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Anisotropic Damage (anisotropic + damage)

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Engineering100%

Selected Abstracts

Anisotropic damage of shock wave-loaded plates

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2006
Marcus Stoffel
In the present study circular metal plates are subjected to impulsive loadings in shock tubes. The damage growth in the plate specimens until failure is predicted by finite element simulations. The aim is to validate the applied isotropic and anisotropic damage laws by means of comparisons between calculated and measured deformations. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Homogenization-based analysis of anisotropic damage in brittle materials with unilateral effect and interactions between microcracks

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 6 2009
Q. Z. Zhu
Abstract This paper is devoted to micromechanical modeling of induced anisotropic damage in brittle geomaterials. The formulation of the model is based on a proper homogenization procedure by taking into account unilateral effects and interactions between microcracks. The homogenization procedure is developed in the framework of Eshelby's inclusion solution and Ponte-Castaneda and Willis (J. Mech. Phys. Solids 1995; 43:1919,1951) estimate. The homogenization technique is combined with the thermodynamics framework at microscopic level for the determination of damage evolution law. A rigorous crack opening,closure transition condition is established and an energy-release-rate-based damage criterion is proposed. Computational aspects on the implementation of micromechanical model are also discussed. The proposed model is evaluated by comparing numerical predictions with experimental data for various laboratory tests on concrete. Parametric studies on unilateral effects and influences of microcracks interactions are finally performed and analyzed. Copyright © 2008 John Wiley & Sons, Ltd. [source]

A rate-dependent cohesive crack model based on anisotropic damage coupled to plasticity

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 9 2006
Per-Ola Svahn
Abstract In quasi-brittle material the complex process of decohesion between particles in microcracks and localization of the displacement field into macrocracks is limited to a narrow fracture zone, and it is often modelled with cohesive crack models. Since the anisotropic nature of the decohesion process in separation and sliding is essential, it is particularly focused in this paper. Moreover, for cyclic and dynamic loading the unloading, load reversal (including crack closure) and rate dependency are essential features that are included in a new model. The modelling of degradation is based on a ,localized' version of anisotropic continuum damage coupled to inelasticity. The concept of strain energy equivalence between the states in the effective and nominal settings is adopted in order to define the free energy of the interface. The proposed fracture criterion is of the Mohr type, with a smooth transition of the failure and kinematics (slip and dilatation) characteristics between tension and shear. The chosen potential, of the Lemaitre-type, for evolution of the dissipative processes is additively decomposed into plastic and damage parts, and non-associative constitutive equations are obtained. The constitutive equations are integrated by applying the backward Euler rule and by using Newton iteration. The proposed model is assessed analytically and numerically and a typical calibration procedure for concrete is proposed. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Modelling of anisotropic damage in brittle rocks under compression dominated stresses

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 10 2002
Y.F. Lu
Abstract A new model for describing induced anisotropic damage in brittle rocks is proposed. Although phenomenological, the model is based on physical grounds of micromechanical analysis. Induced damage is represented by a second rank tensor, which is related to the density and orientation of microcracks. Damage evolution is related to the propagation condition of microcracks. The onset of microcrack coalescence leading to softening behaviour is also considered. The effective elastic compliance of the damaged material is obtained from a specific form of Gibbs potential. Irreversible damage-related strains due to residual opening of microcracks after unloading are also captured. All the model's parameters could be determined from conventional triaxial compression tests. The proposed model is applied to a typical brittle rock. Comparison between test data and numerical simulations shows an overall good agreement. The proposed model is able to describe the main features related to induced microcracks in brittle geomaterials. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Mehraxiales mechanisches Ermüdungsmodell von Ultra-Hochfestem Beton: Experimentelle und analytische Untersuchungen

BETON- UND STAHLBETONBAU, Issue 6 2007
Jürgen Grünberg Prof. Dr.-Ing.
Die besonderen Eigenschaften von ultra-hochfestem Beton (UHPC) gegenüber normalfestem Beton erfordern für numerische Analysen die Entwicklung eines mehraxialen mechanischen Modells. Im Dreiphasenmodell werden sowohl sprödes als auch duktiles Baustoffverhalten durch charakteristische Verläufe der Hauptmeridiane, insbesondere des Druckmeridians der Bruchumhüllenden beschrieben. Die anisotrope Ermüdungsschädigung wird im Hauptspannungsraum durch unterschiedliche Schädigungsraten für den Zug- bzw. Druckmeridian berücksichtigt. In umfangreichen experimentellen Untersuchungen werden zur Kalibrierung des Dreiphasenmodells für UHPC die Modellparameter für die Beschreibung der Hauptmeridianverläufe bestimmt. In dynamischen Untersuchungen werden die Parameter für die anisotrope Schädigung bestimmt. Multiaxial Mechanical Model of Ultra-High-Performance Concrete The special and outstanding characteristics of ultra-high-performance concrete (UHPC) require the development of a multiaxial mechanical model for numerical investigations. With the three phases model it is possible to describe the behaviour of concrete from extremely brittle to more ductile using the characteristic development of the principal meridians, in particular the compressive meridian of the fracture surface. Furthermore, the anisotropic damage due to fatigue is considered in the principal-stressarea by different grades of damage in relation to the tensile and the compressive meridian. In experimental investigations, the necessary parameters are determined to calibrate the three phases model for UHPC by specifying the principal meridians for static loading. In further dynamic investigations the parameters for an anisotropic damage model are determined for fatigue loading. [source]