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Mode I (mode + i)

Distribution by Scientific Domains

Engineering	54%
Polymers and Materials Science	45%

Selected Abstracts

Theoretical crack path prediction

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 1-2 2005
H. A. RICHARD
ABSTRACT In many practical cases, the crack growth leads to abrupt failure of components and structures. For reasons of a reliable quantification of the endangerment due to sudden fracture of a component, therefore, it is of enormous importance to know the threshold values, the crack paths and the growth rates for the fatigue crack growth as well as the limiting values for the beginning of unstable crack growth (fracture toughness). This contribution deals with the complex problem of a,however initiated,crack, that is subjected to a mixed-mode loading. It will present the hypotheses and concepts, which describe the superposition of Mode I and Mode II (plane mixed mode) as well as the superposition of all three modes (Mode I, II and III) for spatial loading conditions. Those concepts admit a quantitative appraisal of such crack situations and a characterization of possible crack paths. [source]

Fracture behaviour of PC/ABS resin under mixed-mode loading

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 12 2001
Husaini
Fracture behaviour of polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) under mixed-mode loading conditions was studied for several weight fractions of PC and ABS. Mode I and mixed-mode fracture tests were carried out by using compact,tension,shear specimens. At a certain value of mixed-mode loading ratio KII,/KI, a crack of the shear type will initiates at the initial crack tip. Fracture toughness increases under mixed-mode loading with an increase in the mode II component, whereas it reduces with the appearance of a shear-type fracture. Fracture toughness and the appearance of a shear-type fracture depends on the blending ratio of PC and ABS. The transition to shear-type fracture occurs at lower value of KII,/KI for resins with higher fracture toughness. [source]

Finite element analysis of corner point displacements and stress intensity factors for narrow notches in square sheets and plates

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 12 2000
L. P. Pook
It is possible to model a crack as a narrow parallel-sided notch with a semicircular tip. Surface displacements of narrow notches in the vicinity of a corner point where the notch tip intersects a free surface were investigated, using finite element analysis, for each of the three modes of crack tip surface displacement. Some reasonably accurate relevant stress intensity factors were determined by analysis of notch tip stresses. The extent of corner regions in which stress intensity measures, rather than stress intensity factors, dominate crack tip stresses was determined by analysis of the notch surface displacements and of relevant stress intensity factors. Under nominal Mode III loading corner point effects are local, but under nominal Mode I and nominal Mode II loadings they are a combination of local and global effects. Volterra distorsioni are useful in the description of crack, and narrow notch, surface displacements under load. [source]

Influence of the Compositional Profile of Functionally Graded Material on the Crack Path under Thermal Shock

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2001
Takao Fujimoto
Thermal cracking under a transient-temperature field in a ceramic/metal functionally graded plate is discussed. When the functionally graded plate is cooled from high-temperature, curved or straight crack paths often occur on the ceramic surface. It is shown that the crack paths are influenced by the compositional profile of the functionally graded plate. Transient-thermal stresses are treated as a linear quasi-static thermoelastic problem for a plane strain state. The crack paths are obtained using finite element method with Mode I and Mode II stress intensity factors. [source]

Fracture and fatigue study of unidirectional glass/epoxy laminate under different mode of loading

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 5 2010
M. KENANE
ABSTRACT Interlaminar fracture is the dominant failure mechanism in most advanced composite materials. The delaminating behaviour of materials is quantified in terms of the strain energy release rate,G. In this paper, the experimental measurements of the fatigue delaminating growth for some combinations of energy release rate mode ratio have been carried out on unidirectional glass/epoxy laminates. On this base the constants in the Paris equation have been determined for each GII/GT considered modal ratio. The fatigue threshold strain energy release rate ,,GTth, below which delaminating doesn't occur, were measured. Three type specimens were tested, namely: double cantilever beam (DCB), end-loaded split (ELS) and mixed-mode bending (MMB) under mode I, mode II and mixed-mode (I + II) loading, respectively. Scanning electron microscopy techniques were used to identify the fatigue delamination growth mechanisms and to define the differences between the various modes of fracture. [source]

Lower and upper bound estimation of isotropic and orthotropic fracture mechanics problems using elements with rotational degrees of freedom

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 5 2008
Antoinette de Klerk
Abstract We use Rice's path-independent J integral, as well as its dual, the I* integral, to estimate lower and upper bounds of the stress intensity factor K in linear elastic fracture mechanics problems. The elements used contain rotational degrees of freedom, and are derived from the correct energy principles to guarantee path independence of the integrals. That is, the displacement-based elements used in calculating the J integral are derived from the principle of potential energy; the assumed stress elements used in calculating the I* integral are derived from complementary energy principles. For lower bound estimation in particular, elements with drilling degrees of freedom are advantageous, due to their superior accuracy. Numerical results are presented for isotropic and orthotropic mode I and mode II fracture mechanics problems. In addition, we reflect on suitable finite element integration schemes, and applicable values for the problem dependent penalty parameter , which is used in deriving the elements. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Numerical simulation of fatigue-driven delamination using interface elements

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 13 2005
Paul Robinson
Abstract This paper presents a computational technique for the prediction of fatigue-driven delamination growth in composite materials. The interface element, which has been extensively applied to predict delamination growth due to static loading, has been modified to incorporate the effects of cyclic loading. Using a damage mechanics formulation, the constitutive law for the interface element has been extended by incorporating a modified version of a continuum fatigue damage model. The paper presents details of the fatigue degradation strategy and examples of the predicted fatigue delamination growth in mode I, mode II and mixed mode I/II are presented to demonstrate that the numerical model mimics the Paris law behaviour usually observed in experimental testing. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Geometrically non-linear damage interface based on regularized strong discontinuity

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 4 2002
Ragnar Larsson
Abstract The contribution of this paper concerns the fracture modelling of an interface with a fixed internal material surface in the context of geometrically non-linear kinematics. Typical applications are composite laminates and adhesive/frictional joints in general. In the model development, a key feature is the concept of regularized strong discontinuity, which provides a regular deformation gradient within the interface. The deformation gradient within the interface is formulated in a multiplicative structure with a continuous part and a discontinuous part, whereby the interface deformation is interpreted as a transformation between the material damaged configuration and the actual spatial configuration. In analogy with the continuum formulation of hyper-inelasticity, a constitutive framework is defined for the relation between the induced material traction and the displacement jump vector, which are defined on the material damaged interface configuration. Within this framework, a simple, but yet still representative, model for the delamination problem is proposed on the basis of a damage,plasticity coupling for the interface. The model is calibrated analytically in the large deformation context with respect to energy dissipation in mode I so that a predefined amount of fracture energy is dissipated. The paper is concluded with a couple of numerical examples that display the properties of the interface. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Re-entrant corner problems for isotropic materials and layered composites

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2005
E. Schnack
Modern materials like composites in different types require new methods in computational fracture mechanics. Besides of classical fracture mechanics we have to solve the asymptotic solution around crack tips. This can be done on the basis of the Kondratievs theorem with the Pietrov-Galerkin method to solve the unknown eigenvalues for those problems. Additionally, we have to de.ne instead classical modes I, II and III, mode I* up to mode IV* to interpret the computational results for the unknown eigenvalues. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

A Finite Interface Crack Interacting With A Subinterface Crack In Metal/Piezoelectric Ceramic Bimaterial

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003
Wen-Ye Tian
The "pseudo-traction-electric-displacement' method was adopted to solve the interaction problem between a finite interface crack and a subinterface crack in metal/piezoelectric bimaterial. After deriving the fundamental solutions for a finite interface crack and a special subinterface crack respectively loaded by the normal and tangential concentrated tractions and the concentrated electric displacement, the present interaction problem was reduced to a system of integral equations, which may be solved numerically. The crack tip mode I stress intensity factor was calculated and detailed comparisons of the results derived under the compound mechanical-electric loading conditions and those derived under the purely mechanical loading condition are performed. [source]