The Experts below are selected from a list of 10266 Experts worldwide ranked by ideXlab platform

Huang Yuan - One of the best experts on this subject based on the ideXlab platform.

  • assessment of low cycle fatigue crack growth under mixed mode loading conditions by using a Cohesive Zone Model
    International Journal of Fatigue, 2015
    Co-Authors: Huang Yuan
    Abstract:

    Abstract Most Cohesive Zone Models were used to reproduce fatigue crack growth under small scale yielding and failed to predict elastic–plastic fatigue crack growth. In the present work a new Cohesive Zone Model is introduced to give a uniform description of both fatigue crack growth and elastoplastic rupture. Damage accumulation of the Cohesive Model contains both monotonic damage as well as cyclic damage and validated by corresponding mixed-mode fracture and fatigue experiments of an austenitic stainless steel. Computations confirm that the present Cohesive Zone Model may provide a uniform description for the whole fatigue crack growth regimes.

  • on damage accumulations in the cyclic Cohesive Zone Model for xfem analysis of mixed mode fatigue crack growth
    Computational Materials Science, 2009
    Co-Authors: Huang Yuan
    Abstract:

    Abstract Predicting mixed-mode fatigue crack propagation is an important and troublesome issue in structure assessment for decades. In the present paper an extended finite element method (XFEM) combined with a new cyclic Cohesive Zone Model (CCZM) is introduced for simulating fatigue crack propagation under mixed-mode loading conditions, which has been implemented in the commercial general purpose software ABAQUS. The algorithm allows introducing a new crack surface at arbitrary locations and directions in a finite element mesh, without re-meshing. The cyclic Cohesive Zone Model is based on the known S–N curves and Goodman diagram for metallic materials and validated by uniaxial tension results. Furthermore, the sensitivity of the Model parameter is investigated for mixed-mode fatigue. The virtual crack closure technique has been extended to the Cohesive Zone Model and proposed to calculate the energy release rate for the generalized Paris’ law. Finally, the crack propagation rate and direction under mixed-mode fatigue loading conditions are studied.

Marco Paggi - One of the best experts on this subject based on the ideXlab platform.

  • an anisotropic large displacement Cohesive Zone Model for fibrillar and crazing interfaces
    International Journal of Solids and Structures, 2015
    Co-Authors: Marco Paggi, J Reinoso
    Abstract:

    A new Cohesive Zone Model to describe fracture of interfaces with a microstructurs made of fibrils with statistically distributed in-plane and out-of-plane orientations is proposed. The elementary force–displacement relation of each fibril is considered to obey the peeling theory of a tape, although other refined constitutive relations could be invoked for the adhesive constitutive response without any lack of generality. The proposed consistent 2D and 3D interface finite element formulations for large displacements account for both the mechanical and the geometrical tangent stiffness matrices, required for implicit solution schemes. After a preliminary discussion on Model parameters identification, it is shown that by tailoring the spatial density of fibrils at different orientations can be a way to realize innovative interfaces enhancing adhesion or decohesion, depending on the need. For instance, it can be possible to realize microstructured adhesives to facilitate debonding of the glass cover in photovoltaic modules to simplify recycling purposes. Moreover, the use of probability distribution functions describing the density of fibrils at different orientations is a very effective approach for Modeling the anisotropy in the mechanical bonding between paper tissues and for simulating the complex process of crazing in amorphous polymers.

  • A coupled Cohesive Zone Model for transient analysis of thermoelastic interface debonding
    Computational Mechanics, 2014
    Co-Authors: Alberto Sapora, Marco Paggi
    Abstract:

    A coupled Cohesive Zone Model based on an analogy between fracture and contact mechanics is proposed to investigate debonding phenomena at imperfect interfaces due to thermomechanical loading and thermal fields in bodies with Cohesive cracks. Traction-displacement and heat flux–temperature relations are theoretically derived and numerically implemented in the finite element method. In the proposed formulation, the interface conductivity is a function of the normal gap, generalizing the Kapitza constant resistance Model to partial decohesion effects. The case of a centered interface in a bimaterial component subjected to thermal loads is used as a test problem. The analysis focuses on the time evolution of the displacement and temperature fields during the transient regime before debonding, an issue not yet investigated in the literature. The solution of the nonlinear numerical problem is gained via an implicit scheme both in space and in time. The proposed Model is finally applied to a case study in photovoltaics where the evolution of the thermoelastic fields inside a defective solar cell is predicted.

  • a nonlocal Cohesive Zone Model for finite thickness interfaces part i mathematical formulation and validation with molecular dynamics
    Computational Materials Science, 2011
    Co-Authors: Marco Paggi, Peter Wriggers
    Abstract:

    A nonlocal Cohesive Zone Model is derived taking into account the properties of finite thickness interfaces. The functional expression of the stress–separation relationship, which bridges the gap between continuum damage mechanics and nonlinear fracture mechanics, depends on the complex failure phenomena affecting the material microstructure of the interface region. More specifically, the shape of the nonlocal Cohesive Zone Model is found to be dependent on the damage evolution. On the other hand, damage is in its turn a function of dissipative mechanisms occurring at lower length scales, such as dislocation motion, breaking of interatomic bonds, formation of free surfaces and microvoids, that are usually analyzed according to molecular dynamics. Hence, the relationship intercurring between the parameters of the damage law and the outcome of molecular dynamics simulations available in the literature is also established. Therefore, the proposed nonlocal Cohesive Zone Model provides also the proper mathematical framework for interpreting molecular dynamics-based stress–separation relationships that are typically nonlocal, since they always refer to a finite number of atom layers.

Franck Gallerneau - One of the best experts on this subject based on the ideXlab platform.

  • a Cohesive Zone Model for fatigue and creep fatigue crack growth in single crystal superalloys
    International Journal of Fatigue, 2009
    Co-Authors: Jeanluc Bouvard, J L Chaboche, Frederic Feyel, Franck Gallerneau
    Abstract:

    Abstract A numerical analysis using Cohesive Zone Model under cyclic loading is proposed to develop a coupled predictive approach of crack growth in single crystal. The process of material damage during fatigue crack growth is described using an irreversible Cohesive Zone Model, which governs the separation of the crack flanks and eventually leads to the formation of free surfaces. The Cohesive Zone element is Modeled to accumulate fatigue damage during loadings and no damage during unloadings. This paper presents the damage Model and its application in the study of the crack growth for precracked specimens. The use of Cohesive Zone approach is validated through a convergence study. Then, a general procedure of parameters calibration is presented in pure fatigue crack growth. In the last section, an extension of the Cohesive Zone Model is presented in the case of creep–fatigue regime at high temperature. The Model showed its capability to predict with a good agreement the crack growth in the case of complex loading and complex specimen geometries.

Thomas Siegmund - One of the best experts on this subject based on the ideXlab platform.

  • computations of fatigue crack growth with strain gradient plasticity and an irreversible Cohesive Zone Model
    Engineering Fracture Mechanics, 2008
    Co-Authors: Steffen Brinckmann, Thomas Siegmund
    Abstract:

    Computations of fatigue crack growth with a first-order strain gradient plasticity (SGP) Model and an irreversible Cohesive Zone Model are reported. SGP plays a significant role in the Model predictions and leads to increased fatigue crack growth rates relative to predictions with classical plasticity. Increased magnitudes of tractions and material separation at the crack tip together with reduced crack closure appear as the cause for accelerated crack growth in SGP. Under plane strain conditions SGP appears as an essential feature of the development of the crack closure Zone. Size effects are explored relative to changes in internal material length scale as well as to structural length scales.

  • a numerical study of transient fatigue crack growth by use of an irreversible Cohesive Zone Model
    International Journal of Fatigue, 2004
    Co-Authors: Thomas Siegmund
    Abstract:

    Abstract Transient fatigue crack growth is studied for a material system in which the crack tip is shielded due to crack bridging. The process of material separation during fatigue crack growth is described by the use of an irreversible Cohesive Zone Model. In contrast to past developments of Cohesive Zone Models, the traction–separation behavior does not follow a predefined path, but is dependent on the evolution of the damage dependent Cohesive Zone properties. The Model definition is given and the basic uniaxial response of the Model documented. The Cohesive Zone Model is subsequently applied in a numerical study of transient fatigue crack growth. Single overload cases are computed to demonstrate the effects of variations in the Cohesive Zone properties. Block loading sequences with variations in the amplitude and the load ratio are computed. Model predictions qualitatively compare well to experimentally observed effects of fatigue crack growth transients in materials with crack bridging Zones.

  • an irreversible Cohesive Zone Model for interface fatigue crack growth simulation
    Engineering Fracture Mechanics, 2003
    Co-Authors: Thomas Siegmund
    Abstract:

    Abstract Fatigue crack growth (FCG) along an interface is studied. Instead of using the Paris equation, the actual process of material separation during FCG is described by the use of an irreversible constitutive equation for the cyclic interface traction–separation behavior within the Cohesive Zone Model (CZM) approach. In contrast to past development of CZMs, the traction–separation behavior does not follows a predefined path. The Model definition, its predicted cyclic material separation behavior and application to a numerical study of interface FCG in double-cantilever beam, end-loaded split and mixed-mode beam specimens are reported.

  • an analysis of crack growth in thin sheet metal via a Cohesive Zone Model
    Engineering Fracture Mechanics, 2002
    Co-Authors: Thomas Siegmund
    Abstract:

    A Cohesive Zone Model (CZM) is applied to crack growth in thin sheet metal. CZM parameters are determined from results of global measurements and micromechanical damage Models. Crack propagation in constrained center-cracked panels is analyzed to verify the choice of CZM parameters. Special attention is paid to the interaction between buckling and crack growth and to crack link-up in multi-site damaged specimens. The good agreement found between the predicted and experimental data demonstrates that the approach is attractive in investigation of structural integrity of thin-walled structures and does not require assumptions regarding the geometry and size dependence of crack growth parameters.

Pablo D. Zavattieri - One of the best experts on this subject based on the ideXlab platform.

  • an inverse analysis of Cohesive Zone Model parameter values for ductile crack growth simulations
    International Journal of Mechanical Sciences, 2014
    Co-Authors: Xin Chen, Xiaomin Deng, Michael A Sutton, Pablo D. Zavattieri
    Abstract:

    Abstract An inverse analysis using a modified Levenberg–Marquardt method is carried out to identify Cohesive Zone Model parameter values for use in 3D finite element simulations of stable tearing crack growth events in Arcan specimens made of 2024-T3 aluminum alloy. The triangular Cohesive law is employed in the simulations. The set of Cohesive parameter values is determined in the inverse analysis by minimizing the difference between simulation predictions of key points on the load–crack extension curve with experimental measurements. From three different initial values, similar Cohesive parameter value sets are reached. Using these sets of values, the predicted load–crack extension curves and the variation of a generalized crack tip opening displacement (CTOD) with crack extension for mixed-mode loading cases are compared with experimental measurements, which provide a validation of the Cohesive parameter values and of the finite element simulation predictions.

  • use of a Cohesive Zone Model to analyze the fracture of a fiber reinforced polymer matrix composite
    Composites Science and Technology, 2005
    Co-Authors: Suyi Li, M D Thouless, Anthony M Waas, Pablo D. Zavattieri
    Abstract:

    Abstract A Cohesive-Zone Model for a fiber-reinforced polymer–matrix composite is presented. A two-parameter Model with a characteristic toughness and a characteristic strength can be used to predict the fracture of notched or cracked specimens. The two parameters can be determined by comparing numerical predictions to experimental observations of a fracture test. It is shown that the engineering behavior, in terms of strength, deformation and energy dissipation is well-described by such a two-parameter Model, but when the characteristic dimensions of the composite structure (e.g., the initial crack length or ligament length) are very small, extra details about the Cohesive law such as the matrix-cracking strength may be required. Finally, it is shown that a Cohesive-Zone Model provides excellent predictions of transitions between stable and catastrophic crack growth in the composite, and, hence, permits an understanding of the energy dissipation during fracture that occurs in these different regimes.