeva, B.; Adriani, O.; Aguilar-Benitez, M.; Ahlen, S.P.; Akbari, H.; Alcaraz, J.; Aloisio, A.; Alverson, G.; Linde, F.L. General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. We present a study of 43 000 3-jet events from Z ° boson decays. Both the measured jet energy distributions and the event orientation are reproduced by second order QCD. An alternative model with scalar gluons fails to describe the data