Home  About us  Contact
 

Crack Opening (crack + opening)

Distribution by Scientific Domains
Engineering57%
Polymers and Materials Science42%

Terms modified by Crack Opening

  • crack opening displacement
    		•

    Selected Abstracts

    Molecular dynamics simulation of crack tip blunting in opposing directions along a symmetrical tilt grain boundary of copper bicrystal

    FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 11 2007
    A. LUQUE
    ABSTRACT Mode I crack growth along some grain boundaries of copper embrittled by solute segregation shows strong anisotropy. For instance, growth along the direction on the symmetrical tilt boundary has been reported to occur by intergranular brittle fracture, whereas growth along the opposite sense occurs in a ductile manner. In this paper, we simulate such crack configurations using molecular dynamics (embedded atom method [EAM]) in 3-dimensional perfect bicrystalline samples of pure copper of the aforementioned orientation at room temperature. In both cases the response is ductile, crack opening taking place by dislocation emission from the crack tip. The critical stress intensity factors (SIFs) for dislocation emission have been calculated by matching the displacement fields of the atoms in the tip neighbourhood with the continuum elastic fields. They are of the same order of magnitude for both growth senses despite the different morphology of their respective blunted crack tips and of the patterns of dislocations constituting their plastic zones. Thus, it seems that, in agreement with published results of continuum crystalline plasticity for the same problem, the plastic anisotropy associated with the different orientation of the slip systems with respect to the crack cannot in this case explain the experimental behaviour observed with solute embrittled bicrystals. [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]

    Computational mechanics of the steel,concrete interface,

    INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 2 2002
    M. R. Ben Romdhane
    Abstract Concrete cracking in reinforced concrete structures is governed by two mechanisms: the activation of bond forces at the steel,concrete interface and the bridge effects of the reinforcement crossing a macro-crack. The computational modelling of these two mechanisms, acting at different scales, is the main objective of this paper. The starting point is the analysis of the micro-mechanisms, leading to an appropriate choice of (measurable) state variables describing the energy state in the surface systems: on the one side the relative displacement between the steel and the concrete, modelling the bond activation; on the other hand, the crack opening governing the bridge effects. These displacement jumps are implemented in the constitutive model using thermodynamics of surfaces of discontinuity. On the computational side, the constitutive model is implemented in a discrete crack approach. A truss element with slip degrees of freedom is developed. This degree of freedom represents the relative displacement due to bond activation. In turn, the bridge effect is numerically taken into account by modifying the post-cracking behaviour of the contact elements representing discrete concrete cracks crossed by a rebar. First simulation results obtained with this model show a good agreement in crack pattern and steel stress distribution with micro-mechanical results and experimental results. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    Towards the algorithmic treatment of 3D strong discontinuities

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 2 2007
    J. Mergheim
    Abstract A geometrically non-linear finite element framework for the modelling of propagating discontinuities in three-dimensional continua is presented. By doubling the degrees of freedom in the discontinuous elements, the algorithm allows for arbitrary discontinuities which are not restricted to inter-element boundaries. The deformation field is interpolated independently on both sides of the discontinuity. In contrast to the X-FEM, the suggested approach thus relies exclusively on displacement degrees of freedom. On the discontinuity surface, the jump in the deformation is related to the cohesive tractions to account for smooth crack opening. Computational difficulties characteristic of three-dimensional crack propagation are addressed. The performance of the method is elaborated by means of a homogeneous three-dimensional tension problem and by means of the classical peel test. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Crack Tip Morphology of Slowly Growing Cracks in Glass

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2000
    Stéphane Hénaux
    We present atomic force microscopy (AFM) observations of crack tips in glass during subcritical propagation. These have been obtained by means of an AFM sample holder which has been specially designed to propagate indentation cracks in glass plates. Crack tips in soda,lime,silica glass are always preceded by a few nanometers deep deformation. In vitreous silica, no other surface deformation than the crack itself could be detected. For both materials, the crack opening is found to largely exceed the elastic solution. [source]

    Beanspruchungsanalyse von Holzbauteilen durch 2D-Photogrammetrie

    BAUTECHNIK, Issue 2 2005
    Bettina Franke Dipl.-Ing.
    Für die Bewertung der Tragsicherheit von Bauteilen aus Voll- und Brettschichtholz in Lasteinleitungs- und Störbereichen mittels der Bruchmechanik ist die Kenntnis von kritischen Bruchkennwerten Voraussetzung. Realitätsnahe Kennwerte können aus der Kombination experimenteller Untersuchungen zur Bestimmung der Rißaufweitung und der Rißlänge mit daran anschließender FE-Simulation gewonnen werden. Aufgrund der, bisher bei konventionellen Meßverfahren, nicht ausreichenden Zuordnung der Meßwerte taktil applizierter Meßaufnehmer lag es nahe das Rißwachstum mit Hilfe der Photogrammetrie zu untersuchen. Mit dem entwickelten Meßsystem ist nunmehr die Möglichkeit der exakten Vermessung der Rißgeometrie zur Bestimmung von bruchmechanischen Kennwerten gegeben. Zusätzlich ermöglicht der Einsatz der Photogrammetrie die Verdichtung der Anzahl variierender diskreter Meßpunkte, so daß ein deutlich vollständigeres Bild der örtlichen Verformungen gewonnen, und damit die Aussagekraft eines Versuchs wesentlich verbessert werden kann. Strain analysis of solid wood and glued laminated timber members by close range photogrammetry. The assumption of critical fracture mechanics parameters for the evaluation of the load-bearing safety of structural units of full and board laminated timber in loaded areas and disturbance ranges the use of fracture mechanics is required. Realistic parameters can be gained only from experimental investigations that are transferred to the determination of the crack opening and the crack length with subsequent FE-simulation. Due to the insufficient appropriation of measured data gained by tactile position encoders in conventional measuring procedures it is advisable to investigate crack growth with the help of the photogrammetry. Using the developed measuring system it is now possible to measure the crack geometry exactly for the determination of fracture mechanics parameters. Additionally a complete picture of the local deformations and the validity of a test can be improved considerably by the possibility of the varying number of discrete measuring points. [source]

    Crack opening displacement in plate with bonded repair patch

    FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 6 2006
    M. M. RATWANI
    ABSTRACT Mathematical techniques are extended to compute crack opening displacements in a cracked plate with an adhesively bonded composite patch. The plate and the patch are considered as orthotropic materials. The problem is reduced to the solution of integral equations. A software program is written to compute shear stresses in adhesive, stress intensity factors in the plate and the crack openings at the centreline of the crack. The effects of adhesive thickness, adhesive modulus, patch thickness and plate thickness on crack openings are investigated. A test program is carried out to obtain crack opening displacements in plate with bonded patch. A good agreement with analytical predictions is obtained. The effects of patches bonded on one or both sides of a plate on stress intensity factors are evaluated. [source]