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Showing papers on "Crack closure published in 1981"


Journal ArticleDOI
TL;DR: In this article, an empirical stress-intensity factor equation for a surface crack as a function of parametric angle, crack depth, crack length, plate thickness and plate width for tension and bending loads was presented.

1,624 citations


Book ChapterDOI
TL;DR: In this article, the development and application of an analytical model of cycle crack growth is presented that includes the effects of crack closure, and the model is used to correlate crack growth rates under constant amplitude loading and to predict crack growth under aircraft spectrum loading on 2219-T851 aluminum alloy sheet material.
Abstract: The development and application of an analytical model of cycle crack growth is presented that includes the effects of crack closure. The model was used to correlate crack growth rates under constant amplitude loading and to predict crack growth under aircraft spectrum loading on 2219-T851 aluminum alloy sheet material. The predicted crack growth lives agreed well with experimental data. The ratio of predicted to experimental lives ranged from 0.66 to 1.48. These predictions were made using data from an ASTM E24.06.01 Round Robin.

656 citations


Journal ArticleDOI
C. F. Shih1
TL;DR: In this paper, the relationship between the J-integral and the crack opening displacement δt is obtained by exploiting the dominance of the Hutchinson-Rice-Rosengren singularity in the crack-tip region.
Abstract: R elationships between the J-integral and the crack opening displacement δt are obtained by exploiting the dominance of the Hutchinson-Rice-Rosengren singularity in the crack-tip region. The coefficient dn that relates J to δt, is dependent on the material deformation properties and is independent of crack configuration under small-scale yielding conditions. For low hardening materials, dn appears to be configuration dependent in the fully yielded state. Similarly, the slope of the J-resistance curve is relatable to an operationally defined crack opening angle if J-controlled crack growth conditions are met. These relationships are corroborated by finite element results for the complete regime of elastic-plastic deformation and experimental data for A533B steels, HY-80 steels and several other ductile metals.

642 citations



Journal ArticleDOI
TL;DR: The concept of oxide-induced crack closure is utilized to explain the role of gaseous and aqueous environments on corrosion fatigue crack propagation at ultralow, near-threshold growth rates in bainitic and martensitic 2 1/4 Cr-1 Mo pressure vessel steels as mentioned in this paper.
Abstract: The concept of oxide-induced crack closure is utilized to explain the role of gaseous and aqueous environments on corrosion fatigue crack propagationat ultralow, near-threshold growth rates in bainitic and martensitic 2 1/4 Cr-1 Mo pressure vessel steels. It is shown that at low load ratios, near-threshold growth rates are significantly reduced in moist environments (such as air or water), compared to dry environments (such as hydrogen or helium gas), due to the formation of excess corrosion deposits on crack faces which enhances crack closure. Using Auger spectroscopy, it is found that at the threshold stress intensity, ΔKo, below which cracks appear dormant, the maximum thickness of excess oxide debris within the crack is comparable with the pulsating crack tip opening displacement. The implications of this model to near-threshold fatigue crack growth behavior, in terms of the role of load ratio, environment, and microstructure are discussed.

478 citations


Journal ArticleDOI
TL;DR: In this article, the authors compared the crack tip stress and strain fields for the edge crack bar subjected to bending and the center cracked panel and single cracked panel subjected to tensile loads at the same level of applied J-integral or crack tip opening displacement.
Abstract: Detailed crack tip stress and strain fields are generated for the edge crack bar subjected to bending and the center cracked panel and single cracked panel subjected to tensile loads. These fields are compared with the singular fields, due to Hutchinson and Rice and Rosengren, at the same level of applied J. The comparisons show that the size R of the region at the crack tip dominated by the HRR singularity is substantially larger in the bend specimen than in the center-cracked panel for contained and large scale plasticity. Hardening properties also have a strong influence on R. The implications of these results on the minimum size requirement essential to a one parameter fracture criterion based on the J-integral or crack tip opening displacement are discussed.

275 citations



Journal ArticleDOI
TL;DR: In this article, the concept of a critical length was examined and three regimes of behavior for different crack lengths were identified, and it was concluded that there is an approximate correlation between the critical length for short crack behaviour and the scale of the microstructure.
Abstract: — –Fatigue cracks shorter than some critical length tend to propagate anomalously quickly. This paper examines the concept of a ‘critical length’, identifying three regimes of behaviour for different crack lengths. Some published work is examined, covering a wide range of different materials. It is concluded that there is an approximate correlation between the critical length for short crack behaviour and the scale of the microstructure. LEFM is difficult, if not impossible, to apply to cracks shorter than this critical length because the material surrounding a crack cannot be assumed to approximate to a homogeneous continuum. Suggestions are made for a fatigue design philosophy which incorporates short crack behaviour.

240 citations


Journal ArticleDOI
TL;DR: In this article, an elastic solution has been found for a screw dislocation near a crack in the absence of any external stresses, where the dislocation produces a stress intensity factor on the crack even without external stresses.

204 citations


Journal ArticleDOI
TL;DR: In this article, a plane-strain shallow Mode I tensile edge crack under constant applied load and creep exponents of 3 and 10 was calculated, using the elastic stress intensity factor with the Riedel-Rice approximation.

179 citations


Journal ArticleDOI
TL;DR: In this article, the maximum normal-strain theory for fracture is modified as a new approach to the study of the angled crack problem, and the authors present predictions on the direction of initial crack extension and the fracture strength for plates containing a slit crack as well as those with an elliptic crack under uniform edge stresses.


BookDOI
01 Jan 1981
TL;DR: In this article, a round-robin analysis was conducted to predict the fatigue crack growth in 2219-T851 aluminum center-cracked specimens subjected to flight loading in random cycle-by-cycle format.
Abstract: Papers are presented in the volume summarizing the baseline data, methodology, procedures, and results of a round-robin analysis which was conducted to predict the fatigue crack growth in 2219-T851 aluminum center-cracked specimens subjected to flight loading in random cycle-by-cycle format. The objective of the analysis was to assess whether data from constant-amplitude fatigue crack growth tests on center-cracked specimens can be used to predict fatigue crack growth lives under random loading. The following approaches are discussed in detail: a root-mean-square approach, a crack-closure model, a multi-parameter yield zone model, and a load-interaction model.

Journal ArticleDOI
TL;DR: In this article, a study of the problem of a penny-shaped crack in an infinite body of power-law material subject to general remote axisymmetric stressing conditions is carried out.
Abstract: A study is carried out of the problem of a penny-shaped crack in an infinite body of power-law material subject to general remote axisymmetric stressing conditions. The plane strain version of the problem is also examined. The material is incompressible and is characterized by small strain deformation theory with a pure power relation between stress and strain. The solutions presented also apply to power-law creeping materials and to a class of strain-rate sensitive hardening materials. Both numerical and analytical procedures are employed to obtain the main results. A perturbation solution obtained by expanding about the trivial state in which the stress is everywhere parallel to the crack leads to simple formulas which are highly accurate even when the remote stress is perpendicular to the crack.

Book ChapterDOI
TL;DR: In this article, a model for the prediction of growth rates of fatigue cracks in aluminium alloys is presented based on an approximate description of the crack closure behavior and can be used to predict effects of crack growth acceleration and retardation observed experimentally under variable-amplitude loading.
Abstract: A model for the prediction of growth rates of fatigue cracks in aluminium alloys is presented. The model is based on an approximate description of the crack closure behavior and can be used to predict effects of crack growth acceleration and retardation observed experimentally under variable-amplitude loading. A computer program was developed for analysis of fatigue crack growth. It was used to analyze the effect of certain parameter variations in a flight simulation load spectrum on the crack growth rate. For 7075-T6 thin sheet material the results are compared with experimental data.

Journal ArticleDOI
TL;DR: In this article, the effects of partial pressure of the aggressive environment and cyclic load frequency in terms of surface reaction and transport processes are discussed, and the experimental basis and the development of models for transport and surface reaction controlled fatigue crack growth are reviewed.
Abstract: Metal fatigue has been well recognized as an important cause for failure of engineering structures. In most applications, fatigue damage results from the conjoint actions of the cyclically applied stress and the external (chemical) environment, and is therefore time dependent. Understanding of this load-environment interaction is essential to the formulation of rational life prediction procedures and to the development of realistic materials evaluation and qualification tests. Research over the past 15 years has led to the suggestion that the rate of fatigue crack growth in an aggressive environment, (da/dN)e, is the sum of three components—the rate of fatigue crack growth in an inert environment, (da/dN)r, which represents the contribution of “pure” fatigue, a cycle-dependent component, (da/dN)cf, that requires the synergistic interaction of fatigue and environmental attack, and the contribution by sustained-load crack growth (i.e., stress corrosion cracking) at K levels above K Iscc, (da/dN)scc. Recent fracture mechanics and surface chemistry studies have provided a clearer understanding of the cycle-dependent term, and, hence, a more complete understanding of environment assisted fatigue crack growth. (da/dN)cf results from the reaction of the environment with fresh crack surfaces produced by fatigue, and is a function of the extent of reaction during one loading cycle. For highly reactive alloy-environment systems, this contribution depends also on the rate of transport of the aggressive environment to the crack tip. The experimental basis and the development of models for transport and surface reaction controlled fatigue crack growth are reviewed. Interpretation of the effects of partial pressure of the aggressive environment and cyclic load frequency in terms of surface reaction and transport processes is discussed. Implications in terms of service performance and life prediction procedures are considered.

Journal ArticleDOI
TL;DR: In this article, the development of fatigue crack shape is used as a diagnostic tool to test the accuracy of these theoretical stress intensity solutions in predictive fatigue crack growth calculations, and those solutions giving the best engineering estimate of crack tip stress intensity factors are identified.
Abstract: Several crack tip stress intensity factor solutions have been published for semi-elliptic, surface breaking cracks in plates subjected to tension or bending forces. These solutions do not agree with each other particularly well and the basis for choosing which one is the best has not been established. In this paper, the development of fatigue crack shape is used as a diagnostic tool to test the accuracy of these theoretical stress intensity solutions in predictive fatigue crack growth calculations. Those solutions giving the best engineering estimate of crack tip stress intensity factors are identified. Single equations are also given for each loading case at the deepest point or surface intersection point of semi-elliptic cracks in order to facilitate calculations on programmable calculators. A rational basis for calculating the progress of a crack which snaps through the thickness and continues to propagate in a stable way by fatigue is suggested.

Journal ArticleDOI
TL;DR: In this paper, it is shown that the use of conventional fracture mechanics concepts to characterize small cracks results in behavior which differs from that of large cracks, due to a breakdown of underlying continuum mechanics assumptions.
Abstract: It is becoming increasingly evident that an understanding of incipient microcracking and growth of small cracks is essential to the development of improved predictions of the fatigue life of structures. Information on the threshold and kinetic properties of small cracks is reviewed and critically discussed. It is shown that the use of conventional fracture mechanics concepts to characterize small cracks results in behavior which differs from that of large cracks—this difference is due to a breakdown of underlying continuum mechanics assumptions. Methods to incorporate small crack behavior in fatigue life predictions are also considered. In these predictions, the importance of separately treating crack initiation and crack growth and of accounting for small crack behavior and plasticity effects (particularly for notched members) is demonstrated.

Journal ArticleDOI
TL;DR: In this paper, the tensile strength, fatigue crack propagation behavior, and fracture toughness of a low-alloy sin tered steel were determined for the porosity range 11-17%.
Abstract: The tensile strength, fatigue crack propagation behaviour, and fracture toughness of a low-alloy sin tered steel were determined for the porosity range 11–17%. Static and cyclic strength were found to increase with density in a non-linear fashion. The pores both exerted a stress-concentrating influence and reduced the load-bearing section. The micromechanism of failure was always ductile fracture in the necks between sintered steel particles. It was concluded that the stress state at the tips of cracks subjected to static or cyclic loading was closer to plane stress than to plane strain. Retardation of fatigue crack propagation appeared to occur due to the blunting action of the pores. The presence of a wear mechanism had little influence upon fatigue crack growth rates. A companion paper (following) attempts to model the static and cyclic behaviour of the steel, based on the known micromechanisms of failure. PM/0172

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the mechanisms behind the cut-off of the stress peak at the notch using the fictitious crack model (FCM), where a fictitious crack is assumed to form when the uniaxial tensile strength is exceeded.

Journal ArticleDOI
TL;DR: In this paper, the influence of a circumferential crack on the torsional dynamic behavior of a shaft is studied, and the results show that the change in dynamic response due to the crack is high enough to allow detection of the crack and estimation of its location or magnitude.

Journal ArticleDOI
TL;DR: In this article, the effects of the stress ratio and the grain size on the fatigue crack growth near the threshold in a low carbon steel were analyzed based on the crackclosure measurement and the microscopic observations of cracktip slip deformation and the fracture surface.

Journal ArticleDOI
TL;DR: In this article, the effects of crack closure on fatigue crack growth rate in 7050 Al were studied with the aid of small-foil strain gages glued at positions near to the crack plane.

Journal ArticleDOI
TL;DR: In this paper, the authors derived a theoretical dependence of crack growth rate and threshold stress intensities on hydrogen pressure in a 3 1/2 NiCrMoV steel (0.2 pct proof stress 1200 MPa) and showed that the crack advances by repeated nucleation of microcracks at microstructural features ahead of the main crack.
Abstract: The crack growth rates and threshold stress intensities,K TH, for a 3 1/2 NiCrMoV steel (0.2 pct proof stress 1200 MPa) have been measured in a hydrogen environment at various temperatures and hydrogen pressures. Fractographic evidence and the observation of alternating fast and slow crack growth nearK TH suggests that the crack advances by the repeated nucleation of microcracks at microstructural features ahead of the main crack. Transient crack growth is observed following load increases just belowK TH. Using the idea, from unstable cleavage fracture theory, that for fracture a critical stress must be exceeded over a critical distance ahead of the crack, and assuming that this critical stress is reduced in proportion to the local hydrogen concentration (in equilibrium with the external hydrogen atK TH), a theoretical dependence ofK TH on hydrogen pressure is derived which compares well with the experimental evidence.

Journal ArticleDOI
TL;DR: In this article, a modified cavity growth model is used to describe the variations observed at crack initiation, based on the results obtained on axisymmetric notched specimens which were used to evaluate the critical cavity growth at rupture, and a statistical approach incorporating the distribution of inclusions located in the vicinity of a crack tip is proposed.

Journal ArticleDOI
TL;DR: In this article, the authors measured the fatigue propagation of short Mode I surface cracks in Al 2219-T851 and compared the measured rates with values predicted from crack growth models, with an underlying assumption that slip responsible for early propagation does not extend in significant amounts beyond the next grain boundary.
Abstract: Rates of fatigue propagation of short Mode I surface cracks in Al 2219-T851 are measured as a function of crack length and of the location of the surface crack tips relative to the grain boundaries. The measured rates are then compared to values predicted from crack growth models. The crack growth rate is modeled with an underlying assumption that slip responsible for early propagation does not extend in significant amounts beyond the next grain boundary in the direction of crack propagation. Two models that contain this assumption are combined: 1) cessation of propagation into a new grain until a mature plastic zone is developed; 2) retardation of propagation by crack closure stress, with closure stress calculated from the location of a crack tip relative to the grain boundary. The transition from short to long crack growth behavior is also discussed.

Journal ArticleDOI
TL;DR: In this article, a study was made of the near-threshold fatigue crack propagation behavior of a wrought nickel-base superalloy, Rene 95, with reference to the effect of crack size on the threshold stress intensity ΔK0 no detectable crack growth.

Journal ArticleDOI
TL;DR: In this article, a grain-boundary creep-crack-growth model is presented based on the assumptions that a crack propagates along the grain boundary by a coupled process of surface and grainboundary self-diffusion, the adjoining grains on either side of the boundary behave elastically, and steady state conditions prevail.
Abstract: A grain-boundary creep-crack-growth model is presented based on the assumptions that a crack propagates along the grain boundary by a coupled process of surface and grain-boundary self-diffusion, the adjoining grains on either side of the boundary behave elastically, and steady state conditions prevail. Under the action of the applied stress, atoms on the crack surfaces are driven by surface diffusion toward the crack tip, from where they are deposited nonuniformly by grain-boundary diffusion along the grain interface so that the grain boundary opens up hi a wedge shape ahead of the advancing tip which, hi turn, produces a misfit residual stress field. The total grain-boundary normal stresses which are the sum of this misfit stress field and that due to applied stress as well as the boundary opening displacements due to materials deposition are solved from a singular integrodifferential equation to give the following equation relating K to v: where K is the applied mode I crack-tip stress intensity factor,Kmin=1.69 kg is the minimum K below which no crack growth is predicted, KG being the critical K based on the Griffith theory; ν is the fixed crack-tip velocity, and νmin is the minimum v for which K=Kmia. In terms of the conventional expression of ν∝Kn, the present model predicts the values of n varying from 12 to infinity. A comparison with a set of creep crack-growth data on Si-Al-O-N at 1400°C shows good agreement between theory and experiment. A detailed analysis of the energy balance for the present model is also presented which indicates that / or (1–ν2)K2/E is indeed the correct energy release rate during the crack growth, as is true in the theory of elastic fracture mechanics. However, the major portion of the energy released in the diffusion processes comes from work done by the normal stress in opening up the grain boundary to accommodate the diffused material rather than from strain energy released by the adjoining grains.

Journal ArticleDOI
TL;DR: In this paper, a n asymptotic analysis of the near-tip fields is given for transient crack propagation in an elastic-plastic material, characterized by J 2 flow theory together with a bilinear effective stress-strain curve.
Abstract: A n asymptotic analysis of the near-tip fields is given for transient crack propagation in an elastic-plastic material. The material is characterized by J 2 flow theory together with a bilinear effective stress-strain curve. Both plane stress and plane strain conditions have been considered. Explicit results are given for the order of the crack-tip singularity, the angular position at which unloading occurs, and the angular variation of the near-tip stresses, all as functions of the crack-tip speed and the ratio of the slopes of the two portions of the bilinear stress-strain relation. It was found that the results are much more sensitive to the elastic-plastic constitutive relation than to the crack speed. This result is important for numerical analyses of dynamic crack propagation problems.

Journal ArticleDOI
TL;DR: In this paper, the birth and growth of short cracks from an elastic-plastic fracture mechanics viewpoint was analysed from an EPM viewpoint. But the authors did not consider the early stages of the crack initiation and the initiation phase terminates when one crack starts to dominate and accelerates to failure.
Abstract: — The birth and growth of short cracks is analysed from an elastic-plastic fracture mechanics viewpoint. Low to high cumulative damage tests from the low stress to high strain regime indicate that there is no crack initiation period in the metallurgical sense and that cracks grow from the first cycle, but at a slow rate. The initiation phase terminates when one crack starts to dominate and accelerates to failure, its initial size being given by for the medium carbon steel tested here, of grain size 56 μm.