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Showing papers on "Crack closure published in 1989"


Journal ArticleDOI
TL;DR: In this paper, the authors examined the competition between deflection and penetration when the materials on either side of the interface are elastic and isotropic and determined the range of interface toughness relative to bulk material toughness which ensures that cracks will be deflected into the interface.

1,195 citations


Journal ArticleDOI
TL;DR: In this paper, a plane strain crack out of the interface between two dissimilar isotropic elastic solids is analyzed and the stress intensity factors and energy release rate of the kinked crack in terms of the corresponding quantities for the interface crack prior to kinking.
Abstract: Kinking of a plane strain crack out of the interface between two dissimilar isotropic elastic solids is analyzed. The focus is on the initiation of kinking and thus the segment of the crack leaving the interface is imagined to be short compared to the segment in the interface. Accordingly, the analysis provides the stress intensity factors and energy release rate of the kinked crack in terms of the corresponding quantities for the interface crack prior to kinking. Roughly speaking, the energy release rate is enhanced if the crack heads into the more compliant material and is diminished if it kinks into the stiff material. The results suggest a tendency for a crack to be trapped in the interface irrespective of the loading when the compliant material is tough and the stiff material is at least as tough as the interface.

635 citations


Journal ArticleDOI
TL;DR: In this article, a crack lying along one interface on an elastic sandwich structure is analyzed and a universal relation is found between the actual interface stress intensity factors at the crack tip and the apparent mode I and mode II stress intensity factor associated with the corresponding problem for the crack in the homogeneous material.
Abstract: A crack lying along one interface on an elastic sandwich structure is analyzed. When the thickness of the middle layer is small compared with the other length scales of the structure, a universal relation is found between the actual interface stress intensity factors at the crack tip and the apparent mode I and mode II stress intensity factors associated with the corresponding problem for the crack in the homogeneous material. Therefore, if the apparent stress intensity factors are known, for example calculated from the applied loads as if the structure was homogeneous, this information can be immediately converted into the interface stress intensity factors with the universal relation. This observation provides the theoretical basis for developing sandwich specimens for measuring interface crack toughness. The universal relation reveals the extent to which the asymmetry inherent to a bimaterial interface induces asymmetry in the near tip crack field. In particular, the result of the study can be used to infer whether stress intensity factors for a homogeneous body can be used with good approximation in place of the actual interface stress intensity factors. A proposal for simplifying the approach to interfacial fracture is made which plays down the role of the so-called oscillatory interface singularity stresses.

419 citations


Journal ArticleDOI
TL;DR: In this article, the fracture resistance of a model bimaterial interface has been measured for a wide range of phase angles: the measure of the relative crack face sliding and opening displacement near the crack tip.

377 citations


01 Jan 1989
TL;DR: In this article, a treatment is given of smeared and discrete crack concepts, which start from the notion of a continuum and a discontinuum respectively, and a distinction is furthermore made between fixed, multi-directional and rotating cracks, whereby the orientation of the crack is kept constant, updated in a stepwise manner or updated continuously.
Abstract: Numerical tools to simulate cracking in concrete and similar materials are developed. Firstly, a treatment is given of smeared and discrete crack concepts, which start from the notion of a continuum and a discontinuum respectively. With the smeared crack concept a distinction is furthermore made between fixed, multi-directional and rotating cracks, whereby the orientation of the crack is kept constant, updated in a stepwise manner or updated continuously respectively. Secondly, descriptions of the material behavior at cracking and fracture are presented. Key-effects herein are the tensile-softening behaviour normal to the crack (mode I) and the shear retention parallel to the crack (mode II). Thirdly, the resulting models are applied to scrutinize localized fracture in concrete. Attention is given to tension-shear problems whereby the principal stresses rotate after crack initiation, as is typical of general crack analysis. The results for the various crack concepts show large discrepancies. Smeared cracks may give rise to stress-locking while discrete cracks do not. Fixed smeared cracks may produce overstiff behavior while rotating smeared cracks do not.

302 citations


Journal ArticleDOI
TL;DR: In this article, a model for the elastic-plastic finite element simulation of fatigue crack growth and crack closure is presented and evaluated, showing that careful attention must be given to a series of critical decisions about mesh and model design if the analysis is to be reliable.

301 citations


Journal ArticleDOI
TL;DR: In this article, the fatigue crack initiation behavior of low-alloy steel in 90 C deionized water was investigated and it was observed that the corrosion fatigue process composed three stages, namely, pit growth and pit growth.
Abstract: Fatigue crack initiation behavior of low-alloy steel in 90 C deionized water was investigated. It was observed that the corrosion fatigue process composed three stages, namely, pit growth,...

293 citations


Journal ArticleDOI
TL;DR: In this article, the sharp-corner technique coupled with scanning electron microscopy has been used for observing morphological changes at the surfaces of fatigued copper monocrystals, revealing PSB encroachments (negative protrusions) which indicate that one mechanism of protrusion propagation is a shuttling mechanism among PSB-matrix lamellae.

189 citations


Journal ArticleDOI
TL;DR: In this article, the effects of different constitutive models, including the influence of mean stress relaxation, were investigated in terms of an interaction between residual deformations and crack opening displacements.

174 citations


Journal ArticleDOI
Sg Lim1, Chang Sun Hong1
TL;DR: In this article, a modified shear lag analysis, taking into account the concept of in terlaminar shear layer, is employed to predict the onset of a transverse crack and multiple transverse cracking.
Abstract: A modified shear lag analysis, taking into account the concept of in terlaminar shear layer, is employed to predict the onset of a transverse crack and multiple transverse cracking. In this analysis, the boundary conditions are satisfied for any trans verse crack spacing. The crack multiplication is simulated by adjusting the crack spacing. Based on this analysis the laminate stiffness reduction due to the multiple transverse crack ing is also evaluated in cross-ply laminated composites. The energy concept is utilized to assess the effect of 90° layer thickness and the constraining effect of 0° layer on the trans verse cracking behavior of cross-ply laminated composites. Predictions of the onset of a transverse crack and stiffness reduction due to transverse cracks are compared with those of previous analyses and existing experimental data. The present analysis is simple, yet its results show reasonable agreement with experimental results.

173 citations


Journal ArticleDOI
TL;DR: In this paper, the role of crack bridging by uncracked ligaments is examined with specific emphasis on the role in the growth of fatigue cracks in metal-matrix composites, and simple analytical models are developed for such bridging induced by both overlapping cracks and by coplanar ligaments in the wake of the crack tip.
Abstract: Micro-mechanisms of crack-tip shielding associated with the growth of fatigue cracks in metalmatrix composites are examined with specific emphasis on the role of crack bridging by uncracked ligaments. Simple analytical models are developed for such bridging induced by both overlapping cracks and by coplanar ligaments in the wake of the crack tip; the models are based on respective notions of a critical tensile strain or critical crack-opening displacement in the ligament. The predicted degree of shielding derived from these mechanisms is not large, but is found to be consistent with experimental observations in high-strength P/M aluminum alloys reinforced with 15 to 20 vol pct of SiC particulate.

Journal ArticleDOI
TL;DR: In this paper, an experimental and numerical study has been made of the mechanisms of fatigue crack growth and crack-closure behavior in an αβ titanium alloy Ti-4A1-4Mo-2Sn-0.5Si (IMI 550), following both single and block tensile overloads.


Journal ArticleDOI
TL;DR: In this paper, the role of SiC-particle size and volume fraction on the fatigue-crack growth threshold condition was investigated in P/M Al-Zn-Mg-Cu metal-matrix composites reinforced with either 15 or 20 vol.% silicon carbide particulate.

Journal ArticleDOI
TL;DR: In this article, a power-law dependence on the peak stress intensity factor (Kmax) was found for cyclically induced crack propagation in alumina subjected to direct tension, and it was suggested that direct compressive loads and crack length are both factors that affect cyclic fatigue behavior.
Abstract: Cyclically induced crack propagation occurs in alumina subjected to direct tension—compression loading. The crack increment per cycle (da/dN) has a power-law dependence on the peak stress intensity factor (Kmax). Cyclic crack growth can occur at lower values of Kmax than are required to produce static fatigue effects. Subcritical crack-growth behavior was found to be dependent on specimen geometry: it is suggested that direct compressive loads and crack length are both factors that affect cyclic fatigue behavior, and that the use of K alone to characterize fatigue crack growth in ceramics may be questionable.

Book ChapterDOI
TL;DR: In this paper, the mechanics of quasi-static crack closing and bonding of surfaces of the same or different linear viscoelastic materials are described, and a study of time-dependent joining of initially curved surfaces under the action of surface forces of attraction and external loading is presented.
Abstract: The mechanics of quasi-static crack closing and bonding of surfaces of the same or different linear viscoelastic materials is described. Included is a study of time-dependent joining of initially curved surfaces under the action of surface forces of attraction and external loading. Emphasis is on the use of continuum mechanics to develop equations for predicting crack length or contact size as a function of time for relatively general geometries; atomic and molecular processes associated with the healing or bonding process are taken into account using a crack tip idealization which is similar to that used in the Barenblatt method for fracture. Starting with a previously developed correspondence principle, an expression is derived for the rate of movement of the edge of the bonded area. The effects of material time-dependence and the stress intensity factor are quite different from those for crack growth. A comparison of intrinsic and apparent energies of fracture and bonding is made, and criteria are given for determining whether or not bonding can occur. Examples are given to illustrate use of the basic theory for predicting healing of cracks and growth of contact area of initially curved surfaces. Finally, the effect of bonding time on joint strength is estimated from the examples on contact area growth.

Journal ArticleDOI
TL;DR: In this article, the authors examined the crack propagation behavior in a 2024-T3 aluminum alloy/aramid-fiber epoxy 3 2 laminated composite, ARALL®-2 LAMINATE, with the objective of quantitatively evaluating the primary mechanisms of crack-tip shielding.

Journal ArticleDOI
TL;DR: In this article, a cohesive crack model is proposed to describe the size effects of fracture mechanics, i.e. the transition from ductile to brittle structure behaviour, by increasing the size scale and keeping the geometric shape unchanged.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the mechanisms of tensile cyclic fatigue crack growth in an A1203-33-vol%-SiC-whisker composite at 1400°C.
Abstract: Experimental results are presented on the mechanisms of tensile cyclic fatigue crack growth in an A1203-33-vol%-SiC-whisker composite at 1400°C. The ceramic composite exhibits subcritical fatigue crack propagation at stress-intensity-fator values far below the fracture toughness. The fatigue characterized by the stressintensity-factor range, ΔK, and crack propagation rates are found to be strongly sensitive to the mean stress (load ratio) and the frequency of the fatigue cycle. Detailed transmission electron microscopy of the fatigue crack-tip region, in conjunction with optical microscopy, reveals that the principal mechanism of permanent damage ahead of the advancing crack is the nucleation and growth of interfacial flaws. The oxidation of Sic whiskers in the crack-tip region leads to the formation of a silica-glass phase in the 1400°C air environment. The viscous flow of glass causes debonding of the whisker-matrix interface; the nucleation, growth, and coalescence of interfacial cavities aids in developing a diffuse microcrack zone at the fatigue crack tip. The shielding effect and periodic crack branching promoted by the microcracks result in an apparently benefcial fatigue crack-growth resistance in the A1203—SiC composite, as compared with the unreinforced alumina with a comparable grain size. A comparison of static and cyclic load crack velocities is provided to gain insight into the mechanisms of elevated temperature fatigue in ceramic composites.

Journal ArticleDOI
TL;DR: In this paper, a model based on a stress intensity factor for growing transverse ply cracks was proposed and applied to experimental observations of crack growth in a trans parent 0/90/0 glass fiber/epoxy laminate under fatigue loading.
Abstract: A model based on a stress intensity factor for a growing transverse ply crack is outlined. The model is applied to experimental observations of crack growth in a trans parent 0/90/0 glass fibre/epoxy laminate under fatigue loading. The crack growth rate is found to be independent of crack length but to depend on the spacing between cracks. Under static loading and fatigue loading at high maximum stress, cracks grow by fast frac ture. Slow crack growth is observed at lower maximum fatigue stresses and in the later stages of fatigue tests at higher stresses when the crack spacing is small. Crack growth rates can be described using a Paris relation.

Journal ArticleDOI
TL;DR: In this article, the influence of porosity produced by underfiring on the crack propagation resistance of two feldspathic porcelains and to determine whether lower stress corrosion susceptibility or higher fracture toughness accounts for the superior thermal shock resistance of one of these ceramics.
Abstract: Static fatigue of dental ceramics results from the interaction of residual tensile stress and an aqueous environment. This phenomenon is a potential cause of delayed crack formation and propagation in ceramic or metal-ceramic restorations. For dental ceramics, the influence of microstructural defects such as porosity or fissures caused by incomplete sintering is not known. The objectives of this study were to characterize the influence of porosity (produced by underfiring) on the crack propagation resistance of two feldspathic porcelains and to determine whether lower stress corrosion susceptibility or higher fracture toughness accounts for the superior thermal shock resistance of one of these ceramics. We underfired bars of each porcelain, 25 mm x 4 mm x 4 mm, by as much as 84 degrees C below their recommended firing temperatures. After polishing the specimens through 0.05 microns alumina, we induced cracks in their surfaces with a Vickers microhardness indenter. Semicircular cracks, which were produced under an applied indenter load of 19.6 N, grew with time during storage in distilled water at 37 degrees C. Underfiring of both ceramics caused a slight increase in fracture toughness and a relatively small change in pore volume fraction until we underfired the ceramics at 30 degrees C or more. The crack propagation data indicate that the higher thermal shock resistance of one of the ceramics--as measured previously by a water-quench technique-may be due to its greater resistance to stress corrosion at the initial stage of crack propagation.

Journal ArticleDOI
TL;DR: In this article, the authors measured the growth rate of fatigue cracks in 12 variations of particulate silicon carbide reinforced aluminum alloy composites and found that they exhibited an approximately linear, or Paris law, region, fitting the function da/dN = BΔK s, and a threshold stress intensity factor, ΔK th.

Journal ArticleDOI
TL;DR: In this paper, the authors present the derivation of the new virtual crack closure technique, evaluate the accuracy of the technique, and finally present the results of a limited parametric study of laminates with a postbuckled delamination.
Abstract: The objectives are to present the derivation of the new virtual crack closure technique, evaluate the accuracy of the technique, and finally to present the results of a limited parametric study of laminates with a postbuckled delamination. Although the new virtual crack closure technique is general, only homogeneous, isotropic laminates were analyzed. This was to eliminate the variation of flexural stiffness with orientation, which occurs even for quasi-isotropic laminates. This made it easier to identify the effect of geometrical parameters on G. The new virtual crack closure technique is derived. Then the specimen configurations are described. Next, the stress analyses is discussed. Finally, the virtual crack closure technique is evaluated and then used to calculate the distribution of G along the delamination front of several laminates with a postbuckled delamination.

Journal ArticleDOI
TL;DR: In this paper, the region surrounding an advancing crack tip is modeled as a zone which has undergone a uniform dilatational phase transformation, and the region is allowed to evolve around the advancing tip under conditions of increasing far-field load while the tip is maintained at a critical stress intensity necessary for fracture.

Journal ArticleDOI
TL;DR: In this paper, the fracture problem for a brittle matrix reinforced by ductile particles is considered, and the authors show that the crack surface bridging forces provided by the unbroken particles improve the fracture toughness of the matrix.
Abstract: The fracture problem for a brittle matrix reinforced by ductile particles is considered. In the usual manner it is assumed that the crack surface bridging forces provided by the unbroken particles improve the fracture toughness of the matrix. Depending on the relative strength of the interfacial bonding between the matrix and the particles, two particle force models are introduced, namely, a force that is independent of the crack opening displacement (δ) and a force that is a highly non-linear function of δ. The problem is studied for a penny-shaped or plane strain crack in an infinite medium and for a surface crack in a semi-infinite medium under plane strain conditions. The toughness improvement in the matrix is shown to depend on a dimensionless bimaterial constant representing the inherent toughness of the matrix and the yield behavior of the particles. The effective toughness of the composite medium is calculated as a function of the crack size and the bimaterial constant.

Journal ArticleDOI
TL;DR: In this paper, the critical strain energy release rate of a unidirectional glass/epoxy composite for crack growth parallel to the fibres was studied in two ways using double cantilever beam specimen geometry.

Journal ArticleDOI
TL;DR: In this article, the authors used caustics in conjunction with a high speed video system to determine critical stress intensity factors at initiation of crack growth and found that the maximum tangential stress criterion originally proposed by Erdogan and Sih was the best criterion in terms of predictive capability.
Abstract: In this paper, mixed-mode fracture is investigated experimentally In the first part, critical conditions for initiation of crack growth are explored The method of caustics was used in conjunction with a high speed video system to determine critical stress intensity factors at initiation of crack growth It was found that the maximum tangential stress criterion originally proposed by Erdogan and Sih [1] was the best criterion in terms of predictive capability Polymethylmethacrylate and Homalite-100 were used in the experiments and Homalite-100 was found to exhibit significant rate dependence In the second part, crack growth initiated under mixed-mode loading is addressed It is shown that subsequent slow crack growth in PMMA is under pure mode-I conditions

Journal ArticleDOI
Y.Z. Itoh1, S. Suruga1, Hideo Kashiwaya1
TL;DR: In this paper, the effect of residual stresses on fatigue crack growth is investigated by paying attention to a fatigue crack that initiates at the weld metal and propagates perpendicular to the weld line, and the experimental results indicate that the crack growth rates are equivalent by use of the effective stress intensity range, based on the measurements of crack opening ratio.

Journal ArticleDOI
TL;DR: In this paper, a cohesive crack model is proposed aiming at describing the size effects of fracture mechanics, i.e. the transition from ductile to brittle structure behavior by increasing the size scale and keeping the geometrical shape unchanged.
Abstract: The nature of the crack and the structure behaviour can range from ductile to brittle, depending on material properties, structure geometry, loading condition and external constraints. The influence of variation in fracture toughness, tensile strength and geometrical size scale is investigated on the basis of the π-theorem of dimensional analysis. Strength and toughness present in fact different physical dimensions and any consistent fracture criterion must describe energy dissipation per unit of volume and per unit of crack area respectively. A cohesive crack model is proposed aiming at describing the size effects of fracture mechanics, i.e. the transition from ductile to brittle structure behaviour by increasing the size scale and keeping the geometrical shape unchanged. For extremely brittle cases (e.g. initially uncracked specimens, large and/or slender structures, low fracture toughness, high tensile strength, etc.) a snap-back instability in the equilibrium path occurs and the load–deflection softening branch assumes a positive slope. Both load and deflection must decrease to obtain a slow and controlled crack propagation (whereas in normal softening only the load must decrease). If the loading process is deflection-controlled, the loading capacity presents a discontinuity with a negative jump. It is proved that such a catastrophic event tends to reproduce the classical LEFM-instability (KI = KIC) for small fracture toughnesses and/or for large structure sizes. In these cases, neither the plastic zone develops nor slow crack growth occurs before unstable crack propagation.

Journal ArticleDOI
TL;DR: In this paper, the authors studied the crack propagation behavior of short Stage I cracks, such as crack population, crack size distribution, crack depth and crack growth rate, by means of the newly developed sharp corner section technique.